Imager Assembly and Method for Solid Imaging

• US 20080169586A1
• Filed: 09/17/2007
• Published: 07/17/2008
• Est. Priority Date: 01/17/2007
• Status: Active Grant

• Current Assignee: 3D Systems, Inc. (3D Systems Corporation)
• Original Assignee: 3D Systems, Inc. (3D Systems Corporation)
• Inventors: Hull, Charles W., Partanen, Jouni
• Granted Patent: US 7,706,910 B2
• Time in Patent Office: Days
• US Class Current: 264/401
• CPC Class Codes: B29C 2791/001 Shaping in several steps
• CPC Class Codes: B29C 64/223 Foils or films, e.g. for transferring layers of building material from one working station to another
• CPC Class Codes: B29C 64/264 Arrangements for irradiation
• CPC Class Codes: B33Y 30/00 Apparatus for additive manufacturing; Details thereof or accessories therefor
• CPC Class Codes: B33Y 50/02 for controlling or regulating additive manufacturing processes

Abstract

Solid imaging apparatus and methods for use are disclosed that reduce the amount of uncured solid imaging build material remaining on a completed build object following the completion of the solid imaging build process. The amount of uncured build material is reduced through the use of either an uncoating web that removes excess build material from the build object during the course of the building process or an ink jet source of build material that uses only as much build material as is necessary for the fabrication of the build part. Also disclosed is an imager assembly for use with such a solid imaging apparatus that incorporates two or more individual imagers in an array and accounts for variations in the intensity and alignment of adjacent imagers. The apparatus can be modified for semi-continuous operation and for integrating into a manufacturing operation, if desired.

Claims

1. An imager assembly for making three-dimensional objects, the imager assembly solidifying a solid imaging build material layer-by-layer to build the three-dimensional object, the solid imaging build material having a predetermined value for the threshold energy of solidification, wherein said imager assembly comprises a source of solid imaging radiation, a controller and at least two or more imagers responsive to said controller, each said imager comprising an array of individually controlled imaging elements for transmitting radiation from said source, each said individually controlled imaging element corresponding to a pixel and each said array producing a projected image area in response to said controller, wherein said pixels of adjacent projected image areas aligningly overlap to produce a single combined image area having boundaries corresponding to a layer of the three-dimensional object and seams corresponding to said pixel overlap located between said projected image areas, one or more of which boundaries cross one or more of said seams, said controller adjusting exposure of each said pixel contributing to said boundaries in said single combined image area for providing to said pixels the predetermined threshold energy for solidification of the build material defining said boundaries.

2. The imager assembly of claim 1 wherein each said projected image area is characterized by predetermined intensity and focus distributions over selected groups of pixels of said projected image area.

3. The imager assembly of claim 1 wherein said controller adjusts exposure of each said pixel contributing to said boundaries in said single combined image area for providing to said pixels the predetermined threshold energy for solidification of said boundaries by controlling one or more exposure parameters for each said pixel, said exposure parameters selected from the group consisting of illumination time, radiation intensity, and focus.

4. The imager assembly of claim 1 wherein pixel overlap is from ½

to 1 pixel.

5. The imager assembly of claim 1 wherein said controller selects one imager as dominant for exposing said overlapping projected image area.

6. The imager assembly of claim 1 wherein said controller adjusts exposure depending on accumulated exposure of overlapping pixels.

7. The imager assembly of claim 1 wherein said controller segments said single combined image area according to which of said imagers produces the segment and adjusts exposure of each said pixel contributing to said boundaries based thereon.

8. The imager assembly of claim 1 wherein said controller shifts said single combined image area boundaries among adjacent ones of said pixels over multiple exposures of said boundary for providing to said pixels the predetermined threshold energy for solidification said boundaries.

9. The imager assembly of claim 1 wherein selected said elements in said array of imaging elements for each said imager are characterized as a group according to a predetermined gray scale setting wherein said gray scale setting is a function of the ratio “

r”

of the area of a said pixel contributing to a said boundary to the total area of said pixel, and said controller adjusts the exposure of each said pixel based on said predetermined gray scale settings to provide the predetermined threshold energy for solidification of said boundaries.

10. The imager assembly of claim 9 wherein said gray scale settings comprise a range of values for a given ratio “

r” and

said predetermined gray scale settings are randomized gray scale settings accounting for said range of values.

11. The imager assembly of claim 1 wherein said imagers are selected selected from the group consisting of ultra violet light (“

UV”

) imagers, liquid crystal display (“

LCD”

) imagers, liquid crystal on silicon (“

LCoS”

) imagers, light emitting diode (“

LED”

) imagers, and digital light processing (“

DLP”

) imagers.

