Patent Publication Number: US-2022234295-A1

Title: Wet wiper apparatuses for use in additive manufacturing apparatuses

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of and priority to U.S. Provisional Application Ser. No. 62/852,041, titled “CLEANING SYSTEMS FOR ADDITIVE MANUFACTURING APPARATUSES AND WET WIPER APPARATUSES INCLUDED THEREIN” filed May 23, 2019, the entire contents of which are hereby incorporated by reference. 
    
    
     BACKGROUND 
     Field 
     The present specification generally relates to additive manufacturing apparatuses and, more specifically, to cleaning systems for additive manufacturing apparatuses and methods for using the same. 
     Technical Background 
     Additive manufacturing apparatuses may be utilized to “build” an object from build material, such as organic or inorganic powders, in a layer-wise manner. Early iterations of additive manufacturing apparatuses were used for prototyping three-dimensional (3D) parts. However, as additive manufacturing technology has improved, there is an increased interest in utilizing additive manufacturing apparatuses for large-scale commercial production of parts. One issue of scaling additive manufacturing apparatuses to commercial production is improving the through-put of additive manufacturing apparatuses to meet commercial demands. 
     Accordingly, a need exists for alternative additive manufacturing apparatuses and components thereof which improve manufacturing through-put. 
     SUMMARY 
     A first aspect A1 is directed to a wet wiper apparatus comprising: a wet wiper body having a top side and a bottom side; a first wiper blade vertically extending from the top side of the wet wiper body; and a fluid channel horizontally extending from a first end of the wet wiper body to a second end of the wet wiper body, the fluid channel having an open top to allow fluid flow out of the fluid channel. 
     A second aspect A2 includes the wet wiper apparatus of aspect A1, further comprising a second wiper blade vertically extending from the top side of the wet wiper body and spaced apart from the first wiper blade. 
     A third aspect A3 includes the wet wiper apparatus of aspect A2, wherein the fluid channel is positioned between the first wiper blade and the second wiper blade. 
     A fourth aspect A4 includes the wet wiper apparatus of any of the foregoing aspects A2-A3, wherein the first wiper blade and the second wiper blade extend from a first end of the wet wiper apparatus to a second end of the wet wiper apparatus. 
     A fifth aspect A5 includes the wet wiper apparatus of any of the foregoing aspects A2-A4, further comprising a pair of walls extending between the first wiper blade and the second wiper blade from a base of the wet wiper apparatus to a top of each of the first wiper blade and the second wiper blade. 
     A sixth aspect A6 includes the wet wiper apparatus of any of the foregoing aspects A1-A5, wherein fluid channel defines a recessed path within the wet wiper body. 
     A seventh aspect A7 includes the wet wiper apparatus of any of the foregoing aspects A1-A6, further comprising a cleaning manifold extending below the fluid channel within the wet wiper body, wherein the cleaning manifold comprises a plurality of fluid ports configured to provide cleaning fluid to the fluid channel. 
     An eighth aspect A8 includes the wet wiper apparatus of aspect A7, further comprising a plurality of cleaning fluid inlets operable to receive the cleaning fluid and provide the cleaning fluid to the cleaning manifold. 
     A ninth aspect A9 includes the wet wiper apparatus of aspect A8, wherein the plurality of cleaning fluid inlets comprise fluid conduits extending vertically upward through the bottom side of the wet wiper body. 
     A tenth aspect A10 includes the wet wiper apparatus of aspect A8, wherein the plurality of cleaning fluid inlets comprise fluid conduits extending from a side of the wet wiper body adjacent to the top side and the bottom side of the wet wiper body. 
     An eleventh aspect A11 includes the wet wiper apparatus of any of the foregoing aspects A1-A6, further comprising a cleaning manifold extending below the fluid channel within the wet wiper body, wherein the cleaning manifold comprises a fluid port extending from the first end of the wet wiper apparatus to the second end of the wet wiper apparatus configured to provide cleaning fluid to the fluid channel. 
     A twelfth aspect A12 includes the wet wiper apparatus of any of the foregoing aspects A1-A11, further comprising at least one motion coupler extending from the wet wiper apparatus and configured to couple the wet wiper apparatus to a cleaning station for vertical motion therein. 
     A thirteenth aspect A13 is directed to a wet wiper apparatus comprising: a wet wiper body having a top side and a bottom side; a wiper blade vertically extending from a top side of the wet wiper body; a manifold comprising at least one fluid port, the manifold being configured to deliver cleaning fluid to the top side of the wet wiper body; and cleaning fluid inlets extending through the wet wiper body, wherein the cleaning fluid inlets are in fluid communication with the at least one fluid port of the manifold. 
     A fourteenth aspect A14 includes the wet wiper apparatus of aspect A13, wherein the wiper blade is a first wiper blade, and the wet wiper apparatus further comprises a second wiper blade vertically extending from a top side of the wet wiper body. 
     A fifteenth aspect A15 includes the wet wiper apparatus of aspect A14, wherein the at least one fluid port is disposed between the first and second wiper blades along the wet wiper body. 
     A sixteenth aspect A16 includes the wet wiper apparatus of any of the foregoing aspects A13-A15, further comprising a fluid channel formed in the wet wiper body and positioned between the first wiper blade and the second wiper blade, wherein the fluid channel is in fluid communication with the at least one fluid port of the manifold. 
     A seventeenth aspect A17 includes the wet wiper apparatus of aspect A16, wherein the fluid channel comprises an open top to allow fluid flow out of the fluid channel. 
     An eighteenth aspect A17 includes the wet wiper apparatus of aspect A16, wherein the cleaning fluid inlets extend vertically upward through the bottom side of the wet wiper body. 
     A nineteenth aspect A19 includes the wet wiper apparatus of any of the foregoing aspects A13-A18, further comprising a pair of walls extending between the first wiper blade and the second wiper blade from the top side of the wet wiper apparatus to a top of each of the first wiper blade and the second wiper blade. 
     A twentieth aspect A20 includes the wet wiper apparatus of any of the foregoing aspects A13-A19, further comprising at least one motion coupler extending from the wet wiper apparatus and configured to couple the wet wiper apparatus to a cleaning station for vertical motion therein. 
     Additional features and advantages of the additive manufacturing apparatuses described herein, and the components thereof, will be set forth in the detailed description which follows, and in part will be readily apparent to those skilled in the art from that description or recognized by practicing the embodiments described herein, including the detailed description which follows, the claims, as well as the appended drawings. 
     It is to be understood that both the foregoing general description and the following detailed description describe various embodiments and are intended to provide an overview or framework for understanding the nature and character of the claimed subject matter. The accompanying drawings are included to provide a further understanding of the various embodiments, and are incorporated into and constitute a part of this specification. The drawings illustrate the various embodiments described herein, and together with the description serve to explain the principles and operations of the claimed subject matter. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  schematically depicts an additive manufacturing apparatus according to one or more embodiments shown and described herein; 
         FIG. 2  schematically depicts an embodiment of an actuator assembly for an additive manufacturing apparatus according to one or more embodiments shown and described herein; 
         FIG. 3A  is a schematic top view of a cleaning station of an additive manufacturing apparatus according to one or more embodiments shown and described herein; 
         FIG. 3B  is a side cross-sectional view of a cleaning station of an additive manufacturing apparatus according to one or more embodiments shown and described herein; 
         FIG. 3C  is a side cross-sectional view of a cleaning station vessel of an additive manufacturing apparatus according to one or more embodiments shown and described herein; 
         FIG. 4A  is a schematic perspective view of a wet wipe member including two blades in a wet wipe cleaning section of an additive manufacturing apparatus according to one or more embodiments shown and described herein; 
         FIG. 4B  is a cross-sectional front view of a wet wipe member in a wet wipe cleaning section of an additive manufacturing apparatus according to one or more embodiments shown and described herein; 
         FIG. 4C  is a schematic perspective view of a wet wipe member including a single blade in a wet wipe cleaning section of an additive manufacturing apparatus according to one or more embodiments shown and described herein; 
         FIG. 4D  is a cross-sectional front view of a wet wipe member in a wet wipe cleaning section of an additive manufacturing apparatus according to one or more embodiments shown and described herein; 
         FIG. 4E  is a cross-sectional side view of a blade-less wet wipe member in a wet wipe cleaning section of an additive manufacturing apparatus according to one or more embodiments shown and described herein; 
         FIG. 4F  is a cross-sectional side view of a vacuum wipe member in a wet wipe cleaning section of an additive manufacturing apparatus according to one or more embodiments shown and described herein; 
         FIG. 4G  is a cross-sectional side view of a wet wipe member including two blades having different vertical positions in a wet wipe cleaning section of an additive manufacturing apparatus according to one or more embodiments shown and described herein; 
         FIG. 5A  is a top view of an angled dry wipe member in a dry wipe cleaning section of an additive manufacturing apparatus according to one or more embodiments shown and described herein; 
         FIG. 5B  is a partial top view of  FIG. 5A  without the angled wipers included for illustration according to one or more embodiments shown and described herein; 
         FIG. 5C  is a cross-sectional front view of the wiper mounting member of the dry wipe member according to one or more embodiments shown and described herein; 
         FIG. 5D  is a cross-sectional front view of the wiper mounting member including blades at different vertical positions of the dry wipe member according to one or more embodiments shown and described herein; 
         FIG. 6A  is a cross-sectional front view of a dry wipe member submerged in cleaning fluid in the dry wipe section of the cleaning station vessel according to one or more embodiments shown and described herein; 
         FIG. 6B  is a cross-sectional front view depicting one end of the dry wipe member of  FIG. 6A  raised above the fluid level of the cleaning fluid according to one or more embodiments shown and described herein; 
         FIG. 6C  is a cross-sectional front view depicting both ends of the dry wipe member of  FIG. 6A  raised above the fluid level of the cleaning fluid according to one or more embodiments shown and described herein; 
         FIG. 6D  is a cross-sectional front view depicting one end of the wet wipe member of  FIG. 6A  raised above the fluid level of the cleaning fluid according to one or more embodiments shown and described herein; 
         FIG. 6E  is a cross-sectional front view depicting both ends of the wet wipe member of  FIG. 6A  raised above the fluid level of the cleaning fluid according to one or more embodiments shown and described herein; 
         FIG. 6F  is a cross-sectional front view depicting an adjustable hard stop for use in coupling of one of the members of the cleaning station within the cleaning station vessel according to one or more embodiment shown and described herein; 
         FIG. 7A  is a cross-sectional side view of a capping section of the cleaning station including a sponge according to one or more embodiments shown and described herein; 
         FIG. 7B  is a cross-sectional side view of a capping section of the cleaning station including a cap according to one or more embodiments shown and described herein; 
         FIG. 7C  is a cross-sectional front view of a cleaning station in which the cleaning station vessel is actuated vertically to cover the print head according to one or more embodiments shown and described herein; 
         FIG. 7D  is a cross-sectional front view of a cleaning station in which seals around the cleaning station vessel are actuated vertically to cover the print head according to one or more embodiments shown and described herein; 
         FIG. 7E  is a cross-sectional front view of a cleaning station in which the cleaning station vessel includes deflated seals according to one or more embodiments shown and described herein; 
         FIG. 7F  is a cross-sectional front view of a cleaning station in which the deflated seals of  FIG. 7E  are inflated to form a seal with the print head according to one or more embodiments shown and described herein; 
         FIG. 8  is a process flow diagram of the fluid management system (binder pathway and the cleaning fluid pathway) according to one or more embodiments shown and described herein; 
         FIG. 9  is a flow chart depicting an embodiment of cleaning fluid maintenance according to one or more embodiments shown and described herein; 
         FIG. 10  schematically depicts a control system for controlling the components of the binder pathway and the cleaning fluid pathway according to one or more embodiments shown and described herein; and 
         FIG. 11  is a cross-sectional side view of a print head having a gauge thereon for use in setting a maximum vertical height of one or more components of the cleaning station according to one or more embodiments shown and described herein. 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in detail to embodiments of additive manufacturing apparatuses, and components thereof, examples of which are illustrated in the accompanying drawings. Whenever possible, the same reference numerals will be used throughout the drawings to refer to the same or like parts. One embodiment of an additive manufacturing apparatus  100  comprising a cleaning station  110  is schematically depicted in  FIG. 1 . The cleaning station  110  may generally include a wet wipe cleaner section and a dry wipe cleaner section. The cleaning station is in fluid communication with a cleaning fluid reservoir and applies cleaning fluid to a print head to clean the print head. Various embodiments of cleaning stations for additive manufacturing apparatuses, additive manufacturing apparatus comprising the cleaning stations, and methods for using the same are described in further detail herein with specific reference to the appended drawings. 
     Ranges can be expressed herein as from “about” one particular value, and/or to “about” another particular value. When such a range is expressed, another embodiment includes from the one particular value and/or to the other particular value. Similarly, when values are expressed as approximations, by use of the antecedent “about,” it will be understood that the particular value forms another embodiment. It will be further understood that the endpoints of each of the ranges are significant both in relation to the other endpoint, and independently of the other endpoint. 
     Directional terms as used herein—for example up, down, right, left, front, back, top, bottom—are made only with reference to the figures as drawn and are not intended to imply absolute orientation unless otherwise expressly stated. 
     Unless otherwise expressly stated, it is in no way intended that any method set forth herein be construed as requiring that its steps be performed in a specific order, nor that with any apparatus specific orientations be required. Accordingly, where a method claim does not actually recite an order to be followed by its steps, or that any apparatus claim does not actually recite an order or orientation to individual components, or it is not otherwise specifically stated in the claims or description that the steps are to be limited to a specific order, or that a specific order or orientation to components of an apparatus is not recited, it is in no way intended that an order or orientation be inferred, in any respect. This holds for any possible non-express basis for interpretation, including: matters of logic with respect to arrangement of steps, operational flow, order of components, or orientation of components; plain meaning derived from grammatical organization or punctuation, and; the number or type of embodiments described in the specification. 
     As used herein, the singular forms “a,” “an” and “the” include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to “a” component includes aspects having two or more such components, unless the context clearly indicates otherwise. 
     During operation of an additive manufacturing apparatus, the efficacy and performance of the print head is essential. The print head is exposed to heat, and is also subject to excess build material distributed by a recoat head and/or binder material from the print head. The combination of these contaminants (i.e., excess build material and binder material) can lead to clogged nozzles in the print head, which can adversely impact operation of the additive manufacturing apparatus. 
     The embodiments described herein are directed to additive manufacturing apparatuses and components for additive manufacturing apparatuses, specifically cleaning systems in additive manufacturing apparatuses, which may be used to conduct automated routine maintenance of the additive manufacturing apparatuses to reduce or eliminate the presence of clogged nozzles in the print head and other contamination. 
     Additive Manufacturing Apparatus 
     Referring now to  FIG. 1 , an embodiment of an additive manufacturing apparatus  100  is schematically depicted. The additive manufacturing apparatus  100  includes a cleaning station  110 , a build platform  120 , and an actuator assembly  102 . The additive manufacturing apparatus  100  may optionally include a supply platform  130 . The actuator assembly  102  comprises, among other elements, a recoat head  140  for distributing build material  400  and a print head  150  for depositing binder material  500 . The actuator assembly  102  may be constructed to facilitate independent control of the recoat head  140  and the print head  150  along the working axis  116  of the additive manufacturing apparatus  100 . This allows for the recoat head  140  and the print head  150  to traverse the working axis  116  of the additive manufacturing apparatus  100  in the same direction and/or in opposite directions and for the recoat head  140  and the print head  150  to traverse the working axis of the additive manufacturing apparatus  100  at different speeds and/or the same speed. Independent actuation and control of the recoat head  140  and the print head  150 , in turn, allows for at least some steps of the additive manufacturing process to be performed simultaneously thereby reducing the overall cycle time of the additive manufacturing process to less than the sum of the cycle time for each individual step. In the embodiments of the additive manufacturing apparatus  100  described herein, the working axis  116  of the additive manufacturing apparatus  100  is parallel to the +/−X axis of the coordinate axes depicted in the figures. 
