Abstract:
A method of manufacturing a three-dimensional object facilitates removal of the three-dimensional object from the platen on which the object was formed. The method includes rotating the platen from a horizontally level position to a position at an angle to the level position to enable gravity to urge the three-dimensional object away from the platen and inductively heating the platen to melt support material at the boundary of the object and the platen to release the three-dimensional object from the platen.

Description:
TECHNICAL FIELD 
       [0001]    The device and method disclosed in this document relates to three-dimensional object printing and, more particularly, to removal of a three-dimensional object from a platen on which the object was formed. 
       BACKGROUND 
       [0002]    Digital three-dimensional manufacturing, also known as digital additive manufacturing, is a process of making a three-dimensional solid object of virtually any shape from a digital model. Three-dimensional printing is an additive process in which one or more printheads or ejector heads eject successive layers of material on a substrate in different shapes. The substrate is supported either on a platform that can be moved three dimensionally by operation of actuators operatively connected to the platform, or the printhead or printheads are operatively connected to one or more actuators for controlled movement of the printhead or printheads to produce the layers that form the object. Three-dimensional printing is distinguishable from traditional object-forming techniques, which mostly rely on the removal of material from a work piece by a subtractive process, such as cutting or drilling. 
         [0003]    Manufacturing of three-dimensional printed parts at high speed is a significant challenge because many of the processes involved are time consuming and often done manually. Automation has provided for higher speed and more efficient processing of three-dimensional printed parts. One area of concern relates to removal of the three-dimensional printed part from the build platen. Often the three-dimensional printed part sticks to the build platen and can be challenging to remove. Current methods for part removal include heating, impacting, scraping, and freezing. These methods are generally cumbersome, time consuming, and risk damaging the part or the build platen. What is needed is a method for removing a three-dimensional printed part from a build platen that is fast, reliable, and easily automated. 
       SUMMARY 
       [0004]    A method of manufacturing a three-dimensional object facilitates the removal of objects from a platen. The method includes operating ejectors with a controller with reference to digital image data of a three-dimensional object to eject drops of material towards a platen and form a plurality of layers that produce the three-dimensional object on the platen, rotating the platen from a first position that is horizontally level to a second position that enables gravity to urge the three-dimensional object off of the platen, and operating an inductive heater to heat the platen and release the three-dimensional object from the platen. 
         [0005]    A printer for manufacturing a three-dimensional object includes a plurality of ejectors configured to eject drops of material, a platen positioned opposite the plurality of ejectors, the platen being oriented at a first position that is horizontally level, an inductive heater positioned to heat the platen, and a controller operatively connected to the platen, inductive heater and the plurality of ejectors. The controller is configured to operate the plurality of ejectors to eject the drops of material towards the platen and form layers of material with reference to digital image data of the three-dimensional object to produce the three-dimensional object on the platen, rotate the platen to a second position that enables gravity to urge the three-dimensional object off of the platen, and operate the inductive heater to heat the platen and release the three-dimensional object from the platen. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]    The foregoing aspects and other features of method and printer are explained in the following description, taken in connection with the accompanying drawings. 
           [0007]      FIG. 1  shows a three-dimensional object printer configured for automated part removal. 
           [0008]      FIG. 2  shows the printer of  FIG. 1  with the platen rotated to a position that facilitates removal of objects formed on the platen. 
           [0009]      FIG. 3  shows a method for operating the printer of  FIG. 1  to release a printed part. 
           [0010]      FIG. 4  shows a wax base that is formed to support formation of an object on the platen of the printer shown in  FIG. 1 . 
           [0011]      FIG. 5  shows an alternative embodiment of the three-dimensional object printer that rotates the platen as it moves along a track. 
           [0012]      FIG. 6  depicts a change in the track along which the platen moves to enable the platen to rotate to a position to discharge an object. 
           [0013]      FIG. 7  shows an alternative embodiment of the three-dimensional object printer that inverts the platen as it moves along a track. 
       
    
    
     DETAILED DESCRIPTION 
       [0014]    For a general understanding of the environment for the method and printer disclosed herein as well as the details for the method and printer, reference is made to the drawings. In the drawings, like reference numerals designate like elements. 
