Method of making a three-dimensional object by stereolithography

• US 5,256,340 A
• Filed: 06/25/1992
• Issued: 10/26/1993
• Est. Priority Date: 04/18/1988
• Status: Expired due to Term

• Current Assignee: 3D Systems, Inc. (3D Systems Corporation)
• Original Assignee: 3D Systems, Inc. (3D Systems Corporation)
• Inventors: Smalley, Dennis R., Hull, Charles W., Richter, Jan, Jacobs, Paul F., Allison, Joseph W., Childers, Craig M.
• Primary Examiner(s): Tentoni, Leo B.
• Application Number:
  US07/906,207
• Time in Patent Office: 488 Days
• Field of Search: 264/22, 264/308, 264/344, 264/DIG. 59, 425/174.4, 156/273.3, 156/273.5, 156/275.5, 156/307.1, 156/379.6, 427/508, 427/510, 427/512, 427/553, 427/554, 118/620, 250/492.1, 364/468, 364/476, 365/106, 365/107, 395/119
• 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 64/40 Structures for supporting 3D objects during manufacture and intended to be sacrificed after completion thereof
• CPC Class Codes: B29C 67/02 Moulding by agglomerating B29C67/20 takes precedence
• CPC Class Codes: B33Y 10/00 Processes of additive manufacturing
• CPC Class Codes: B33Y 50/02 for controlling or regulating additive manufacturing processes
• CPC Class Codes: B44B 1/006 using computer control means
• CPC Class Codes: G01J 1/4257 applied to monitoring the characteristics of a beam, e.g. laser beam, headlamp beam monitoring arrangements for lasers in general H01S3/0014
• CPC Class Codes: G03F 7/0037 Production of three-dimensional images
• CPC Class Codes: G03F 7/70416 2.5D lithography
• CPC Class Codes: G05B 2219/49013 Deposit layers, cured by scanning laser, stereo lithography SLA, prototyping
• CPC Class Codes: G06T 17/00 Three dimensional [3D] modelling, e.g. data description of 3D objects
• CPC Class Codes: G06T 17/10 Constructive solid geometry [CSG] using solid primitives, e.g. cylinders, cubes
• CPC Class Codes: G06T 17/20 Finite element generation, e.g. wire-frame surface description, tesselation
• CPC Class Codes: Y10S 264/59 Processes in which a partial cure is involved

Abstract

An improved method for stereolithographically forming a three-dimensional object wherein ordinarily solidified internal walls of the object remain at least partially unsolidified. Any unsolidified medium within the object can be drained from the internal walls of the object prior to post-curing so that a hollow three-dimensional object is formed. The object is formed on a layer by layer basis with the internal portion of each layer of the object formed as a grid of solidified portions and unsolidified portions wherein the solidified and unsolidified portions are different on each layer. Objects formed in this manner can be used as patterns in investment casting.

Claims

1. In a method for stereolithographically forming a three-dimensional object with drainable walls on substantially a layer by layer basis comprising the steps of forming successive layers of building material in preparation for forming successive layers of building material in preparation for forming successive cross-sections of said three-dimensional object and selectively solidifying said successive layers of said building material to form successive cross-sections of said three-dimensional object by selectively exposing said successive layers to synergistic stimulation whereby the object is formed from a plurality of cross-section, the improvement comprising the steps of:

forming an internal portion of a first cross-section by exposing first spaced hatch paths to synergistic stimulation to form solidified first hatch lines wherein at least some unsolidified building material remains between said first hatch lines and wherein said first hatch lines have a first side and a second side; and

forming an internal portion of a second cross-section by exposing second spaced hatch paths to synergistic stimulation to form solidified second hatch lines wherein at least some unsolidified building material remains between said second hatch paths wherein at least some of said second hatch paths do not overlie said first hatch paths such that unsolidified material on said first side of said first hatch lines can travel to said second side of said first hatch lines.

2. The method of claim 1, wherein at least a portion of said object is formed without skin.

3. The method of claim 2, wherein the entire object is formed without skin.

4. The method of claim 1, wherein the hatch paths are such that the unsolidified internal portion of said three-dimensional objects forms a single interconnected volume.

5. The method of claim 1, additionally comprising the step of draining said unsolidified building material from the internal portion of said walls of said object.

6. The method of claim 5 wherein the building material is a photopolymer.

7. The method of claim 6 further comprising the step of using the drained object as a pattern for investment casting.

8. The method of claim 1 wherein said first hatch paths include a first set of substantially parallel hatch paths.

9. The method of claim 8 wherein a plurality of cross-sectional forming said three-dimensional object have non-aligned hatch lines.

10. The method of claim 8 wherein hatch paths between at least said first and second cross-sections are parallel but offset.

11. The method of claim 10 wherein the hatch paths on one of said first and second cross-sections are offset to the middle of the hatch paths of the other of said first and second cross-sections.

