Patent Publication Number: US-2021162652-A1

Title: Apparatus and process of additive manufacturing using an extruder

Description:
BACKGROUND 
     Technical Field 
     Embodiments disclosed herein relate generally to three dimensional printers and methods for performing three dimensional printing. Three dimensional printers are used to print three dimensional objects by depositing successive layers of molten material, such that each layer has a desired shape and successive layers are arranged relative to each other in a desired manner. 
     Three dimensional printers receive solidified polymer material as an input. The polymer may be formed into an elongated string, which may be wound onto a spool and advanced into the three dimensional printer. Thus, the polymer may be required to be formed into a thread prior to being printed. This may add additional time, equipment, personnel, cost, and/or material to the overall printing process. 
     Three dimensional printers which do not receive an elongated string of material as an input may have pulses of material form therein. Pulses may comprise distinct volumes of material separated from each other by empty space. If pulsed material is output from a three dimensional printer, the quality and/or integrity of the three dimensional object which is printed may be reduced. In some cases, the printing process may have to be slowed to reduce pulses to an acceptable level. 
     Many three dimensional printers may also deposit material at a limited range of angles. The angles at which material may be deposited may be limited by the flow path of material through the three dimensional printer, because the flow path may have to be oriented in a particular manner for material to flow from an input end/element of the three dimensional printer to the output end/element of the three dimensional printer. Limiting the range of angles at which three dimensional printers may deposit material may limit the complexity and/or variety of three dimensional objects which may be printed and/or increase the time required to print three dimensional objects. 
     SUMMARY 
     This summary is provided to introduce a selection of concepts that are further described below in the detailed description. This summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to be used as an aid in limiting the scope of the claimed subject matter. 
     In one aspect, embodiments disclosed herein relate to a three dimensional printer which may include at least one feed chamber supplying a solidified material, an extruder configured to receive the solidified material from the at least one feed chamber and to process the solidified material into a molten phase, a melt pump configured to receive the molten phase from the extruder, and a printing head configured to receive the molten phase from the melt pump and to deposit the molten phase in successive layers to form a three-dimensional object. 
     In another aspect, embodiments disclosed herein relate to a method of performing three dimensional printing which may include the following steps: extruding polymer granulates to form a molten phase, pumping the molten phase of the polymer with a melt pump, and depositing the molten phase of the polymer in successive layers to form a three-dimensional object. 
     Other aspects and advantages of the claimed subject matter will be apparent from the following description and the appended claims. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1 a    is a schematic view of a three dimensional printer in accordance with the present disclosure. 
         FIG. 1 b    is a schematic view of a three dimensional printer in accordance with the present disclosure. 
         FIG. 2  is a schematic view of a three dimensional printer in accordance with the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments of the present disclosure relate to a three dimensional printer and to methods of performing three dimensional printing. A three dimensional printer according to embodiments of the present disclosure may receive a solidified material, process the solidified material into a molten phase, and deposit the molten phase in successive layers to form a three dimensional object. A method according to the present disclosure may involve processing a solidified material to form a molten phase and depositing the molten phase in successive layers to form a three dimensional object. Embodiments of the present disclosure may allow a three dimensional printer to receive polymer granulate and may allow polymer granulate to be formed into three dimensional objects, which may present advantages compared to previous three dimensional printers and methods of three dimensional printing. In particular, embodiments of the present disclosure relate to the regulation or control of the flow of the molten phase to a print head, to allow for a more uniform flow of material to be printed. 
     In one aspect, embodiments of the present disclosure relate to a three dimensional printer. The three dimensional printer may be configured to process polymer granulate to form a three dimensional object. 
       FIGS. 1 a -1 b    illustrates a three dimensional printer  100 . The three dimensional printer  100  may include a feed chamber  102 , an extruder  104 , a melt pump  106 , and a printing head  108 . The three dimensional printer  100  may have a flowpath such that material received by the feed chamber  102  may flow through the feed chamber  102 , the extruder  104 , the melt pump  106 , and the printing head  108  in succession. The material may exit the three dimensional printer  100  through the printing head  108 . 