     In the embodiment depicted in  FIG. 1 , the additive manufacturing apparatus  100  includes a cleaning station  110 , a build platform  120 , a supply platform  130 , and an actuator assembly  102 . However, it should be understood that, in other embodiments, the additive manufacturing apparatus  100  does not include a supply platform  130 , such as in embodiments where build material is supplied to the build platform  120  with, for example and without limitation, a build material hopper. In the embodiment depicted in  FIG. 1 , the cleaning station  110 , the build platform  120 , and the supply platform  130  are positioned in series along the working axis  116  of the additive manufacturing apparatus  100  between a print home position  158  of the print head  150  located proximate an end of the working axis  116  in the −X direction, and a recoat home position  148  of the recoat head  140  located proximate an end of the working axis  116  in the +X direction. That is, the print home position  158  and the recoat home position  148  are spaced apart from one another in a horizontal direction that is parallel to the +/−X axis of the coordinate axes depicted in the figures and the cleaning station  110 , the build platform  120 , and the supply platform  130  are positioned therebetween. In the embodiments described herein, the build platform  120  is positioned between the cleaning station  110  and the supply platform  130  along the working axis  116  of the additive manufacturing apparatus  100 . 
     The cleaning station  110  is positioned proximate one end of the working axis  116  of the additive manufacturing apparatus  100  and is co-located with the print home position  158  where the print head  150  is located or “parked” before and after depositing binder material  500  on a layer of build material  400  positioned on the build platform  120 . The cleaning station  110  may include one or more cleaning sections (shown in greater detail below) to facilitate cleaning the print head  150  between depositing operations. 
     The build platform  120  is coupled to a lift system comprising a build platform actuator  122  to facilitate raising and lowering the build platform  120  relative to the working axis  116  of the additive manufacturing apparatus  100  in a vertical direction (i.e., a direction parallel to the +/−Z directions of the coordinate axes depicted in the figures). The build platform actuator  122  may be, for example and without limitation, a mechanical actuator, an electro-mechanical actuator, a pneumatic actuator, a hydraulic actuator, or any other actuator suitable for imparting linear motion to the build platform  120  in a vertical direction. Suitable actuators may include, without limitation, a worm drive actuator, a ball screw actuator, a pneumatic piston, a hydraulic piston, an electro-mechanical linear actuator, or the like. The build platform  120  and build platform actuator  122  are positioned in a build receptacle  124  located below the working axis  116  (i.e., in the −Z direction of the coordinate axes depicted in the figures) of the additive manufacturing apparatus  100 . During operation of the additive manufacturing apparatus  100 , the build platform  120  is retracted into the build receptacle  124  by action of the build platform actuator  122  after each layer of binder material  500  is deposited on the build material  400  located on build platform  120 . 
     The supply platform  130  is coupled to a lift system comprising a supply platform actuator  132  to facilitate raising and lowering the supply platform  130  relative to the working axis  116  of the additive manufacturing apparatus  100  in a vertical direction (i.e., a direction parallel to the +/−Z directions of the coordinate axes depicted in the figures). The supply platform actuator  132  may be, for example and without limitation, a mechanical actuator, an electro-mechanical actuator, a pneumatic actuator, a hydraulic actuator, or any other actuator suitable for imparting linear motion to the supply platform  130  in a vertical direction. Suitable actuators may include, without limitation, a worm drive actuator, a ball screw actuator, a pneumatic piston, a hydraulic piston, an electro-mechanical linear actuator, or the like. The supply platform  130  and supply platform actuator  132  are positioned in a supply receptacle  134  located below the working axis  116  (i.e., in the −Z direction of the coordinate axes depicted in the figures) of the additive manufacturing apparatus  100 . During operation of the additive manufacturing apparatus  100 , the supply platform  130  is raised relative to the supply receptacle  134  and towards the working axis  116  of the additive manufacturing apparatus  100  by action of the supply platform actuator  132  after a layer of build material  400  is distributed from the supply platform  130  to the build platform  120 , as will be described in further detail herein. 
     Referring now to  FIGS. 1 and 2 ,  FIG. 2  schematically depicts the actuator assembly  102  of the additive manufacturing apparatus  100  of  FIG. 1 . The actuator assembly  102  generally comprises the recoat head  140 , the print head  150 , a recoat head actuator  144 , a print head actuator  154 , an upper support  182 , and a lower support  184 . In the embodiments described herein, the upper support  182  and the lower support  184  extend in a horizontal direction (i.e., a direction parallel to the +/−X direction of the coordinate axes depicted in the figures) parallel to the working axis  116  ( FIG. 1 ) of the additive manufacturing apparatus  100  and are spaced apart from one another in the vertical direction (i.e., a direction parallel to the +/−Z direction of the coordinate axes depicted in the figures). When the actuator assembly  102  is positioned over the cleaning station  110 , the build platform  120 , and the supply platform  130  as depicted in  FIG. 1 , the upper support  182  and the lower support  184  extend in a horizontal direction from at least the cleaning station  110  to beyond the supply platform  130 . 
     In one embodiment, such as the embodiment of the actuator assembly  102  depicted in  FIGS. 1 and 2 , the upper support  182  and the lower support  184  are opposite sides of a rail  180  that extends in a horizontal direction and is oriented such that the upper support  182  is positioned above and spaced apart from the lower support  184 . For example, in one embodiment, the rail  180  may be rectangular or square in vertical cross section (i.e., a cross section in the Y-Z plane of the coordinate axes depicted in the figures) with the top and bottom surfaces of the rectangle or square forming the upper support  182  and the lower support  184 , respectively. In an alternative embodiment (not depicted), the rail  180  may have an “I” configuration in vertical cross section (i.e., a cross section in the Y-Z plane of the coordinate axes depicted in the figures) with the upper and lower flanges of the “I” forming the upper support  182  and the lower support  184 , respectively. However, it should be understood that other embodiments are contemplated and possible. For example and without limitation, the upper support  182  and the lower support  184  may be separate structures, such as separate rails, extending in the horizontal direction and spaced apart from one another in the vertical direction as depicted in an alternative embodiment of the actuator assembly. 
     In the embodiments described herein, the recoat head actuator  144  is coupled to one of the upper support  182  and the lower support  184  and the print head actuator  154  is coupled to the other of the upper support  182  and the lower support  184  such that the recoat head actuator  144  and the print head actuator  154  are arranged in a “stacked” configuration. For example, in the embodiment of the actuator assembly  102  depicted in  FIGS. 1 and 2 , the recoat head actuator  144  is coupled to the lower support  184  and the print head actuator  154  is coupled to the upper support  182 . However, it should be understood that, in other embodiments (not depicted) the recoat head actuator  144  may be coupled to the upper support  182  and the print head actuator  154  may be coupled to the lower support  184 . 
     In the embodiments described herein, the recoat head actuator  144  is bi-directionally actuatable along a recoat motion axis  146  and the print head actuator  154  is bi-directionally actuatable along a print motion axis  156 . That is, the recoat motion axis  146  and the print motion axis  156  define the axes along which the recoat head actuator  144  and the print head actuator  154  are actuatable, respectively. The recoat motion axis  146  and the print motion axis  156  extend in a horizontal direction and are parallel with the working axis  116  ( FIG. 1 ) of the additive manufacturing apparatus  100 . In the embodiments described herein, the recoat motion axis  146  and the print motion axis  156  are parallel with one another and spaced apart from one another in the vertical direction due to the stacked configuration of the recoat head actuator  144  and the print head actuator  154 . In some embodiments, such as the embodiment of the actuator assembly  102  depicted in  FIG. 2 , the recoat motion axis  146  and the print motion axis  156  are located in separate vertical planes (i.e., a plane parallel to the X-Z plane of the coordinate axes depicted in the figures). However, it should be understood that other embodiments are contemplated and possible, such as embodiments in which the recoat motion axis  146  and the print motion axis  156  are located in the same vertical plane. 
     In the embodiments described herein, the recoat head actuator  144  and the print head actuator  154  may be, for example and without limitation, mechanical actuators, electro-mechanical actuators, pneumatic actuators, hydraulic actuators, or any other actuator suitable for providing linear motion. Suitable actuators may include, without limitation, worm drive actuators, ball screw actuators, pneumatic pistons, hydraulic pistons, electro-mechanical linear actuators, or the like. In one particular embodiment, the recoat head actuator  144  and the print head actuator  154  are linear actuators manufactured by Aerotech® Inc. of Pittsburgh, Pa., such as the PRO225LM Mechanical Bearing, Linear Motor Stage. 
     As shown in  FIGS. 1 and 2 , the recoat head  140  is coupled to the recoat head actuator  144  such that the recoat head  140  is positioned below (i.e., in the −Z direction of the coordinate axes depicted in the figures) the upper support  182  and the lower support  184 . When the actuator assembly  102  is assembled over the cleaning station  110 , the build platform  120 , and the supply platform  130  as depicted in  FIG. 1 , the recoat head  140  is situated on the working axis  116  ( FIG. 1 ) of the additive manufacturing apparatus  100 . Thus, bi-directional actuation of the recoat head actuator  144  along the recoat motion axis  146  affects bi-directional motion of the recoat head  140  on the working axis  116  of the additive manufacturing apparatus  100 . In the embodiment of the actuator assembly  102  depicted in  FIGS. 1 and 2 , the recoat head  140  is coupled to the recoat head actuator  144  with support bracket  176  such that the recoat head  140  is positioned on the working axis  116  ( FIG. 1 ) of the additive manufacturing apparatus  100  while the recoat head actuator  144  is positioned above the working axis  116 . Positioning the recoat head actuator  144  above the working axis  116  of the additive manufacturing apparatus  100  reduces fouling of the recoat head actuator  144  with powder from either the build platform  120  or the supply platform  130 . This increases the maintenance interval for the recoat head actuator, increases the service life of the recoat head actuator, reduces machine downtime, and reduces build errors due to fouling of the recoat head actuator  144 . In addition, positioning the recoat head actuator  144  above the working axis  116  of the additive manufacturing apparatus  100  allows for improved visual and physical access to the build platform  120  and the supply platform  130 , improving the ease of maintenance and allowing for better visual observation (from human observation, camera systems, or the like) of the additive manufacturing process. In some embodiments described herein, the recoat head  140  may be fixed in directions orthogonal to the recoat motion axis  146  and the working axis  116  (i.e., fixed along the +/−Z axis and/or fixed along the +/−Y axis). 
     Similarly, the print head  150  is coupled to the print head actuator  154  such that the print head  150  is positioned below (i.e., in the −Z direction of the coordinate axes depicted in the figures) the upper support  182  and the lower support  184 . When the actuator assembly  102  is assembled over the cleaning station  110 , the build platform  120 , and the supply platform  130  as depicted in  FIG. 2 , the print head  150  is situated on the working axis  116  ( FIG. 2 ) of the additive manufacturing apparatus  100 . Thus, bi-directional actuation of the print head actuator  154  along the print motion axis  156  affects bi-directional motion of the print head  150  on the working axis  116  of the additive manufacturing apparatus  100 . In the embodiment of the actuator assembly  102  depicted in  FIG. 2 , the print head  150  is coupled to the print head actuator  154  with support bracket  174  such that the print head  150  is positioned on the working axis  116  ( FIG. 2 ) of the additive manufacturing apparatus  100  and the print head actuator  154  is positioned above the working axis  116 . Positioning the print head actuator  154  above the working axis  116  of the additive manufacturing apparatus  100  reduces fouling of the print head actuator  154  with powder from either the build platform  120  or the supply platform  130 . This increases the maintenance interval for the print head actuator  154 , increases the service life of the print head actuator  154 , reduces machine downtime, and reduces build errors due to fouling of the print head actuator  154 . In addition, positioning the print head actuator  154  above the working axis  116  of the additive manufacturing apparatus  100  allows for improved visual and physical access to the build platform  120  and the supply platform  130 , improving the ease of maintenance and allowing for better visual observation (from human observation, camera systems, or the like) of the additive manufacturing process. In some embodiments described herein, the print head  150  may be fixed in directions orthogonal to the print motion axis  156  and the working axis  116  (i.e., fixed along the +/−Z axis and/or fixed along the +/−Y axis). That is, in embodiments, the entire print head is fixed in directions orthogonal to the print motion axis  156 , however, sub-components of the print head, such individual arrays of nozzles or the like, may be translatable in directions that are non-parallel to the print motion axis  156 , such as directions that are orthogonal to the print motion axis. 
     As noted above, in the embodiments described herein the recoat head  140  and the print head  150  are both located on the working axis  116  of the additive manufacturing apparatus  100 . As such, the movements of the recoat head  140  and the print head  150  on the working axis  116  occur along the same axis and are thus co-linear. With this configuration, the recoat head  140  and the print head  150  may occupy the same space (or portions of the same space) along the working axis  116  of the additive manufacturing apparatus  100  at different times during a single build cycle. However, the recoat motion axis  146  of the recoat head actuator  144  and the print motion axis  156  of the print head actuator  154  are spaced apart from one another in a vertical direction due to the stacked configuration of the actuators  144 ,  154 . The spacing of the recoat motion axis  146  and the print motion axis  156  permits the recoat head  140  and the print head  150  to be moved along the working axis  116  of the additive manufacturing apparatus  100  simultaneously in a coordinated fashion, in the same direction and/or in opposing directions, at the same speeds or different speeds. This, in turn, allows for individual steps of the additive manufacturing process, such as the distributing step (also referred to herein as the recoating step), the depositing step (also referred to herein as the printing step), the curing (or heating) step, and/or the cleaning step to be performed with overlapping cycle times. For example, the distributing step may be initiated while the cleaning step is being completed; the depositing step may be initiated while the distributing step in completed; and/or the cleaning step may be initiated while the distributing step is being completed. This may reduce the overall cycle time of the additive manufacturing apparatus  100  to less than the sum of the distributing cycle time (also referred to herein as the recoat cycle time), the depositing cycle time (also referred to herein as the print cycle time), and/or the cleaning cycle time. 
     While  FIGS. 1 and 2  schematically depict an embodiment of an actuator assembly  102  which comprises an upper support  182  and a lower support  184  with the recoat head actuator  144  and the print head actuator  154  mounted thereto, respectively, it should be understood that other embodiments are contemplated and possible, such as embodiments which comprise more than two supports and more than two actuators. Moreover, it is contemplated that embodiments may include a single support having the recoat head actuator  144  and the print head actuator  154  mounted thereto. 
     Cleaning Station 
     Turning now to  FIGS. 3A and 3B , an embodiment of the cleaning station  110  is shown in greater detail. Although described in various embodiments as being associated with the additive manufacturing apparatus  100  of  FIGS. 1 and 2 , it is contemplated that the cleaning station  110  and fluid management system coupled thereto may be used with other types of additive manufacturing apparatuses known and used in the art. 
     The cleaning station  110  may comprise a cleaning station vessel  314  positioned proximate at least one binder purge bin  302 . As shown in  FIGS. 3A and 3B , the cleaning station  110  is positioned between two binder purge bins  302 , each of which is configured to receive material, such as contaminants and binder material, discharged by the print head. Although shown in  FIGS. 3A and 3B  as including two binder purge bins  302 , it is contemplated that in embodiments, only one binder purge bin, or more than two binder purge bins, may be included. In embodiments, the binder purge bin  302  optionally includes a purge wiper  303  ( FIG. 3B ) positioned between the binder purge bin  302  and the wet wipe cleaner section  304 . When included, the purge wiper  303  can contact the print head after contaminants and binder material are discharged into the binder purge bin  302  to remove loose contaminants and binder material from the face of the print head before the print head is introduced to the wet wipe cleaner section  304 . In embodiments, the purge wiper  303  redirects the loose contaminants and binder material into the binder purge bin  302  for disposal, thereby reducing the amount of contaminants and binder material introduced into the cleaning station  110  during the cleaning process. 
     Further as shown, the cleaning station vessel  314  is a container which includes a wet wipe cleaner section  304 , a dry wipe cleaner section  306 , and a capping section  308 . In various embodiments, the wet wipe cleaner section  304 , the dry wipe cleaner section  306 , and the capping section  308  are sections of a cleaning station vessel  314  containing a volume of cleaning fluid. The wet wipe cleaner section  304  applies cleaning fluid to the print head, specifically, a faceplate of the print head. The dry wipe cleaner section  306 , which in some embodiments is downstream of the wet wipe cleaner section  304 , removes excess liquid (e.g., cleaning fluid and contaminants) from the print head in advance of binder jetting. The capping section  308 , which may be also considered an idle section, is a location where the print head may be temporarily placed in advance of binder jetting. In embodiments, the capping section  308  supplies cleaning fluid to the print head faceplate to prevent binder from drying on the print head. Without being limited to theory, maintaining the wet wipe cleaner section  304 , the dry wipe cleaner section  306 , and the capping section  308  within a single cleaning station vessel  314  is highly advantageous as it streamlines cleaning fluid management by eliminating the need to control three separate cleaning station vessels. In this embodiment, cleaning fluid maintenance is limited to a single cleaning station vessel  314 . 