13. The imager assembly of claim 1 wherein said imagers is a digital light processing (“

DLP”

) imager.

12. An imager assembly for making three-dimensional objects by solidifying layer-by-layer a solid imaging build material having a predetermined threshold energy requirement for solidification, said imager assembly comprising a source of solid imaging radiation, a controller and at least two or more imagers responsive to said controller, each said imager producing in response to said controller and from said radiation source a projected image area defined by a plurality of illuminated pixels characterized according to a predetermined gray scale setting wherein said gray scale setting is a function of the ratio “

r”

of the area of a said pixel to the total area of said pixel, wherein said pixels of adjacent projected image areas aligningly overlap from about ½

to 1 pixel to produce a single combined image area having boundaries corresponding to a layer of the three-dimensional object and seams corresponding to said pixel overlap located between said projected image areas, one or more of which boundaries cross one or more of said seams, said controller individually controlling said pixels for exposing said boundaries in said single combined image area according to said gray scale settings for providing to said pixels the predetermined threshold energy for solidification of said boundaries.

14. A method for increasing build size in solid imaging comprising the steps of producing a single combined image area from an imager assembly of two or more imagers and controlling exposure of the image border to supply the threshold energy exposure value for solidifying a layer of build material at the border.

15. The method of claim 14 wherein the step of producing a single combined image area from an imager assembly of two or more imagers comprises aligning the images produced by each imager and overlapping the images to produce a single combined image area having seams between the individual projected areas corresponding to the overlap.

16. The method of claim 15 wherein the single combined image area comprises a plurality of pixels, the step of overlapping the images and producing seams comprises overlapping the image areas by from about ½

to 1 pixel, and the step of controlling exposure of the image border to supply the threshold energy exposure value for solidifying a layer of build material at the border includes the step of determining the blending characteristics of the pixels on opposite sides of the seam.

17. The method of claim 16 wherein the step of controlling exposure of the image border to supply the threshold energy exposure value for solidifying a layer of build material at the border includes the step of accounting for accumulated exposure of overlapping pixels.

18. The method of claim 14 wherein the step of controlling exposure of the image border to supply the threshold energy exposure value for solidifying a layer of build material at the border comprises separately determining the intensity and focus distributions for each imager and controlling each imaging element of the imagers with respect to an exposure parameter selected from the group consisting of time, intensity, focus, and one or more of these.

19. The method of claim 18 wherein the step of determining the intensity distribution for each imager comprises determining the intensity distribution for selected groups of imaging elements.

20. The method of claim 18 wherein the exposure parameter is intensity and the step of controlling each imaging element with respect to intensity comprises adjusting the gray scale exposure level for the imaging element.

21. A method for solid imaging comprising the step of supplying at least the threshold energy exposure value for solidifying a layer of build material by:

a) providing an imager assembly of two or more imagers selected from the group consisting of ultra violet light (“

UV”

) imagers, liquid crystal display (“

LCD”

) imagers, liquid crystal on silicon (“

LCoS”

) imagers, light emitting diode (“

LED”

) imagers, and digital light processing (“

DLP”

) imagers;

b) determining the intensity and focus distributions for each individual imager;

c) aligning the images produced by each imager and overlapping the images to produce a single combined image area having seams between the individual projected areas corresponding to the overlap;

d) segmenting the single combined image area according to the individual projected image areas;

e) imaging a layer of solid imaging build material to solidify the image in the build material; and

f) controlling exposure of the image at the image border in accordance with the predetermined intensity and focus distributions to supply the threshold energy exposure value for solidifying a layer of build material at the border.

22. The method of claim 21 wherein the step of controlling exposure further comprises the steps of determining gray scale settings for each imager and controlling each imager with respect to its predetermined gray scale settings.

23. The method of claim 21 wherein the step of controlling exposure further comprises the step of displacing the image at the image border over a plurality of exposures to supply at least the threshold energy exposure value for solidifying a layer of build material at the border.

24. The method of claim 21 further comprising the step of adjusting the exposure levels of the imagers in the region of the seams to account for accumulated exposure by comparing the intensity profile for the image in the region of the seams to the threshold exposure level for solidifying the build material.

25. The method of claim 21 wherein the step of aligning the imagers comprises imaging the individual projected imager areas on a target, adjusting the individual imager positions to fill the respective target area, overlapping portions of adjacent image areas;

determining the amount of overlap, and selecting a dominant imager for exposing the overlapped area; and

the step of controlling exposure of the image at the image border includes adjusting the gray scale for the overlapped area.