Method for machining workpiece

• US 7,331,739 B2
• Filed: 08/12/2004
• Issued: 02/19/2008
• Est. Priority Date: 08/12/2004
• Status: Active Grant

• Current Assignee: Makino Milling Machine Company Limited
• Original Assignee: Makino Milling Machine Company Limited
• Inventors: Kawana, Akira, Kurahashi, Yasuhiro, Yoshida, Jun
• Primary Examiner(s): Ross; Dana
• Application Number:
  US10/538,148
• Publication Number:
  US 20060251484A1
• Time in Patent Office: 1,286 Days
• Field of Search: 409/131, 409/80, 409/84, 409/186, 409/192, 700/175, 415/14, 415/148
• US Class Current: 409/131
• CPC Class Codes: B23Q 15/16 Compensation for wear of the tool
• CPC Class Codes: B23Q 15/28 with compensation for tool wear
• CPC Class Codes: B23Q 17/09 for indicating or measuring cutting pressure or for determining cutting-tool condition, e.g. cutting ability, load on tool arrangements preventing overload of tools B23Q11/04; devices for indicating failure of drills during boring B23B49/00
• CPC Class Codes: B23Q 17/2233 for adjusting the tool relative to the workpiece
• CPC Class Codes: G05B 19/404 characterised by control arrangements for compensation, e.g. for backlash, overshoot, tool offset, tool wear, temperature, machine construction errors, load, inertia G05B19/19, G05B19/41 take precedence
• CPC Class Codes: Y10T 409/300896 with sensing of numerical information and regulation without mechanical connection between sensing means and regulated means [i.e., numerical control]
• CPC Class Codes: Y10T 409/30112 Process
• CPC Class Codes: Y10T 409/303752 Process
• CPC Class Codes: Y10T 409/306832 with infeed control means energized in response to activator stimulated by condition sensor

Abstract

A wear amount of a working tool T during the machining of a workpiece is estimated during the machining, and a positional command generated in accordance with a predetermined machining program is sequentially corrected during the machining based on the estimated wear amount of the working tool T. The workpiece W is machined in accordance with the corrected positional command. Also, the wear amount of the working tool T upon the interruption of the machining operation is calculated, and the positional command generated in accordance with the predetermined machining program is corrected based on the calculated wear amount of the working tool so that a tool edge position of the working tool T upon the interruption of the machining operation coincides with the tool edge position of the working tool T upon the restart of the machining operation when the machining operation is restarted at a position where the machining operation has been interrupted. The workpiece is machined in accordance with the corrected positional command.

Claims

1. A method for machining a workpiece by moving a working tool and the workpiece relative to each other, said method comprising steps of:

generating a positional command based on a predetermined NC machining program;

carrying out the machining operation for the workpiece in accordance with the generated positional command;

interrupting the machining operation for the workpiece;

detecting a wear amount of the working tool upon the interruption of the machining operation for the workpiece; and

correcting a tool edge position of the working tool upon the restart of the machining operation for the workpiece to coincide with the tool edge position of the working tool upon the interruption of the machining operation for the workpiece, based on the detected wear amount of the working tool, and restarting the machining operation for the workpiece from the set tool edge position of the working tool.

2. The method according to claim 1, further comprising a step of accumulating the detected wear amount of the working tool whenever the machining operation for the workpiece is interrupted, wherein said correcting and restarting steps are carried out based on the accumulated wear amount of the working tool.

3. The method according to claim 1, wherein said detecting step comprises steps of measuring a tool edge position of the working tool and calculating the wear amount of the working tool.