     In embodiments, the cleaning station vessel  314  includes at least one moveable wall  316  extending vertically upward (e.g., +/−Z) from the cleaning station vessel  314  and in a direction parallel to a direction of movement of the print head  150  through the cleaning station  110  (e.g., +/−X). When included, the moveable wall  316  redirects cleaning fluid into the cleaning station vessel  314 . For example, cleaning fluid that is splashed, such as from the movement of the wet wipe member  310  and/or the dry wipe member  312  into and out of the cleaning station vessel  314 , may be redirected back into the cleaning station vessel  314  rather than being lost into the environment (e.g., onto the floor). In embodiments, the moveable wall  316  may be coupled to one or more actuators to enable movement of the wall. For example, the moveable wall  316  may be moved in the +Z direction when the print head  150  enters the cleaning station  110 , and in the −Z direction when the print head  150  leaves the cleaning station  110 . Additionally or alternatively, the moveable wall  316  may be moved along the +/−X direction through the cleaning station  110  along a path parallel to the path of the print head  150 . 
     In embodiments, the moveable wall  316  is coupled to the wall of the cleaning station vessel  314  through a guide slot (not shown), and is moveable within the guide slot. Accordingly, in the event that the print head  150  or another item contacts the moveable wall  316 , the moveable wall  316  will yield (e.g., move) rather than causing damage to the print head  150  or other part of the additive manufacturing apparatus  100 . It is contemplated that the moveable wall  316  could be coupled to the wall of the cleaning station vessel  314  in other ways, including through the use of magnetic mounts, bolts, or slotted holes, for example. 
     In embodiments, the cleaning station vessel  314  is in fluid communication with an overflow vessel  318 , as shown in  FIG. 3C , such as through a fluid level wall  320 . Accordingly, the cleaning fluid may be continuously pumped into the cleaning station vessel  314 , as will be described in greater detail below. When the cleaning fluid in the cleaning station vessel  314  reaches the top of the fluid level wall  320 , the cleaning fluid flows over the fluid level wall  320  and into the overflow vessel  318 . In embodiments, the overflow vessel  318  includes at least two fluid level sensors  322 , each positioned at a different vertical position within the overflow vessel  318 . Accordingly, cleaning fluid is pumped into the cleaning station vessel  314 , flows over the fluid level wall  320  and into the overflow vessel  318  until both of the fluid level sensors  322  detect cleaning fluid, indicating that the fluid level of the cleaning fluid within the overflow vessel  318  is at or above the vertical position of the fluid level sensor  322  that is closer to the top of the overflow vessel  318 . In response to both of the fluid level sensors  322  detecting the fluid, cleaning fluid is pumped out of the overflow vessel  318 , such as through a drain  824  in the overflow vessel  318 , until neither of the fluid level sensors  322  detects the fluid, indicating that the fluid level of the cleaning fluid within the overflow vessel  318  is below the vertical position of the fluid level sensor  322  that is closer to the bottom of the overflow vessel  318 . In embodiments, the fluid level wall  320  can be adjusted to control the vertical height of the top of the fluid level wall  320  and, accordingly, the fluid level within the cleaning station vessel  314 . 
     Referring again to  FIGS. 1, 2, 3A, and 3B , in the embodiments described herein, the print head  150  may deposit the binder material  500  on a layer of build material  400  distributed on the build platform  120  through an array of nozzles  172  located on the underside of the print head  150  (i.e., the surface of the print head  150  facing the build platform  120 ). In one or more embodiments, the nozzles  172  may be piezoelectric print nozzles and, as such, the print head  150  is a piezo print head. In alternative embodiments, the nozzles  172  may be thermal print nozzles and, as such, the print head  150  is a thermal print head. 
     In general, after the print head  150  has deposited the binder material  500  on the layer of build material  400  positioned on the build platform  120  ( FIG. 1 ), it is moved to the binder purge bin  302 , where contaminants are dislodged via backpressure and, in embodiments, using binder material  500  ejected from the nozzles  172 . In embodiments including a purge wiper  303  (FIG.  3 B), the print head  150  is wiped by the purge wiper  303  as it is moved from the binder purge bin  302  toward the wet wipe cleaner section  304  to direct loose contaminants and binder material from the face of the print head  150  into the binder purge bin  302 . Next, the print head  150  is moved to the wet wipe cleaner section  304  where a cleaning fluid is applied to the print head  150  and contaminants are mechanically removed from the print head  150 . The print head  150  is then moved to the dry wipe cleaner section  306  where the cleaning fluid and remaining contaminants are removed, before the print head  150  is moved to the second binder purge bin  302 . At the second binder purge bin  302 , any remaining contaminants are dislodged and the binder meniscus is reestablished by ejecting binder material  500  from the nozzles  172 . In embodiments in which the print head  150  is idle, instead of moving to the second binder purge bin  302 , the print head  150  may be moved to the capping section  308  where it is kept moist to prevent the binder material from drying out and clogging the nozzles  172  of the print head  150 . Each of the sections of the cleaning station  110  will now be described in greater detail. 
     Cleaning Station—Wet Wipe Cleaner Section 
     Various suitable embodiments are contemplated for the wet wipe cleaner section  304 . As shown in  FIGS. 3A and 3B , the wet wipe cleaner section  304  comprises a wet wipe member  310 . The wet wipe member  310  comprises any suitable mechanism for passively applying cleaning fluid to a print head, for example, a brush, a squeegee, and the like. As used herein, “passively applying” means the wet wipe member  310  contacts the print head as it traverses the wet wipe cleaner section  304 . The wet wipe member  310  is connected to one or more actuators  311  that raise or lower the wet wipe member within the wet wipe cleaner section  304  of the cleaning station vessel  314 . The actuators may comprise linear actuators, rotary actuators, or electric actuators. While various actuators and actuator locations are considered suitable, the actuators  311  depicted in  FIGS. 3A and 3B  are disposed primarily outside the cleaning station vessel  314 . Without being bound by theory, minimizing actuator  311  contact with the cleaning fluid, especially contact with any electronic components of the actuators  311 , may be beneficial in maintaining actuator performance. Thus, some embodiments will include the actuators  311  primarily positioned outside the cleaning station vessel  314 . 
     Referring now to  FIGS. 4A-4E , additional embodiments of the wet wipe cleaner section  304  are schematically depicted. Specifically as shown in  FIGS. 4A-4E , a wet wipe member  310  for applying cleaning fluid to the print head  150  is depicted. The wet wipe member  310  includes a wet wiper body  401  having a top side  402  and a bottom side  404 . The wet wipe member  310  includes at least one wiper blade  406  vertically extending from the top side  402  of the wet wiper body  401 . In the embodiment shown in  FIGS. 4A and 4B , the wet wipe member  310  includes a first wiper blade  406   a  and a second wiper blade  406   b  (collectively, the wiper blades  406 ), spaced apart from one another. In the embodiment shown in  FIG. 4C , the wet wipe member  310  includes a single wiper blade  406 . Accordingly, any number wiper blades may be included in the wet wipe member  310 . 
     Although the wet wipe member  310  is described in various embodiments as including at least one wiper blade  406 , in embodiments, the wet wipe member  310  does not include wiper blades, as shown in  FIG. 4E . 
     A fluid channel  408  extends horizontally from a first end  410  of the wet wiper body  401  to a second end  412  of the wet wiper body  401 , as shown in  FIGS. 4A-4C , and defines a recessed path within the wet wiper body  401 . The fluid channel  408  has an open top to allow cleaning fluid to flow out of the fluid channel  408 . The rate of the flow of the cleaning fluid through the fluid channel  408  is controlled in embodiments, thereby enabling control of the height of a fluid wall  418  created by the cleaning fluid, shown in  FIG. 4E . In embodiments, such as the embodiment shown in  FIGS. 4A and 4B , the fluid channel  408  is positioned between the first wiper blade  406   a  and the second wiper blade  406   b . Although the wiper blades  406  and the fluid channel  408  are described herein as extending from a first end  410  to the second end  412  of the wet wiper body  401 , in embodiments, the wet wiper body  401  has a length from the first end  410  to the second end  412  that is greater than a length of the wiper blades  406  and/or the fluid channel  408 . For example, in embodiments, the wiper blades  406  and/or the fluid channel  408  may be positioned within the wet wiper body  401  with the wet wiper body  401  extending about 1 mm, about 2 mm, about 5 mm, or about 10 mm on each end. This additional length of the wet wiper body  401  can enable, for example, the wet wiper body  401  to extend from end to end of the cleaning station while the wiper blades  406  and/or the fluid channel  408  are sized to have substantially the same length as the print head. 
     As shown in  FIG. 4E , in embodiments in which the wet wipe member  310  does not include wiper blades  406 , the flow of the cleaning fluid through the fluid channel  408  is controlled to provide a touchless wiping system that uses the fluid wall  418  to wipe contaminants from the print head without requiring the use of wiper blades. Moreover, in embodiments, a vacuum wipe member  420  ( FIG. 4F ) may be included. The vacuum wipe member  420  may be similar in structure to the wet wipe member  310 , including a channel  422  and optionally one or more wiper blades  406 . However, the channel  422  in the vacuum wipe member  420  enables process gasses (e.g., air, argon, nitrogen, or the like) to be drawn through the channel, thereby generating a vacuum effective to pull liquids and contaminants off of the print head as it passes over the vacuum wipe member  420 . When included, the vacuum wipe member  420  is coupled to a pump (not shown) for generating the vacuum as well as at least one filter (not shown) to prevent contaminants from being pulled into the pump. In embodiments, the vacuum wipe member  420  can be included with a wet wipe member  310 , such as the wet wipe member  310  shown in any of  FIGS. 4A-E , or can be independently included in the cleaning station  110 . 
     In embodiments, each of the wiper blades  406   a  has the same vertical (e.g., +/−Z) position as the other blades  406   b , as shown in  FIG. 4A . Accordingly, all of the wiper blades  406   a ,  406   b  has the same engagement distance with the print head  150  during wiping operations. As is known in the art, the “engagement distance” refers to the amount by which the vertical position of the print head  150  and the vertical position of an undeflected wiper blade  406  overlap. However, in embodiments, one or more wiper blades  406   a  are positioned at a first vertical position while one or more wiper blades  406   b  are positioned at a second vertical position, as shown in  FIG. 4G . In such embodiments, a least one wiper blade  406   a  has a different engagement distance than the wiper blades  406   b . For example, the wiper blades  406  may be positioned such that the engagement distance with the print head  150  increases along the path of the print head  150  during the wet wiping process. 
     As shown in  FIGS. 4A-4C , the wet wipe member  310  further includes a cleaning manifold  414  that extends below the fluid channel  408  within the wet wiper body  401 . The cleaning manifold  414  is in fluid communication with the fluid channel  408  through at least one fluid port  407  to provide cleaning fluid from the cleaning manifold  414  to the top side  402  of the wet wiper body  401 , e.g., via the fluid channel  408 . In the embodiment shown in  FIG. 4B , twelve fluid ports  407  provide cleaning fluid from the cleaning manifold  414  to the fluid channel  408 . Each fluid port  407  may have a circular cross-section, a square cross-section, or other cross-section suitable for fluid flow. However, in the embodiment shown in  FIG. 4D , one fluid port  407  provides cleaning fluid from the cleaning manifold  414  to the fluid channel  408 . The fluid port  407  in  FIG. 4D  extends from the first end  410  to the second end  412  of the wet wiper body  401  and has a substantially rectangular cross-section. Other shapes, sizes, and quantities of fluid ports are possible and contemplated. In embodiments, such as the embodiment shown in  FIG. 4B  where the fluid channel  408  is positioned between first and second wiper blades  406 , the fluid port  407  is also disposed between the first and second wiper blades  406 . 
     In various embodiments, the cleaning fluid is provided to the cleaning manifold  414  through a plurality of cleaning fluid inlets  416  that are fluidly coupled to a cleaning fluid reservoir or cleaning fluid management system, described in greater detail below. The plurality of cleaning fluid inlets  416  may be, for example, fluid conduits that extend vertically upward through the bottom side  404  of the wet wiper body  401 . However, in embodiments, the plurality of cleaning fluid inlets  416  additionally or alternatively extend from a side  403  of the wet wiper body  401  adjacent to the top side  402  and the bottom side  404  of the wet wiper body  401 . The plurality of cleaning fluid inlets  416  are operable to receive the cleaning fluid and provide the cleaning fluid to the cleaning manifold  414 . The cleaning fluid inlets  416  are in fluid communication with the fluid port  407  through the cleaning manifold  414  such that cleaning fluid enters the cleaning manifold  414  through the cleaning fluid inlets  416  and exits the cleaning manifold  414  through the fluid port  407 . 
     As stated above, the wet wipe member  310  is coupled to one or more actuators  311  which are operable to raise or lower the wet wipe member  310  into and out of the volume of the cleaning fluid. For example, the wet wipe member  310  may be actuated just prior to the print head  150  moving to the wet wipe cleaner section  304  such that the wet wipe member  310  is raised out of the volume of the cleaning fluid and contacts the print head  150  as it is moved through the wet wipe cleaner section  304 . In various embodiments, the wet wipe member  310  is actuated as close to the time that it will make contact with the print head  150  as possible, so as to ensure that the wiper blades  406  are wet with cleaning fluid, although it is contemplated that some period of time may pass between the wet wipe member  310  being raised out of the volume of the cleaning fluid and making contact with the print head  150 . 
     As another example, the wet wipe member  310  may be actuated after the print head  150  has moved to the dry wipe cleaner section  306  such that the wet wipe member is lowered into the volume of the cleaning fluid. The lowering of the wet wipe member into the cleaning fluid may wash away contaminants on the surface of the wiper blades  406  and clean the wet wipe member  310 , thereby reducing the likelihood that the wet wipe member  310  will introduce contaminants to the print head  150 . Additional details on the actuation of wet wipe member  310  embodiments are described below. 
     In various embodiments, the cleaning manifold  414  fills with the cleaning fluid and feeds the fluid channel  408 , which fills from the bottom of the fluid channel  408 . In embodiments in which the fluid channel  408  is positioned between the wiper blades  406 , the cleaning fluid forms a pool of cleaning fluid between the wiper blades  406 . In one or more embodiments, the cleaning fluid flows over the sides of the fluid channel  408  and into overflow drains, which return the cleaning fluid to the cleaning manifold  414 . In further embodiments, the cleaning fluid is fed through the wet wipe member  310  continuously during operation of the additive manufacturing apparatus. After the wet wipe member applies liquid to the print head, the liquid then overflows back into the cleaning station vessel  314 . As described more below, within the cleaning station vessel  314 , there is a drain  824  (see  FIG. 3B ), which directs cleaning fluid into a cleaning fluid reservoir  816  (see  FIG. 8 ), and is then pumped back into the wet wipe member  310 . The continuous cleaner circulation and recirculation is described more below. 
     Accordingly, when the wet wipe member  310  is actuated, cleaning fluid is supplied to the print head  150  to dissolve contaminants while the wiper blades  406  mechanically remove contaminants. While the cleaning fluid may dissolve the contaminants in some cases, the contaminants may also be considered as mixed or suspended within the cleaning fluid. The cleaning manifold  414  and the fluid channel  408  ensure that cleaning fluid can be directly applied to the print head  150  during cleaning while compensating for any delay that may result from the use of pumps in the fluid management system, as will be discussed in greater detail below. In particular, the cleaning manifold  414  and the fluid channel  408  provide a local reservoir of cleaning fluid that can be used even when the pumps are not actively providing cleaning fluid to the wet wipe member  310 . 
     In the embodiment depicted in  FIG. 4A , the cleaning fluid does not flow to the top of the wiper blades  406 . However, it is contemplated that in other embodiments, a pair of walls extends between the first wiper blade  406   a  and the second wiper blade  406   b  from the top side  402  of the wet wiper body  401  to a top of each of the first wiper blade  406   a  and the second wiper blade  406   b . The pair of walls thus extends the depth of the fluid channel  408  to the top of the wiper blades  406 , enabling the cleaning fluid to fill up to the top of the wiper blades  406 . Such embodiments may enable greater dissolution of contaminants on the print head  150 , and may facilitate the wiping by further wetting both the wiper blades  406  and the print head  150 . 
