Layer orientation control for pixel-based additive manufacturing

Abstract

A method of making a workpiece in an additive manufacturing process includes determining a preferred angular orientation of the grid array about a build axis extending perpendicular to a layer to be built for a first layer of a workpiece. The preferred angular orientation is selected to align an edge of one or more pixels with an edge of the layer of the workpiece being built. The method further includes orienting a patterned image of radiant energy to the preferred angular orientation by rotating a projector before solidifying a portion of a resin that forms the first layer of the workpiece.

1 - 20 . (canceled) 
     
     
         21 . An apparatus for making a workpiece, comprising:
 a platform movable along a build axis;   a projector operable to project a patterned image of radiant energy comprising rows and columns of pixels along a surface of a resin; and   an actuator configured to change a relative angular orientation of the platform and the projector about the build axis from a nominal orientation for a first layer of the workpiece to an off-nominal orientation for a second layer of the workpiece.   
     
     
         22 . The apparatus of  claim 21 , wherein the platform is moved downward along the build axis between the first layer and the second layer. 
     
     
         23 . The apparatus of  claim 21 , wherein the projector comprises:
 a radiant energy source; and   an image forming apparatus.   
     
     
         24 . The apparatus of  claim 23 , wherein the radiant energy source comprises an ultraviolet flash lamp. 
     
     
         25 . The apparatus of  claim 21 , wherein the actuator is positioned above the projector along the build axis. 
     
     
         26 . The apparatus of  claim 21 , wherein the relative angular orientation of the first layer and the second layer are selected based on a surface quality of the workpiece along the build axis. 
     
     
         27 . The apparatus of  claim 21 , further comprising:
 a controller operably coupled with the projector and the actuator, the controller configured to determine the relative angular orientation of the platform and the projector about the build axis from the nominal orientation.   
     
     
         28 . The apparatus of  claim 21 , wherein the rows and the columns of the pixels projected from the projector are rotated as the relative angular orientation of the platform and the projector about the build axis is moved from the nominal orientation to the off-nominal orientation. 
     
     
         29 . An apparatus for making a workpiece, comprising:
 a platform movable along a build axis;   a projector operable to project a patterned image of radiant energy comprising rows and columns of pixels along a surface of a resin; and   an actuator configured to change a relative angular orientation of the platform and the projector about the build axis from a nominal orientation for a first layer of the workpiece to an off-nominal orientation for a second layer of the workpiece; and   a controller operably coupled with the projector and the actuator, the controller configured to implement an optimization algorithm to minimize a number or area of the pixels crossing a periphery of an edge of the first layer of the workpiece.   
     
     
         30 . The apparatus of  claim 29 , wherein the patterned image of radiant energy is configured as a two-dimensional grid array of the pixels. 
     
     
         31 . The apparatus of  claim 29 , wherein the resin is a photopolymer and the patterned image is projected using ultraviolet light. 
     
     
         32 . The apparatus of  claim 29 , wherein the controller is configured to determine a preferred angular orientation of a grid array of one or more pixels about the build axis extending perpendicular to the second layer from the first layer of the workpiece, wherein the preferred angular orientation is selected to align an edge of the one or more pixels with an edge of the second layer of the workpiece being built. 
     
     
         33 . The apparatus of  claim 32 , wherein the controller is configured to orient the patterned image of radiant energy to the preferred angular orientation by rotating the projector before solidifying a portion of the resin that forms the first layer of the workpiece. 
     
     
         34 . The apparatus of  claim 32 , wherein the projector comprises:
 a radiant energy source; and   an image forming apparatus.   
     
     
         35 . The apparatus of  claim 32 , wherein at least the second layer is stacked on the first layer along the build axis, and the preferred angular orientation of the first layer and the second layer are selected based at least partially on a surface quality of the workpiece along the build axis. 
     
     
         36 . An apparatus for making a workpiece, comprising:
 a platform movable along a build axis;   a projector operable to project a patterned image of radiant energy comprising rows and columns of pixels along a surface of a resin; and   an actuator configured to change a relative angular orientation of the platform and the projector about the build axis from a nominal orientation for a first layer of the workpiece to an off-nominal orientation for a second layer of the workpiece, wherein the rows and the columns of the pixels projected from the projector are rotated as the relative angular orientation of the platform and the projector about the build axis is moved from the nominal orientation to the off-nominal orientation.   
     
     
         37 . The apparatus of  claim 36 , further comprising:
 a controller operably coupled with the projector and the actuator, the controller configured to implement an optimization algorithm to minimize a number or area of the pixels crossing a periphery of an edge of the first layer of the workpiece.   
     
     
         38 . The apparatus of  claim 36 , wherein the platform is moved downward along the build axis between the first layer and the second layer. 
     
     
         39 . The apparatus of  claim 36 , wherein the projector comprises:
 a radiant energy source; and   an image forming apparatus.   
     
     
         40 . The apparatus of  claim 39 , wherein the radiant energy source comprises an ultraviolet flash lamp.