Method and apparatus for preparing data on tool moving path, and machining method and system

• US 6,311,098 B1
• Filed: 09/28/1998
• Issued: 10/30/2001
• Est. Priority Date: 03/26/1996
• Status: Expired due to Fees

• Current Assignee: Nihon Unisys Limited, Toyota Jidosha Kabushiki Kaisha (Toyota Motor Corporation)
• Original Assignee: Nihon Unisys Limited, Toyota Jidosha Kabushiki Kaisha (Toyota Motor Corporation)
• Inventors: Higasayama, Haruhisa, Tamaoka, Kouji, Kajisa, Eisuke, Kato, Hagemu, Muta, Yoshiki
• Primary Examiner(s): Wiley, David
• Assistant Examiner(s): Backer, Firmin
• Application Number:
  US09/155,409
• Time in Patent Office: 1,128 Days
• Field of Search: 700/159, 700/188, 700/145, 700/160, 700/186, 700/184, 711/158
• US Class Current: 700/159
• CPC Class Codes: G05B 19/4099 Surface or curve machining, making 3D objects, e.g. desktop manufacturing
• CPC Class Codes: G05B 2219/35108 Generate offset tool moving path in restrained curved plane

Abstract

Method of generating tool movement path data 9 includes determining a tool constraining surface (12) which is offset from a three-dimensional surface (22) to be generated, by a distance equal to a radial dimension of rotary machining tool (20), in a direction normal to the three-dimensional surface, determining tool path constraining surfaces (32) for constraining the tool according to the geometry of the three-dimensional surface, and obtaining three-dimensional curved line equations representing intersection lines (34) between the constraining surfaces (12, 32). Since desired curved surfaces may be used as the tool path constraining surfaces (32), the tool movement path can be suitably determined with high freedom depending upon the geometry of the three-dimensional surface (22) to be generated. The tool movement path data generated from three-dimensional curved line equations have a reduced volume but assure high machining accuracy, as compared with tool movement path data consisting of a multiplicity of cutter location points to which the tool is moved.

Claims

1. A method of generating tool movement path data for moving a machining tool and a workpiece relative to each other for machining a desired three-dimensional surface, characterized by comprising:

a first constraining surface determining step of determining a first constraining surface for constraining said machining tool to machine said three-dimensional surface, said first constraining surface corresponding to said three-dimensional surface;

a second constraining surface determining step of determining a second constraining surface for constraining a movement path of said machining tool, said second constraining surface consisting of a surface other than a straight surface and other than said three-dimensional surface, and intersecting said first constraining surface;

an intersection line calculating step of obtaining a three-dimensional curved line equation representing a line of intersection between said first and second constraining surfaces; and

a movement path data obtaining step of obtaining said movement path data including said three-dimensional curved line equation obtained in said intersection line calculating step.

2. A method according to claim 1, further comprising:

a normal vector calculating step of obtaining normal vectors of said first constraining surface on the intersection line between said first and second constraining surfaces, at a predetermined spacing interval; and

a normal curved line calculating step of obtaining a three-dimensional curved line equation representing a smooth normal curved line passing end portions of said normal vectors, in relation to the intersection line between said first and second constraining surfaces,

and wherein said movement path data obtaining step comprises generating the tool movement path data including the three-dimensional curved line equation of the intersection line between said first and second constraining surfaces, and the three-dimensional curved line equation of said normal curved line so that the tool movement path data include data indicative of an attitude of said machining tool.

3. A method according to claim 1 wherein said intersection line calculating step comprises obtaining the three-dimensional curved line equation of the intersection line between said first and second constraining surfaces, according to a patch boundary method, where there exist two points of intersection between an edge of said first constraining surface and said second constraining surface.

4. A method according to claim 1, wherein said intersection line calculating step comprises obtaining the three-dimensional curved line equation of the intersection line between said first and second constraining surfaces, according to a geometrical intersection tracing method, where the number of points of intersection between an edge of said first constraining surface and said second constraining surface is not equal to two;

where the number of the intersecting points is not equal to two, it is desirable to obtain.

5. A method according to claim 1, wherein said machining tool has a machining end portion having a semi-spherical shape, and said first constraining surface constrains a center of a sphere of said semi-spherical machining end portion,

and wherein said first constraining surface determining step comprises determining, where it is determined that the normal direction cannot be correctly recognized in at least a portion of said three-dimensional surface to be generated, a multiplicity of reference points on said three-dimensional surface at a predetermined spacing interval, locating spheres having a radius equal to that of said semi-spherical machining end portion of said machining tool, in alignment with centers of the reference points, respectively, and defining said first constraining surface based on segments of spherical surfaces of the spheres which are most distant from the three-dimensional surface.

