Wall Smoothness, Feature Accuracy and Resolution In Projected Images Via Exposure Levels In Solid Imaging

• US 20080054531A1
• Filed: 08/29/2006
• Published: 03/06/2008
• Est. Priority Date: 08/29/2006
• Status: Active Grant

• Current Assignee: 3D Systems, Inc. (3D Systems Corporation)
• Original Assignee: 3D Systems, Inc. (3D Systems Corporation)
• Inventors: Partanen, Jouni P., Chen, Yong, Hull, Charles W., Kerekes, Thomas Alan
• Granted Patent: US 9,415,544 B2
• Time in Patent Office: Days
• US Class Current: 264/401
• CPC Class Codes: B29C 64/135 the energy source being concentrated, e.g. scanning lasers or focused light sources
• CPC Class Codes: B29C 64/393 for controlling or regulating additive manufacturing processes
• CPC Class Codes: B29C 64/40 Structures for supporting 3D objects during manufacture and intended to be sacrificed after completion thereof
• CPC Class Codes: B29K 2995/0073 smooth
• 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
• CPC Class Codes: B33Y 70/00 Materials specially adapted for additive manufacturing
• CPC Class Codes: B33Y 80/00 Products made by additive manufacturing
• CPC Class Codes: G05B 19/4099 Surface or curve machining, making 3D objects, e.g. desktop manufacturing
• CPC Class Codes: G05B 2219/49019 Machine 3-D slices, to build 3-D model, stratified object manufacturing SOM

Abstract

A solid imaging apparatus and method employing levels of exposure varied with gray scale or time or both of digitally light projected image of a cross-section of a three-dimensional object on a solidifiable photopolymer build material. The gray scale levels of exposure of projected pixels permits the polymerization boundaries in projected boundary pixels to be controlled to achieve preserved image features in a three-dimensional object and smooth out rough or uneven edges that would otherwise occur using digital light projectors that are limited by the number of pixels in an image projected over the size of the image. Software is used to control intensity parameters applied to pixels to be illuminated in the image projected in the cross-section being exposed in the image plane.

Claims

1. A method for forming a three-dimensional object layer-by-layer comprising the steps of:

a. forming bit-map data of cross-sectional layers of a three-dimensional object to be built;

b. delivering a solidifiable photopolymer build material to an imaging area;

c. projecting an image representative of the bit-map data of a single cross-sectional layer from a radiation source onto the solidifiable photopolymer build material in the imaging area to illuminate pixels in the image area to selectively solidify the photopolymer build material;

d. controlling boundary polymerization of the build material by controlling the exposure in the image area either by varying the gray scales of the boundary pixels of the radiation source, by controlling the illumination time of different pixels differently, by varying the degree of focus of the pixels to control the width of light distribution of each pixel illumination or by varying the light intensity versus the age of the radiation source, or by combination thereof, thereby defining the object'"'"'s borders; and

e. repeating steps b, c and d multiple times until a plurality of object cross-sections are formed to obtain an object with smooth walls and fine feature retention.

2. The process of claim 1 wherein said bit-map data is formed by (i) receiving digital data of the three-dimensional object to be built;

(ii) processing the three-dimensional digital data to form slice data representative of cross-sectional layers of the object; and

(iii) converting the slice data into bit-map data.

3. The method according to claim 2 wherein step (d) is carried out by varying the gray scales of the boundary pixels of the radiation source while holding the exposure time constant for all boundary pixels.

4. The method according to claim 1 wherein step (a) comprises receiving three-dimensional CAD data of the three-dimensional object to be built.

5. The method according to claim 1 wherein step (a) comprises digitizing a physical article.

6. The method according to claim 1 wherein at least one step (d) is carried out by the combination of controlling the exposure in an image area by the combination of focusing the radiation source to control a width of light distribution for each pixel illumination, controlling the level of gray scale exposure by the radiation source, and controlling the time of illumination of pixels by the radiation source.

7. The method according to claim 1 wherein the radiation source being selected from the group consisting of a UV radiation source, a visible light source and a combination thereof.

8. The method according to claim 7 wherein the radiation source being a digital light projector.

9. The method according to claim 1 wherein said comprising using a solidifiable photopolymer build material is selected from the group consisting of a solidifiable photopolymer liquid resin formulation, a solidifiable photopolymer paste, a solidifiable photopolymer gel, a solidifiable photopolymer semi-liquid and combinations thereof.

10. The method of claim 1 wherein randomization is introduced into the gray scale values at the boundary pixels.

11. A method for forming a three-dimensional object layer-by-layer comprising the steps of:

a. forming bit-map data of cross-sectional layers of a three-dimensional object to be built;

b. characterizing a light projector for its focus of pixels in an image area to control the width of light distribution of each pixel illumination of the object to be formed;

c. characterizing the light projector for light intensity distribution versus gray scale levels in pixels in the image area and for illumination time of each pixel within the image area to control the amount of light energy delivered during an exposure to each pixel in the image area;

d. delivering a solidifiable photopolymer build material to an imaging area via a radiation transparent carrier; and

e. projecting an image representative of cross-sectional image data from the light projector through the radiation transparent carrier to illuminate pixels in an illumination pattern on an image plane exposure to selectively solidify the liquid medium and control the polymerization boundary of the solidifiable photopolymer build material in the projected pixels by applying different exposure parameters to different areas of the image plane; and

f. repeating steps (d) and (e) for each cross-sectional image data until the three-dimensional object is built.

12. The method of claim 11 wherein said bit-map data is formed by:

i. receiving digital data of a three-dimensional object to be built;

ii. processing the digital data to form slice data representative of cross-sectional layers of the object; and

iii. converting the slice data into bit-map data;

13. The method according to claim 11 wherein the light projector is further characterized for the light intensity versus the age of a lamp in the light projector, and the exposure parameters of the light projector are calibrated for the solidifiable photopolymer build material employed.