     The material may be a polymer. When the material is received by the feed chamber  102 , the material may be in the form of solidified granulate. In some embodiments, the granulate may include powders or pellets having a size typical for injection molding. A size and shape of the granulate may be chosen based on the production rate, screw diameter, screw length, and screw design of the three dimensional printer. The size of the pellets may be determined based on properties of the polymer (such as melting properties), dimensions of the printer, and/or other considerations. 
     The feed chamber  102  may be of any type and arrangement suitable to feed solidified material into the printer. In some embodiments, the feed chamber  102  may include a first chamber  110  and a second chamber  112 , which may be connected by a flowline  114 . The use of two chambers may allow for flexibility in the movement of printer along the x-, y-, and z-axes, or as a moveable arm having six degrees of freedom. However, it is also envisioned that in some embodiments, where the printer does not have six degrees of freedom, a single chamber may suffice. 
     As illustrated, the first chamber  110  may be configured to receive polymer granulate from an external source. The external source may be manual, automatic, or some combination of manual and automatic. For example, a human operator may pour granulate into the first feed chamber  110  or granulate may be automatically conveyed to the first chamber  110  from a storage vessel (not shown). In some embodiments, the first chamber  110  may have a funnel shape, which may promote the movement of granulate to the bottom of the first chamber  110 . 
     A first end of the flowline  114  may be connected to the bottom of the first chamber  110 , such that granulate may flow from the first chamber  110  into the flowline  114 . A second end of the flowline  114  may be connected to the top of the second chamber  112 , such that granulate may flow from the flowline  114  into the second chamber  112 . In some embodiments, the flowline  114  may be a flexible hose. In some embodiments, the three dimensional printer  100  may be configured such that granulate may only flow through the flowline  114  from the first chamber  110  to the second chamber  112 , and may not flow in the opposite direction, i.e. from the second chamber  112  to the first chamber  110 . 
     The second chamber  112  may receive granulate from the flowline  114 . The three dimensional printer  100  may be controlled to maintain a level of granulate in the second chamber  112 , such that the second chamber  112  is full or nearly full of granulate whenever the three dimensional printer  100  is operating. In some embodiments, the second chamber  112  may have a funnel shape. 
     A control valve  116  may be disposed between the first chamber  110  and the second chamber  112  and may be disposed along the flowline  114 . The control valve  116  may be a metering valve. The control valve  116  may be configured to prevent a flow of granulate through the flowline  114  or permit a flow of pellets through the flowline  114 . In some embodiments, the control valve  116  may be able to be configured to permit flow of granulate through the flowline  114  at various rates. In some embodiments, the control valve may prevent any flow of granulate through the flowline  114  from the second chamber  112  to the first chamber  110 . 
     As described above, granulate may flow from the flow chamber  102  into the extruder  104 . The second chamber  112  of the flow chamber  102  may be connected to the extruder  104 , proximate a first end  126  of the extruder  104 , such that granulate may flow out of the second chamber  112  and into extruder  104 . 
     The extruder  104  may be heated, such that granulate in the extruder  104  may be transformed from a solid phase into a molten phase. In some embodiments, the extruder  104  may include a heating element  118 . In some embodiments, the granulate  104  may also or instead be heated by shear heating from the extrusion screw or an external heat source (not shown). The extruder  104  may be heated such that the molten phase material therein may be maintained at a constant temperature, or at a desired temperature gradient along the length of the extruder  104 . 
     The extruder may include a screw  120  and a housing  122 . The screw  120  may be disposed within the housing  120  such that an annular space  124  is formed within the housing  120  around the screw  122 . Once transformed from solid to molten material, molten phase material within the extruder  104  may occupy the annular space  124 . The extruder  104  may be configured such that rotating the screw  122  within the housing  120  moves the molten phase material from the first end  126  of the extruder  104  towards a second end  128  of the extruder  104 . A rate of rotation of the screw  122  and a size of the annular space  124 , specifically an inner diameter and an outer diameter of the annular space  124 , may determine a rate of flow of the molten phase material through the extruder  104 . 
     In some embodiments, the extruder  104  may be any type of extruder known in the art and molten phase material may be flowed through the extruder  104  by any means known in the art. 