12. In a method for stereolithographically forming a three-dimensional object with hollow walls on substantially a layer by layer basis comprising the steps of forming successive layers of building material in preparation for forming successive cross-sections of said three-dimensional object and selectively solidifying said successive layers of said building material to form said successive cross-sections of said three-dimensional object by selectively exposing said successive layers to synergistic stimulation whereby the object is formed from a plurality of cross-sections, the improvement comprising the steps of:

exposing a first portion of an internal region of a first cross-section to synergistic stimulation to solidify said first portion while leaving a second portion of said internal region of said first cross-section unsolidified wherein said second portion is divided into at least first and second parts by said first portion;

exposing a first portion of an internal region of a second cross-section to synergistic stimulation to solidify said first portion of said second cross-section while leaving a second portion of said internal region of said second cross-section unsolidified, wherein said first portion of said first cross-section is different from said first portion of said second cross-section, and wherein said unsolidified building material within said first part of said second portion of said first cross-section is connected to said second part of said second portion of said first cross-section through unsolidified building material via said second portion of said second cross-section;

forming an opening in at least a portion of a surface of said three-dimensional object such that unsolidified building material from said at least first and second parts of said second portion of said first cross-section can be removed from said object; and

removing said unsolidified building material from said first and second parts of said second portion of said first cross-section from the object, after completion of said object, via said opening, to form a three-dimensional object with hollow walls.

13. The method of claim 12, wherein said opening is caused by forming at least a portion of said object without skin.

14. The method of claim 13, wherein the entire object is formed without skin.

15. The method of claim 12, wherein the first portions of said first and second cross-sections are formed by exposing parallel hatch paths and wherein the unsolidified internal portions of said object form an interconnected volume.

16. The method of claim 12 wherein the building material is a photopolymer.

17. The method of claim 12 further comprising the step of using the drained object as a pattern for investment casting.

18. In an apparatus for stereolithographically forming a three-dimensional object with drainable walls on substantially a layer by layer basis comprising a source of synergistic stimulation, means for forming successive layers of building material in preparation for forming successive cross-sections of said three-dimensional object and means for selectively solidifying said successive layers of said building material to form successive cross-sections of said three-dimensional object including means for selectively exposing said successive layers to synergistic stimulation whereby the object is formed from a plurality of cross-sections, the improvement comprising:

means for specifying first hatch paths;

means for forming an internal portion of a first cross-section including means configured to expose said first hatch paths to synergistic stimulation to form solidified first hatch lines wherein at least some unsolidified building material remains between said first hatch lines and wherein said first hatch lines have a first side and a second side;

means for specifying second hatch paths which do not overlay said first hatch paths;

means for forming an internal portion of a second cross-section including means configured to expose said second hatch paths to synergistic stimulation to form solidified second hatch lines wherein at least some unsolidified building material remains between said second hatch paths, wherein solidified material on said first side of said first hatch lines is connected to said second side of said first hatch lines through unsolidified building material via said unsolidified material between said second hatch lines.

19. The method of claim 18 further comprising means for forming at least a portion of the object without skin.

20. The apparatus of claim 19 further comprising means for forming the entire object without skin.

21. The method of claim 18 further comprising means for making all hatch paths cause hatch lines to be formed such that substantially all unsolidified building material within said internal portion of said three-dimensional object forms an interconnected volume.

22. The apparatus of claim 18, further comprising means for draining said unsolidified building material from the internal portion of said walls of said object.

23. The method of claim 18 further comprising means for forming said first hatch paths with a first set of substantially parallel lines.

24. The method of claim 23 further comprising means for forming a plurality of cross-sections having non-aligned hatch lines.

25. The method of claim 23 further comprising means for forming parallel but offset hatch paths between said first and second cross-sections.

26. The method of claim 25 further comprising means for forming the hatch paths on one of said first and second cross-sections so that they are offset to the middle of the hatch paths on the other of said first and second cross-sections.

27. In an apparatus for stereolithographically forming a three-dimensional object with hollow walls on substantially a layer by layer basis comprising a source of synergistic stimulation, means for forming successive layers of building material in preparation for forming successive cross-sections of said three-dimensional object, and means for selectively solidifying said successive layers of building material to form said successive cross-sections of said three-dimensional object including means for selectively exposing said successive layer to synergistic stimulation whereby the object is formed from a plurality of cross-sections, the improvement comprising:

means for specifying a first exposure pattern for the internal portion of a first cross-section wherein the exposure pattern includes a first portion of said first cross-section to be solidified and a second portion of said first cross-section to remain unsolidified and wherein the second portion of said first cross-section is divided into at least two parts by said first portion of said first cross-section;

means for exposing said first cross-section to synergistic stimulation according to said first exposure pattern;

means for specifying a second exposure pattern for an internal portion of a second cross-section wherein the exposure pattern includes a first portion of said second cross-section to be solidified and a second portion of said second cross-section to remain unsolidified, wherein said first portion of said first cross-section is different from said first portion of said second cross-section, and wherein said unsolidified building material within a first part of said second portion of said first cross-section is connected to a second part of said second portion of said first cross-section through unsolidified building material via said second portion of said second cross-section;

means for exposing said cross-section to synergistic stimulation according to said second exposure pattern;

means for causing an opening to e made in at least a portion of a surface of said three-dimensional object such that unsolidified building material from said at least two parts of said second portion of said first cross-section can be removed from said object; and

means for renewing said unsolidified building material from said at least two parts of said second portion of said first cross-section from the object, after completion of said object, via said opening, to form said three-dimensional object with hollow walls.

28. The apparatus of claim 27 further comprising means for forming said opening by forming at least a portion of said object without skin.

29. The apparatus of claim 28 further comprising means for forming the entire object without skin.

30. The apparatus of claim 27 further comprising means for forming the first portions of said first and second cross-sections by parallel hatch paths and substantially all unsolidified internal portions of said object form an interconnected volume.