Stereolithographic curl reduction

• US 5,772,947 A
• Filed: 06/07/1995
• Issued: 06/30/1998
• Est. Priority Date: 04/18/1988
• Status: Expired due to Fees

• Current Assignee: 3D Systems, Inc. (3D Systems Corporation)
• Original Assignee: 3D Systems, Inc. (3D Systems Corporation)
• Inventors: Smalley, Dennis R., Hull, Charles W., Lewis, Charles W., Spence, Stuart T., Vinson, Wayne, Freed, Raymond S.
• Primary Examiner(s): Tentoni, Leo B.
• Application Number:
  US08/473,829
• Time in Patent Office: 1,119 Days
• Field of Search: 264/40.1, 264/236, 264/255, 264/303, 264/401, 425/135, 425/174.4, 156/64, 156/272.8, 156/273.5, 156/275.3, 156/307.1, 156/378, 156/379.6, 427/8, 427/510, 427/512, 427/553, 427/554, 427/555, 118/423, 118/429, 118/620, 118/712, 250/432 R, 250/492.1, 364/468, 364/476, 364/468.27, 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: 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: 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

Abstract

An improved stereolithography system for generating a three-dimensional object by creating a cross-sectional pattern of the object to formed at a selected surface of a fluid medium capable of altering its physical state in response to appropriate synergistic stimulation by impinging radiation, particle bombardment or chemical reaction, information defining the object being structurally specified to reduce curl, stress and distortion in the ultimately formed object, the successive adjacent laminae, representing corresponding successive adjacent cross-sections of the object, being automatically formed and integrated together to provide a step-wise laminar buildup of the desired object, whereby a three-dimensional object is formed and drawn from a substantially planar surface of the fluid medium during the forming process. A stereolithographic distortion known as curl is defined, and several techniques to eliminate or reduce curl are described, including dashed line, bent line, secondary structure, rivets, and multi-pass techniques. In addition, a quantitative measurement of curl known as the curl factor, and a test part known as a quarter cylinder are described, which together can be used to measure the effectiveness of the above techniques in reducing curl.

Claims

1. A method of forming a three-dimensional object by selectively solidifying successive layers of a transformable fluid medium by subjecting each layer to a selected pattern of a prescribed stimulation whereby the object is built of a succession of superposed laminae, wherein the selected pattern for each layer is obtained by processing stored data defining a desired configuration of the object, wherein,

said data processing step comprising modifying a portion of the stored data defining a solid volume of the desired object configuration, to provide modified data that converts said solid volume into a volume that comprises regions of material to be solidified according to a first exposure level and regions to be solidified according to a second lower exposure level or to remain unsolidified during formation of an individual lamina.

2. An apparatus for forming three-dimensional object from stored data defining a desired configuration of the object, the object being built of a succession of superposed laminae, each of which is formed by solidifying a layer of a transformable fluid medium by selective application thereto of a prescribed stimulation, the apparatus including a data processing means for generating from the stored data the pattern of stimulation applied to each fluid layer, wherein,

said data processing means comprises data-modifying means responsive to said stored data to produce modified data converting a solid volume of the desired object configuration into a volume that comprises regions of material to be solidified according to a first exposure level and regions to be solidified according to a second lower exposure level or to remain unsolidified during formation of an individual lamina.

3. A process for the formation of a three-dimensional object in which the object is built of superposed laminae comprising the step of:

forming and adhering each lamina to an adjacent lamina by selective solidification of a layer of a transformable fluid medium by exposure to a prescribed stimulation, wherein the formation of at least one lamina from a layer of the fluid medium includes at least one initial exposure of the layer to the prescribed stimulation according to a predetermined pattern to form an initial section of the lamina that does not adhere directly to a preceding lamina, and at least one further exposure of the layer to the prescribed stimulation according to a predetermined pattern to form a further section of the lamina linking, at least in part, the initial section directly to the preceding lamina.

4. A process as claimed in claim 3 wherein the initial exposure comprises the exposure of at least one line and wherein the further exposure reexposes the at least one line.

5. The process of claim 3 wherein the initial exposure comprises the exposure of at least one line and wherein the further exposure reexposes only part of the at least one line.