         [0015]      FIG. 1  shows a three-dimensional object printer  100  configured for automated part removal. The printer  100  includes a platen  104 , an ejector head  108 , an actuator  116 , an inductive heater  124 , a sensor  122 , a controller  120 , a wiper  130 , and an actuator  134 . The ejector head  108  has a plurality of ejectors configured to eject material onto a surface  112  of the platen  104 . The printer  100  also includes an actuator  116 , which is operatively connected to the platen  104  to rotate the platen from the horizontally level position shown in  FIG. 1  to the position shown in  FIG. 2 . The printer  100  further includes a controller  120  operatively connected to the ejector head  108 , the actuator  116 , the inductive heater  124 , and the sensor  128 . The controller  120  is configured to operate the ejectors in the ejector head  108  with reference to digital image data of a three-dimensional object to form layers of material and produce a three-dimensional object  138  on the platen  104 . The controller is also configured to operate the actuator  116  to rotate the platen to the second position where gravity urges the object towards the edge at which the sensor  122  is positioned and to operate the inductive heater  124  to melt support material adhering to the platen so the object slides towards the edge of the platen. While the heater  124  is shown connected to the platen, it need only be positioned sufficiently close to the platen to heat the platen to the appropriate temperature to release the object and need not be connected to the platen. Once the controller  120  receives a signal from the sensor that indicates the object has been removed from the platen, the controller operates the actuator  116  to return the platen to the horizontal level position for the production of the next object. As used in this document, “horizontally” means a direction that is parallel to the surface  112  of the platen  104  in  FIG. 1  and parallel to a face of the ejector head  108 . 
         [0016]    The position of the platen  104  is depicted as being at a forty-five degree angle to the horizontally level position of  FIG. 1 . In one embodiment, this angle is the minimum angle at which gravity sufficiently induces the object  138  to move once the inductive heater has melted the material adhering to the platen; however, the angle at which gravity begins to urge movement of an object can be more or less depending upon the platen surface treatment and object support material. The angle of rotation can be up to one hundred and eighty degrees, if the object is to be dropped onto another surface, such as a conveyor as explained below. In embodiments in which the object is to slide onto another surface the orientation can be limited to some angle that is less than one hundred and eighty degrees, depending again on the platen surface treatment and object support material. The platen  104  needs to be made of a ferromagnetic material to ensure that the inductive heater  124  produces heat in the platen  104 . Because the fluctuating fields generated by the inductive heater do not interact with the object  138 , the temperature of the object does not change so the integrity of the object remains intact. The controller  120  is configured to operate the inductive heater for a period of time that ensures the platen reaches a temperature of at least sixty degrees Celsius, which is the melting temperature for the most commonly used support material, namely, paraffin wax. 
         [0017]    The printer shown in  FIG. 1  and  FIG. 2  also includes a wiper  130  that is operatively connected to an actuator  134 . The controller  120  is also connected to the actuator  134  to enable the controller to operate the actuator and move the wiper  130  across the surface  112  of the platen  104  when the platen is in the position shown in  FIG. 2 . The controller  120  operates the actuator  134  to move the wiper in response to the sensor  122  generating a signal indicative of the object sliding off the platen and past the sensor  122 . The sensor  122  can be, for example, an optical sensor that generates a light beam at the edge of the platen  104  and detects the absence of the beam at a receiver as the object moves between the light generator and the receiver. Other sensors can be used, such as, a mechanical sensor that generates a signal to the controller in response to the object moving a mechanical arm. 
         [0018]    An alternative embodiment of a three-dimensional object printer that rotates the platen through the movement of the platen along a track is shown in  FIG. 5 . In this figure, like reference numbers refer to like components in the embodiment of  FIG. 1 . The platen  104  is configured to move along a track  110 . The platen  104  moves underneath the ejector head  108  to enable the formation of one or more layers of an object. The platen can move along the track  110  to enable the top layer of the object to be planerized, UV material cured, or the object to be imaged and the image data analyzed to verify proper formation of the object. A switch in the track is configured to enable the track  110  either to return the platen to the ejector  108  for the formation of additional layers or it can divert the platen to the object discharge area  150 . In discharge area  150 , the configuration of the track  110  changes to tilt the platen  104  as shown in  FIG. 6 . As shown in that figure, rails  156  and  158  are configured with a U-shape to hold the wheels  160  of the platen  104 . Rail  156  changes elevation while rail  158  turns to enable the platen to rotate at an angle to the horizontal position of the platen. In this position, the part  138  is urged by gravity toward the edge of the platen closest to rail  156 . Alternatively, as shown in  FIG. 7 , both rails can change elevation in opposite directions to turn the platen over and drop the object. 
