Simultaneous multiple layer curing in stereolithography

• US 5,999,184 A
• Filed: 04/25/1995
• Issued: 12/07/1999
• Est. Priority Date: 10/30/1990
• 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., Earl, Jocelyn M., Vorgitch, Thomas J.
• Primary Examiner(s): Zimmerman, Mark K.
• Application Number:
  US08/428,951
• Time in Patent Office: 1,687 Days
• Field of Search: 395/119, 395/120, 395/121, 395/122, 395/141, 345/419, 345/420, 345/421, 345/422, 345/441, 364/468.25, 364/468.27, 364/468.26
• US Class Current: 345/419
• 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 50/00 Data acquisition or data processing for additive manufacturing
• 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: G16Z 99/00 Subject matter not provided for in other main groups of this subclass

Abstract

A method and apparatus for making high resolution objects by stereolithography utilizing low resolution materials which are limited by their inability to form unsupported structures of desired thinness and/or their inability to form coatings of desired thinness. Data manipulation techniques, based on layer comparisons, are used to control exposure in order to delay solidification of the material on at least portions of at least some cross-sections until higher layers of material are deposited so as to allow down-facing features of the object to be located at a depth in the building material which is equal to or exceeds a minimum cure depth that can effectively be used for solidifying these features. Similar data manipulations are used to ensure minimum reliable coating thicknesses exist, above previously solidified material, before attempting solidification of a next layer. In addition, horizontal comparison techniques are used to provide enhanced cross-sectional data for use in forming the object. Further, several techniques for automatically performing Z-error correction through the manipulation of a three-dimensional object representation are described.

Claims

1. A method for deriving data for use in forming a three-dimensional object from a plurality of solidified and adhered laminae, comprising:

manipulating a representation of a three-dimensional object to compress the object representation in a Z-direction by more than one layer thickness to at least partially account for any excess solidified material in the Z-direction which might otherwise result from forming laminae of the object when using a layer thickness for forming a down-facing region of the object that is less than a solidification depth used in forming the down-facing, region; and

utilizing the manipulated data to form said object from the plurality of laminar.

2. The method of claim 1 wherein manipulating includes:

manipulating an object representation comprising a first list of vertices of polygons which substantially span a surface of the object, and a second list of representations of said polygons comprising identifiers of the vertices in said first list.

3. The method of claim 2 wherein said polygons are triangles.

4. The method of claim 3 wherein said object will be formed such that the Z-direction is orientated in the vertical direction and said laminae are formed in planes perpendicular to the Z-axis and said manipulating comprises adjusting the vertices of selected ones of said triangles in the vertical direction.

5. The method of claim 4 wherein said manipulating comprises adjusting upwards the vertices of flat down-facing triangles.

6. The method of claim 5 wherein said manipulating further comprises adjusting upwards the vertices of near-flat down-facing triangles.

7. The method of claim 4 wherein said manipulating further comprises:

overlaying the object representation with a plurality of slicing planes; and

rounding said triangle vertices to slicing planes prior to said adjusting.

8. The method of claim 4 wherein said manipulating further comprises:

overlaying the object representation with a plurality of slicing planes; and

rounding said triangle vertices to slicing planes after said adjusting.

9. The method of claim 3 wherein said manipulating comprises adjusting downwards the vertices of selected ones of said triangles.

10. The method of claim 1 wherein said manipulating comprises:

taking as an input a first representation of the object which comprises a plurality of polygons which substantially span a surface of the object, wherein said representation is defined in terms of vertices of the polygons;

converting said first representation into a second representation comprising a first list of the vertices of the polygons, and a second list of representations of the polygons comprising identifiers of the vertices of said first list; and

manipulating said second representation to correct for Z-error.

11. The method of claim 10 wherein said converting comprises:

sorting the vertices of said first representation into a hash table to eliminate redundant vertices;

assigning the remaining non-redundant vertices unique identifiers; and

defining the representations of the polygons in terms of the identifiers.

12. The method of claim 1 wherein said manipulating includes:

taking as input a first representation of the object;

converting said first representation into a second representation comprising a plurality of groupings of Z-coordinates of points representing intersections between transition points in and out of the object associated with at least some cells in a grid; and

manipulating said second representation to correct for Z-error.

13. The method of claim 1 wherein manipulating comprises:

taking as input a representation of the object comprising a plurality of polygons which substantially span a surface of the object, wherein the polygons are defined in tenrs of their vertices; and

manipulating selected ones of said vertices to compress the object representation in the Z-direction.

14. The method of claim 1 wherein manipulating comprises:

taking as input a NURBS representation of the object which includes a plurality of control points; and

manipulating selected ones of said control points to compress the object representation in the Z-direction.