     As described above, molten phase material may flow from the extruder  104  into a melt pump  106 . The second end  128  of the extruder may be connected to an inlet  130  of the melt pump  106 , such that molten phase material may flow from the extruder  104  into the melt pump  106 . 
     In some embodiments, the melt pump  106  may be an external gear pump. The melt pump  106  may include a housing  132  and one or more gears  134 ,  136 . In some embodiments, as shown in  FIGS. 1 a -1 b   , the melt pump  106  may include two gears  134 ,  136 . A flowpath  138  from the inlet  130  to an outlet  140  may be formed through the melt pump  106 , such that the flowpath  138  includes a space between the gears  134 ,  136 . 
     The melt pump  106  may be configured such that molten phase material flows along the flowpath  138 . Rotation of the gears  134 ,  136  may flow the molten phase material from the inlet  130  to the outlet  140  along the flowpath  138 . The molten phase material may flow between the gears  134 ,  136  as the molten phase material flows along the flowpath  138 . Any gap formed between the gears  134 ,  136  and the housing  132  may be small enough that the molten phase material does not flow between the gears  134 ,  136  and the housing  132 . The rate of rotation of the gears  134 ,  136  and the diameter of the flowpath  138  may determine the flow rate of molten phase material through the melt pump  106 . It is observed that molten material exiting an extruder may experience a pulsed flow. The incorporation of melt pump  106  may mitigate such pulsing that occurs so that the flow of molten material exiting the melt pump  106  is more uniform than the flow coming into the melt pump  106 . 
     Flow rate sensors  144 ,  146  may be disposed proximate the inlet  130  and/or the outlet  140  of the melt pump  106 . The flow rate sensors  144 ,  146  may measure a rate of flow of molten phase material into and out of the melt pump  106 . In some embodiments, the flow rate sensors  144 ,  146  may be part of a control system, which may command rates of rotation of the screw  122  of the extruder  104  and the gears  134 ,  136  of the melt pump  106 . In some embodiments, data from the flow rate sensors  144 ,  146  may be displayed to a human operator and/or used for quality control. 
     The three dimensional printer  100  may be configured such that material disposed in the melt pump  106  may be maintained in a molten phase. In some embodiments, the melt pump  106  may comprise a heating element (not shown). In some embodiments, the melt pump  106  may be heated by an external heat source (not shown). If the extruder  104  is heated by an external heat source, the external heat source which heats the melt pump  106  may or may not be the same external heat source as that heating the extruder  104 . In some embodiments, the melt pump  106  may not be heated, but the three dimensional printer  100  may be configured such that material disposed therein maintains heat which was transferred to the material while the material was in the extruder  104 , such that the material remains in a molten phase in the melt pump  106 . In such embodiments, the melt pump  106  may be insulated and/or have a relatively small size. 
     As described above, molten phase material may flow from the melt pump  106  and into a printing head  108 . The printing head  108  may be connected to the outlet  140  of the melt pump  106 , such that molten phase material flows out of the melt pump  106  and into the printing head  108 . 
     The printing head  108  may include a tip  142 , through which molten phase material may exit the three dimensional printer  100 . In one or more embodiments, the tip  142  may be configured such that molten phase material which flows through the tip  142  is formed into a string having a particular diameter and a particular shape. The string of molten phase material may be deposited onto a substrate or onto a layer of material previously deposited by the printer. The string of molten phase material may be deposited to form a portion of a three dimensional object. 
     The three dimensional printer  100  may be configured such that material disposed in the printing head  108  may be maintained in a molten phase. In some embodiments, the printing head  108  may comprise a heating element (not shown). In some embodiments, the printing head  108  may be heated by an external heat source (not shown). If the extruder  104  and/or the melt pump  106  is heated by an external heat source, the external heat source which heats the printing head  108  may or may not be the same external heat source as that heating the extruder  104  and/or the melt pump  106 . In some embodiments, the printing head  108  may not be heated, but the three dimensional printer  100  may be configured such that material disposed therein maintains heat which was transferred to the material while the material was in the extruder  104  and/or the melt pump  106 , such that the material remains in a molten phase in the melt pump  106 . In such embodiments, the printing head  108  may be insulated and/or have a relatively small size. 
