FABRICATING PARTS FROM PHOTOPOLYMER RESIN

• US 20130123988A1
• Filed: 07/15/2011
• Published: 05/16/2013
• Est. Priority Date: 07/16/2010
• Status: Active Grant

• Current Assignee: Georgia Tech Research Corporation (University System of Georgia)
• Original Assignee: Georgia Institute of Technology (University System of Georgia)
• Inventors: Rosen, David W., Jariwala, Amit S., Ding, Fei
• Granted Patent: US 9,367,049 B2
• Time in Patent Office: Days
• US Class Current: 700/266
• CPC Class Codes: B29C 64/135 the energy source being concentrated, e.g. scanning lasers or focused light sources
• CPC Class Codes: B29C 64/386 Data acquisition or data processing for additive manufacturing
• CPC Class Codes: B33Y 50/02 for controlling or regulating additive manufacturing processes
• CPC Class Codes: G05B 11/01 electric

Abstract

Methods, systems, and apparatus, including computer programs encoded on a computer storage medium, for fabricating parts from photopolymer resin. In one aspect, a method includes iteratively determining a deviation measurement based on a simulated cured geometry and adjusted target geometry data until the deviation measurement is at or less than a threshold. The simulated cured geometry is determined, based in part, on an inhibition model.

Claims

1. A method performed by a data processing apparatus for controlling a projection lithography system, the method comprising:

accessing, by a data processing apparatus, target geometry data defining a target geometry of an apparatus to be generated from a photopolymer resin by the projection lithography system;

setting adjusted target geometry data equal to the target geometry data, the output model defining an output geometry of an apparatus to be generated from a photopolymer resin by the projection lithography system;

iteratively determining a first deviation measurement based on a simulated cured geometry and the adjusted target geometry data until the first deviation measurement is at or less than a threshold, wherein each iteration comprises;

determining, by the data processing apparatus, first image data defining at least one image that is used to control irradiation of the photopolymer resin in a resin chamber, the first image data being based on the adjusted target geometry data;

determining, by the data processing apparatus, the simulated cured geometry based on an oxygen inhibition model of the photopolymer resin and the first image data;

determining the first deviation measurement based on the simulated cured geometry and the target geometry;

comparing the first deviation measurement to a convergence threshold; and

adjusting the adjusted target geometry data by an adjustment factor when the first deviation measurement is greater than the convergence threshold; and

providing the first image data to a projection lithography system when the first deviation measurement is less than or equal to the convergence threshold.

2. The method of claim 1, wherein determining the simulated cured geometry comprises determining the simulated cured geometry based on rates of initiation, propagation, termination and inhibition mechanisms of the photopolymer resin.

3. The method of claim 2, further comprising:

determining an incident intensity of an irradiation source; and

setting a rate constant for initiator decomposition as a function of depth based, in part, on the incident intensity;

wherein the rate constant for initiator decomposition is determinative of the differential change in concentration of an initiator in the photopolymer resin with respect to time.

4. The method of claim 1, further comprising:

determining an incident intensity of an irradiation source at a resin chamber; and

setting a rate constant for initiator decomposition as a function of depth based, in part, on the incident intensity;

wherein the rate constant for initiator decomposition is determinative of the differential change in concentration of an initiator in the photopolymer resin with respect to time; and

wherein determining the simulated cured geometry comprises determining the simulated cured geometry based, in part, on the differential change in concentration of an initiator in the photopolymer resin with respect to time.

5. The method of claim 1, wherein determining the simulated cured geometry further comprises determining the simulated cured geometry based, in part, on an optical self focusing model that models the intensity of irradiation energy emerging out of the simulated cured geometry at instantaneous heights z.

6. The method of claim 5, wherein determining the simulated cured geometry based, in part, on an optical self focusing model comprises:

determining, for each of plurality of time increments, each of which are a sub-portion of a total exposure time, and for each of a plurality of locations on a surface of the simulated cured geometry;

determining an instantaneous height z of the surface of the simulated cured geometry at the location and at a time corresponding to the time increment;

determining an intensity of irradiation energy emerging out of the surface of the simulated cured geometry at the location and a corresponding ray path;

estimating, based on the intensity, the height z, and the ray path, a change in the instantaneous height z of the surface at the location, the change in the instantaneous height z corresponding to the instantaneous height z for a next time increment.

7. The method of claim 1, further comprising:

determining, by the data processing apparatus, the simulated cured geometry based on volumetric shrinkage of the cure photopolymer resin.

8. The method of claim 1, further comprising:

determining, by the data processing apparatus, the simulated cured geometry based on chemical erosion attributed to developer solution.

9. The method of claim 1, wherein determining first image data defining at least one image that is used to control irradiation of the photopolymer resin in a resin chamber comprises:

discretizing the output geometry into a plurality of voxels; and

determining an amount of irradiation energy required at a base of each voxel.

10. The method of claim 9, wherein the first image data comprises a plurality of bitmaps, each bitmap corresponding to an exposure time, and wherein, for each bitmap:

each bit in the bitmap is mapped to one of the corresponding plurality of voxels; and

each bit in the bitmap defines a corresponding irradiation energy value that corresponds to the irradiation energy required at the base of the voxel at the corresponding exposure time.

11. The method of claim 1, further comprising:

receiving, by the data processing apparatus, actual geometry data defining an actual geometry of an apparatus generated from the photopolymer resin by the projection lithography system using the first image data;

setting adjusted target geometry data equal to the actual geometry data;

iteratively determining a second deviation measurement based on a simulated cured geometry and the adjusted target geometry data until the second deviation measurement is at or less than the threshold, wherein each iteration comprises;

determining, by the data processing apparatus, second image data defining at least one image that is used to control irradiation of the photopolymer resin in a resin chamber, the second image data being based on the adjusted target geometry data;

determining, by the data processing apparatus, the simulated cured geometry based on an oxygen inhibition model of the photopolymer resin and the second image data;

determining the second deviation measurement based on the simulated cured geometry and the target geometry;

comparing the second deviation measurement to the convergence threshold; and

adjusting the adjusted target geometry data by the adjustment factor when the second deviation measurement is greater than the convergence threshold; and

providing the second image data to a projection lithography system.