6. A process as claimed in claim 5 wherein the further exposure provides portions of the lamina at selected locations by which the lamina is joined to the preceding lamina.

7. A process as claimed in claim 3 wherein the initial exposure is a single exposure.

8. The process as claimed in claim 3 wherein the initial exposure comprises at least two exposures.

9. A process as claimed in claim 3 wherein the further exposure is a single exposure.

10. A process as claimed in claim 3 wherein the further exposure comprises at least two exposures.

11. A process as claimed in claim 3 wherein each exposure of the layer is of the same predetermined pattern, and wherein a succession of such exposures progressively deepens the solidification of the layer toward the preceding lamina such that at least one exposure adheres the initial section to the preceding lamina.

12. A process as claimed in claim 5 wherein the initial exposure and the further exposure are performed by tracing a beam of prescribed stimulation on a surface of the medium.

13. A process as claimed in claim 12 wherein both the initial exposure and the further exposure comprise the exposure of at least one line and are made to occur on a portion of the line prior to performing any exposure on any remaining portion of the line.

14. A process as claimed in claim 11 wherein different quantities of exposure are applied on at least two of the exposures.

15. A process as claimed in claim 3 wherein a boundary portion of the lamina is formed and made to adhere to the previously formed lamina in two exposures and more than two exposures are used to form and adhere at least a portion of an interior part of the lamina to the previously formed lamina.

16. A process as claimed in claim 3 wherein a boundary portion of the lamina is made to adhere to the previously formed lamina in only one exposure.

17. A process as claimed in claim 3 wherein the initial exposure and the further exposure are applied in a critical region of the layer susceptible to curl distortion.

18. A process as claimed in claim 3 wherein the at least one lamina includes a consecutive sequence of laminae.

19. A process as claimed in claim 18 in which exposure of successive layers of the transformable fluid medium, to form the consecutive sequence of laminae, is performed automatically under the control of a prescribed program.

20. A process as claimed in claim 3 wherein the prescribed stimulation is at least one of radiation, ultra-violet light, visible light, invisible light, particle bombardment, electron beams or reactive chemicals.

21. A process as claimed in claim 20 wherein the prescribed stimulation is a beam of ultra-violet light.

22. A process as claimed in claim 3 wherein the transformable fluid medium is a liquid photopolymer.

23. A process as claimed in claim 3 wherein the transformable fluid medium comprises a metal or plastic powder.

24. An apparatus for forming a three-dimensional object from superposed laminae each formed by the selective solidification of a layer of a transformable fluid medium by exposure to a prescribed stimulation, comprising:

a source of prescribed stimulation;

means for providing successive layers of transformable fluid medium in preparation for forming successive laminae of the object; and

means for selectively exposing each of the layers to prescribed stimulation to form successive laminae, wherein the means for selectively exposing each of the layers is controlled according to a prescribed program, wherein during the formation of at least one lamina, the prescribed program, controls the means for selectively exposing a layer to apply at least one initial exposure of prescribed stimulation to the layer according to a predetermined pattern to form an initial section of the lamina that does not adhere directly to a preceding lamina, and wherein the prescribed program controls the application of at least one further exposure of prescribed stimulation to the layer according to a predetermined pattern to form a further section of the lamina linking, at least in part, the initial section directly to the preceding lamina.

25. Apparatus as claimed in claim 24 wherein the prescribed program is programmed to apply the initial exposure to at least one line and to apply the further exposure by reexposing the line.

26. Apparatus as claimed in claim 24 wherein the prescribed program is programmed to apply the initial exposure to at least one line and to apply the further exposure to only part of the line.

27. Apparatus as claimed in claim 26 wherein the prescribed program applies the further exposure such that the initial section is joined to the preceding lamina at selected locations.

28. Apparatus as claimed in claim 24 wherein the prescribed program is programmed to apply the initial exposure as a single exposure.

29. Apparatus as claimed in claim 24 wherein the prescribed program is programmed to apply the initial exposure as an application of at least two exposures.

30. Apparatus as claimed in claim 24 wherein the prescribed program applies the further exposure as an application of a single exposure.

31. Apparatus as claimed in claim 24 wherein the prescribed program applies the further exposure as an application of at least two exposures.