     Cleaning Station—Dry Wipe Cleaner Section 
     Similar to the wet wipe cleaner section  304 , various suitable embodiments are contemplated for the dry wipe cleaner section  306 . Referring to the embodiments depicted in  FIGS. 3A-3B , the dry wipe cleaner section  306  comprises a dry wipe member  312 . The dry wipe member  312  comprises any suitable mechanism (e.g., brush, a squeegee, and the like) for removing cleaning fluid and contaminants. For example, the dry wipe member  312  may remove cleaning fluid and contaminants from the print head  150 . Like the wet wipe member  310 , the dry wipe member  312  is coupled to one or more actuators  313  that raise or lower the dry wipe member  312  within the dry wipe cleaner section  306  of the cleaning station vessel  314 . While various actuators and actuator locations are considered suitable, the actuators  313  depicted in  FIGS. 3A-3B  are disposed primarily outside the cleaning station vessel  314 . Without being bound by theory, minimizing actuator  313  contact with the cleaning fluid, especially contact with any electronic components of the actuators  313 , may be beneficial in maintaining actuator performance. Thus, some embodiments will include the actuators  313  primarily positioned outside the cleaning station vessel  314 . The actuators  313  can be linear actuators, rotary actuators, pneumatic actuators, or electric actuators. Additional details on the actuators  313  is provided hereinbelow. 
     An embodiment of the dry wipe member  312  is depicted in  FIG. 5A . The dry wipe member  312  may define a wiper array, which includes a wiper mounting member  501  and a plurality of dry wiper blades  502  mounted to the wiper mounting member  501 . Each of the plurality of dry wiper blades  502  may include a body member  514  and a blade  516  extending from the body member  514 . The wiper mounting member  501  extends along a longitudinal axis LA, and a length l of each of the plurality of dry wiper blades  502  extends in a direction that is at an angle θ that is greater than 0 and less than 90° relative to the longitudinal axis LA. In some embodiments, each of the plurality of dry wiper blades  502  extends in a direction that is at an angle θ of from 5° to 50°, 5° to 45°, or from 10° to 30° relative to the longitudinal axis LA. The angle θ may be varied to provide for additional contact with the print head  150 , as may be desired in embodiments. 
     As described above, each of the plurality of dry wiper blades  502  has an overlap of at least part of its length l with the length l of an adjacent dry wiper blade  502  in a direction orthogonal to the longitudinal axis LA. In embodiments, each of the plurality of dry wiper blades  502  has an overlap of at least 30% of its length l with the length of an adjacent dry wiper blade in a direction orthogonal to the longitudinal axis LA. For example, in some embodiments, each of the plurality of dry wiper blades  502  may have an overlap of from 30% to 70% of its length with the length of an adjacent dry wiper blade in a direction orthogonal to the longitudinal axis LA. Such an arrangement enables the dry wipe member  312  to contact the print head  150  with at least two blades  516  over the entire length of the print head  150 . Other arrangements are contemplated, such as arrangements that enable the dry wipe member  312  to contact the print head  150  with three or more blades  516  over the entire length of the print head  150 . Without being bound by theory, it is believed that because the dry wiper blades are angled with respect to the longitudinal axis LA and their lengths overlap with adjacent dry wiper blades, the dry wipe member  312  imparts less drag on the print head  150  as it wipes cleaning fluid from the print head  150  and is thereby more effective in wiping off the cleaning fluid. Additionally, the use of the array of angled dry wiper blades may result in the cleaning fluid being drained away from the print head  150  in less time compared to a single wiper blade extending along the longitudinal axis LA. 
     In embodiments, each of the blades  516  has the same vertical (e.g., +/−Z) position as the other blades  516 . Accordingly, all of the blades  516  has the same engagement distance with the print head  150  during wiping operations. As is known in the art, the “engagement distance” refers to the amount by which the vertical position of the print head  150  and the vertical position of an undeflected blade  516  overlap. However, as shown in  FIG. 5D , in embodiments, one or more blades  516  are positioned at a first vertical position Z 1  while one or more blades  516  are positioned at a second vertical position Z 2 . In such embodiments, a least one blade  516  has a different engagement distance than the blades  516 . For example, the blade  516  positioned at the first vertical position Z 1  has a smaller engagement distance than the blade  516  positioned at the second vertical position Z 2 . In embodiments, the blades  516  may be positioned such that the engagement distance with the print head  150  increases along the path of the print head  150  during the dry wiping process. Such embodiments can, for example, reduce the amount of cleaning fluid that is expelled from the cleaning station  110  during the cleaning process. 
     In some embodiments, the wiper mounting member  501  includes channels  504 , as shown in  FIG. 5B . Each channel  504  is formed in a top face  506  of the wiper mounting member  501  and is shaped to receive one of the plurality of dry wiper blades  502 . The formation of the channels  504  to receive the plurality of dry wiper blades  502  may enable the plurality of dry wiper blades  502  to be securely and accurately coupled to the wiper mounting member, which may ease manufacturing of the dry wipe member  312  and prevent movement of the dry wiper blades  502  with respect to the wiper mounting member  501  during use. 
     As depicted in  FIG. 5B , in embodiments, each channel may include a hole  508  extending through the thickness of the wiper mounting member  501 . In embodiments in which the wiper mounting member  501  does not include channels, a plurality of holes  508  may be positioned along the length of the wiper mounting member  501 , with each of the plurality of holes  508  extending through the thickness from the top face  506  to a bottom face  510  of the wiper mounting member  501 , as shown in  FIG. 5C . In various embodiments, an attachment member  512 , such as a screw, bolt, or other attachment mechanism, may be coupled to the body member  514  of each of the plurality of dry wiper blades  502  through the hole  508 . Although in various embodiments, the plurality of dry wiper blades  502  are coupled to the wiper mounting member  501  by coupling an attachment member  512  to the body member  514 , other methods of mounting the plurality of dry wiper blades  502  to the wiper mounting member  501  are possible and contemplated. For example, each of the plurality of dry wiper blades  502  can be secured within the wiper mounting member  501  using end caps that are bolted in place. While the above wiper array of  FIGS. 5A-5D  is discussed for use as a dry wipe member  312 , it is further contemplated that the wiper array could also be included as a wet wipe member  310  or a purge wiper  303  ( FIG. 3B ). 
     In further embodiments, the dry wipe member  312  is coupled to two actuators (e.g., actuators  313 ) which are operable to raise or lower the dry wipe member  312  into and out of the volume of the cleaning fluid. For example, the dry wipe member  312  may be actuated such that the dry wipe member  312  is raised out of the volume of the cleaning fluid with sufficient time to allow the cleaning fluid to drain away from the dry wiper blades  502 . The dry wipe member  312  contacts the print head  150  as it is moved through the dry wipe cleaner section  306  to remove cleaning fluid, contaminants and other debris from the print head  150  after the print head  150  is cleaned by the wet wipe member  310 . 
     As another example, the dry wipe member  312  may be actuated after the print head  150  has moved to the capping section  308  or the build platform  120  such that the dry wipe member  312  is lowered into the volume of the cleaning fluid. The lowering of the dry wipe member  312  into the cleaning fluid may wash away contaminants on the surface of the dry wiper blades  502  and clean the dry wipe member  312 , thereby reducing the likelihood that the dry wipe member  312  will introduce (or reintroduce) contaminants to the print head  150 . In some embodiments, the dry wipe member  312  is lowered into the volume of the cleaning fluid for a period of time sufficient to rinse the dry wipe member  312 , and then is raised out of the volume of the cleaning fluid until it has been used to wipe the print head  150  again. 
     Cleaning Station—Capping Section 
     As described with reference to  FIGS. 3A-3C , in various embodiments, the cleaning station  110  includes a capping section  308  including a cover  701  to create or maintain a non-curing environment around the print head  150 . As used herein, a “non-curing environment” means an environment in which the binder material does not cure within or on the surface of the nozzles of the print head  150 . The non-curing environment may be maintained, for example, by maintaining a particular humidity level, temperature, or the like, that prevents the binder material from curing. Various suitable embodiments are contemplated. 
     An example embodiment of a capping section  308  is shown in greater detail in  FIG. 7A . In particular, the capping section  308  includes a cover  701  in the form of a sponge  702  supported by a sponge support  704  coupled to an actuator  706  operable to raise and lower the sponge  702  into and out of the cleaning fluid within the cleaning station  110 . Accordingly, the sponge  702  may be used to soak up cleaning fluid from the cleaning station  110  and the sponge  702  may be applied to the print head  150  while the print head  150  is idle. Without being bound by theory, the application of the wet sponge  702  to the print head  150  may reduce evaporation of binder material in one or more jet nozzles of the print head  150  and/or prevent the curing thereof. In other words, when the print head  150  is in an idle state, the print head  150  may be located at the capping section  308  to maintain the print head  150  in a non-curing environment, which, in embodiments, includes maintaining the print head  150  in a humid, moist, wet, or submerged state. 
     The sponge  702  can be formed of any suitable material capable of absorbing and holding the cleaning fluid for a predetermined period of time. In some embodiments, the sponge  702  may be made from cellulose wood fibers or foamed plastic polymers. In some particular embodiments, the sponge  702  may be made from a silicone material, such as a foamed silicone, a polyurethane, a polyimide, or combinations thereof. 
     The sponge support  704  can be a metal or plastic plate sized to support the sponge  702 . In some embodiments, the sponge  702  may be coupled to the sponge support  704 , such as through the use of an adhesive layer between the sponge  702  and the sponge support  704 , or an attachment member, such as a bolt, screw, or other mechanism to attach the sponge  702  to the sponge support  704 . In some embodiments, the sponge  702  may be removably coupled to the sponge support  704  such that the sponge  702  can be easily replaced without also replacing the sponge support  704  and actuator  706 . 
     As shown in  FIG. 7A , in some embodiments, the sponge support  704  may include edges  704   a  that extend in an upward direction from a base  704   b . However, it is contemplated that in other embodiments, the sponge support  704  includes only the base  704   b , and does not include raised edges  704   a . In embodiments, the sponge support  704  may be perforated or otherwise include one or more holes through the thickness of the sponge support  704  to enable cleaning fluid in the cleaning station to be absorbed by the sponge  702 . In other embodiments, the sponge  702  and sponge support  704  may be positioned such that the fluid level  600  of the cleaning fluid is above the edges  704   a  (if any) of the sponge support  704  such that the cleaning fluid is in contact with the sponge  702 . 
     The sponge support  704  is coupled to an actuator  706  that is operable to raise and lower the sponge  702  within the cleaning fluid. The actuator  706  may be a linear actuator, a rotary actuator, a pneumatic actuator, an electric actuator, or any other suitable type of actuator selected based on the particular embodiment. Although depicted in  FIG. 7A  as being coupled to the sponge  702  through the sponge support  704 , it is contemplated that in some embodiments, the actuator  706  may be directly coupled to the sponge  702 , and a sponge support  704  may not be included. Such embodiments, for example, may be employed when the sponge  702  is made from a stiff, yet absorbent, material. 
     In the embodiment shown in  FIG. 7A , the actuator  706  is coupled to a passive resistance mechanism  708 , which biases the sponge  702  toward a raised position such that at least a portion of the sponge  702  is above the fluid level  600  of the cleaning fluid and able to contact the print head  150 . The passive resistance mechanism  708  may be, by way of example and not limitation, a spring biased in an upward direction. The incorporation of a passive resistance mechanism  708 , though optional, serves as a fail-safe to ensure that, in the event of an actuator failure, the sponge  702  is positioned for use to maintain the print head  150  in a non-curing environment. Additionally or alternatively, the incorporation of the passive resistance mechanism  708  may enable energy savings by enabling power to the actuator  706  to be reduced or turned off while the print head  150  is idle without causing the sponge  702  to be retracted below the fluid level of the cleaning fluid. 
     In various embodiments, when the print head  150  is located at the capping section  308  of the cleaning station  110 , the sponge  702  is at least partially submerged in the cleaning fluid. In other words, some or all of the sponge  702  extends below the fluid level  600  of the cleaning fluid to enable the sponge  702  to be constantly absorbing cleaning fluid from the cleaning station  110 . In some such embodiments, at least a portion of the sponge  702  extends above the fluid level  600  of the cleaning fluid such that the sponge  702  is in contact with the print head  150  without submerging the print head  150  in the cleaning fluid. In embodiments, 1%, 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 95%, or even 99% of the volume of the sponge  702  may extend above the fluid level  600  of the cleaning fluid. 
     In practice, to clean the print head  150 , cleaning fluid is applied to the print head  150  using the wet wipe member  310  by passing the print head  150  through the wet wipe cleaner section  304 . Then, cleaning fluid is removed from the print head  150  using the dry wipe member  312  by passing the print head  150  through the dry wipe cleaner section  306 . Then, when the print head  150  will be idle or the additive manufacturing apparatus  100  is undergoing maintenance, the print head  150  is moved to the capping section  308  and into contact with the sponge  702  that is at least partially submerged in the cleaning fluid. In other embodiments (not shown), it is not required for the sponge to be submerged in the cleaning fluid. The sponge  702  is maintained in contact with the print head  150  while the print head  150  is idle or the additive manufacturing apparatus  100  is undergoing maintenance, thereby reducing evaporation of binder material in the nozzles of the print head  150 , preventing the curing of the binder material around the print head  150 , and the like. 
     Although described above as including a sponge  702 , in some embodiments, the cover  701  of the capping section  308  is a cap  710 , as shown in  FIG. 7B . In embodiments, the cap  710  may be sealed around the print head  150  when the print head  150  is idle to prevent the evaporation of binder material from the nozzles of the print head  150 , to maintain a humidity level around the print head  150 , and/or to maintain or create a non-curing environment around the print head  150 . As shown in  FIG. 7B , in embodiments, the cap  710  may include a volume of cleaning fluid, thereby forming a smaller cleaning vessel within the cleaning station vessel  314 , so as to create a humid, non-curing environment around the nozzles of the print head  150 , although in some embodiments, the cap  710  may not include a volume of fluids. 
     As with the sponge  702 , the cap  710  is coupled to an actuator  706  that is operable to raise and lower the cap  710  within the cleaning fluid. The actuator  706  may be a linear actuator, a rotary actuator, a pneumatic actuator, an electric actuator, or any other suitable type of actuator selected based on the particular embodiment. In the embodiment shown in  FIG. 7B , the actuator  706  is coupled to a passive resistance mechanism  708 , which biases the cap  710  toward a raised position such that at least a portion of the cap  710  is above the fluid level  600  of the cleaning fluid and able to contact the print head  150 . The passive resistance mechanism  708  may be, by way of example and not limitation, a spring biased in an upward direction. The incorporation of a passive resistance mechanism  708 , though optional, serves as a fail-safe to ensure that, in the event of an actuator failure, the cap  710  is positioned for use to maintain the print head  150  in a non-curing environment. Additionally or alternatively, the incorporation of the passive resistance mechanism  708  may enable energy savings by enabling power to the actuator  706  to be reduced or turned off while the print head  150  is idle without causing the cap  710  to be retracted below the fluid level of the cleaning fluid. 
     In embodiments, the actuator  706  enables the height of the cap  710  to be adjusted relative to the print head  150 . Accordingly, the cap  710  may be positioned to contact the print head  150  with fluid contained within the cap  710 , or the cap  710  may be positioned to cap the print head  150  such that the face of the print head  150  is not contacted by the fluid. 
     In embodiments, the cap  710  may further include one or more gaskets or seals  712  to create a seal between the cap  710  and the print head  150  when the cap  710  is in use. The creation of a seal may minimize or even eliminate evaporation of the cleaning fluid in the cap  710 , the binder material in the print head  150 , or both. Moreover, in embodiments, the cap  710  may include one or more ports  714  (e.g., inlet and outlet ports) to enable cleaning fluid to be flowed through the cap  710  during use. Accordingly, the cleaning fluid in the cap  710  can be replenished or refreshed. 
     In still other embodiments, the cap  710  of  FIG. 7B  may be combined with the capping section  308  shown and described with respect to  FIG. 7A , such that the sponge  702  may be actuated into and out of the cap  710 , which seals around the print head  150 . In such embodiments, the cap  710  may be selectively sealed around the print head  150  and may be actuated independent of the sponge  702 . For example, the sponge may be actuated such that it is in contact with the print head  150  during relatively short periods of idleness, while the sponge may be retracted and the cap may be actuated and sealed around the print head  150  during longer periods of idleness, such as when the additive manufacturing apparatus  100  is powered off or undergoing maintenance. 
