US4907164A
Expired / Lapsed
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Automatically optimized NC tool path generation for machining
Assignee: General Electric Co
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Filing: 1988-09-26
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Granted: 1990-03-06
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Expires: 2008-09-26
Abstract
Abstract A method is presented to generate 2D tool paths and to optimize the ordering of these tool paths for 21/2 axis milling of cavities for molds and dies. All motion of the cutting tool is dictated and the number of retractions is reduced to a minimum without violating a prechosen set of ordering guidelines. Predrill locations for tool plunges are specified. A 3D solid model of the cavity region with optional islands, avoidance and containment regions is constructed and a planar section through the model forms a closed curve with nested and disjoint loops. Successive inset curves are taken until there are no arcs in the curve. An ordered list of roughing tool paths is generated with a retraction indicated when necessary to prevent gouging, and finishing tool paths are augmented with tangential approach and exit arcs and milled last.
Inventors
- 👤 Margaret K. Guyder
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-03 14:04
CPC Classifications
G; G05; G05B; G05B19/00; G05B19/02; G05B19/18; G05B19/41; G05B2219/00; G05B2219/30; G05B2219/36; G05B2219/36214
Claims Analysis
Total Claims: 19
Claim 1
Independent Claim
217 words
A method of generating optimized tool paths for milling mold and die parts with a cutting tool comprising: providing a three-dimensional solid model of a part cavity to be milled, taking a planar section through said model and obtaining a closed curve which describes boundaries of said cavity and has a plurality of loops oriented such that material to be cut is on the left; deriving a first inset curve at a given distance from said closed curve each loop of which is a finishing tool path across which said tool cannot move without gouging and each starting a nest of tool paths; repeatedly generating other inset curves at a constant distance from a previous inset curve every loop of which is a roughing tool path and is a member of one nest or starts a new nest, numbering all of said roughing tool paths in sequence, and stopping when a last inset curve has no arcs; ordering said roughing tool paths in an optimized sequence to mill said cavity so as to follow a prechosen set of ordering guidelines while minimizing retraction of said tool to go to another roughing tool path, and generating tool motion paths to move between said roughing tool paths; and augmenting said finishing tool paths with tangential approach and finish routes.
Claim 2
Independent Claim
217 words
A method of generating optimized tool paths for milling mold and die parts with a cutting tool comprising: providing a three-dimensional solid model of a part cavity to be milled, taking a planar section through said model and obtaining a closed curve which describes boundaries of said cavity and has a plurality of loops oriented such that material to be cut is on the left; deriving a first inset curve at a given distance from said closed curve each loop of which is a finishing tool path across which said tool cannot move without gouging and each starting a nest of tool paths; repeatedly generating other inset curves at a constant distance from a previous inset curve every loop of which is a roughing tool path and is a member of one nest or starts a new nest, numbering all of said roughing tool paths in sequence, and stopping when a last inset curve has no arcs; ordering said roughing tool paths in an optimized sequence to mill said cavity so as to follow a prechosen set of ordering guidelines while minimizing retraction of said tool to go to another roughing tool path, and generating tool motion paths to move between said roughing tool paths; and augmenting said finishing tool paths with tangential approach and finish routes.
Claim 3
Dependent Claim
29 words
The method of claim 1 further comprising generating a list of predrill locations at starting points of said tool paths where said cutting tool plunges from a retracted position.
Claim 4
Dependent Claim
16 words
The method of claim 1 wherein said numbering comprises assigning highest numbers to innermost tool paths.
Claim 5
Dependent Claim
33 words
The method of claim 3 which further comprises generating an ordered list of said tool path numbers in the order to be milled separated by a retraction symbol where required to prevent gouging.
Claim 6
Dependent Claim
24 words
The method of claim 4 wherein said nest of tool paths are milled from innermost to outermost unless one of said guidelines is violated.
Claim 7
Dependent Claim
17 words
The method of claim 4 wherein said tool motion paths between roughing tool paths are straight lines.
Claim 8
Dependent Claim
52 words
The method of claim 4 wherein said ordering said roughing tool paths is an optimized sequence comprises making interference checks to determine that there is no intersection with said first inset curve and with an unmilled nest of tool paths and with an about-to-be milled tool path except at a starting point.
Claim 9
Dependent Claim
101 words
The method of claim 1 wherein said set of ordering guidelines are that (a) gouge free milling is required, (b) prevent milling both sides of one tool path before milling the tool path itself, (c) prevent cutting all or part of one tool path more than once, (d) mill the tool paths that are innermost first, (e) finishing tool paths are milled separately from roughing paths and last, (f) the tool intersects the path-to-be milled only at a starting point, (g) the tool intersects no unmilled nest of tool paths, and (h) the tool may cross milled nest of tool paths.