     The three dimensional printer  100  may be configured such that molten phase material may be output or may not be output from the printing head  108  when the printing head is in operation. For example, material may be required at both a first location and a second location, but not between the locations, to form a desired three dimensional printed object. The printing head  108  may be moved from the first location to the second location and may not output molten phase material during that movement. The three dimensional printer  100  may include a mechanism which may prevent a flow of molten phase material from exiting the printing head  108  when desired. In some embodiments, such a mechanism may comprise preventing the rotation of the gears  134 ,  136  of the melt pump  106 . 
     As mentioned above, the three dimensional printer  100  may be configured to compensate for pulses of molten phase material which flow out of the extruder  104 . Pulses may comprise distinct volumes of molten phase material which may be separated from each other by empty space. It may be desired to not output the molten material from the printing head  108  as pulses, as doing so may leave gaps in the layers of a three dimensional object which may be printed or non-uniform deposits. 
     The melt pump  106  may process the molten phase material so that the molten material does not enter the printing head  108  in pulses. The melt pump  106  may control the rate of flow of molten phase material therethrough by controlling a rate of rotation of the gears  134 ,  136 . The extruder  104  may control the rate of flow of molten phase material therethrough by controlling a rate of rotation of the screw  122 . The screw  122  and the gears  134 ,  136  may be independently controllable, such that the extruder  104  and the melt pump  106  may have the same flow rate or different flow rates of molten phase material therethrough. 
     The rates of rotation of the screw  122  and the gears  134 ,  136  may be chosen such that the flow rate of the molten phase material through the melt pump  106  is slower than the flow rate of the molten phase material through the extruder  104 . Molten phase material may accumulate ahead of the inlet  130  of the melt pump  106  while the extruder  104  is outputting a pulse of molten phase material. In the time in between two pulses, during which the extruder  104  is not outputting molten phase material, the accumulated molten phase material may flow through the melt pump  106 . In this way, the melt pump  106  may output a continuous stream of molten phase material. 
     Because of the structure and control described above, the three dimensional printer  100  may be able to output a continuous stream of molten phase material while receiving solidified material in the form of polymer pellets. Thus, the three dimensional printer  100  may be able to print a three dimensional object from polymer pellets. The three dimensional printer  100  may not require a strand of plastic thread as an input. 
     As shown in  FIG. 1 b   , the three dimensional printer  100  may be disposed on an arm  150 , which may or may not be a robotic arm. Specifically, in some embodiments, the second chamber  112  of the feed chamber  102 , the extruder  104 , the melt pump  106 , and the printing head  108  may be disposed on the arm  150 . The first chamber  110  of the feed chamber  102  may be disposed in a fixed position. The flowline  114  may connect the first chamber  110  to the second chamber  112  as described above. The flowline  114  may have sufficient length and flexibility to accommodate movement of the second chamber  112  on the arm  150  relative to the fixed first chamber  110 . In some embodiments, the first chamber  110  may be fixed at a sufficient height that pellets from the first chamber may flow downward to the second chamber  112  when the arm  150  is in any configuration. 
     As described above, the three dimensional printer  100  may include a control valve  116  which may function to maintain a level of pellets in the second chamber  112 . The level of pellets in the second chamber  112  may be maintained such that the second chamber  112  is full or nearly full whenever the three dimensional printer  100  is in operation. In this way, pellets may flow from the second chamber  112  to the extruder  104  when the arm  150  is in any configuration. For example, the arm  150  may be oriented such that the extruder  104  is above the second chamber  112  and pellets may flow from the second chamber  112  to the extruder  104  in such a configuration. In this way, the orientations/positions in which the three dimensional printer  100  is capable of printing may not be limited by considerations about the flow of pellets. This may increase the variety and/or complexity of three dimensional objects which may be printed by the three dimensional printer  100  and may decrease the number and/or complexity of printer motions needed to print three dimensional objects. 
     The printing head  108  may be disposed proximate an end of the arm  150 . The printing head  108  may be positioned such that molten phase material which flows out of the printing head  108  may be deposited onto a substrate or onto a layer of printed material. The arm  150  may be capable of positioning the printing head  108  in a range of positions and orientations. The printing head  108  may be configured such that molten phase material may exit the printing head  108  and be deposited onto the substrate or printed material in a desired manner when the printing head  108  is oriented at any angle. This may increase the variety and/or complexity of three dimensional objects which may be printed by the three dimensional printer  100  and may decrease the number and/or complexity of printer motions needed to print three dimensional objects. 