         [0019]    With continued reference to  FIG. 5 , as the platen travels through the discharge area  150 , the track enables the platen  104  to rotate and the controller  120  operates the inductive heaters  124  to heat the platen and raise its temperature to a level that enables the part  138  to be released from the platen. The sensor  122 , which is positioned at the edge from which the part falls away, generates a signal that enables the departure of the part  138  from the platen  104  to be detected. The platen  104  continues to move along the track  110  past the wiper  130  that extends across the path of the track  110 . As the platen passes the wiper  130 , the wiper removes residual material from the platen surface. A receptacle can be positioned beneath the wiper  130  to receive the falling debris cleared from the platen  104  by the wiper  130 . The platen  104  continues on the track  110  and returns to the ejector head  108  for production of another part. 
         [0020]    In the embodiment shown in  FIG. 7 , three platens  104  are shown moving along the track  110 . Again the platens  104  are configured with wheels  160  for movement along the track. The middle platen has entered an area where the rails  156 ,  158  of the track  110  are configured to rotate the platen ninety degrees as shown in the figure. The rails  156 ,  158  to right of that position are configured to further rotate the platen  104  another ninety degrees to invert the platen when it reaches the position of the rightmost platen as shown in the figure. Once the platen is inverted, the controller  120  operates the heaters  124  to heat the platen  104  to a temperature that releases the part  138  from the platen  104  so it falls under the effect of gravity onto a conveyor  170 . The conveyor  170  can carry the part to another processing area or it can drop the parts into a receptacle located at the end of the conveyor. A wiper  130  is positioned to remove residual material from the platen as the inverted platen passes the wiper. The platen  104  then passes through another section of the track  110  that returns the platen to the un-inverted position and the platen can be routed to the ejector head for production of another part. 
         [0021]    A method  300  for operating the printer  100  to automatically remove printed parts from the platen  104  is shown in  FIG. 3 . In the description of the method, statements that the method is performing some task or function refers to a controller or general purpose processor executing programmed instructions stored in non-transitory computer readable storage media operatively connected to the controller or processor to manipulate data or to operate one or more components in the printer to perform the task or function. The controller  120  noted above can be such a controller or processor. Alternatively, the controller can be implemented with more than one processor and associated circuitry and components, each of which is configured to form one or more tasks or functions described herein. 
         [0022]    When the method  300  is performed, it begins with the controller  120  operating ejectors in the ejector head  108  to eject drops of material and form layers of material with reference to digital image data of a three-dimensional object to produce the object on the platen (block  304 ). In one embodiment, the controller  120  operates a first plurality of ejectors of the ejector head  108  to eject material onto the surface  112  of the platen  104  to form one or more parts on the platen. In another embodiment, the controller  120  first operates a second plurality of ejectors of the ejector head  108  to eject wax onto the surface  112  of the platen  104  to form a wax base  304 , as shown in  FIG. 4 . After forming the wax base  304 , the controller  120  operates the first plurality of ejectors of the ejector head  108  to eject material onto the wax base  304  to form the object  138 . Once the part has been produced, the cart is tilted to rotate the platen to the second position where gravity urges the object towards the edge at which the sensor  128  is positioned (block  308 ). As the platen rotates, the controller connects the inductive heater  124  to an electrical power source to operate the heater and melt support material adhering to the platen so the object slides towards the edge of the platen or drops from the platen (block  312 ). Once the controller  120  receives a signal from the sensor that indicates the object has been removed from the platen, the cart rotates to return the platen to the horizontal level position for the production of the next object (block  316 ). 
         [0023]    It will be appreciated that variants of the above-disclosed and other features and functions, or alternatives thereof, may be desirably combined into many other different systems, applications or methods. Various presently unforeseen or unanticipated alternatives, modifications, variations, or improvements therein may be subsequently made by those skilled in the art, which are also intended to be encompassed by the following claims.