Wall smoothness, feature accuracy and resolution in projected images via exposure levels in solid imaging

Patent metadata

Field	Value
Publication number	US-9415544-B2
Application number	US-46809006-A
Country	US
Kind code	B2
Filing date	Aug 29, 2006
Priority date	Aug 29, 2006
Publication date	Aug 16, 2016
Grant date	Aug 16, 2016

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.

First claim

Having thus described the invention, what is claimed is:

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, wherein the solidifiable photopolymer build material is solidified when exposed to an accumulated light intensity equal or exceeding a critical energy needed to solidify the solidifiable photopolymer build material;
c. projecting an image representative of the bit-map data of a single cross-sectional layer from a digital 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 with sub-pixel resolution the boundary polymerization of the build material by providing a desired accumulated light intensity equal or exceeding the critical energy at a point within a pixel by setting light intensities of neighboring pixels, wherein setting light intensities of neighboring pixels comprises summing the neighboring pixel's light intensity contributions to the point; and
e. repeating steps b, c and d multiple times until a plurality of object cross-sections are formed to obtain an object with at least one boundary defining sub-pixel resolution.

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 boundary pixels of the digital 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 digital radiation source to control a width of light distribution for each pixel illumination, controlling the level of gray scale exposure by the digital radiation source, and controlling the time of illumination of pixels by the digital radiation source.

7. The method according to claim 1 wherein the digital 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 digital 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 gray scale values at boundary pixels.

11. The method according to claim 1 wherein the setting the light intensities of neighboring pixels comprises setting the light intensities of eight neighboring pixels.

12. 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 digital 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 digital 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, wherein the solidifiable photopolymer build material is solidified when exposed to an accumulated light intensity equal or exceeding a critical energy needed to solidify the solidifiable photopolymer build material;
e. projecting an image representative of cross-sectional image data from the digital light projector to illuminate pixels in an illumination pattern on an image plane exposure to selectively solidify the liquid medium and control with sub-pixel resolution 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 by providing a desired accumulated light intensity equal or exceeding the critical energy at a point within a pixel by setting light intensities of neighboring pixels, wherein setting light intensities of neighboring pixels comprises summing the neighboring pixel's light intensity contributions to the point; and
f. repeating steps (d) and (e) for each cross-sectional image data until the three-dimensional object is built.

13. The method of claim 12 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.

14. The method according to claim 12 wherein the digital light projector is further characterized for the light intensity versus the age of a lamp in the digital light projector, and the exposure parameters of the digital light projector are calibrated for the solidifiable photopolymer build material employed.

15. The method according to claim 12 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.

16. The method according to claim 12 wherein randomization is introduced into gray scale values at the boundary pixels.

17. The method according to claim 12 wherein the solidifiable photopolymer build material is delivered to the imaging area via a radiation transparent carrier.

18. The method according to claim 17 wherein the image representative of cross-sectional image data is projected through the radiation transparent carrier.

19. The method according to claim 12 wherein the setting the light intensities of neighboring pixels comprises setting the light intensities of eight neighboring pixels.

Assignees

• Kerekes Thomas Alan
• Partanen Jouni P
• Chen Yong
• Hull Charles W
• 3D Systems Inc

Inventors

• Kerekes Thomas Alan
• Partanen Jouni P
• Chen Yong
• Hull Charles W

Classifications

• B33Y30/00

  Apparatus for additive manufacturing; Details thereof or accessories therefor · CPC title

• B33Y50/02

  for controlling or regulating additive manufacturing processes · CPC title

• B33Y80/00 Primary

  Products made by additive manufacturing · CPC title

• B29K2995/0073

  smooth · CPC title

• G05B2219/49019

  Machine 3-D slices, to build 3-D model, stratified object manufacturing SOM · CPC title