12. A system comprising:

a projection lithography apparatus that receives image data and irradiates a photopolymer resin according to the image data; and

a data processing apparatus storing instructions in an electronic memory device and executable by the data processing apparatus, and the data processing apparatus, upon such execution, performs operations comprising;

accessing target geometry data defining a target geometry of an apparatus to be generated from a photopolymer resin by the projection lithography system;

setting adjusted target geometry data equal to the target geometry data, the output model defining an output geometry of an apparatus to be generated from the photopolymer resin by the projection lithography apparatus;

iteratively determining a first deviation measurement based on a simulated cured geometry and the adjusted target geometry data until the first deviation measurement is at or less than a threshold, wherein each iteration comprises;

determining first image data defining at least one image that is used to control irradiation of the photopolymer resin in a resin chamber, the first image data being based on the adjusted target geometry data;

determining the simulated cured geometry based on an oxygen inhibition model of the photopolymer resin and the first image data;

determining the first deviation measurement based on the simulated cured geometry and the target geometry;

comparing the first deviation measurement to a convergence threshold; and

adjusting the adjusted target geometry data by an adjustment factor

when the first deviation measurement is greater than the convergence threshold; and

providing the first image data to the projection lithography system as the image data when the first deviation measurement is less than or equal to the convergence threshold.

13. The system of claim 12, wherein determining the simulated cured geometry comprises determining the simulated cured geometry based on rates of initiation, propagation, termination and inhibition mechanisms of the photopolymer resin.

14. The system of claim 13, wherein the instructions cause the data processing apparatus to perform further operations comprising:

determining an incident intensity of an irradiation source; and

setting a rate constant for initiator decomposition as a function of depth based, in part, on the incident intensity;

wherein the rate constant for initiator decomposition is determinative of the differential change in concentration of an initiator in the photopolymer resin with respect to time.

15. The system of claim 12, wherein the instructions cause the data processing apparatus to perform further operations comprising:

determining an incident intensity of an irradiation source at a resin chamber; and

setting a rate constant for initiator decomposition as a function of depth based, in part, on the incident intensity;

wherein the rate constant for initiator decomposition is determinative of the differential change in concentration of an initiator in the photopolymer resin with respect to time; and

wherein determining the simulated cured geometry comprises determining the simulated cured geometry based, in part, on the differential change in concentration of an initiator in the photopolymer resin with respect to time.

16. The system of claim 12, wherein determining the simulated cured geometry further comprises determining the simulated cured geometry based, in part, on an optical self focusing model that models the intensity of irradiation energy emerging out of the simulated cured geometry at instantaneous heights z.

17. The system of claim 16, wherein determining the simulated cured geometry based, in part, on an optical self focusing model comprises:

determining, for each of plurality of time increments, each of which are a sub-portion of a total exposure time, and for each of a plurality of locations on a surface of the simulated cured geometry;

determining an instantaneous height z of the surface of the simulated cured geometry at the location and at a time corresponding to the time increment;

determining an intensity of irradiation energy emerging out of the surface of the simulated cured geometry at the location and a corresponding ray path;

estimating, based on the intensity, the height z, and the ray path, a change in the instantaneous height z of the surface at the location, the change in the instantaneous height z corresponding to the instantaneous height z for a next time increment.

18. The system of claim 12, wherein the instructions cause the data processing apparatus to perform further operations comprising determining the simulated cured geometry based on volumetric shrinkage of the cure photopolymer resin.

19. The system of claim 12, wherein the instructions cause the data processing apparatus to perform further operations comprising determining the simulated cured geometry based on chemical erosion attributed to developer solution.

20. The system of claim 12, wherein determining first image data defining at least one image that is used to control irradiation of the photopolymer resin in a resin chamber comprises:

discretizing the output geometry into a plurality of voxels; and

determining an amount of irradiation energy required at a base of each voxel.

21. The system of claim 20, wherein the first image data comprises a plurality of bitmaps, each bitmap corresponding to an exposure time, and wherein, for each bitmap:

each bit in the bitmap is mapped to one of the corresponding plurality of voxels; and

each bit in the bitmap defines a corresponding irradiation energy value that corresponds to the irradiation energy required at the base of the voxel at the corresponding exposure time.

22. A computer readable storage device storing instructions executable by a data processing apparatus that upon such execution cause the data processing apparatus to perform operations comprising:

accessing target geometry data defining a target geometry of an apparatus to be generated from a photopolymer resin by the projection lithography system;

setting adjusted target geometry data equal to the target geometry data, the output model defining an output geometry of an apparatus to be generated from a photopolymer resin by the projection lithograph system;

iteratively determining a first deviation measurement based on a simulated cured geometry and the adjusted target geometry data until the first deviation measurement is at or less than a threshold, wherein each iteration comprises;

determining first image data defining at least one image that is used to control irradiation of the photopolymer resin in a resin chamber, the first image data being based on the adjusted target geometry data;

determining the simulated cured geometry based on an oxygen inhibition model of the photopolymer resin and the first image data;

determining the first deviation measurement based on the simulated cured geometry and the target geometry;

comparing the first deviation measurement to a convergence threshold; and

adjusting the adjusted target geometry data by an adjustment factor when the first deviation measurement is greater than the convergence threshold; and

providing the first image data to a projection lithography system when the first deviation measurement is less than or equal to the convergence threshold.