     In embodiments, as an alternative to a dedicated capping section  308 , the cleaning station vessel  314  itself may form a cover for the print head. In such embodiments, the cleaning station vessel  314  is coupled to one or more actuators  706  to move the cleaning station vessel  314  in a vertical direction with respect to the print head  150 , as shown in  FIG. 7C . Accordingly, the cleaning station vessel  314  can serve as a capping section  308  in such embodiments, and the print head  150  is capped by the entire cleaning station vessel  314 . In embodiments, the cleaning station vessel  314  may be equipped with seals  712  that may be actuated, either independently ( FIG. 7D ) or with the cleaning station vessel  314  ( FIG. 7C ) to create a seal between the cleaning station vessel  314  and the print head  150 . In addition to, or as an alternative to, actuation of the seals  712 , it is contemplated that the seals  712  around the perimeter of the cleaning station vessel  314  may be inflatable seals that are inflated to provide a seal between the cleaning station vessel and the print head  150 , as shown in  FIGS. 7E and 7F . 
     It is further contemplated that, in embodiments, the print head  150  is actuatable in the vertical direction for sealing with the cleaning station vessel  314 . Accordingly, depending on the particular embodiment, one or more of the cleaning station vessel  314 , seals positioned around the perimeter of the cleaning station vessel  314 , and the print head  150  are moved in a vertical direction to enable a seal to be formed between the cleaning station vessel  314  and the print head  150 . As with the previously-described embodiments of the capping section  308 , in embodiments, vertical movement of one or more of the cleaning station vessel  314 , seals positioned around the perimeter of the cleaning station vessel  314 , and the print head  150  is effective to maintain the print head  150  in a non-curing environment. 
     Cleaning Station—Motion of Components 
     As has been described herein, various components of the cleaning station  110 , including the wet wipe member  310 , the dry wipe member  312 , and the capping section  308 , are configured to move in a vertical (e.g., +/−Z) direction during the cleaning of the print head  150 . Although described herein with reference only to the vertical component of the movement, it is contemplated that, in embodiments, the motion of the various components may have motion in other directions in addition to the vertical direction. For example, the motion may be in the form of an arc that includes both horizontal and vertical motion. 
     In general, the various components of the cleaning station  110  each independently moves between an extended position, in which the component is positioned to engage with or clean the print head  150 , and a retracted position, in which the component is submerged within the cleaning fluid within the cleaning station vessel  314 . For example, in embodiments, and with reference to  FIGS. 3A and 3B , the print head  150  enters the cleaning station  110  from the right hand side of the figure, passing over the second binder purge bin  302  first. In embodiments, as the print head  150  proceeds from right to left, the capping section  308 , the wet wipe member  310 , and the dry wipe member  312  are in the retracted position such that they do not contact or clean the print head  150 . The print head  150  arrives at the first binder purge bin  302 , where backpressure is applied to the print head  150  to discharge contaminants from the print head  150  into the first binder purge bin  302 . In embodiments, during an additive manufacturing process, the print head  150  discharges contaminants into the first binder purge bin  302  while the recoat head  140  is moving in the −X direction (e.g., a forward direction) in  FIG. 1 , supplying build material to a working surface of the build platform  120 . The print head  150  then moves to the right, where the print head  150  is introduced to the wet wipe member  310 . The wet wipe member  310  is in an extended position to apply cleaning fluid to the print head  150 . Next, the print head  150  is introduced to the dry wipe member  312 , which has moved to an extended position to wipe excess cleaning fluid from the print head  150 , as described herein. In embodiments, the wet wipe member  310  and/or the dry wipe member  312  are vertically raised out of the cleaning fluid before the completion of the discharge of the contaminants from the print head  150  over the first binder purge bin  302 . The wet wipe member  310  and/or the dry wipe member  312  are retracted into the cleaning fluid in the cleaning station vessel  314  after the print head  150  proceeds past them. For example, the wet wipe member  310  may be submerged in the cleaning fluid while the print head  150  is being wiped by the dry wipe member  312 . In embodiments, during an additive manufacturing process, the wet wiping and dry wiping steps performed by the wet wipe member  310  and the dry wipe member  312 , respectively, are performed while the recoat head  140  is moving in the +X direction (e.g., a reverse direction) from the build platform  120  toward a recoat home position  148 . 
     After being wiped, the print head  150  may be capped in the capping section  308 , or it may proceed to the second binder purge bin  302 , where it is prepared for printing. For example, back pressure may be applied to the print head  150  to equilibrate the print head  150  for printing. In embodiments, the print head  150  then returns to the build platform  120  to deposit binder material onto the powder layer, as described with respect to  FIG. 1 . 
     Alternative orders in the operations of the components of the cleaning station  110  are contemplated. For example, in embodiments, the print head  150  enters the cleaning station  110  from the right hand side of the figure, passing over the second binder purge bin  302  first. However, as the print head  150  proceeds from right to left, the wet wipe member  310 , the dry wipe member  312 , or the wet wipe member  310  and the dry wipe member  312  are in the extended position such that they contact the print head  150  along its path to the first binder purge bin  302 . In such embodiments, this can be a pre-cleaning step to remove surface contaminants prior to the discharging of additional contaminants over the first binder purge bin  302 . 
     In some embodiments, the wet wipe member  310  and/or the dry wipe member  312  may be actuated using a two-stage actuation process to raise and lower the members out of and into the volume of cleaning fluid. Without being bound by theory, the two stage actuation improves cleaning fluid draining from one or both of the dry and wet wipe members, because the cleaning fluid easily flows back into the cleaning station vessel  314  when only one side of the wipe member is raised above the cleaning fluid level in stage one of the two stage actuation process. Because the dry wipe member  312  is directed to removing cleaning fluid, not applying it, ensuring the cleaning fluid is quickly drained from the dry wipe member  312  in the two-stage actuation process is desirable. However, in embodiments, other actuation processes, including single-stage actuation processes, are contemplated and possible. 
     The embodiment shown in  FIGS. 6A-6C  schematically depict a two-stage actuation process for raising the dry wipe members  312  out of the cleaning fluid of the cleaning station vessel  314 . As shown in  FIG. 6A , the dry wipe member  312  may be submerged in the cleaning station vessel  314  of the cleaning station  110  such that the dry wipe member  312  is below a fluid level  600  of the cleaning fluid within the cleaning station  110 . Each of the wet wipe member  310  and the dry wipe member  312  are coupled to a first actuator  602   a  and a second actuator  602   b , respectively, for raising and lowering the members. Actuators  602   a ,  602   b  in embodiments, may correspond to actuators  311  and  313  described in accordance with  FIGS. 3A and 3B . The first actuator  602   a  is coupled proximate a first end of the wet wipe member  310  or the dry wipe member  312  and the second actuator  602   b  is coupled proximate a second end of the wet wipe member  310  or the dry wipe member  312 . By “coupled proximate,” it is meant that the actuator is coupled at or near the respective end of the member. In embodiments, the first actuator  602   a  is coupled to the wet wipe member  310  or the dry wipe member  312  at a point that is closer to the first end than the second end of the corresponding member, and the second actuator  602   b  is coupled to the wet wipe member  310  or the dry wipe member  312  at a point that is closer to the second end than the first end of the corresponding member. Each of the actuators  602   a  and  602   b  are independently operable to raise or lower the corresponding end of the dry wipe member  312  to which they are coupled into and out of the volume of the cleaning fluid. 
     In  FIG. 6A , dry wipe member  312  is not shown, as it is positioned behind, and obscured by, the wet wipe member  310  in this view. As shown in  FIG. 6B , the first actuator  602   a  coupled to the dry wipe member  312  is actuated to raise a first end  604  of the dry wipe member  312  above the fluid level  600  of the cleaning fluid while a second end  606  of the dry wipe member  312  remains below the fluid level  600 . Although depicted in  FIG. 6B  as raising the first end  604  of the dry wipe member  312  to completely remove the first end  604  from the volume of cleaning fluid, it is contemplated that in some embodiments, the dry wipe member  312  may be raised such that the dry wiper blades  502  (not shown in  FIGS. 6A-6C ) are above the fluid level while at least a portion of the wiper mounting member  501  remains submerged in the cleaning fluid, below the fluid level  600 . After the first end  604  of the dry wipe member  312  is raised, the second actuator  602   b  coupled to the dry wipe member  312  is actuated to raise the second end  606  of the dry wipe member  312  above the fluid level  600  of the cleaning fluid, as shown in  FIG. 6C . As would be understood, lowering the dry wipe member  312  into the cleaning fluid may be achieved by reversing the process described above and depicted in  FIGS. 6A-6C . In embodiments, actuators  602   a  and  602   b  may be actuated simultaneously to lower the first end  604  and the second end  606  of the dry wipe member  312  at the same time, or during overlapping time periods. 
     Similarly, the embodiment shown in  FIGS. 6D and 6E  schematically depict a two-stage actuation process for raising the wet wipe member  310  out of the cleaning fluid of the cleaning station vessel  314 . In particular, as shown in  FIG. 6D , the first actuator  602   a  coupled to the wet wipe member  310  is actuated to raise the first end  410  of the wet wipe member  310  above the fluid level  600  of the cleaning fluid while the second end  412  of the wet wipe member  310  remains below the fluid level  600 . Although depicted in  FIG. 6D  as raising the first end  410  of the wet wipe member  310  to completely remove the first end  410  from the volume of cleaning fluid, it is contemplated that in some embodiments, the wet wipe member  310  may be raised such that the wiper blades  406  are above the fluid level while at least a portion of the wet wiper body  401  remains submerged in the cleaning fluid, below the fluid level  600 . After the first end  410  of the wet wipe member  310  is raised, the second actuator  602   b  coupled to the wet wipe member  310  is actuated to raise the second end  412  of the wet wipe member  310  above the fluid level  600  of the cleaning fluid, as shown in  FIG. 6E . As above, the wet wipe member  310  can be resubmerged in the cleaning fluid by reversing the process, actuating the second actuator  602   b  and then actuating the first actuator  602   a  of the wet wipe member  310 . Alternatively, in embodiments, actuators  602   a  and  602   b  may be actuated simultaneously to lower the first end  410  and the second end  412  of the wet wipe member  310  at the same time, or during overlapping time periods. 
     In some embodiments, the two-stage actuation process may occur for both the dry wipe members  312  and the wet wipe members  310 . This embodiment, which is sequentially illustrated in  FIGS. 6A-6E , may be completed before or while the print head  150  is moved to the binder purge bin  302 . After the print head  150  is moved passed the wet wipe cleaner section  304  and the dry wipe cleaner section  306 , the wet wipe member  310  and the dry wipe member  312  may be returned to the cleaning fluid. In particular, after the print head  150  is passed over the wet wipe member  310  and the dry wipe member  312 , the actuators  602   a - 602   b  may be actuated to lower the wet wipe member  310  and the dry wipe member  312  below the fluid level  600  of the cleaning fluid. In some embodiments, two or more of the actuators may be actuated simultaneously to lower the wet wipe member  310  and the dry wipe member  312  into the cleaning fluid, while in other embodiments, each of the actuators is independently actuated. 
     For example, in embodiments, the actuator  602   b  is actuated while the first actuator  602   a  is actuated to lower the first and second ends of the wet wipe member  310  or the dry wipe member  312  at substantially the same time or during an overlapping time period. In embodiments, such as the embodiment shown in  FIGS. 6D and 6E , the actuator  602   a  is actuated to lower the first end  410  of the wet wipe member  310  into the volume of cleaning fluid, then the actuator  602   b  is actuated to lower the second end  412  of the wet wipe member  310  into the cleaning fluid. Then, as shown in  FIGS. 6A-6C , the actuator  602   a  is actuated to lower the second end  606  of the dry wipe member  312  into the volume of cleaning fluid, and finally, the actuator  602   b  is actuated to lower the first end  604  of the dry wipe member  312  into the cleaning fluid. Alternatively, as shown in to  FIGS. 6D and 6E , the actuator  602   a  is actuated to lower the first end  410  of the wet wipe member  310  into the volume of cleaning fluid, then the actuator  602   b  is actuated to lower the second end  412  of the wet wipe member  310  into the cleaning fluid. As shown in  FIGS. 6A-6C , then the actuator  602   a  is actuated to lower the first end  604  of the dry wipe member  312  into the volume of cleaning fluid, and finally, the actuator  602   b  is actuated to lower the second end  606  of the dry wipe member  312  into the cleaning fluid. In still other embodiments, the order of the lowering of the first end  410  and the second end  412  of the wet wipe member  310  is reversed, and in still other embodiments, the dry wipe member  312  is lowered into the cleaning fluid before the wet wipe member  310  is lowered into the cleaning fluid. In embodiments, some or all of the actuators may be actuated simultaneously. 
     In embodiments, the first and second actuators  602   a ,  602   b  (and, accordingly, actuators  311  and  313 ) are electric actuators that are independently operable to raise or lower the corresponding end of the wipe member (e.g., wet wipe member  310  or dry wipe member  312 ) at a plurality of speeds. Accordingly, in embodiments, the first actuator  602   a  is actuated to raise a first end of the wipe member at a first speed r 1 , the second actuator  602   b  is actuated to raise a second end of the wipe member at a second speed r 2 , the second actuator  602   b  is actuated to lower the second end of the wipe member at a third speed r 3 , and the first actuator  602   a  is actuated to lower the first end of the wipe member at a fourth speed r 4 , with at least one of the speeds differing from at least one of the other speeds. For example, the wet wipe member  310  or the dry wipe member  312  may be raised at one speed and lowered at another speed (e.g., r 1 =r 2 , r 3 =r 4 , r 1 ≠r 3 ), the first side may be actuated at one speed and the second side may be actuated at another speed (e.g., r 1 =r 4 , r 2 =r 3 , r 1 ≠r 3 ), each actuation may be at a different speed from each other actuation (e.g., r 1 ≠r 2 ≠r 3 ≠r 4 ), or the like. Such actuation can enable, for example, the wet wipe member  310  to emerge from the cleaning fluid quickly to project cleaning fluid toward the print head and to be submerged in the cleaning fluid to reduce or prevent splashing. 
     Although the wet wipe member  310  and the dry wipe member  312  are described herein as being coupled to two actuators, it is contemplated that in other embodiments, each wipe member may be coupled to a single actuator, or to more than two actuators. Moreover, although the actuators are described herein as being operable to raise and lower the corresponding wipe member, it is contemplated that the actuators may be used in embodiments to cause additional movement of the wipe member. For example, in embodiments in which the actuators are electric actuators, the actuators may be actuated to cause agitation of the wipe member within the cleaning station vessel  314 , to adjust the position of the wipe member within the cleaning station vessel  314  or with respect to the print head  150 , or the like. Electric actuators may further enable “just in time” positioning of the wipe member and/or automatic calibration routines. Other features and advantages are possible, depending on the particular embodiment. Commercially available electric actuators suitable for use include, by way of example and not limitation, ERD electric cylinders available from Tolomatic, Inc. (Hamel, Minn.). 
     Although it is contemplated in embodiments that the actuators are controlled using a controller, such as control system  1000 , in embodiments, one or more additional mechanisms may be included to monitor, set, or limit the motion of the various components of the cleaning station  110 . Such mechanisms may be desired, for example, to ensure that the print head  150  is not damaged by the components of the cleaning station  110 , while enabling the components to contact the print head  150  as may be necessary to clean the print head  150 . Accordingly, in embodiments, an adjustable hard stop  614  ( FIG. 6F ) may be present to limit the vertical movement of one or more of the components within the cleaning station vessel  314 . 
     In embodiments, a member  610  is coupled to an actuator  602  through a motion coupler  608  to provide or control of the upper position of the member  610  within the cleaning station  110 , and specifically, the cleaning station vessel  314 , as shown in  FIG. 6F . The member  610  can be, for example, the wet wipe member  310 , the dry wipe member  312 , and/or the cover of the capping section  308  (described in greater detail below), and the actuator  602  can be, for example, the one or more corresponding actuators (e.g., actuators  311 ,  313 , and  706 , respectively). The at least one motion coupler  608  extends from the member  610  and is configured to couple the member  610  to the cleaning station vessel  314  for vertical motion (e.g., along the +/−Z axis shown in the FIGS.) therein. In embodiments, the motion coupler  608  may be made from metal coated with polytetrafluoroethylene (e.g., TEFLON™) or other suitable materials. 