       FIG. 2  illustrates a three dimensional printer  200 . The three dimensional printer  200  may include a feed chamber  202 , an extruder  204 , a melt pump  206 , and an actuated printing head  258 . The three dimensional printer  200  may have a flowpath such that material received by the feed chamber  202  may flow through the feed chamber  202 , the extruder  204 , the melt pump  206 , and the actuated printing head  258  in succession. The material may exit the three dimensional printer  200  through the actuated printing head  258 . The feed chamber  202 , the extruder  204 , and the melt pump  206  may be similar to the features described above with respect to  FIGS. 1 a   - 1   b.    
     The actuated printing head  258  may include a discharge channel  260 , an actuator  262 , a needle  264 , and an outlet  266 . The needle  264  may be actuated by the actuator  266 . The needle  264  may move through the discharge channel  260  in a direction transverse to the discharge channel  260  and through the outlet  266 . 
     The discharge channel  260  may be connected to the melt pump  206 . Molten phase material may pass from the melt pump  206  into the discharge channel  260 . When the needle  264  is actuated, the actuated printing head  258  may discharge a droplet of molten phase material from through the outlet  266 . Thus, in such embodiment, the molten phase material may be deposited as discrete droplets onto a substrate or onto a previously deposited layer of printed material, rather than as a string of material. 
     The three dimensional printer  200  may receive solidified polymer granulate as an input material. The three dimensional printer  200 , including the melt pump  206 , may function to compensate for pulses as described above, such that a continuous stream of material is available to be output from the actuated printing head  258  through the outlet  266  as droplets. The three dimensional printer  200  may be disposed on an arm (not shown) as illustrated with respect to the three dimensional printer  100  described above with respect to  FIG. 1 b   . The three dimensional printer  200  may provide the same or similar advantages to those discussed above with respect to the three dimensional printer  100  shown in  FIGS. 1 a   - 1   b.    
     One skilled in the art will recognize that a three dimensional printer in accordance with the present disclosure may have any type of printing head known in the art. The three dimensional printer may further deposit molten phase material in any manner known in the art. Such a three dimensional printer may be configured to receive polymer pellets and to compensate for pulses in molten phase material output by an extruder of the three dimensional printer. 
     In another aspect, embodiments of the present disclosure relate to a method of performing three dimensional printing. A method in accordance with the present disclosure may be performed using any embodiments of the three dimensional printer described above, or any other means known in the art. For example, the method may be performed using a three dimensional printer having a combination of features described above with respect to different embodiments, or with a three dimensional printer which is not described above. 
     A method of performing three dimensional printing may include the steps described below. In some embodiments, the method may include a subset of the described steps and/or may include additional steps not described below. The steps included in a particular embodiment of the method may depend in part on the equipment with which the method is performed. 
     A solidified material may be processed to form a molten phase material. The processing may include at least heating the solidified material. In some embodiments, the processing may comprise extruding the material. Extruding the material may transform a solidified material into a molten material that may be subsequently deposited (printed). 
     The solidified material may be a polymer, for example, acrylonitrile-butadiene-styrene (ABS), poly(lactic acid) (PLA), polycarbonate (PC), polystyrene (PS), high impact polystyrene (HIPS), polycaprolactone (PCL), polyamide, polyolefins (including homopolymers or copolymers), or any other polymer known in the art. The polymer may be chosen based on desired characteristics of the object which is being printed using the method. The solidified polymer may have the form of granulates. The pellets may or may not be uniform. In some embodiments, the granulates may have a spherical, cylindrical, ellipsoid, or polygonal shape. In some embodiments, the granulate may be standard pellets which are known in the art and produced for applications other than three dimensional printing. 
     Extruding the material may cause pulses of material to form. Pulses may comprise distinct volumes of material separated by empty space. The pulses may be uniform or non-uniform. In some embodiments, the extruding may be performed in a manner to reduce the formation of pulses and/or to increase the volume of each pulse and to decrease the empty space formed between pulses. In some embodiments, the extruding may be performed such that the pulses are controlled in a desired manner. 