6. A method according to claim 1, said machining tool has a machining end portion having a semi-spherical shape, and said first constraining surface constrains a center of a sphere of said semi-spherical machining end portion,

and wherein the three-dimensional curved line equation of the intersection line between said first and second constraining surfaces is obtained by one of three calculating methods consisting of a first method, a second method and a third method, said first method being practiced where it is determined that a normal direction of the three-dimensional surface to be generated can be correctly recognized, said first method comprising obtaining normal vectors of said three-dimensional surface and determining as said first constraining surface an offset surface which is offset from said three-dimensional surface in the normal direction by a distance equal to a radius of said semi-spherical machining end portion of said machining tool, in said first constraining surface determining step, said first method further comprising obtaining the three-dimensional curved line equation of the intersection line between said first and second constraining surfaces according to a patch boundary method, in said intersection line calculating step, where there exist two points of intersection between an edge of said first constraining surface and said second constraining surface,

said second method being practiced where it is determined that the normal direction of the three-dimensional surface to be generated can be correctly recognized, said second method comprising obtained normal vectors of said three-dimensional surface and determining as said first constraining surface an offset surface which is offset from said three-dimensional surface in the normal direction by a distance equal to the radius of said semi-spherical machining end portion of said machining tool, in said first constraining surface determining step, said second method further comprising obtaining the three-dimensional curved line equation of the intersection line between said first and second constraining surfaces according to a geometrical intersection tracing method, in said intersection line calculating step, where the number of said points of intersection between the edge of said first constraining surface and said second constraining surface,

said third method being practiced where it is determined that the normal direction cannot be correctly recognized in at least a portion of said three-dimensional surface to be generated, said third method comprising determining a multiplicity of reference points on said three-dimensional surface at a predetermined spacing interval, locating spheres having a radius equal to that of the semi-spherical machining end portion of said machining tool, in alignment with centers of the reference points, respectively, and defining said first constraining surface based on segments of spherical surfaces of the spheres which are most distant from the three-dimensional surface, in said first constraining surface determining step, said third method further comprising obtaining the three-dimensional curved line equation of the intersection line between said first and second constraining surfaces in a predetermined calculating manner, in said intersection line calculating step,

and wherein if an error is constituted in said one of said three methods, the three-dimensional curved line equation is obtained according to another of said three methods.

11. A method according to claim 2, characterized in that said intersection line calculating step comprises obtaining the three-dimensional curved line equation of the intersection line between said first and second constraining surfaces, according to a patch boundary method, where there exist two points of intersection between an edge of said first constraining surface and said second constraining surface.

12. A method according to claim 2, characterized in that said intersection line calculating step comprises obtaining the three-dimensional curved line equation of the intersection line between said first and second constraining surfaces, according to a geometrical intersection tracing method, where the number of points of intersection between an edge of said first constraining surface and said second constraining surface is not equal to two where the number of the intersecting points is not equal to two, it is desirable to obtain.

13. A method according to claim 3, characterized in that said intersection line calculating step comprises obtaining the three-dimensional curved line equation of the intersection line between said first and second constraining surfaces, according to a geometrical intersection tracing method, where the number of points of intersection between an edge of said first constraining surface and said second constraining surface is not equal to two where the number of the intersecting points is not equal to two, it is desirable to obtain.

14. A method according to claim 2, characterized in that said machining tool has a machining end portion having a semi-spherical shape, and said first constraining surface constrains a center of a sphere of said semi-spherical machining end portion,

and wherein said first constraining surface determining step comprises determining a multiplicity of reference points on said three-dimensional surface at a predetermined spacing interval, locating spheres having a radius equal to that of said semi-spherical machining end portion of said machining tool, in alignment with centers of the reference points, respectively, and defining said first constraining surface based on segments of spherical surfaces of the spheres which are most distant from the three-dimensional surface.

15. A method according to claim 3, characterized in that said machining tool has a machining end portion having a semi-spherical shape, and said first constraining surface constrains a center of a sphere of said semi-spherical machining end portion,

and wherein said first constraining surface determining step comprises determining a multiplicity of reference points on said three-dimensional surface at a predetermined spacing interval, locating spheres having a radius equal to that of said semi-spherical machining end portion of said machining tool, in alignment with centers of the reference points, respectively, and defining said first constraining surface based on segments of spherical surfaces of the spheres which are most distant from the three-dimensional surface.