     In the embodiment shown in  FIG. 6F , the member  610  moves up and down within the cleaning station vessel  314  on a rail  612  through the motion coupler  608 . The rail  612  is coupled to an adjustable hard stop  614 . The adjustable hard stop  614  includes a threaded portion through which the adjustable hard stop  614  is coupled with a controlling bolt  616 . The controlling bolt  616  is additionally coupled with a rail cap  618  that is fixedly mounted on the rail  612 . For example, the rail cap  618  may include a clearance hole through which the controlling bolt  616  passes before it is coupled with the adjustable hard stop  614  through the threaded portion of the adjustable hard stop  614 . A nut  620  may be used to prevent the controlling bolt  616  from moving upward. To adjust the adjustable hard stop  614 , the controlling bolt  616  is tightened (to move the adjustable hard stop  614  in the upward direction) or loosened (to move the adjustable hard stop  614  in the downward direction). Accordingly, the position of the adjustable hard stop  614  is set to the desired maximum height for the member  610 . When the member  610  reaches to the desired maximum height, the adjustable hard stop  614  prevents the motion coupler  608  from continuing in the upward direction on the rail  612 . 
     Although only one end of the member  610  is shown in  FIG. 6F , it is contemplated in such embodiments, the member  610  includes a motion coupler  608  on each end and, accordingly, each end of the member  610  may be controlled in this fashion. In embodiments, a gauge or other indicia (not shown) may be included (e.g., machined into the rail  612  or cleaning station vessel  314 ) to enable the position of each end of the member  610  to be set at an equivalent position. Such indicia may additionally enable multiple members  610  to be set at a common desired position relatively easily. 
     In addition to, or as an alternative to, the hard stop, in embodiments a gauge  1100  on the underside of the print head  150  is used to vertically align one or more of the components of the cleaning station  110 , as shown in  FIG. 11 . In  FIG. 11 , the gauge  1100  is affixed to the bottom face  1102  of the print head  150 , such as through the use of bolts, clips, or another attachment mechanism. When affixed to the print head  150  the gauge  1100  includes a first section  1104  at a first vertical position Z 1  and a second section  1106  at a second vertical position Z 2 . As shown in  FIG. 11 , the first vertical position Z 1  is vertically higher than, or above, the second vertical position Z 2 . In embodiments, the first section  1104  and the second section  1106  can have different indicia or colors to enhance visual differentiation between the first and second vertical positions. 
     In practice, the print head  150  may be moved over the cleaning station  110 , and the member  610  (e.g., wet wipe member  310 , dry wipe member  312 , or cap  710 ) is raised to an initial maximum vertical position. As used herein, the “maximum vertical position” of a member refers to the vertical position of the top edge  1108  of the member  610  when the member  610  is at a set maximum vertical height out of the cleaning station vessel  314 . The print head  150  may be positioned directly over the member  610 , or the print head  150  may be located elsewhere over the cleaning station  110  to enable visual comparison of the vertical position of the member  610  with the gauge  1100 . The maximum vertical position Z m  of the member  610  is then adjusted such that the top edge  1108  of the member  610  is vertically below or lower than the first vertical position Z 1 . In embodiments, the maximum vertical position Z m  of the member  610  is also greater than or equal to the second vertical position Z 2 . Put another way, the member  610  is adjusted such that the maximum vertical position Z m  of the member  610  is Z 1 &gt;Z m ≥Z 2 . Adjustments of the maximum vertical position Z m  of the member  610  can be made by adjusting an adjustable hard stop, as shown and described herein above, adjusting one or more parameters or settings of an actuator coupled to the member  610 , or by other methods that will be known to those of skill in the art, depending on the particular embodiment. In embodiments, adjustments can be made using the gauge  1100  to any or all of the components of the cleaning station  110 . 
     Having described various sections of a cleaning station  110 , a fluid management system suitable for providing cleaning fluid to the cleaning station  110  and binder material to the print head  150  will now be described in detail. 
     Fluid Management System 
     Referring now to  FIG. 8  in conjunction with  FIG. 1 , a fluid management system  800  includes a binder material pathway for providing binder material  500  to a print head  150  and for recycling binder material  500  not deposited on build material  400  positioned on the build platform  120  and a cleaning fluid pathway for providing cleaning fluid to the cleaning station  110  for cleaning the print head  150  between depositing operations and recycling and reconditioning cleaning fluid to minimize the amount of cleaning fluid that is wasted. 
     In general, the binder material pathway includes a binder reservoir  802  that is in fluid communication with the print head  150  and at least one binder purge bin  302 . As depicted in  FIGS. 3A and 3B , the cleaning station  110  includes two binder purge bins  302 . The binder purge bins  302  may each include an active drain  806 , which allows binder flow from the binder purge bin  302  into the binder reservoir  802 . Further, as shown, the binder purge bins  302  may each include an overflow drain  812  disposed on the sidewall of the binder purge bin  302 , which releases binder from the binder purge bin  302  if a level of binder in the binder purge bin  302  exceeds a desired binder fluid level. In some embodiments, level sensors may be included to ensure binder fluid level is properly monitored and maintained. 
     Referring again to  FIG. 8 , the binder material pathway enables recirculation of the binder material to reduce or even eliminate clogging of the binder material in the nozzles of the print head  150 . In the binder material pathway depicted in  FIG. 8 , two binder purge bins  302  are included. In embodiments, one of the binder purge bins  302  may receive binder material and contaminants discharged from the print head  150  via backpressure prior to cleaning of the print head  150  at the cleaning station  110 . 
     In embodiments including multiple binder purge bins, the first binder purge bin is located upstream from the cleaning station vessel  314  and the second binder purge bin (binder purge bin  302  in  FIGS. 3A and 3B ) is positioned downstream of the cleaning station vessel  314  and the dry wipe cleaner section of the cleaning station  110  along a path of the print head  150 . In embodiments, the second binder purge bin is positioned upstream of the build area in order to receive binder material ejected (i.e., “spit”) from the print head  150  during preparation of the print head  150  before printing. The second binder purge bin  302 , in some embodiments, can include a non-porous medium (e.g., thermal, pH, hydrochromic or wax paper, cloth media, etc.) for receiving a pattern test printed by the print head  150  when the print head  150  is positioned over the additional binder purge bin  302 . The pattern can be inspected, such as by using a camera configured to capture an image of the pattern, to determine if the printed pattern is suitable. For example, if the printed pattern matches a predetermined reference pattern, the printed pattern may be determined to be suitable. As another example, if the printed pattern differs from the predetermined reference pattern, the printed pattern may be determined to be unsuitable. In such embodiments, the print head may be prevented from supplying binder material to a working surface of the build area, or adjusted prior to supplying the binder material. 
     The binder material is provided from the binder reservoir  802  to an ink delivery system  804  which in turn delivers the binder material to the print head  150 . The ink delivery system  804  enables the separation of storage of the binder material from the print head  150  and allows for the binder material to be replaced or refilled while the additive manufacturing apparatus  100  is actively printing. The print head  150  discharges the binder material through nozzles into, for example, the build area and the binder purge bins  302 . 
     Binder material discharged into the one or more binder purge bins  302  passes through an active drain  806 . In the embodiment depicted in  FIG. 8 , the active drain  806  is located at or near a bottom of each of the binder purge bins  302 , to enable the binder material to be recirculated without requiring the accumulation of the binder material in the binder purge bins  302 . In embodiments, the active drain  806  is in fluid communication with a pump  808  that actively moves the binder material from the active drain  806  through a filter  810  and back to the binder reservoir  802 . The filter  810  may remove contaminants or large particles, such as polymers that have agglomerated as a result of partial evaporation of the binder material and build material particles, to ensure that the binder material that is returned to the binder reservoir  802  is suitable for recirculation through the binder material pathway. 
     As shown in  FIG. 8 , each binder purge bin  302  further includes an overflow drain  812  located through a sidewall of the binder purge bin  302 . In embodiments, the overflow drain  812  is located within the top half of the height of the sidewall of the binder purge bin  302 . The overflow drain  812  is in fluid communication with a waste reservoir  814 . Accordingly, in the event that the active drain  806  becomes clogged or binder material otherwise accumulates to a level greater than or equal to the position of the overflow drain  812 , the binder material can be drained from the binder purge bin  302  and removed from the binder material pathway via the waste reservoir  814 . In the event of a clog in the active drain  806 , the binder material removed from the binder purge bin  302  is directed from the overflow drain  812  to the waste reservoir  814  so as to minimize the amount of contaminants recirculated through the system, although in some embodiments, it is contemplated that the overflow drain  812  may be in fluid communication with the binder reservoir  802 , such as through the filter  810 . 
     In embodiments, the binder material pathway may optionally include an overflow tank  813  fluidly coupled to the overflow drain  812  of the binder purge bin  302 . The overflow tank  813 , when included, is fluidly coupled to the binder reservoir  802  and the waste reservoir  814 . In embodiments, the overflow tank  813  is coupled to the binder reservoir  802  and the waste reservoir  814  through a valve  815 , although other pathways are contemplated. Valve  815  can be, for example, a pinch valve, a three-way valve, or a four-way valve, although other types of valves are contemplated. It is further contemplated that the overflow tank  813  can be fluidly coupled to another part of the main circulation path instead of being fluidly coupled to the binder reservoir  802 . 
     In embodiments including the overflow tank  813 , binder material overflowing from the binder purge bin  302  flows through the overflow drain  812  into the overflow tank  813 . Binder material in the overflow tank  813  is evaluated and, if verified that the binder material in the overflow tank  813  is still usable, the binder material is returned to the binder reservoir  802 . If, however, the binder material in the overflow tank  813  is not still suitable for use (e.g., it contains too many contaminants or does not otherwise meet specifications for use), the binder material is sent to the waste reservoir  814 . In embodiments including the valve  815 , the valve  815  can be controlled by a computing device, such as control system  1000  that is configured to verify the suitability of the binder material for use and send a signal to the valve  815  to direct the binder material to the binder reservoir  802  or the waste reservoir  814 . 
     Turning now to the cleaning fluid pathway depicted in  FIG. 8 , the cleaning fluid pathway generally includes a cleaning fluid reservoir  816  that is in fluid communication with the cleaning station vessel  314  of the cleaning station  110 . The cleaning fluid pathway enables cleaning fluid to be applied to the print head  150  to fluidize particles deposited on the print head  150 , such as build material particles and binder material particles, while further enabling the cleaning fluid to be recirculated and reconditioned to reduce the amount of cleaning fluid that is wasted. 
     In embodiments, the cleaning fluid is provided from the cleaning fluid reservoir  816  through a filter  818  to a pump  820 , which in turn delivers the cleaning fluid to the cleaning station vessel  314  through a cleaning fluid inlet  822 . As shown in  FIG. 8 , the cleaning fluid inlet  822  may be positioned in the bottom of the cleaning station vessel  314 , although in other embodiments, the cleaning fluid inlet  822  may be provided in another location along one of the sidewalls of the cleaning station vessel  314 . Additionally or alternatively, multiple cleaning fluid inlets  822  may be positioned within the cleaning station vessel  314  along with one or more cleaning fluid outlets to enable a directional flow of cleaning fluid through the cleaning station vessel  314 . The directional flow of cleaning fluid can, for example, agitate the cleaning fluid and debris in the cleaning station vessel  314  and prevent the debris from settling at the base of the cleaning station vessel  314  where it may clog the active drain. In embodiments, tubes are connected to one or more cleaning fluid inlets  822  to direct the cleaning fluid within the cleaning station vessel  314 . It is further contemplated that the contents of the cleaning station vessel  314  can be agitated using ultrasonic waves, oscillating or other non-static jets, turbulators or other vortex generators, or the like. 
     As the cleaning fluid is pumped into the cleaning station vessel  314 , the volume of the cleaning fluid accumulates to a fluid level  600  within the cleaning station vessel  314 . The volume of cleaning fluid is used to supply cleaning fluid to the wet wipe member  310  and the capping section  308 , as described hereinabove, and to supply cleaning fluid to the dry wipe cleaner section  306  for cleaning the dry wipe member  312  between uses. In embodiments, the cleaning fluid inlet  822  can be left open to simply fill the cleaning station vessel  314 . Alternatively, the cleaning fluid inlet  822  can be connected to the cleaning fluid inlets  416  of the wet wipe member  310  which then fills the fluid ports  407  and then fills the area between the wiper blades  406 . In this setup, cleaning fluid is constantly fed when the machine is in operation and is then overflowed into the cleaning station vessel  314 . 
     The cleaning station vessel  314  includes a drain  824  that is in fluid communication with the cleaning fluid reservoir  816 . The drain  824 , which is also depicted in  FIGS. 3A and 3B , is positioned within the cleaning station vessel  314  to maintain the fluid level  600  at a predetermined level. Accordingly, when the volume of cleaning fluid rises above the predetermined level, cleaning fluid is drained from the cleaning station vessel  314  via the drain  824  and returned to the cleaning fluid reservoir  816 . In one or more embodiments, the drain  824  may be an active drain coupled to a pump, or may be a passive drain, which allows the cleaning fluid to pass out of the cleaning station vessel  314  without the use of a pump or other active mechanism. 
     In the embodiment shown in  FIG. 8 , the cleaning station vessel  314  further includes an active drain  826  that is in fluid communication with the waste reservoir  814 . The active drain  826  can be activated to allow at least a portion of the cleaning fluid that is in the cleaning station vessel  314  to be removed from the cleaning station vessel  314  and directed to the waste reservoir  814 . As will be described in greater detail below, a portion of the cleaning fluid may be removed from the cleaning fluid pathway via the waste reservoir  814  in response to determining that the cleaning fluid contains an unsuitable amount of contaminants or that the cleaning fluid should otherwise be replaced, either partially or fully. 
     In various embodiments, the cleaning station vessel  314  further includes a level sensor  828 . The level sensor  828  is used to maintain a constant height of cleaning fluid within the cleaning station vessel  314 . For example, the level sensor  828  can determine that the fluid level  600  of the cleaning fluid is low and, responsive to the determination, additional cleaning fluid can be pumped into the cleaning station vessel  314  using the pump  820 . The level sensor may be any suitable type of sensor. In some embodiments, the level sensor comprises a sensor that it is able to withstand submersion within the cleaning fluid. In other embodiments, the level sensor is not disposed within the cleaning fluid, and can detect the fluid level via other means. For example, a laser level sensor may be used. In embodiments, the level sensor  828  may be coupled to a control system  1000  which receives signals from the level sensor  828  and provides signals to other system components, such as the pump  820  and/or the active drain  826 , as will be described in greater detail below. Additionally or alternatively, the level sensor  828  may include the fluid level sensors  322  positioned within the overflow vessel  318 , as described in accordance with  FIG. 3C  above. Accordingly, it is contemplated that the fluid level sensors  322  can be incorporated into the cleaning fluid pathway, and coupled to the control system  1000 , as has been described with respect to the level sensor  828 . 
     In various embodiments, one or more additional components (not shown in  FIG. 8 ) may be included in the fluid management system  800  as part of one or both of the binder material pathway or the cleaning fluid pathway. For example, additional level sensors, flow sensors, cameras, heaters, cooling units, temperature sensors, pumps, filters, valves, or the like may be included in the fluid management pathways to enable monitoring, control, and adjustment of the fluids in the pathways. Such additional components may be included in any of a variety of locations within the fluid management system  800  and may be communicatively coupled to the control system  1000 . For example, in embodiments, the cleaning fluid path includes a heater to heat the cleaning fluid prior to it entering the cleaning station vessel  314 . When included, the heater may be positioned at any of a number of points along the cleaning fluid path, such as between the pump  820  and the cleaning station vessel  314 , or within the cleaning station vessel  314  or the cleaning fluid reservoir  816 . 
     As another example, in embodiments a three-way or four-way valve may be positioned within the drain  824  and the cleaning fluid reservoir  816  to redirect a predetermined amount of the cleaning fluid to the waste reservoir  814 . Accordingly, in embodiments, the three-way or four-way valve may replace or replicate the functionality of the active drain  826 . Moreover, it is contemplated that one or more on/off valves (e.g., pinch valves) may be used in place of or in addition to the three- or four-way valves described herein. 
     In embodiments, one or more of the pumps described herein, including but not limited to pump  808  and pump  820 , are capable of moving ferrous metals as well as other types of metals. Moreover, in embodiments, one or more of the pumps described herein may include a tunable flow rate, such as through flow regulators, which enable the flow rate to be tuned, such as to enable cleaning fluid to be provided to the wet wipe member at a first flow rate and to the inlet of the cleaning station vessel at a second flow rate. 