     The molten phase material, which may be formed by the processing described above, may be pumped with a melt pump. Pumping the material may comprise reducing or eliminating pulsing of the material which may be caused by the extruding. Pumping may be performed such that molten phase material flows out of the pump continuously while printing is being performed. Gaps may not be formed in the material which is pumped out of the melt pump. In some embodiments, pumping may be performed by any apparatus known in the art, which may or may not be a melt pump. 
     The molten phase material which flows out of the melt pump may be deposited in successive layers. A first layer may be deposited onto a substrate, and successive layers may be deposited onto previously deposited layers. Each layer of molten phase material may partially or fully solidify prior to the deposition of the next layer of molten phase material. The molten phase material may form a three dimensional object. 
     In some embodiments, the molten phase material may be deposited in extended strings. One or more extended strings may make up each deposited layer. Extended strings may be straight, curved, angled, or may include a combination of straight, curved, and/or angled portions. In such embodiments, the melt pump discussed above may be controlled to pump out molten phase material whenever a string is being formed. 
     In some embodiments, the molten phase material may be deposited in droplets. One or more droplets may make up each deposited layer. Droplets in a single layer may be deposited at a distance from each other or touching each other, such that a successive layer of droplets may be deposited on top of the layer. In such embodiments, material which has been pumped by the melt pump discussed above may be output whenever a droplet is being formed. 
     In some embodiments, the molten phase material may be deposited at any angle. For example, a tip/head through which the molten phase material is deposited onto the substrate may be oriented at any angle relative to the substrate while the material is flowing out of the tip/head. Orienting the tip/head may comprise orienting an arm to which the tip/head is attached. In some embodiments, other components used in the three dimensional printing method may be attached to the arm as well. 
     In come embodiments, flow rates of materials used in the method may be controlled. The flow rate of pellets into the extruder may be controlled. The extrusion rate/flow rate of material through the extruder as it is being processed from solid phase to molten phase may be controlled, for example, by controlling the rate of rotation of a screw in the extruder. The flow rate of material through the melt pump may be controlled, for example, by controlling the rate of rotation of one or more gears in the melt pump. The flow rate of the material onto the substrate may be controlled. 
     The flow rates discussed above may be controlled using any means known in the art. For example, a flow rate sensor may measure a flow rate, a processor and/or a human operator may compare the measured flow rate to a desired value, and a valve may throttle the amount of material flowing into the equipment based on the comparison. In some embodiments, the flow rate may be measured indirectly. Flow rate sensors, valves, processors, and any other equipment used to control flow rates of the material may or may not be part of a wired or a wireless network. The network may be any type of network known in the art. 
     The devices and methods disclosed herein may present advantages over previously used devices and methods for three dimensional printing. Polymer granulates may be used as an input for the three dimensional printer and/or method of the present disclosure. This may eliminate the need to form the polymer into an elongated filament prior to printing, and may thereby reduce the time, equipment, and cost necessary to print, and/or allow materials which previously could not be used for three dimensional printing to be printed. Pulses of material may be reduced or eliminated from the material which is deposited to form a three dimensional object. This may improve the quality of the printed object, reduce the need to reprint objects, and/or increase the rate at which objects may be printed. 
     Although only a few example embodiments have been described in detail above, those skilled in the art will readily appreciate that many modifications are possible in the example embodiments without materially departing from this invention. Accordingly, all such modifications are intended to be included within the scope of this disclosure as defined in the following claims. In the claims, means-plus-function clauses are intended to cover the structures described herein as performing the recited function and not only structural equivalents, but also equivalent structures. Thus, although a nail and a screw may not be structural equivalents in that a nail employs a cylindrical surface to secure wooden parts together, whereas a screw employs a helical surface, in the environment of fastening wooden parts, a nail and a screw may be equivalent structures. It is the express intention of the applicant not to invoke 35 U.S.C. § 112, paragraph 6 for any limitations of any of the claims herein, except for those in which the claim expressly uses the words ‘means for’ together with an associated function.