32. Apparatus as claimed in claim 24 wherein the source is arranged to provide the prescribed stimulation as a beam and the means for selectively exposing the layer is arranged to control the selective tracing of the beam of prescribed stimulation on a surface of the fluid medium.

33. Apparatus as claimed in claim 32, wherein the prescribed program is programmed to apply both the initial exposure and the further exposure to at least one line, wherein both are controlled to expose a portion of the line prior to performing any exposure on any remaining portion of the line.

34. Apparatus as claimed in claim 32 wherein the prescribed program further controls the exposure such that different quantities of exposure are applied on at least two of the exposures.

35. Apparatus as claimed in claim 24 in which the prescribed program has associated with it data for exposing a boundary portion of a lamina to be formed from a layer of the fluid medium such that the boundary portion is formed and adhered to the previously formed lamina in two exposures and more than two exposures are used in forming and adhering at least a portion of an interior part of the same lamina to the previously formed lamina.

36. Apparatus as claimed in claim 24 wherein a boundary portion of the lamina is made to adhere to previously formed lamina in only one exposure.

37. Apparatus as claimed in claim 24 wherein the applying of the initial exposure and the applying of the further exposure are configured to expose the layer of fluid medium in a critical region susceptible to curl distortion.

38. Apparatus as claimed in claim 24 wherein the program provides that the applying of the initial exposure and the applying of the further exposure is performed in the exposure of a plurality of consecutive layers.

39. Apparatus as claimed in claim 24 wherein the means for providing successive layers to the transformable fluid medium and the means for selectively exposing each of the layers is operable under the prescribed program to automatically control the provision of successive layers of the fluid medium and formation of laminae therefrom.

40. Apparatus as claimed in claim 24 wherein the source of prescribed stimulation is a source of at least one of radiation, ultra-violet light, visible light, invisible light, particles, electrons or reactive chemicals.

41. Apparatus as claimed in claim 40 wherein the source of prescribed stimulation is a source of a beam of ultra-violet radiation.

42. Apparatus as claimed in claim 24 wherein the transformable fluid medium is a liquid photopolymer and the source of prescribed stimulation is a source of at least one of radiation, ultra-violet light, visible light, invisible light, particles, electrons or reactive chemicals.

43. Apparatus as claimed in claim 24 wherein the transformable fluid medium comprises a metal or plastic powder and the source of prescribed stimulation is a source of at least one of radiation, ultra-violet light, visible light, invisible light, particles, electrons or reactive chemicals.

44. A process for the formation of a three-dimensional object in which the object is built of superposed laminae comprising the step of:

forming and adhering each lamina to an adjacent lamina by the selective solidification of a layer of a transformable fluid medium by exposure to a prescribed stimulation wherein the formation of at least one lamina from a layer of the fluid medium includes at least one initial exposure for the layer to the prescribed stimulation according to a predetermined pattern to form two laterally separated sections of the lamina that do not adhere directly together, and at least one further exposure to the prescribed stimulation according to a predetermined pattern to form structure connecting the separated sections and leaving unsolidified portions of the layer between the sections.

45. The process as claimed in claim 44 in which the separated sections have sides facing each other over a given length and the structure connects the sides over less than the given length.

46. An apparatus for forming a three-dimensional object from superposed laminae each formed by the selective solidification of a layer of a transformable fluid medium by exposure to a prescribed stimulation, comprising:

a source of prescribed stimulation;

means for providing successive layers of transformable fluid medium in preparation for forming successive laminae of the object; and

means for selectively exposing each of the layers to prescribed stimulation to form successive laminae, wherein the means for selectively exposing each of the layers is controlled according to a prescribed program, wherein during the formation of at least one lamina, the prescribed program controls the means for selectively exposing a layer to apply at least one initial exposure of prescribed stimulation to the layer according to a predetermined pattern to form two laterally separated sections of the lamina that do not adhere directly together, and to apply at least one further exposure of prescribed stimulation to the layer according to a predetermined pattern to form structure connecting the separated sections and leaving unsolidified portions of the layer between the sections.

47. Apparatus as claimed in claim 46, wherein the formation of the laterally separated sections is controlled so that the separated sections have sides facing each other over a given length, and the formation of the structure is controlled so that the structure connects the sides over less than the given length.