14. The method according to claim 11 wherein the solidifiable liquid build material is selected from the group consisting of a solidifiable photopolymer liquid resin formulation, a solidifiable photopolymer paste, a solidifiable photopolymer gel, a solidifiable photopolymer semi-liquid and combinations thereof.

15. The method according to claim 11 wherein randomization is introduced into gray scale values at the boundary pixels.

16. An apparatus for forming a three-dimensional object layer-by-layer by solid imaging comprising in combination:

a. a frame;

b. a radiation transparent carrier moveably mounted to the frame;

c. a radiation source mounted to the frame for projecting an image one cross-section at a time of a three-dimensional object to be built through the radiation transparent carrier;

d. a source of solidifiable photopolymer build material in fluid flow communication with the radiation transparent carrier effective to apply the solidifiable photopolymer build material to the radiation transparent carrier;

e. a support platform moveably mounted to the frame to support the three-dimensional object as it is built layer-by-layer;

f. a controller mounted to the frame effective to control movement of the radiation transparent carrier and the support platform and to control illumination of selected pixels by the radiation source in an image exposure of a cross-section of the three-dimensional object on the solidifiable photopolymer build material;

g. a computer in data flow communication with the controller to receive the digital data relating to the three-dimensional object to be built and convert the digital data into data representative of cross-sections of the three-dimensional object;

wherein the radiation source projects an image representative of cross-sectional digital data through the radiation transparent carrier to selectively illuminate pixels in an illumination pattern on an image area exposure and to selectively solidify the photopolymer build material by applying different exposure parameters to different portions of the image area to control the polymerization boundary of the solidifiable photopolymer build material to obtain a high resolution image and a three-dimensional object that has all features properly positioned and smooth walls.

17. The apparatus according to claim 16 wherein the radiation source is selected one from the group consisting of a UV radiation source, a visible light source and a combination thereof.

18. The apparatus according to claim 17 wherein the radiation source is a digital light projector.

19. The apparatus according to claim 16 wherein the radiation transparent carrier is an endless belt.

20. The apparatus according to claim 16 wherein the radiation transparent carrier further is a flexible film.

21. The apparatus according to claim 16 wherein the radiation transparent carrier is a plate.

22. The apparatus according to claim 16 wherein the controller is a microprocessor that selects pixels to be illuminated in the exposure of a cross-section of the three-dimensional object on the solidifiable liquid by use of an algorithm.

23. The apparatus according to claim 22 wherein the microprocessor uses software to control light intensity versus gray scale levels across an image projected by the digital light projector onto the solidifiable photopolymer build material in order to optimize the image projection of the three-dimensional object.

24. The apparatus according to claim 22 wherein the microprocessor uses software to apply light intensity levels of exposure, illumination pattern width and time of illumination of pixels in the image area as the exposure parameters applied to the image area to position a boundary of a projected boundary pixel of the three-dimensional object in a single exposure.

25. An apparatus for forming a three-dimensional object layer-by-layer by solid imaging comprising in combination:

a. a frame;

b. a source of solidifiable photopolymer build material effective to supply the solidifiable photopolymer build material to form a layer of build material to be solidified with an exposed surface;

c. a radiation source mounted to the frame for projecting onto the surface of the solidifiable photopolymer build material a cross-section at a time of a three-dimensional object to be built effective to solidify each cross-section of the three-dimensional object;

d. a support platform moveably mounted to the frame to support the three-dimensional object as it is built layer-by-layer;

e. a controller mounted to the frame effective to control recoating of an exposed layer of the liquid medium with a fresh layer of the solidifiable liquid medium, control movement of the support platform, and to control illumination of selected pixels by the radiation source in an image exposure of a cross-section of the three-dimensional object on the solidifiable liquid medium;

f. a computer in data flow communication with the controller to receive three-dimensional digital data in relation to the three-dimensional object to be built and convert the digital data into data representative of cross-sections of the three-dimensional object; and

g. software to control light intensity versus gray scale levels across an image projected by the digital light projector onto the solidifiable photopolymer build material in order to optimize the image projection of a three-dimensional object to control the polymerization boundary of the solidifiable photopolymer build material in boundary pixels to obtain a high resolution image and a three-dimensional object that has all features properly positioned and smooth walls.

26. The apparatus according to claim 25 wherein the radiation source is selected one from the group consisting of a UV radiation source, a visible light source and a combination thereof.

27. The apparatus according to claim 25 wherein the radiation source is a digital light projector.

28. The apparatus according to claim 25 further comprising a recoater moveably mounted to the frame for recoating an exposed layer of the photopolymer build material with a fresh layer of the solidifiable photopolymer build material.

29. The apparatus according to claim 25 wherein the solidifiable photopolymer build material selected from the group consisting of a solidifiable photopolymer liquid resin formulation, a solidifiable photopolymer paste, a solidifiable photopolymer gel, a solidifiable photopolymer semi-liquid and combinations thereof.

30. The apparatus according to claim 25 wherein said software also applies light intensity levels of exposure, illumination pattern width and time of illumination of pixels in the image plane as intensity parameters applied to the image plane medium by controlling the polymerization boundary of a projected boundary pixel of the three-dimensional object in a single exposure in order to optimize the image projection of the three-dimensional object and obtain a three-dimensional object that has all features properly positioned and smooth walls.

31. The apparatus according claim 25 wherein the source of solidifiable photopolymer build material being a vat mounted to the frame containing the surface of the solidifiable photopolymer build material onto which the image is projected.

32. The apparatus according to claim 25 wherein the solidifiable photopolymer build material is image exposed on a radiation transparent carrier.