Planning of computer numerical control (CNC) machining operations with the aid of a digital computer

Patent metadata

Field	Value
Publication number	US-10564626-B2
Application number	US-201615011312-A
Country	US
Kind code	B2
Filing date	Jan 29, 2016
Priority date	Jan 29, 2016
Publication date	Feb 18, 2020
Grant date	Feb 18, 2020

Abstract

A Web-based system and method creates one or more qualitatively distinct process plans for machining a part. The surfaces of the part are modeled and parameters for a plurality of CNC machining tools are obtained, including the orientations along which the tool cuts away raw material. A maximal set of translations for each tool is also obtained, where each translation includes a collision-free orientation of the tool and a maximal machinable volume of material removable from the part in that orientation. A search engine navigates through a hierarchically-structured search space that starts at an initial state and transitions to successive states based on actions that satisfy a cost constraint function. Each state and each action includes a tool, orientation of the tool, and a maximal machinable volume. The search ends when a goal condition is satisfied. The actions constitute the process plan.

First claim

What is claimed:

1. A system for planning of computer numerical control (CNC) machining operations with the aid of a digital computer, comprising:
a storage device, comprising:
a geometric model of a part to be machined, the geometric model defining surfaces of the part;
parameters for a plurality of CNC machining tools, the parameters for each CNC machining tool comprising a plurality of orientations at which the CNC machining tool is able to longitudinally traverse a rotating cutting edge; and
a maximal set of translations for each of the CNC machining tools, each translation comprising one of the orientations of the CNC machining tool where the CNC machining tool's orientation will avoid collisions between the rotating cutting edge and the surfaces of the part and a maximal sub-volume of material removable from the part by the CNC machining tool in the CNC machining tool's orientation for the translation; and

a processor and memory within which code for execution by the processor is stored, further comprising:
a search engine, comprising:
a set of states, each state identifying one of the CNC machining tools, one of the orientations of the CNC machining tool, and each of the states describing a negative volume of the part, with one of the states representing an initial state;
a set of actions, each action identifying one of the CNC machining tools, one of the orientations of the CNC machining tool, and each of the actions describing the maximal sub-volume of material removable from the negative volume of the part in one of the states by the CNC machining tool in the CNC machining tool's orientation; and
a transition module configured to repetitively transition, starting at the initial state, from one of the states to another of the states until a goal condition is met by choosing one of the actions as guided by a heuristic that is based on an aggregate cost associated with the chosen actions and the negative volume that remains after subtracting the maximal sub-volume for the action chosen;

a process planner configured to form a process plan comprising each of the actions chosen when the negative volume that remains is minimal;
a programming module configured to program at least one of the CNC machining tools with the process plan downloaded and comprising machining operations by the CNC machining tool based on the process plan; and
the at least one CNC machining tool configured to operate per the machining operations in the downloaded process plans by machining off the part the maximal sub-volumes through traversals of the rotating cutting edge over the surfaces of the part.

2. A system according to claim 1 , wherein the initial state is defined as comprising none of the CNC machining tools, no orientations of any of the CNC machining tools, and describing a negative volume of the part prior to any machining by any of the CNC machining tools.

3. A system according to claim 1 , wherein the aggregate cost is based on a cost constraint and the cost constraint is expressed as a function of the time to remove from the part the maximal sub-volume of material removable for the action chosen.

4. A system according to claim 3 , wherein the cost constraint is adjusted as a function of the time taken to change from the CNC machining tool for the one state to the CNC machining tool for the action chosen.

5. A system according to claim 4 , wherein the cost constraint is adjusted as a function of the time taken to change the orientation of the CNC machining tool for the one state to the orientation of the CNC machining tool for the action chosen.

6. A system according to claim 5 , wherein the cost constraint C is determined in accordance with the equation:
C ( V S ,T S ,θ S , V a ,T a θ a )= t V ( V S ∩V a T a )+ t T ( T a ,T S )+ t θ (θ a ,θ S )

where V S is the negative volume of the part in state S, T S is the CNC machining tool in state S, θ S is the orientation of the CNC machining tool in state S, V a is the maximal sub-volume of material removable for action a, T a is the CNC machining tool for action a, θ a is the orientation of the CNC machining tool for action a, t V (V,T) is the time to remove from the part the maximal sub-volume of material removable for the action chosen, t T (T a , T S ) is the time taken to change from the CNC machining tool for the one state to the CNC machining tool for the action chosen, and t θ (θ a ,θ S ) is the time taken to change the orientation of the CNC machining tool for the one state to the orientation of the CNC machining tool for the action chosen.

7. A system according to claim 1 , wherein an upper limit is imposed on a size of a search frontier comprised of the set of other states transitionable from the one state based on the set of actions.

8. A system according to claim 1 , further comprising:
a greedy search module configured to set an upper bound based on a pure greedy search through the set of states and to prune transitions from the one state those actions comprising a cost constraint that exceed the upper bound.

9. A system according to claim 1 , the search engine further comprising:
a multiple plan generator configured to perform the repetitive transitioning for a plurality of process plans and to provide a subset of the plurality of process plans as qualitatively distinct.

10. A system according to claim 1 , wherein at least one of the negative volume of the part and the maximal sub-volume of material removable are selected from the group comprising features, slices, polygons, and voxels.

11. A system according to claim 1 , wherein the repetitive transitioning is expressed as a weighted A* search.

12. A method for planning of computer numerical control (CNC) machining operations with the aid of a digital computer, comprising the steps of:
providing a computer comprising a processor, memory and storage with a geometric model of a part to be machined, the geometric model defining surfaces of the part;
providing the computer with parameters for a plurality of CNC machining tools, the parameters for each CNC machining tool comprising a plurality of orientations at which the CNC machining tool is able to longitudinally traverse a rotating cutting edge;
providing the computer with a maximal set of translations for each of the CNC machining tools, each translation comprising one of the orientations of the CNC machining tool where the CNC machining tool's orientation will avoid collisions between the rotating cutting edge and the surfaces of the part and a maximal sub-volume of material removable from the part by the CNC machining tool in the CNC machining tool's orientation for the translation;
representing in the computer a set of states, each state identifying one of the CNC machining tools, one of the orientations of the CNC machining tool, and each of the states describing a negative volume of the part, with one of the states representing an initial state;
representing in the computer a set of actions, each action identifying one of the CNC machining tools, one of the orientations of the CNC machining tool, and each of the actions describing the maximal sub-volume of material removable from the negative volume of the part in one of the states by the CNC machining tool in the CNC machining tool's orientation;
repetitively transitioning, starting at the initial state, by the computer from one of the states to another of the states until a goal condition is met by choosing one of the actions as guided by a heuristic that is based on an aggregate cost associated with the chosen actions and the negative volume that remains after subtracting the maximal sub-volume

Assignees

• Palo Alto Res Ct Inc
• Sandvik Intellectual Property

Inventors

• Nelaturi Saigopal
• Fritz Christian
• Burton Gregory
• Kurtoglu Tolga

Classifications

• G05B19/4097 Primary

  characterised by using design data to control NC machines, e.g. CAD/CAM (G05B19/4093 takes precedence) · CPC title

• G05B2219/32099

  CAPP computer aided machining and process planning · CPC title

• G05B19/4093 Primary

  characterised by part programming, e.g. entry of geometrical information as taken from a technical drawing, combining this with machining and material information to obtain control information, named part program, for the NC machine · CPC title

• Y02P90/265

  Cross-Sectional Technologies · mapped topic

• Y02P90/02

  Total factory control, e.g. smart factories, flexible manufacturing systems [FMS] or integrated manufacturing systems [IMS] · CPC title