Simplified stereolithographic object formation methods of overcoming minimum recoating depth limitations

• US 5,902,538 A
• Filed: 08/29/1997
• Issued: 05/11/1999
• Est. Priority Date: 08/29/1997
• Status: Expired due to Term

• Current Assignee: 3D Systems, Inc. (3D Systems Corporation)
• Original Assignee: 3D Systems, Inc. (3D Systems Corporation)
• Inventors: Manners, Chris R., Nguyen, Hop D., Kruger, Theodore R.
• Primary Examiner(s): Tentoni, Leo B.
• Application Number:
  US08/920,428
• Time in Patent Office: 620 Days
• Field of Search: 264/308, 264/401, 264/497, 364/468.27
• US Class Current: 264/401
• CPC Class Codes: B29C 41/12 Spreading-out the material on a substrate , e.g. on the surface of a liquid
• CPC Class Codes: B29C 41/36 Feeding the material on to the mould, core or other substrate
• CPC Class Codes: B29C 64/124 using layers of liquid which are selectively solidified
• 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 10/00 Processes of additive manufacturing

Abstract

A rapid prototyping and manufacturing (e.g. stereolithography) method and apparatus for making high resolution objects utilizing low resolution materials which are limited by their inability to reliably form coatings of a desired thickness. The formation of coatings of such materials is limited to a Minimum Recoating Depth (MRD), when formed over entirely solidified laminae, which is thicker than the desired layer thickness or object resolution. Data manipulation techniques result in layers of material (and laminae) of the object being categorized as non-consecutive primary layers (laminae) and secondary layers (laminae) positioned intermediate to the primary layers (laminae). Substantially, all portions of primary laminae are exposed in association with primary layers and portions of the secondary laminae are formed in association with their respective secondary layers while other portions of the secondary laminae are formed in association with primary layers so as to form the object with a higher resolution than that dictated by the spacing between the primary layers. Recoating techniques are described which can be used when the thickness between consecutive layers is less than a leading edge bulge phenomena that results from the use of a particular recoating device such that direction of sweeping and/or order of sweeping of the recoating device is varied between consecutive primary layers.

Claims

1. A method of forming at least a portion of three-dimensional object from a plurality of adhered laminae, comprising the steps of:

forming successive layers of material adjacent to any last formed layers of material in preparation for forming subsequent laminae of the object;

identifying some non-consecutive layers as primary layers;

identifying layers intermediate to the primary layers as secondary layers; and

exposing the material to prescribed stimulation, in association with the primary layers, to form substantially all portions of the laminae associated with the primary layers and to form portions of laminae associated with the secondary layers; and

exposing at least a portion of the material to prescribed stimulation, in association with the secondary layers, to form at least some outward-facing portions of the laminae associated with the secondary layers;

such that the at least portion of the three-dimensional object is formed from a plurality of adhered laminae with an object resolution substantially equal to or better than the resolution defined by a thickness between successive layers.

2. The method of claim 1 wherein every other layer is a primary layer.

3. The method of claim 1 wherein the at least some outward-facing portions of the laminae associated with the secondary layers include substantially all outward-facing portions of the laminae associated with the secondary layers.

4. The method of claim 1 wherein the at least some outward-facing portions of the laminae associated with the secondary layers includes up-facing portions of the laminae associated with the secondary layers.

5. The method of claim 3 wherein exposure occurs via vector data and the step of exposing, in association with the secondary layers, includes exposure of boundaries, downward facing regions and up-ward facing regions associated with the secondary layers.

6. The method of claim 5 wherein the boundaries exposed in association with the secondary layers include down-facing boundaries, up-facing boundaries, and continuing boundaries.

7. The method of claim 1 wherein a spacing between successive layers is less than a minimum recoating depth (MRD) which is considered desirable for forming coatings over entirely solidified laminae.

8. The method of claim 7 wherein a spacing between successive primary layers is at least as large as the MRD of the material.

9. The method of claim 7 wherein data representing the object is tailored data to account for a minimum solidification depth of the medium being greater than the thickness between successive layers.

10. The method of claim 1 wherein every 4th layer is a primary layer.

11. The method of claim 1 wherein the spacing between the primary layers is variable.

12. The method of claim 1 additionally comprising the step of manipulating cross-sectional data representing laminae of the object to produce modified data descriptive of portions of laminae to be exposed in association with primary and secondary layers.

13. The method of claim 1 wherein at least some of the steps of exposing material occur simultaneously with the step of forming successive layers.