16. A method according to claim 4, characterized in that said machining tool has a machining end portion having a semi-spherical shape, and said first constraining surface constrains a center of a sphere of said semi-spherical machining end portion,

and wherein said first constraining surface determining step comprises determining a multiplicity of reference points on said three-dimensional surface at a predetermined spacing interval, locating spheres having a radius equal to that of said semi-spherical machining end portion of said machining tool, in alignment with centers of the reference points, respectively, and defining said first constraining surface based on segments of spherical surfaces of the spheres which are most distant from the three-dimensional surface.

17. A method according to claim 2, characterized in that said machining tool has a machining end portion having a semi-spherical shape, and said first constraining surface constrains a center of a sphere of said semi-spherical machining end portion,

and wherein the three-dimensional curved line equation of the intersection line between said first and second constraining surfaces is obtained by one of the three calculation methods consisting of a first method, a second method and a third method, said first method being practiced where it is determined that a normal direction of the three-dimensional surface to be generated can be correctly recognized, said first method comprising obtaining normal vectors of said three-dimensional surface and determining as said first constraining surface an offset surface which is offset from said three-dimensional surface in the normal direction by a distance equal to a radius of said semi-spherical machining end portion of said machining tool, in said first constraining surface determining step, said first method further comprising obtaining the three-dimensional curved line equation of the intersection line between said first and second constraining surfaces according to a patch boundary method, in said intersection line calculation step, where three exist two points of intersection between an edge of said first constraining intersection between an edge of said first constraining surface and said second constraining surface,

said second method being practiced where it is determined that the normal direction of the three-dimensional surface to be generated can be correctly recognized, said second method comprising obtained normal vectors of said three-dimensional surface and determining as said first constraining surface an offset surface which is offset from said three-dimensional surface in the normal direction by a distance equal to the radius of said semi-spherical machining end portion of said machining took, in said first constraining surface determining step, said second method further comprising obtaining the three-dimensional curved line equation of the intersection line between said first and second constraining surfaces according to a geometrical intersection tracing method, in said intersection line calculating step, where the number of said points of intersection between the edge of said first constraining surface and said second constraining surface,

said third method being practiced where it is determined that the normal direction cannot be correctly recognized in at least a portion of said three-dimensional surface to be generated, said third method comprising determining a multiplicity of reference points on said three-dimensional surface at a predetermined spacing interval, locating spheres having a radius equal to that of the semi-spherical machining end portion of said machining took, in alignment with centers of the reference points, respectively, and defining said first constraining surface based on segments of spherical surfaces of the spheres which are most distant from the three-dimensional surface, in said first constraining surface determining step, said third method further comprising obtaining the three-dimensional curved line equation of the intersection line between said first and second constraining surfaces in a predetermined calculating manner, in said intersection line calculating step,

and wherein if an error is constituted in said one of said three methods, the three-dimensional curved line equation is obtained according to another of said three methods.

18. A method according to claim 1, wherein said machining tool has a semi-spherical shape in an end portion thereof, and wherein said second constraining surface is determined such that a center of a sphere of said end portion of said machining tool is moved on said second constraining surface.

7. A method of generating tool movement path data for moving a machining tool and a workpiece relative to each other for machining a desired three-dimensional surface, characterized by comprising:

a first constraining surface determining step of determining a first constraining surface for constraining said machining tool to machine said three-dimensional surface, said first constraining surface corresponding to said three-dimensional surface;

a second constraining surface determining step of determining a second constraining surface for constraining a movement path of said machining tool, said second constraining surface consisting of a straight or curved surface which is other than said three-dimensional surface, and intersecting said first constraining surface and said three-dimensional surface to be machined;

an intersection line calculating step of obtaining a three-dimensional curved line equation representing a line of intersection between said first and second constraining surfaces;

a normal vector calculating step of obtaining normal vectors of said first constraining surface on the intersection line between said first and second constraining surfaces, at a predetermined spacing interval;

a normal curved line calculating step of obtaining a smooth normal curved line passing end points of said normal vectors; and

a movement path data generating step of obtaining said movement path data including data representing an attitude of said machining tool, based on the intersection line between said first and second constraining surface and said normal curved line.

