Numerical control apparatus and control method fo machine tool

• US 20010012972A1
• Filed: 02/05/2001
• Published: 08/09/2001
• Est. Priority Date: 02/03/2000
• Status: Active Grant

• Current Assignee: Toshiba Kikai Kabushiki Kaisha (Shibaura Machine Co., Ltd.)
• Original Assignee: Toshiba Kikai Kabushiki Kaisha (Shibaura Machine Co., Ltd.)
• Inventors: Matsumoto, Ichiro, Fujita, Jun
• Granted Patent: US 6,597,968 B2
• Time in Patent Office: Days
• US Class Current: 700/160
• CPC Class Codes: G05B 19/4166 Controlling feed or in-feed G05B19/4163 takes precedence
• CPC Class Codes: G05B 2219/43063 Acceleration deceleration as function of maximum allowable speed
• CPC Class Codes: Y02P 90/02 Total factory control, e.g. smart factories, flexible manufacturing systems [FMS] or integrated manufacturing systems [IMS]

Abstract

A numerical control apparatus of a machine tool capable of shortening a machining time while maintaining a machining precision of a workpiece, provided with an analyzer for analyzing a machining program defining machining process of a workpiece by the machine tool to extract information for specifying a feed speed of a cutting tool to the workpiece and cutting/non-cutting information for defining actual cutting by the cutting tool added to a cutting feed command program from the cutting feed command program contained in this machining program, a feed speed optimizer for calculating a permissible feed speed of the cutting tool in accordance with content of the cutting/non-cutting information based on the extracted information and optimizing the feed speed of the cutting tool so as to be within the permissible feed speed, and a distribution unit for calculating control commands to be distributed to the control axes of the machine tool based on the optimized feed speed.

Claims

1. A numerical control apparatus of a machine tool comprising:

an analyzing means for analyzing a machining program defining machining process of a workpiece by the machine tool to extract from, a cutting feed command program included in said machining program, information for specifying a feed speed of a cutting tool to the workpiece and cutting/non-cutting information defining actual cutting by said cutting tool added to said cutting feed command program,

a feed speed optimizing means for calculating a permissible feed speed of said cutting tool in accordance with the content of the cutting/non-cutting information based on said extracted information and optimizing the feed speed of the cutting tool to be within said permissible feed speed, and

a distributing means for calculating control commands to be distributed to the control axes of the machine tool based on the optimized feed speed.

2. A numerical control apparatus of a machine tool as set forth in

claim 1

, wherein said feed speed optimizing means comprises

a non-cutting feed permissible error setting means for setting a permissible error defining a permissible range of error from a path of movement of said cutting tool at the time of non-cutting feed,

a cutting feed permissible error setting means for setting a permissible error at the time of cutting feed, and

a target feed speed calculating means for selecting one of the permissible errors set by the non-cutting feed permissible error setting means and cutting feed permissible error setting means in accordance with the content of said cutting/non-cutting information, calculating the permissible feed speed based on the selected permissible error, and restricting the feed speed of the cutting tool to the permissible feed speed to optimize it.

3. A numerical control apparatus of a machine tool as set forth in

claim 2

, wherein said feed speed optimizing means comprises

a non-cutting feed acceleration setting means for setting a permissible acceleration at the time of non-cutting feed of the cutting tool,

a cutting feed acceleration setting means for setting a permissible acceleration at the time of cutting feed of the cutting tool, and

an acceleration/deceleration processing means for selecting one of the permissible accelerations set by the non-cutting feed acceleration setting means and cutting feed acceleration setting means in accordance with the content of said cutting/non-cutting information and calculating the permissible feed speed of said cutting tool restricting the acceleration of the cutting tool to the permissible acceleration to optimize the feed speed.

4. A numerical control apparatus of a machine tool as set forth in

claim 1

, wherein said cutting feed command program defines the path of movement of the machining point of the cutting tool by a curve.

5. A numerical control apparatus of a machine tool as set forth in

claim 2

, wherein said target feed speed calculating means calculates the permissible feed speed from the permissible error, a position loop gain of a servo controlling means controlling the control axes based on said distributed control commands, and a radius of curvature of the path of movement of a machining point of said cutting tool.

6. A numerical control apparatus of a machine tool as set forth in

claim 5

, wherein said acceleration/deceleration processing means calculates said permissible feed speed from said radius of curvature of the path of movement of the machining point of said cutting tool and the permissible acceleration.