     Having described a fluid management system  800  for use in providing binder material and cleaning fluid to various components of the additive manufacturing apparatus  100 , and specifically, the cleaning station  110 , the binder material and cleaning fluid will now be described in detail. 
     Binder Materials 
     In various embodiments, the binder material is a reversible binder. As defined herein, a “reversible binder” is intended to denote a thermoplastic or thermoset polymer that, during decomposition, is broken down into oligomers and other molecules that are similar or identical to the monomers used to derive the polymer. The reversible binder may be polymerized via radical chain reactions to bond particles and layers of a powder used to print the article. While many of the embodiments described below are directed to metal powder, it is contemplated that other non-metal powders are suitable, for example, for sand, ceramic, and polymer binder jetting. 
     Although reference is made to a “metal powder” in various embodiments herein, it is contemplated that the material used to print the article may vary depending on the type of the article and the end use of the article. In embodiments in which a metal powder is employed, the metal powder may include nickel alloys, cobalt alloys, cobalt-chromium alloys, cast alloys, titanium alloys, aluminum-based materials, tungsten, steel, stainless steel, or any other suitable material and combinations thereof. 
     Following deposition of a layer of the metal powder, the binder material is selectively deposited into the layer of metal powder in a pattern representative of the structure of the article being printed. According to various embodiments, the binder material may include polymers derived from unsaturated monomers. For example, the binder material may include one or more polymers having the following formulas: (CH 2 CHR) n , where R=—H, —OH, phenyl, alkyl, aryl. The binder material may also include one or more monofunctional acrylic polymers having the formula (CH 2 —CR 2 COOR 1 ) n , where R 1  is an alkyl or aryl, and R 2  is H or CH 3 ; di-acrylic polymers having the formula [(CH 2 —CR 2 COO) 2 —R 3 ] n , where R 2  is H or CH 3  and R 3  is a divalent hydrocarbon radical; tri-acrylic polymers having the following formula [(CH 2 CR 1 COO) 3 —R 4 ] n , where R 1  is H or CH 3  and R 4  is a trivalent hydrocarbon radical and/or poly(alkylene carbonates) including co-polymeric alkylene carbonates, such as poly(ethylene-cyclohexene carbonate) and those having the following formulas: 
     
       
         
         
             
             
         
       
     
     By way of example and not limitation, the binder material may include poly (methyl methacrylate) (PMMA), polystyrene (PS), poly (vinyl alcohol) (PVA), polyacrylic acid (PAA), Poly vinyl pyrrolidone (PVP), poly (alkylene carbonates), and polymers derived from hexanediol diacrylate (HDDA), trimethylolpropane triacrylate (TMPTA), and diethylene glycol diacrylate (DGD), derivatives of any of the above, or combinations of the above. 
     In some embodiments described herein, the binder material further includes one or more fluorescent dyes. The inclusion of the fluorescent dyes enables an otherwise clear binder material (e.g., a binder material including PVA and water) to be detectable under certain lighting conditions, as will be described in greater detail below. In specific embodiments, the fluorescent dyes/pigments should be photochromic dyes that respond to specific light intensities, for example near IR or UV (including UVA, UVB, or UVC) light. In embodiments including the fluorescent dye, the intensity of the fluorescence is a function of the concentration of the fluorescent dye. Accordingly, the inclusion of a fluorescent dye can provide information regarding where the binder material has been deposited, how much binder material has been deposited, and/or the extent to which the binder material has cured. Moreover, the fluorescence of the binder material can enable detection of leaks or spills, fluid management applications, such as monitoring tank levels, binder material concentration, and contamination, and part detection. Specific embodiments of using the fluorescent dye in process control are provided below. 
     In various embodiments, the fluorescent dye in the binder material may be any suitable fluorescent dye that is compatible with the binder material. In some embodiments, the fluorescent dye is not quenched by the metal powder. Moreover, the fluorescent dye should not negatively impact the material properties of the green body, brown body, or final part. Examples of fluorescent binders are fluorescent inorganic pigments and solid solutions of fluorescent dyes in transparent synthetic resins, polymer encapsulated fluorescent dyes. 
     Fluorescent pigments are solid solutions of fluorescent dyes. These fluorescent dyes may include polyenes, rhodamines, coumarins, naphthalimides, fluoresceins, diazonium salt, acridines, benzoxanthenes, or combinations thereof. The fluorescent color achieved can be from a combination of a single fluorescent dye embedded in a medium (e.g., polymer or resin carrier) or by combining multiple fluorescent dyes at different ratio. When incorporated in a resin dispersion, it is contemplated that the dispersion may be water or solvent based. The dyes may be proteins or non-proteins, and may be organic or synthetic. It is contemplated that the particular dye selected will vary based on the particular embodiment employed. Examples of suitable fluorescent dyes are described in PCT Publication WO 03/029340, which is incorporated by reference herein in its entirety. 
     Various sizes are contemplated for the fluorescent pigment. For example, the fluorescent pigment or fluorescent dye resin may have a typical average particle size from about 0.01 to about 1 μm. The amount of fluorescent pigment or fluorescent dye resin may be in the typical range of 0.01 to 5% by weight, or from 0.1 to 2% by weight. 
     The binder material may further include one or more additives that facilitate deposition of the binder material into the layer of metal powder. For example, the binder material may include one or more additives such as viscosity modifiers, dispersants, stabilizers, surfactants (e.g., surface active agents) or any other suitable additive that may facilitate the jettability of the binder material and deposition of the binder material into the layer of metal powder. The surfactants may be ionic (e.g., zwitterionic, cationic, or anionic) or non-ionic, depending on the properties of the binder material and/or the metal powder. 
     In some embodiments, the additive(s) may improve the wettability of the metal powder to facilitate coating the metal powder with the binder material. The additive(s) may also modify the surface tension of the binder material to facilitate jettability of the binder material. For example, in embodiments, the binder material is considered jettable if the Ohnesorge number (e.g., the ratio of viscous forces to inertial and surface tension forces) is between approximately 0.01 and approximately 2. 
     In embodiments, the additive(s) may also include a solvent that dissolves the binder material. The solvent may be aqueous or non-aqueous, depending on the particular polymers selected and other additives that may be in the binder material. The solvent is generally non-reactive (e.g., inert) such that it does not react with the metal powder, the polymers in the binder material, or any other additives that may be in the binder material. Additionally, the solvent should readily evaporate after selective deposition of the binder material into the layer of metal powder to facilitate bonding of the binder-coated particles and the printed layers. Example solvents that may be used in the binder material include, but are not limited to, water, methylene chloride (CH 2 Cl 2 ), chloroform (CHCl 3 ), toluene, xylenes, mesitylene, anisole, 2-methoxy ethanol, Butanol, diethylene glycol, tetrahydrofuran (THF), methyl ethyl ketone (MEK), trichloroethylene (TCE), or any other suitable solvent. 
     The binder material may include the reversible binder, one or more monomers used to derive the reversible binder, or both. For example, in some embodiments, the reversible binder is polymerized before selective deposition into the layer of metal powder. Accordingly, in such embodiments, the binder material may include the reversible binder as a pre-formed, dissolved polymer. The reversible binder may be solubilized in a suitable solvent to facilitate jettability and deposition into the layer of the metal powder. Following deposition, the solvent may evaporate and the reversible binder may coalesce and bond the binder-coated particles and the printed layers to form the green body part. 
     In other embodiments, the reversible binder is polymerized after depositing the binder solution into the layer of metal powder. That is, the reversible binder may be polymerized in situ. For such embodiments, the binder material may include one or more polymerizable monomers (e.g., reactive monomers) that react to form the reversible binder. In one particular embodiment, the binder material includes the one or more polymerizable monomers and a suitable solvent. In other embodiments, the binder material does not include a solvent. Rather, the binder material may be a neat liquid of the one or more polymerizable monomers. Once the binder solution is deposited onto the layer of metal powder, the one or more polymerizable monomers may be polymerized to form the reversible binder within the layer of metal powder to form the printed layer of the green body part. In certain embodiments, the binder material may include initiators such as, for example, azobis (isobutyronitrile) (AIBN), to facilitate in situ polymerization of the one or more polymerizable monomers in the layer of metal powder. 
     By way of non-limiting example, in some embodiments, the binder material may include between about 0.5 weight percent (wt. %) and about 30 wt. % of the polymerized reversible binder or the polymerizable monomers used to derive the reversible binder in situ. In one embodiment, the binder material include from about 3 wt. % to about 7 wt. % of the polymer or polymerizable monomers. Additionally, the binder material may include suitable viscosity modifiers to enable a viscosity of the binder material that is from about 2 centipoise (cP) and about 200 cP. For example, depending on the viscosity of the mixture of the solvent and polymer/polymerizable monomer solution or the neat polymerizable monomer solution, the binder material may have from about 0.1 wt. % to about 15 wt. % of a viscosity modifier, such that the viscosity of the binder material is within the desired range for efficient and effective jettability. 
     Following deposition of the metal powder and printing of the binder material, the reversible binder is cured to form a layer of the green body part. While a portion of the solvent in the binder material may be evaporated during deposition (e.g., printing) of the binder material, a certain amount of the solvent may remain within the layer of metal powder. Therefore, in certain embodiments, the green body part may be thermally cured at a temperature that is suitable for evaporating the solvent remaining in the printed layer and allowing efficient bonding of the printed layers of the green body part. 
     In embodiments, the green body part may be cured to allow polymerization of the polymerizable monomers in the binder material to yield the reversible binder. For example, as discussed above, the reversible binder may be polymerized in situ after printing the binder material into the layer of metal powder. Following deposition of the binder material, the one or more polymerizable monomers in the binder material may be cured to polymerize the one or more monomers and form the printed layer of the green body part. For example, the printed layers may be exposed to heat, moisture, light, or any other suitable curing method that polymerizes the one or more polymerizable monomers in the binder material before the next layer of metal powder is deposited on top of the printed layer. In certain embodiments, the binder material may include a radical initiator (e.g., AIBN) to facilitate polymerization of the one or more polymerizable monomers. In one embodiment, the one or more polymerizable selectively deposited may be cured immediately after forming the printed layer. In other embodiments, the one or more polymerizable monomers may be cured after a desired number of printed layers has been formed. Excess metal powder (e.g., the metal powder that is not bonded by the reversible binder) may be removed after curing to prepare the green body for post-printing processing. After curing, the green body may undergo a drying step to remove any solvent and/or other volatile materials that remain in the green body part. For example, the green body may be dried in a vacuum, under an inert atmosphere (e.g., nitrogen or argon), or air. 
     Additional details on binder materials suitable for use in the embodiments described herein may be found in U.S. Patent Application Publication No. 2018/0071820 to Natarajan et al., entitled “Reversible binders for use in binder jetting additive manufacturing techniques” and filed on Sep. 9, 2016, the entire contents of which is hereby incorporated by reference. Moreover, it is contemplated that other binder materials may be used with the cleaning station and/or additive manufacturing apparatus described herein, depending on the particular embodiment. 
     Cleaning Fluids 
     In various embodiments, the cleaning fluid is compatible with the binder material (e.g., capable of dissolving or otherwise enabling with binder material to be wiped away) and is safe for the components of the additive manufacturing apparatus  100  (e.g., does not cause the need for excessive maintenance or cleaning). In some embodiments, such as embodiments in which the binder material is water-based, the cleaning fluid is a water-miscible cleaning fluid. 
     In various embodiments, the cleaning fluid includes from 0.1 wt. % to 30 wt. % of a cleaning agent. For example, the cleaning fluid can include from 0.1 wt. % to 30 wt. %, from 0.1 wt. % to 20 wt. %, from 0.5 wt. % to 10 wt. %, from 1 wt. % to 10 wt. %, or from 1 wt. % to 5 wt. % of the cleaning agent. In embodiments, the cleaning agent is an organic solvent. Suitable organic solvents for use in the cleaning fluid include dimethyl formamide (DMF), dimethyl sulfoxide (DMSO), methylpyrrolidone (NMP), N—N-dimethylacetamide (DMAc), 1,3-dimethyl-2-imidazolidnone (DMI), 1,3-dimethyl-3,4,5,6-tetrahydro-2(1H)-pyrimidinone (DMPU), ethylene glycol, diethyl glycol, dipropylene glycol dimethyl ether, cyrene, dimethyl isosorbide, propylene glycol, and mixtures thereof. In particular embodiments, the cleaning agent is DMF, NMP, DMSO, dipropylene glycol dimethyl ether, cyrene, dimethyl isosorbide, ethylene glycol, or combinations thereof. 
     It is contemplated that in some embodiments, the cleaning fluid may include one or more additives, although in other embodiments, the cleaning fluid includes the cleaning agent and water. Accordingly, in various embodiments, the cleaning fluid includes from 80 wt. % to 99.9 wt. % water, from 90 wt. % to 99.5 wt. % water, from 90 wt. % to 99 wt. % water, or from 95 wt. % to 99 wt. % water. 
     The cleaning fluid of various embodiments has a viscosity that enables the cleaning fluid to flow through the cleaning fluid pathway without issue. In embodiments, the cleaning fluid has a viscosity of less than 10 cP or less than 5 cP at 25° C. For example, the cleaning fluid may have a viscosity of from 0.5 cP to 5 cP, 0.5 cP to 3 cP, from 1 cP to 2 cP, or from 1 cP to 1.5 cP. 
     Additionally, or alternatively, the cleaning fluid of various embodiments has a boiling point that is greater than or equal to the boiling point of water. By having a boiling point that is greater than or equal to that of water, the cleaning fluid can resist evaporation and keep the print head  150  moist by preventing the binder material from drying. In various embodiments, the cleaning fluid has a boiling point that is greater than or equal to 100° C. at 1 atm, greater than or equal to 110° C. at 1 atm, greater than or equal to 125° C. at 1 atm, or even greater than or equal to 150° C. at 1 atm. 
     In embodiments, the cleaning fluid is formulated such that the density of the cleaning fluid is close to the density of water (e.g., 1 g/cm 3 ). In such embodiments, contaminants within the cleaning fluid, such as binder material and other debris, can be detected based on a change in density of the cleaning fluid, as will be described in greater detail below. Accordingly, in various embodiments, the cleaning fluid has a density of from 0.900 g/cm 3  to 1.400 g/cm 3  from 0.900 g/cm 3  to 1.200 g/cm 3  or from 0.900 g/cm 3  to 1.100 g/cm 3 . For example, the cleaning fluid may have a density of from 0.905 g/cm 3  to 1.195 g/cm 3 , from 0.910 g/cm 3  to 1.175 g/cm 3 , from 0.950 g/cm 3  to 1.150 g/cm 3 , from 0.905 g/cm 3  to 1.095 g/cm 3 , from 0.910 g/cm 3  to 1.075 g/cm 3 , or from 0.950 g/cm 3  to 1.050 g/cm 3 . 
     The cleaning fluid may be heated, such as by a heater positioned along the cleaning fluid pathway, although in other embodiments, the cleaning fluid may be applied to the print head  150  at approximately ambient temperature. As used herein, “ambient temperature” within the machine may differ from room temperature outside the machine. For example, the temperature of the machine may be elevated. In other embodiments, the cleaning fluid may be cooled to a temperature below ambient temperature before application to the print head  150 . For example, the cleaning fluid may be cooled to a temperature sufficient to cool the print head. Cooling of the cleaning fluid may be accomplished using a cooling apparatus, or simply by recirculation of the cleaning fluid through the cleaning fluid pathway. 
     As described herein, the cleaning fluid can be applied to the print head  150  to dissolve precipitant (e.g., resulting from partial evaporation of binder material) and other debris deposited on the print head  150  and within the nozzles of the print head  150 . Because the cleaning fluid is recirculated through the system and is also specially formulated to be compatible with the cleaning station  110 , the print head  150 , and the binder material ejected from the print head  150 , in various embodiments, the cleaning fluid is monitored to determine when the cleaning fluid should be reconditioned or replaced. An example method  900  of monitoring a status of the cleaning fluid is described in  FIG. 9 . In some embodiments, the method  900  or similar methods may be used to check the “health” of the cleaning fluid by determining the potency of the cleaning fluid. 
     In the method depicted in  FIG. 9 , the method  900  begins by obtaining an initial value of a physical property of the cleaning fluid (block  902 ). The physical property can be, for example, a density of the cleaning fluid, a viscosity of the cleaning fluid, a haze measurement, a surface tension of the cleaning fluid, a color of the cleaning fluid, a pH of the cleaning fluid, a conductivity of the cleaning fluid, or a fluorescence of the cleaning fluid. The initial value can be obtained in any one of a number of suitable ways, including through the use of sensors, cameras, or user input into a control system, such as control system  1000 . In various embodiments, the initial value can be stored in the memory of the control system  1000 . 