15. The method of claim 1 wherein manipulating comprises:

taking as input a plurality of layer representations of said object; and

manipulating selected ones of said layer representations to compress the object representation in the Z-direction.

16. A method for deriving data for use in forming a three-dimensional object from a plurality of solidified and adhered laminae, comprising:

manipulating a representation of a three-dimensional object to compress the object representation in a Z-direction to at least partially account for any excess solidified material in the Z-direction which might otherwise result from forming laminae of the object; and

providing the manipulated data for utilization in forming said object;

wherein said manipulating step includes manipulating an object representation comprising a plurality of groupings of Z-coordinates representing intersection points of said object representation over at least a portion of cells of a grid.

17. The method of claim 16 wherein said manipulating step comprises adjusting upwards selected ones of said Z-coordinates.

18. The method of claim 17 wherein said manipulating step comprises adjusting upwards Z-coordinates of points representing locations where imaginary lines extending upward from the at least a portion of the grid enter the object representation.

19. In a computer system where a three dimensional object is represented by a plurality of polygons having vertices, a method for converting a first representation of said object to a second representation of said object, for use in forming the three-dimensional object from a plurality of successively solidified layers of a solidifiable medium, comprising:

taking as an input said first representation of the object;

converting said first representation into said second representation of the object, wherein said second representation includes a first list of the vertices of the polygons, and a second list of representations of said polygons including identifiers of the vertices in said first list;

manipulating said second representation of the three-dimensional object to compress at least a portion of the object representation in a Z-direction by more than one layer thickness to at least partially account for excess solidified material which might otherwise result from forming at least one of said successive layers of the object when using a layer thickness for forming a down-facing region of the object that is less than a solidification depth used in forming the down-facing region; and

using said second representation to form the three-dimensional object from the solidifiable medium.

20. The method of claim 19 wherein said first representation comprises a plurality of polygons, defined in terms of their vertices, substantially spanning a surface of the object, and said converting comprises:

sorting said vertices into a hash table to eliminate redundant vertices;

associating non-redundant vertices with unique identifiers; and

defining the representations of said polygons in terms of said identifiers of said vertices.

21. The method of claim 20 wherein eliminating redundant vertices comprises:

calculating an index to the hash table using the coordinates of a vertex;

comparing using a selected delta value the vertex with any entries at the indexed location of the table; and

determining that the vertex is redundant if it is within the delta value of any of the entries in the table at the indexed location.

22. The method of claim 21, wherein increasing the delta value increases the speed at which the resultant object representation is displayed and moved.

23. A method for altering a representation of a three-dimensional object, for use in forcing the three-dimensional object from solidified building material, comprising:

taking as input a representation of the object comprising a first list of vertices of polygons which substantially span a surface of the object, and a second list of representations of the polygons defined in terms of identifiers of the vertices in the first list;

manipulating selected ones of said first list of vertices without having to manipulate said second list of polygonal representations to form an altered representation, said altered representation reflecting an adjustment to a Z-component of one or more vertices by more than one layer thickness to at least partially account for excess solidified material that would otherwise be formed during object formation when using a layer thickness for forming a down-facing region of the object that is less than a solidification depth used in forming the down-facing region; and

using the altered representation to form the three-dimensional object from solidified building material.

24. A method for converting a first object representation into a second object representation, for use in forming the object from solidified building material, comprising:

associating a grid of cells with the first object representation;

overlaying the first object representation with a plurality of conceptual lines emanating from cells in the grid;

determining the Z-components of the points of intersection between the lines and the first object representation;

associating the Z-components with the cells from which the lines used to determine the components emanate; and

forming the second object representation from the associated Z-components;

manipulating said second object representation to form an altered representation, said altered representation reflecting an adjustment to one or more of said Z-components by more than one layer thickness to at least partially account for excess solidified material that would otherwise be formed during object formation when using a layer thickness for forming a down-facing region of the object that is less than a solidification depth used in forming the down-facing region; and

using the altered representation to form the object from solidified building material.

25. A computer program media, embodying a program of instructions executable by a computer to perform a method for forming a three-dimensional object from a plurality of successively solidified layers of a solidifiable medium, wherein said object is represented in the computer by a plurality of polygons, the method comprising:

compiling a list of vertices of said plurality of polygons, wherein each vertex shared by two or more polygons is listed only once;

representing each of said vertices in said list with a unique identifier;

redefining said plurality of polygons using said unique identifiers of said vertices; and

adjusting a Z-component of one or more of said vertices, resulting in adjusted polygonal data, by more than one layer thickness to at least partially account for excess solidified material which would otherwise result from solidifying at least one of said successive layers during object formation when using a layer thickness for forming a down-facing region of the object that is less than a solidification depth used in forming the down-facing region;

wherein as a result of said list structure, an adjustment of a first vertex of a first polygon results in an adjustment of that same first vertex for a second polygon which shares said same vertex; and

wherein said polygon data is adapted for use in forming a physical object.