7. A numerical control apparatus of a machine tool comprising:

an analyzing means for analyzing a machining program defining machining process of a workpiece by the machine tool to extract from, a cutting feed command program included in said machining program, information for specifying a feed speed of a cutting tool to the workpiece and permissible error defining a permissible range of error from the path of movement of said cutting tool added to said cutting feed command program,

a feed speed optimizing means for calculating a permissible feed speed of said cutting tool in accordance with the permissible error based on said extracted information and optimizing the feed speed of the cutting tool to be within said permissible feed speed, and

a distributing means for calculating control commands to be distributed to the control axes of the machine tool based on the optimized feed speed.

8. A numerical control apparatus of a machine tool as set forth in

claim 7

, wherein said feed speed optimizing means further comprises an acceleration/deceleration processing means for calculating the permissible feed speed of said cutting tool restricting the acceleration of the cutting tool to the permissible acceleration and further optimizing the optimized feed speed based on the permissible feed speed.

9. A numerical control apparatus of a machine tool comprising:

an analyzing means for analyzing a machining program defining machining process of a workpiece by the machine tool to extract from, a cutting feed command program included in said machining program, information for specifying a feed speed of a cutting tool to the workpiece and machining information added to said cutting feed command program,

a feed speed optimizing means for optimizing a feed speed of said cutting tool based on said extracted information, and

a distributing means for calculating control commands to be distributed to the control axes of the machine tool based on the optimized feed speed.

10. A control method of a machine tool comprising the steps of:

preparing a machining program defining machining process of a workpiece by the machine tool provided with a cutting tool able to move in the directions of a plurality of control axes by a driving means,

adding cutting/non-cutting information defining actual cutting by said cutting tool to a cutting feed command program included in said machining program,

downloading the machining program added with the cutting/non-cutting information to a numerical control apparatus and executing said machining program,

extracting at said numerical control apparatus, from said cutting feed command program, information for specifying a feed speed of said cutting tool to a workpiece and cutting/non-cutting information,

calculating the permissible feed speed of said cutting tool in accordance with the content of the cutting/non-cutting information based on said information for specifying the feed speed of the cutting tool and optimizing the feed speed of the cutting tool to be within said permissible feed speed, and

calculating control commands to be distributed to the control axes of the machine tool based on the optimized feed speed and controlling the control axes.

11. A control method of a machine tool as set forth in

claim 10

, further comprises a step of selecting one of the preset permissible errors at the time of non-cutting feed and at the time of cutting feed in accordance with the extracted cutting/non-cutting information and calculating the permissible feed speed based on the selected permissible error.

12. A control method of a machine tool as set forth in

claim 11

, further comprises a step of selecting one of the preset permissible acceleration at the time of non-cutting feed of the cutting tool and permissible acceleration at the time of cutting feed in accordance with the cutting/non-cutting information and calculating the permissible feed speed of the cutting tool restricting the acceleration of the cutting tool to the permissible acceleration.

13. A control method of a machine tool provided with a numerical control apparatus for driving a machine tool to execute cutting of a workpiece in accordance with a machining program, comprising the steps of:

preparing a machining program defining machining process of a workpiece by the machine tool,

adding information of a permissible error defining a permissible range of error from a path of movement of a cutting tool to a cutting feed command program included in said machining program,

downloading the machining program added with the information of the permissible error to a numerical control apparatus and executing said machining program,

extracting at said numerical control apparatus, from said cutting feed command program, information for specifying a feed speed of said cutting tool to the workpiece and said information of the permissible error,

calculating the permissible feed speed of said cutting tool in accordance with the permissible error based on said extracted information and optimizing the feed speed of the cutting tool to be within said permissible feed speed, and

calculating control commands to be distributed to the control axes of the machine tool based on the optimized feed speed and controlling the control axes.

14. A control method of a machine tool provided with a numerical control apparatus for driving a machine tool to execute cutting of a workpiece in accordance with a machining program, comprising the steps of:

preparing a machining program defining a machining process of a workpiece by the machine tool,

adding predetermined machining information to a cutting feed command program included in said machining program,

downloading the machining program added with the machining information to a numerical control apparatus and executing said machining program,

extracting at said numerical control apparatus, from said cutting feed command program, information for specifying a feed speed of said cutting tool to a workpiece and said machining information,

optimizing the feed speed of the cutting tool based on the extracted information, and

calculating control commands to be distributed to the control axes of the machine tool based on the optimized feed speed and controlling the control axes.