14. A method of forming at least a portion of a three-dimensional object from a plurality of adhered laminae, comprising the steps of:

forming successive layers of material adjacent to any last formed layers of material in preparation for forming subsequent laminae of the object, some of the successive layers being primary layers spaced one from the other and some being secondary layers positioned intermediate to the primary layers, wherein a spacing between successive primary layers is greater than or equal to an MRD of the material and the spacing between successive layers is less than the MRD of the material;

selectively exposing the primary layers to form at least majority portions of primary laminae including at least a portion of the external boundary regions of the laminae in association therewith; and

selectively exposing the secondary layers to form at least minority portions of the secondary laminae in association therewith;

wherein the exposure of the primary layers and secondary layers results in adhesion of laminae to previously formed laminae so as to form the at least portion of the object from a plurality of adhered laminae with a resolution substantially equal to or better than the resolution defined by a thickness between successive layers.

15. A method of forming at least a portion of a three-dimensional object from a plurality of adhered laminae, comprising the steps of:

forming successive layers of material adjacent to any last formed layers of material in preparation for forming subsequent laminae of the object;

identifying some non-consecutive layers as primary layers;

identifying layers intermediate to the primary layers as secondary layers;

identifying continuing regions of the object as those regions which are neither up-facing nor down-facing;

identifying outward-facing-regions of the object as those regions which are either up-facing, down-facing or both;

exposing at least portions of material to prescribed stimulation, in association with the primary layers, to form at least portions of laminae associated with the primary layers and to form portions of laminae associated with the secondary layers; and

exposing at least portions of the material to prescribed stimulation, in association with the secondary layers, to form at least a portion of the outward-facing regions of the laminae associated with the secondary layers;

wherein exposure of interior portions of continuing regions associated with the primary and secondary layers occurs substantially in association with only the primary layers or in association with exposure of outward-facing portions associated with the secondary layers,

such that the at least portion of the three-dimensional object is formed from a plurality of adhered laminae with an object resolution substantially equal to or better than the resolution defined by a thickness between successive layers.

16. A method of forming at least a portion of a three-dimensional object from a plurality of adhered laminae, comprising the steps of:

forming successive layers of material adjacent to any last formed layers of material in preparation for forming subsequent laminae of the object, some of the successive layers being primary layers spaced one from the other by an odd number of secondary layers positioned intermediate therebetween;

selectively exposing the primary layers to form at least majority portions of primary laminae in association therewith and to form at least portions of the secondary laminae; and

selectively exposing the secondary layers to form at least minority portions of the secondary laminae in association therewith;

wherein the exposure of the primary layers and secondary layers results in adhesion of laminae to previously formed laminae so as to form the at least portion of the object from a plurality of adhered laminae;

wherein the step of forming the primary layers and at least some of the secondary layers comprises the step of sweeping a recoating device at or near a surface of the material a desired number of times such that the sweeping directions and/or order of sweeping over successive primary laminae vary.

19. The method of claim 16 wherein the forming steps include the steps of selectively dispensing material.

20. The method of claim 16 wherein the forming steps include the steps of forming layers of a powder material and selectively solidifing those layers of powder material.

21. The method of claim 16 wherein the forming steps include the steps of forming layers of a liquid photopolymer material and selectively solidifying those layers of material.

17. A method of forming at least a portion of a three-dimensional object from a plurality of adhered laminae, comprising the steps of:

forming successive layers of material adjacent to any last formed layers of material in preparation for forming subsequent laminae of the object, some of the successive layers being primary layers spaced one from the other by an even number of secondary layers positioned intermediate therebetween;

selectively exposing the primary layers to form at least majority portions of primary laminae in association therewith and to form at least portions of secondary laminae;

selectively exposing the secondary layers to form at least minority portions of the secondary laminae in association therewith;

wherein the exposure of the primary layers and secondary layers results in adhesion of laminae to previously formed laminae so as to form the at least portion of the object from a plurality of adhered laminae;

wherein the step of forming the primary and at least some of the secondary layers comprises the step of sweeping a recoating device at or near a surface of the material a desired number of times such that the sweeping directions over successive primary laminae occur in different directions or a different order of directions and wherein a different number of sweeps of the recoating device are made over at least two laminae within a group of laminae comprising a primary lamina, a next consecutive primary lamina and all secondary laminae therebetween.

18. A method of forming at least a portion of a three-dimensional object from a plurality of adhered laminae, comprising the steps of:

identifying some non-consecutive cross-sections as primary crosssections;

identifying cross-sections intermediate to the primary cross-sections as secondary cross-sections;

forming, in association with the primary cross-sections, substantially all portions of laminae associated with the primary cross-sections and forming portions of laminae associated with secondary cross-sections; and

forming, in association with the secondary cross-sections, at least some outward-facing portions of the laminae associated with the secondary cross-sections including at least some of any flat up-facing or flat down-facing regions;

such that the at least portion of the three-dimensional object is formed from a plurality of adhered laminae with an object resolution substantially equal to or better than the resolution defined by a thickness between successive layers.