Method and apparatus for stereolithographic curl balancing

• US 5,238,639 A
• Filed: 08/31/1992
• Issued: 08/24/1993
• Est. Priority Date: 10/31/1990
• 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., Jacobs, Paul F., Allison, Joseph W., Vinson, Wayne A.
• Primary Examiner(s): Tentoni, Leo B.
• Application Number:
  US07/939,549
• Time in Patent Office: 358 Days
• Field of Search: 264/22, 264/40.1, 264/255, 264/308, 425/135, 425/174, 425/174.4, 156/64, 156/242, 156/273.3, 156/273.5, 156/275.5, 156/307.1, 156/378, 156/379.6, 427/8, 427/393.5, 427/407.1, 427/412.1, 427/430.1, 427/508, 427/553, 427/554, 118/423, 118/428, 118/429, 118/620, 118/712, 250/432 R, 250/492.1, 364/468, 364/476, 365/106, 365/107, 365/119, 365/120, 365/126, 365/127, 395/119, 430/270, 430/327, 430/328
• 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: G05B 2219/49013 Deposit layers, cured by scanning laser, stereo lithography SLA, prototyping

Abstract

A method and apparatus for eliminating or substantially reducing curling effects in stereolithographically formed objects. Synergistic stimulation is applied to a curable material to form a three dimensional object through the build up of successive layers. Curling between successive layers is eliminated or substantially reduced by curing a balancing layer in relation to a balanced layer such that reverse curl of the balanced layer caused by the balancing layer offsets or negates normal curl of the balanced layer caused by the balancing layer.

Claims

1. An improved stereolithographic apparatus for producing a three-dimensional object from a material curable in response to synergistic stimulation including means for forming layers of said material and means for selectively applying said synergistic stimulation to said layers of said material to form said three-dimensional object from a plurality of cured layers of material, the improvement comprising:

means for curing a balanced layer and then curing a balancing layer in relation to said balanced layer such that reverse curl of said balanced layer caused by said balancing layer substantially offsets normal curl of said balanced layer caused by said balancing layer.

2. The improved stereolithographic apparatus of claim 1 further comprising means for curing said balanced layer and said balancing layer to form a desired net cure thickness.

3. The improved stereolithographic apparatus of claim 1 wherein said means for curing a balanced layer comprises means for curing an initial balanced layer and an initial balancing layer which are cured in relation to each other to form said balanced layer.

4. The improved stereolithographic apparatus of claim 1 further comprising means for curing the balanced layer to a cure depth less than a balanced layer thickness.

5. The improved stereolithographic apparatus of claim 1 further comprising means for curing the balanced layer to a cure depth equal to a balanced layer thickness and for curing said balancing layer to a cure depth greater than a balancing layer thickness.

6. The improved stereolithographic apparatus of claim 1 further comprising means for curing the balancing layer to a cure depth less than a desired net cure thickness.

7. The improved stereolithographic apparatus of claim 1 further comprising means for curing said balancing layer to a depth equal to a desired net cure thickness.

21. The apparatus of claim 1 wherein said means for curing said balanced layer cures at least two adjacent layers of material and said means for curing said balancing layer cures at least one other layer of material.

23. The apparatus of claim 1 wherein said means for selectively applying said synergistic stimulation distinguishes a first region of a layer of material which serves as a balanced layer, and a second region of said layer of material which serves as a balancing layer.

8. An improved stereolithographic method for producing a three-dimensional object from a material curable in response to synergistic stimulation including the steps of forming layers of said material, selectively applying said synergistic stimulation to said layers to form said three-dimensional object from a plurality of cured layers of material, the improvement comprising the step of:

curing a balanced layer and then curing a balancing layer in relation to said balanced layer such that reverse curl of said balanced layer caused by said balancing layer substantially offsets normal curl of said balanced layer caused by said balancing layer.

9. The improved stereolithographic method of claim 8 wherein said balanced layer and said balancing layer form a desired net cure thickness.

10. The improved method of claim 8 wherein said step of curing said balanced layer further comprises the steps of curing an initial balanced layer and curing an initial balancing layer in relation to each other to form said balanced layer.

11. The improved stereolithographic method of claim 8 wherein the balanced layer is cured to a depth less than a balanced layer thickness.

12. The improved stereolithographic method of claim 8 wherein said balanced layer is cured to a depth equal to a balanced layer thickness and said balancing layer is cured to a depth greater than a balancing layer thickness.