26. The computer program media of claim 25, wherein said method further comprises receiving data in the form of a plurality of polygons representing a three-dimensional object.

27. The computer program media of claim 25, wherein said method further comprises converting the adjusted polygonal data to layer data.

28. A computer program media, embodying a program of instructions executable by a computer to perform a method for forming a three-dimensional object from a plurality of successively solidified layers of a solidifiable medium, wherein said object is represented in the computer by a plurality of polygons, the method comprising:

receiving a plurality of polygons representing the object and a list of vertices for said plurality of polygons, wherein said list includes a unique identifier for each unique vertex; and

adjusting a position-component of one or more vertices in said list by more than one layer thickness to at least partially account for excess solidified material which would otherwise result from solidifying at least one of said successive layers during object formation when using a layer thickness for forming a down-facing region of the object that is less than a solidification depth used in forming the down-facing region;

wherein an adjustment of a position component for a first vertex of a first polygon results in an adjustment of that same first vertex for a second polygon which shares said same vertex; and

wherein said list contains data used to eventually form a three-dimensional physical object from a plurality of successively solidified layers of a solidifiable medium.

29. The computer program media of claim 28, wherein said adjusted position component is that associated with at least one polygon having a down-facing component.

30. The computer program media of claim 28, wherein said adjusted position component is that associated with at least one polygon having an up-facing component.

31. A computer program media, embodying a program of instructions executable by a computer to perform a method for forming a three-dimensional object from a plurality of solidified laminar, the method comprising:

manipulating a representation of a three-dimensional object to compress the object representation in a Z-direction by more than one layer thickness to at least partially account for any excess solidified material in the Z-direction which might result from solidifying laminae of the object when using a layer thickness for forming a down-facing region of the object that is less than a solidification depth used in forming the down-facing region; and

providing the manipulated data to a device configured to form a three-dimensional object from a plurality of solidified laminae.

32. A computer program media, embodying a program of instructions executable by a computer to perform a method for altering a representation of a three-dimensional object, for use in forming the three-dimensional object from solidified building material, the method comprising:

taking as input a first representation of the object comprising a first list of vertices of polygons which substantially span a surface of the object, and a second list of representations of the polygons defined in terms of identifiers of the vertices in the first list;

manipulating selected ones of said first list of vertices without having to manipulate said second list of polygonal representations to form an altered representation, said altered representation reflecting an adjustment to a depth component of one or more vertices by more than one thickness layer to at least partially account for excess solidified material that would otherwise be formed during object formation when using a layer thickness for forming a down-facing region of the object that is less than a solidification depth used in forming the down-facing region; and

supplying the altered representation for use in forming the three-dimensional object from solidified building material.

33. A computer program media, embodying a program of instructions executable by a computer to perform a method for converting a first object representation into a second object representation, for use in forming a three-dimensional object from solidified building material, comprising:

associating a grid of cells with the first object representation;

overlaying the first object representation with a plurality of conceptual lines emanating from cells in the grid;

determining Z-components of the points of intersection between the lines and the first object representation;

associating the Z-components with the cells from which the lines used to determine the components emanate;

forming the second object representation from the associated Z-components; and

manipulating said object representation to form an altered representation, said altered representation reflecting an adjustment to one or more of said Z-components by more than one layer thickness to at least partially account for excess solidified material that is otherwise formed during object formation when using a layer thickness for forming a down-facing region of the object that is less than a solidification depth used in forming the down-facing region;

wherein said altered representation comprises data configured for use by a stereolithography device to form a three-dimensional object.

34. A computer program media, embodying a program of instructions executable by a computer to perform a method for converting, a first object representation to a second object representation, for use in forming a three-dimensional object from solidified building material, comprising:

taking as input a first representation of the object;

converting said first representation of the object into said second representation of the object, said second representation including a first list of vertices of a plurality of polygons spanning a surface of the object, and a second list of representations of said plurality of polygons defined in terms of identifiers of the vertices in said first list; and

manipulating said second representation of the three-dimensional object to compress at least a portion of the object representation in a Z-direction by more than one layer thickness to account for cure depth error which might result from solidifying at least one of said successive layers of the object during the formation of said object when using a layer thickness for forming a down-facing region of the object that is less than a solidification depth used in forming the down-facing region.