Claim 10
Dependent Claim
39 words
The method of claim 1 wherein the distance of said first inset curve from said closed curve is equal to the radius of said cutting tool plus a prescribed thickness to be left on a surface of the part.
Claim 11
Dependent Claim
43 words
The method of claim 1 wherein there is a containment region to which milling is restricted and said providing a three-dimensional solid model comprises modeling the containment region and intersecting with a model of said part cavity to thereby form a milling region.
Claim 12
Dependent Claim
43 words
The method of claim 1 wherein there is an avoidance region where milling is prohibited and said providing a three dimensional solid model comprises modeling the avoidance region and subtracting from a model of said part cavity to thereby form a milling region.
Claim 13
Dependent Claim
30 words
The method of claim 1 further comprising repeating the foregoing steps beginning with taking a planar section and generating optimized two-dimensional tool paths at other levels of said part cavity.
Claim 14
Independent Claim
286 words
A method of generating optimized tool paths for milling molds and dies with a cutting tool comprising: providing a three-dimensional solid model of a part cavity and of-any containment and avoidance regions to which milling is respectively restricted and is prohibited, and forming a milling region by intersecting said cavity and any containment region and subtracting therefrom any avoidance region; taking a planar section through said milling region and obtaining a closed curve which describes boundaries of said milling region and has a plurality of loops oriented such that material to be cut is on the left; deriving a first inset curve at a given distance from said closed curve each loop of which is a finishing tool path across which said tool cannot move without gouging and each starting a nest of tool paths, and numbering every finishing tool path in sequence; repeatedly generating other inset curves at a constant distance from a previous inset curve each loop of which is a roughing tool path and is a member of one nest or starts a new nest, numbering said roughing tool paths in sequence such that the innermost path has the highest number, and stopping when a last inset curve has no arcs; ordering said roughing tool paths in an optimized sequence to mill said cavity so as to follow a prechosen set of ordering guidelines while minimizing the number of retractions of said tool to mill a next tool path, outputting a list of said tool paths in the order to be milled separated by a retraction indication, and generating straight line tool motion paths to move to the next tool path; and augmenting said finishing tool paths with tangential approach and finish arcs.
Claim 15
Independent Claim
286 words
A method of generating optimized tool paths for milling molds and dies with a cutting tool comprising: providing a three-dimensional solid model of a part cavity and of-any containment and avoidance regions to which milling is respectively restricted and is prohibited, and forming a milling region by intersecting said cavity and any containment region and subtracting therefrom any avoidance region; taking a planar section through said milling region and obtaining a closed curve which describes boundaries of said milling region and has a plurality of loops oriented such that material to be cut is on the left; deriving a first inset curve at a given distance from said closed curve each loop of which is a finishing tool path across which said tool cannot move without gouging and each starting a nest of tool paths, and numbering every finishing tool path in sequence; repeatedly generating other inset curves at a constant distance from a previous inset curve each loop of which is a roughing tool path and is a member of one nest or starts a new nest, numbering said roughing tool paths in sequence such that the innermost path has the highest number, and stopping when a last inset curve has no arcs; ordering said roughing tool paths in an optimized sequence to mill said cavity so as to follow a prechosen set of ordering guidelines while minimizing the number of retractions of said tool to mill a next tool path, outputting a list of said tool paths in the order to be milled separated by a retraction indication, and generating straight line tool motion paths to move to the next tool path; and augmenting said finishing tool paths with tangential approach and finish arcs.
Claim 16
Dependent Claim
29 words
The method of claim 13 further comprising generating a list of predrill locations at starting points of said tool paths where said cutting tool plunges from a retracted position
Claim 17
Dependent Claim
50 words
The method of claim 14 wherein said ordering tool paths in an optimized sequence comprises making interference checks to determine that there is no intersection with said first inlet curve and with an unmilled nest of tool paths and with an about-to-be milled tool path except at the starting point.
Claim 18
Dependent Claim
101 words
The method of claim 13 wherein said set of ordering guidelines are that (a) gouge free milling is required, (b) prevent milling both sides of one tool path before milling the tool path itself, (c) prevent cutting all or part of one tool path more than once, (d) mill the tool paths that are innermost first, (e) finishing tool paths are milled separately from roughing paths, and last, (f) the tool intersects the path-to-be milled only at a starting point, (g) the tool intersects no unmilled nest of tool paths, and (h) the tool may cross milled nest of tool paths.
Claim 19
Dependent Claim
30 words
The method of claim 13 further comprising repeating the foregoing steps beginning with taking a planar section and generating optimized two-dimensional tool paths at other levels of said part cavity.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1993-03-05 | 1993-09-04 | 1994-03-06 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1997-03-05 | 1997-09-04 | 1998-03-06 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2001-03-05 | 2001-09-04 | 2002-03-06 | $7700.00 | Window Closed / Lapsed |