13. The improved stereolithographic method of claim 8 wherein said balancing layer is cured to a depth less than a desired net cure thickness.

14. The improved stereolithographic method of claim 8 wherein said balancing layer is cured to a depth equal to a desired net cure thickness.

22. The method of claim 8 wherein said step of curing said balanced layer comprises curing at least two adjacent layers of material and said step of curing said balancing layer comprises curing at least one other layer of material.

24. The method of claim 8 wherein said step of applying said synergistic stimulation includes distinguishing a first region of a layer of material which serves as a balanced layer and a second region of said layer of material which serves as a balancing layer.

15. A method of determining a range of optimum balancing layer cure depths for a balanced layer cure depth, a balanced layer thickness, and a balancing layer thickness for curl balancing for stereolithographic applications, comprising the steps of:

specifying said balanced layer cure depth;

specifying said balanced layer thickness;

specifying said balancing layer thickness; and

determining said range of optimum balancing layer cure depths for curl balancing based on known material properties and said balanced layer cure depth, said balanced layer thickness and said balancing layer thickness.

16. A method of determining a range of optimum balancing layer cure depths for a balanced layer thickness, a balancing layer thickness, and a balanced layer cure depth for curl balancing for stereolithographic applications, comprising the steps of:

specifying said balanced layer thickness;

specifying said balancing layer thickness;

specifying said balanced layer cure depth; and

stereolithographically forming a series of test parts having said balanced layer thickness, said balancing layer thickness and said balanced layer cure depth to determine said range of optimum balancing layer cure depths for adequate curl balancing results.

17. A method of determining a range of optimum balanced layer cure depths for a balanced layer thickness, a balancing layer thickness, and a balancing layer cure depth for curl balancing for stereolithographic applications, comprising the steps of:

specifying said balanced layer thickness;

specifying said balancing layer thickness;

specifying said balancing layer cure depth; and

stereolithographically forming a series of test parts having said balanced layer thickness, said balancing layer thickness, and said balancing layer cure depth, to determine aid range of optimum balanced layer cure depths for adequate curl balancing results.

18. A method for producing a three-dimensional object by applying synergistic stimulation to successive layers of material curable in response to said synergistic stimulation comprising the steps of:

(a) dividing a three-dimensional object into a plurality of cross-sections;

(b) identifying curl balancing regions and curl balanced regions existing on said cross-sections;

(c) exposing a surface of said curable material to a pattern of synergistic stimulation corresponding to a cross-section of said object to form a respective layer of said object;

(d) coating the layer formed in step (c) with said curable material to provide a surface of said curable material thereon;

(e) repeating steps (c) and (d) until said object is formed;

(f) exposing a curl balanced region to synergistic stimulation wherein exposure thereof induces a cure depth less than the thickness of a layer of said object;

(g) exposing a curl balancing region to synergistic stimulation in relation to said curl balanced region wherein exposure of said balancing region is sufficient to induce a cure depth equal to the thickness of two layers of the object while substantially eliminating curl.

19. An improved stereolithographic apparatus for producing a three-dimensional object from a material curable in response to synergistic stimulation including means for forming layers of said material and means for selectively applying said synergistic stimulation to said layers of said material to form said three-dimensional object from a plurality of cured layers of material, the improvement comprising:

at least one computer programmed to cure at least a first portion of at least one of said layers of material as a balanced layer, and programmed to then cure at least a second portion of at least one of said layers of material as a balancing layer in relation to said first portion wherein reverse curl of said first portion caused by curing of said second portion substantially offsets normal curl of said first portion caused by said curing of said second portion.

25. The apparatus of claim 19 wherein said computer cures said balanced layer using a first penetration depth and cures said balancing layer using a second penetration depth.

20. An improved stereolithographic method for producing a three-dimensional object from a material curable in response to synergistic stimulation including the steps of forming layers of said material, selectively applying said synergistic stimulation to said layers to form said three-dimensional object from a plurality of cured layers of material, the improvement comprising the steps of:

curing at least a first portion of at least one of said layers of material as a balanced layer, and

then curing at least a second portion of at least one of said layers of material as a balancing layer in relation to said first portion, wherein reverse curl of said first portion caused by curing of said second portion substantially offsets normal curl of said first portion caused by said second portion.

26. The method of claim 20 wherein said step of curing said balanced layer uses a first penetration depth and said step of curing said balancing layer uses a second penetration depth.