     Next, the cleaning fluid is circulated through the cleaning fluid pathway for a predetermined amount of time (block  904 ). In embodiments, circulation of the cleaning fluid through the cleaning fluid pathway includes using the cleaning fluid to clean the print head  150 . The predetermined period of time can vary depending on the particular embodiment. For example, the “predetermined time” may be the sampling rate of an instrument, which would ostensibly yield an effective “continuous” monitoring system. In other embodiments, the predetermined period of time can be a period of 1 minute, 5 minutes, 10 minutes, 30 minutes, an hour, 2 hours, or the like. After the passage of the predetermined period of time, a subsequent value corresponding to the physical property of the cleaning fluid is obtained (block  906 ). The subsequent value can be determined in the same way as the initial value was determined, or by a different method. For example, a user may input the initial value for a cleaning fluid when the cleaning fluid is introduced to the system, but a sensor may be used to obtain subsequent values corresponding to the physical property. 
     Next, an amount of contaminant in the cleaning fluid is estimated based on the initial value and the subsequent value corresponding to the physical property of the cleaning fluid (block  908 ). For example, the initial and subsequent values may be stored in a look up table (LUT) stored in the memory of the control system  1000  along with an estimated contaminant amount. Alternatively, the control system  1000  may perform one or more calculations to determine the amount of contaminant in the cleaning fluid. The contaminant may include, for example, dissolved, mixed and/or suspended binder material removed from the print head  150 , dissolved, mixed and/or suspended build material (e.g., metal powder), or the like. As used herein, “contaminant” includes, but is not limited to, precipitant deposited on the print head. In embodiments, the contaminant comprises polyvinyl alcohol (PVA), polyvinyl pyrrolidone (PVP), polyacrylic acid (PVA), or derivatives thereof. In embodiments, as an alternative to or in addition to determining an estimated contaminant amount, an amount of evaporation is estimated. For example, the initial and subsequent values may be stored in a look up table (LUT) stored in the memory of the control system  1000  along with an estimated evaporation amount. Based on the amount of contaminant in the cleaning fluid, the amount of evaporation of the cleaning fluid, or both, a cleaning fluid maintenance process is selected from a plurality of available maintenance processes (block  910 ). In some embodiments, available maintenance processes may include adding water (or another solvent) to the cleaning fluid, replacing a portion of the cleaning fluid containing contaminants with fresh cleaning fluid, replacing a majority of the volume of the cleaning fluid with fresh cleaning fluid, or returning the cleaning fluid containing the contaminants to the cleaning fluid reservoir. Finally, the selected cleaning fluid maintenance process is performed (block  912 ). 
     By way of illustration, the process may include using a density meter to automatically determine an initial density of the cleaning fluid. Then, after the cleaning fluid has been used for a period of about 15 minutes, the density meter again measures the density of the cleaning fluid. Various time periods are considered suitable and can be tailored based on print cycles, cleaning cycles, and the like. In one or more embodiments, the density of the cleaning fluid may be measured as frequently as every 30 seconds or after 15 minutes, or in a further embodiment, density may be measured every 30-60 seconds. The density meter transmits both the initial density and the subsequent density of the cleaning fluid to the control system  1000 , which then estimates an amount of contaminant in the cleaning fluid based on the change in density. When the estimated amount of contaminant is within a suitable range, the cleaning fluid recirculated through the cleaning fluid pathway. When the estimated amount of contaminant is moderate, water may be added to the cleaning fluid, or a portion of the cleaning fluid may be diverted to the waste reservoir by activating a three-way valve (described above) while new cleaning fluid is added to the cleaning fluid reservoir. Alternatively, when the estimated amount of contaminant is high, the entire volume of the cleaning fluid is diverted to the waste reservoir and fresh cleaning fluid is added to the cleaning fluid reservoir. 
     As another example, the process may include using a camera to detect an initial fluorescence of the cleaning fluid. Then, after the cleaning fluid has been used for a period of about an hour, the camera again measures the fluorescence of the cleaning fluid. In embodiments in which the binder material includes a fluorescent dye, an increase in the fluorescence of the cleaning fluid can indicate the presence of binder material in the cleaning fluid. The camera transmits both the initial fluorescence and the subsequent fluorescence of the cleaning fluid to the control system  1000 , which then estimates an amount of contaminant in the cleaning fluid based on the change in fluorescence. When the estimated amount of contaminant is within a suitable range, the cleaning fluid recirculated through the cleaning fluid pathway. When the estimated amount of contaminant is moderate, water may be added to the cleaning fluid, or a portion of the cleaning fluid may be diverted to the waste reservoir by activating a three-way valve (described above) while new cleaning fluid is added to the cleaning fluid reservoir. Alternatively, when the estimated amount of contaminant is high, the entire volume of the cleaning fluid is diverted to the waste reservoir and fresh cleaning fluid is added to the cleaning fluid reservoir. 
     Although various embodiments are described herein with reference to measurement of a single physical property of the cleaning fluid, it is contemplated that in other embodiments, more than one physical property can be monitored and used to determine a cleaning fluid maintenance process to be performed. For example, both density and viscosity can be used to select a cleaning fluid maintenance process. By way of example, the control system  1000  may select a maintenance process that includes adding water to the cleaning fluid based on a change in the density of the cleaning fluid, but the control system  1000  may instead select a maintenance process that includes partial replacement of the cleaning fluid or replacement of the majority of the volume of the cleaning fluid when the density has decreased too much, indicating that the cleaning fluid may be becoming too diluted to function properly. In embodiments, the selection of the cleaning fluid maintenance process can be based on the viscosity, the surface tension, or both, of the cleaning fluid. 
     Control System 
     Referring now to  FIG. 10 ,  FIG. 10  schematically depicts a control system  1000  for controlling the components of the cleaning station and the binder and the cleaning fluid pathways. The control system  1000  is communicatively coupled to at least the print head, the pump  808 , the pump  820 , the active drain  826 , and the level sensor  828 . In embodiments, the control system  1000  may additionally be communicatively coupled to at least one additional sensor  1006 , such as a sensor for monitoring one or more physical properties of the cleaning fluid, as described in greater detail above, the actuators  602   a ,  602   b  coupled to the wet wipe member  310  and the dry wipe member  312 , and the actuator  706  coupled to the sponge support  704  or cap  710 . In the embodiments described herein, the control system  1000  comprises a processor  1002  communicatively coupled to a memory  1004 . The processor  1002  may include any processing component(s), such as a central processing unit or the like, configured to receive and execute computer readable and executable instructions stored in, for example, the memory  1004 . In the embodiments described herein, the processor  1002  of the control system  1000  is configured to provide control signals to (and thereby actuate) the print head  150 , the pump  808 , the pump  820 , and the active drain  826 . 
     In embodiments, the control system  1000  may be configured to receive signals from one or more sensors of the fluid management system and, based on these signals, actuate one or more of the print head  150 , the pump  808 , the pump  820 , the active drain  826 , or other valves, pumps, and drains that may be included in the fluid management system. In some embodiments, the control system  1000  may be configured to receive signals from one or more additional sensors in the additive manufacturing apparatus  100  and, based on these signals, actuate one or more of the actuators  602   a ,  602   b  coupled to the wet wipe member  310  and the dry wipe member  312 , and the actuator  706  coupled to the sponge support  704  or cap  710  to raise and/or lower the components of the cleaning station  110  for use. 
     In various embodiments, the control system  1000  is configured to receive signals from and send signals to one or more components described herein. Accordingly, the control system  1000 , in embodiments, can enable one or more of the functions described herein, including, without limitation, movement of any or all of the components of the cleaning station (e.g., the wet wipe member, the dry wipe member, the capping section, and the cleaning station vessel), adjustment of one more components described herein, monitoring the status of binder material and/or cleaning fluid described herein, monitoring performance of the additive manufacturing apparatus or any component thereof, measurements of various components, opening and closing of ports and valves, and the like. In embodiments, the control system  1000  is configured to control motion of the recoat head, the print head, and other components of the additive manufacturing device described herein. 
     Moreover, it is contemplated that, although control system  1000  is shown in  FIG. 10  as being a single computing device, the control system  1000  may be a distributed system that includes multiple computing devices interconnected to perform the functions herein. 
     In the embodiments described herein, the computer readable and executable instructions for controlling the additive manufacturing apparatus  100 , and particularly, the cleaning station  110  and the fluid management system, are stored in the memory  1004  of the control system  1000 . The memory  1004  is a non-transitory computer readable memory. The memory  1004  may be configured as, for example and without limitation, volatile and/or nonvolatile memory and, as such, may include random access memory (including SRAM, DRAM, and/or other types of random access memory), flash memory, registers, compact discs (CD), digital versatile discs (DVD), and/or other types of storage components. 
     Various methods have been described herein that may be executed by the control system  1000 . For example, the monitoring of the status of the cleaning fluid and the selection and implementation of a cleaning fluid maintenance process, the actuation of the wet wipe member, the dry wipe member, and the sponge, and the ejection of binder material from the print head may each be performed through execution of computer readable and executable instructions stored in the memory  1004  by the processor  1002 . It is contemplated that one or more of these functions may alternatively be performed by one or more additional computing devices, which may be communicatively coupled to the control system  1000 . For example, the monitoring of the status of the cleaning fluid and the selection and implementation of a cleaning fluid maintenance process may be performed from a computing device that is separate from, but communicatively coupled to, the control system  1000 . It is also contemplated that additional functions may be performed by the control system  1000  and/or additional computing devices communicatively coupled thereto. 
     For example, in some embodiments in which the binder material includes a fluorescent dye, as described above, the control system  1000  (or other computing device communicatively coupled thereto) may determine an amount of cure of the printed part (e.g., through storage and execution of computer readable and executable instructions). A UV camera, a visible or other detection system can be used to detect the fluorescence of the binder. 
     During the operation of a an additive manufacturing apparatus, it may be difficult to assess the quantity, geometric fidelity, and extent of cure of binder deposited into the powder bed. Powder soaked with binder often provides poor visual contrast for reliable optical observation of each layer or multiple layers of the green body part. However, the present embodiments address this problem by including in the binder composition one or more fluorescent photochromic dyes. After layerwise jetting deposition into the powder and any subsequent thermal treatment, the subsequent exposure of the binder-powder surface to UV or other electromagnetic radiation will cause the fluorescent dyes to emit light. 
     Based on the emitted light, a control system including a UV camera can be used to image each layer of the 3D print. Using the control system, the acquired image(s) at specified time(s) can be compared to the expected quantity of binder jetted and identify spatial defects including binder jet print head misfires, inaccurate binder quantity deposition (saturation), as well as insufficient binder cure. 
     In one embodiment, the control system can determine the presence of binder solvent increases the quantum yield of emitted light as compared to a solvent free sample. If there is solvent in the binder-powder layer, the control system can pinpoint locations where solvent has not been effectively removed. Improper solvent removal may thus indicate areas of incomplete curing. Alternatively, the control system may detect areas of low binder based on the emitted light. This could indicate the clogging of the print head. 
     After detecting these defects, the control system enables the operator of the apparatus to troubleshoot or perform diagnostic checks on the additive manufacturing device, for example, by checking the recoat head and/or print head for clogging issues. In one embodiment, the detection of a defect may trigger a pattern test to determine if one or more print head nozzles are clogged. 
     In one embodiment for monitoring the performance of an additive manufacturing device using a fluorescent binder, the method comprise exposing at least one layer comprising the fluorescent binder to electromagnetic radiation. The fluorescent binder includes fluorescent material which emits light in response to the electromagnetic radiation. Next, the method includes recording the emitted light intensity of the at least one layer after exposure, and computing a level of binder, solvent, or both within the layer by utilizing a control system which correlates the recorded emitted light intensity to the level of binder, solvent, or both in the layer versus time. Defects may be located in the layer when the recorded emitted light intensity deviates from expected emitted light intensity values, or when the level of binder, solvent or both deviates from expected levels. 
     Further aspects of the invention are provided by the subject matter of the following clauses: 
     1. A wet wiper apparatus comprising: a wet wiper body having a top side and a bottom side; a first wiper blade vertically extending from the top side of the wet wiper body; and a fluid channel horizontally extending from a first end of the wet wiper body to a second end of the wet wiper body, the fluid channel having an open top to allow fluid flow out of the fluid channel. 
     2. The wet wiper apparatus of any preceding clause, further comprising a second wiper blade vertically extending from the top side of the wet wiper body and spaced apart from the first wiper blade. 
     3. The wet wiper apparatus of any preceding clause, wherein the fluid channel is positioned between the first wiper blade and the second wiper blade. 
     4. The wet wiper apparatus of any preceding clause, wherein the first wiper blade and the second wiper blade extend from a first end of the wet wiper apparatus to a second end of the wet wiper apparatus. 
     5. The wet wiper apparatus of any preceding clause, further comprising a pair of walls extending between the first wiper blade and the second wiper blade from a base of the wet wiper apparatus to a top of each of the first wiper blade and the second wiper blade. 
     6. The wet wiper apparatus of any preceding clause, wherein fluid channel defines a recessed path within the wet wiper body. 
     7. The wet wiper apparatus of any preceding clause, further comprising a cleaning manifold extending below the fluid channel within the wet wiper body, wherein the cleaning manifold comprises a plurality of fluid ports configured to provide cleaning fluid to the fluid channel. 
     8. The wet wiper apparatus of any preceding clause, further comprising a plurality of cleaning fluid inlets operable to receive the cleaning fluid and provide the cleaning fluid to the cleaning manifold. 
     9. The wet wiper apparatus of any preceding clause, wherein the plurality of cleaning fluid inlets comprise fluid conduits extending vertically upward through the bottom side of the wet wiper body. 
     10. The wet wiper apparatus of any preceding clause, wherein the plurality of cleaning fluid inlets comprise fluid conduits extending from a side of the wet wiper body adjacent to the top side and the bottom side of the wet wiper body. 
     11. The wet wiper apparatus of any preceding clause, further comprising a cleaning manifold extending below the fluid channel within the wet wiper body, wherein the cleaning manifold comprises a fluid port extending from the first end of the wet wiper apparatus to the second end of the wet wiper apparatus configured to provide cleaning fluid to the fluid channel. 
     12. The wet wiper apparatus of any preceding clause, further comprising at least one motion coupler extending from the wet wiper apparatus and configured to couple the wet wiper apparatus to a cleaning station for vertical motion therein. 
     13. A wet wiper apparatus comprising: a wet wiper body having a top side and a bottom side; a wiper blade vertically extending from a top side of the wet wiper body; a manifold comprising at least one fluid port, the manifold being configured to deliver cleaning fluid to the top side of the wet wiper body; and cleaning fluid inlets extending through the wet wiper body, wherein the cleaning fluid inlets are in fluid communication with the at least one fluid port of the manifold. 
     14. The wet wiper apparatus of any preceding clause, wherein the wiper blade is a first wiper blade, and the wet wiper apparatus further comprises a second wiper blade vertically extending from a top side of the wet wiper body. 
     15. The wet wiper apparatus of any preceding clause, wherein the at least one fluid port is disposed between the first and second wiper blades along the wet wiper body. 
     16. The wet wiper apparatus of any preceding clause, further comprising a fluid channel formed in the wet wiper body and positioned between the first wiper blade and the second wiper blade, wherein the fluid channel is in fluid communication with the at least one fluid port of the manifold. 
     17. The wet wiper apparatus of any preceding clause, wherein the fluid channel comprises an open top to allow fluid flow out of the fluid channel. 
     18. The wet wiper apparatus of any preceding clause, wherein the cleaning fluid inlets extend vertically upward through the bottom side of the wet wiper body. 
     19. The wet wiper apparatus of any preceding clause, further comprising a pair of walls extending between the first wiper blade and the second wiper blade from the top side of the wet wiper apparatus to a top of each of the first wiper blade and the second wiper blade. 
     20. The wet wiper apparatus of any preceding clause, further comprising at least one motion coupler extending from the wet wiper apparatus and configured to couple the wet wiper apparatus to a cleaning station for vertical motion therein. 
     It will be apparent to those skilled in the art that various modifications and variations can be made to the embodiments described herein without departing from the spirit and scope of the claimed subject matter. Thus it is intended that the specification cover the modifications and variations of the various embodiments described herein provided such modification and variations come within the scope of the appended claims and their equivalents.