19. A method according to claim 7, wherein said machining tool has a semi-spherical shape in an end portion thereof, and wherein said second constraining surface is determined such that a center of a sphere of said end portion of said machining tool is moved on said second constraining surface.

8. A device for generating tool movement path data for moving a machining tool and a workpiece relative to each other for machining a desired three-dimensional surface, characterized by comprising:

first constraining surface determining means for determining a first constraining surface for constraining said machining tool to machine said three-dimensional surface, said first constraining surface corresponding to said three-dimensional surface;

second constraining surface determining means for determining a second constraining surface for constraining a movement path of said machining tool, said second constraining surface consisting of a surface other than a straight surface and other than said three-dimensional surface, and intersecting said first constraining surface;

intersection line calculating means for obtaining a three-dimensional curved line equation representing a line of intersection between said first and second constraining surfaces; and

movement path data generating means for obtaining said movement path data including data three-dimensional curved line equation obtained by said intersection line obtaining means.

20. A method according to claim 8, wherein said machining tool has a semi-spherical shape in an end portion thereof, and wherein said second constraining surface is determined such that a center of a sphere of said end portion of said machining tool is moved on said second constraining surface.

9. A method of machining a desired three-dimensional surface in a workpiece, by moving a machining tool and a workpiece, said method comprising:

a first constraining surface determining step of determining a first constraining surface for constraining said machining tool to machine said three-dimensional surface, said first constraining surface corresponding to said three-dimensional surface;

a second constraining surface determining step of determining a second constraining surface for constraining a movement path of said machining tool, said second constraining surface consisting of a surface other than a straight surface and said three-dimensional surface, and intersecting said first constraining surface;

an intersection line calculating step of obtaining a three-dimensional curved line equation representing a line of intersection between said first and second constraining surfaces;

a movement path determining step of determining the movement path of the machining tool by using said three-dimensional curved line equation obtained in said intersection line obtaining step; and

a tool moving step of determining successive target positions on the movement path which is determined in said movement path determining step and which is a three-dimensional curved line represented by said three-dimensional curved line equation, and moving said machining tool relative to said workpiece.

21. A method according to claim 9, wherein said machining tool has a semi-spherical shape in an end portion thereof, and wherein said second constraining surface is determined such that a center of a sphere of said end portion of said machining tool is moved on said second constraining surface.

10. A machining system for machining a desired three-dimensional surface in a workpiece by moving a machining tool and a workpiece relative to each other said machining system comprising:

first constraining surface determining means for determining a first constraining surface for constraining said machining tool to machine said three-dimensional surface, said first constraining surface corresponding to said three-dimensional surface;

second constraining surface determining means for determining a second constraining surface for constraining a movement path of said machining tool, said second constraining surface consisting of a surface other than a straight surface and said three-dimensional surface, and intersecting said first constraining surface;

intersection line calculating means for obtaining a three-dimensional curved line equation representing a line of intersection between said first and second constraining surfaces;

movement path determining means for determining the movement path of the machining tool by using said three-dimensional curved line equation obtained in said intersection line obtaining step; and

tool movement control means for determining successive target positions on the movement path which is determined in said movement path determining step and which is a three-dimensional curved line represented by said three-dimensional curved line equation, and moving said machining tool relative to said workpiece.

22. A method according to claim 10, wherein said machining tool has a semi-spherical shape in an end portion thereof, and wherein said second constraining surface is determined such that a center of a sphere of said end portion of said machining tool is moved on said second constraining surface.

23. A method of generating tool movement path data for moving a machining tool and a workpiece relative to each other for machining a desired three-dimensional surface, characterized by comprising:

a first constraining surface determining step of determining a first constraining surface for constraining said machining tool to machine said three-dimensional surface, said first constraining surface corresponding to said three-dimensional surface;

a second constraining surface determining step of determining a second constraining surface for constraining a movement path of said machining tool, on the basis of a geometry of said three-dimensional surface, in such a manner that makes it possible to avoid abrupt changes in a direction in which said machining tool and said workpiece are moved relative to each other, said second constraining surface consisting of a surface other than a straight surface and other than said three-dimensional surface, said second constraining surface intersecting said first constraining surface and being parallel to an axis of said machining tool;

an intersection line calculating step of obtaining a three-dimensional curved line equation representing a line of intersection between said first and second constraining surfaces; and

a movement path data obtaining step of obtaining said movement path data including said three-dimensional curved line equation obtained in said intersection line calculating step.