4. A method for machining a workpiece by moving a working tool and the workpiece relative to each other, said method comprising steps of:

generating a positional command based on a predetermined NC machining program;

carrying out the machining operation for the workpiece in accordance with the generated positional command;

sequentially estimating a wear amount of the working tool during the machining of the workpiece;

sequentially correcting the tool edge position of the working tool so as to compensate for the estimated wear amount of the working tool;

interrupting the machining operation for the workpiece;

detecting the wear amount of the working tool upon the interruption of the machining operation for the workpiece;

accumulating a difference between the detected wear amount of the working tool and the estimated wear amount of the working tool; and

correcting a tool edge position of the working tool upon the restart of the machining operation to coincide with the tool edge position of the working tool upon the interruption of the machining operation for the workpiece, based on the accumulated wear amount of the working tool, and restarting the machining operation for the workpiece from the set tool edge position of the working tool.

5. The method according to claim 4, wherein said detecting step comprises steps of measuring a tool edge position of the working tool and calculating the wear amount of the working tool.

6. The method according to claim 4, wherein said estimating step comprises a step of estimating a wear amount of the working tool from a cuffing length and a predetermined wear amount per unit cuffing length.

7. The method according to claim 4, wherein said estimating step comprises a step of estimating the wear amount from one or both of a cutting condition and a machining load.

8. The method according to claim 4, wherein said estimating step comprises a step of estimating the wear amount from a cuffing length and a predetermined wear amount per unit cutting length as well as one or both of a cuffing condition and a machining load.

9. The method according to claim 4, wherein said estimating step comprises steps of measuring the tool edge position of the working tool, calculating the wear amount of the working tool, comparing the calculated wear amount of the working tool with the estimated wear amount of the working tool, and sequentially correcting the wear amount per unit cutting length used for the estimation so that the calculated wear amount and the estimated wear amount coincide with each other.

10. A machine tool for machining a workpiece by moving a working tool and the workpiece relative to each other, said machine tool having a function for correcting the wear of the working tool, said machine tool comprising:

a positional command generating means for generating a positional command based on a predetermined NC machining program and moving the working tool and the workpiece relative to each other in accordance with the generated positional command;

a tool wear amount detection means for detecting a wear amount of the working tool upon the interruption of the machining operation for the workpiece; and

a tool edge position control means for correcting a tool edge position of the working tool upon the restart of the machining operation for the workpiece to coincide with the tool edge position of the working tool upon the interruption of the machining operation for the workpiece, based on the wear amount of the working tool detected by said tool wear amount detection means.

11. The machine tool according to claim 10, further comprising a wear amount accumulation means for accumulating the wear amount of the working tool detected by said tool wear amount detection means whenever the machining operation for the workpiece is interrupted, wherein said tool edge position control means corrects the tool edge position of the working tool upon the restart of the machining operation for the workpiece to coincide with the tool edge position of the working tool upon the interruption of the machining operation for the workpiece, based on the accumulated wear amount of the working tool calculated by said wear amount accumulation means, and restarts the machining operation for the workpiece from the set tool edge position of the working tool.

12. A machine tool for machining a workpiece by moving a working tool and the workpiece relative to each other, said machine tool having a function for correcting the wear of the working tool, said machine tool comprising:

a positional command generating means for generating a positional command based on a predetermined NC machining program and moving the working tool and the workpiece relative to each other in accordance with the generated positional command;

a tool wear amount detection means for detecting a wear amount of the working tool upon the interruption of the maching operation for the workpiece;

a tool wear amount estimation means for sequentially estimating a wear amount of the working tool during the machining of the workpiece;

a tool edge position correction means for sequentially correcting the tool edge position of the working tool so as to compensate for the wear amount of the working tool estimated by said tool wear amount estimation means;

a wear amount accumulation means for accumulating a difference between the detected wear amount of the working tool and the estimated wear amount of the working tool; and

a tool edge position control means for correcting a tool edge position of the working tool upon the restart of the machining operation for the workpiece to coincide with the tool edge position of the work tool upon the interruption of the machining operation for the workpiece, based on the accumulated wear amount of the working tool.

13. The machine tool according to claim 12, further comprising a wear coefficient correction means for comparing the wear amount of the working tool detected by said tool wear amount detection means with the wear amount of the working tool estimated by said tool wear amount estimation means and sequentially correcting a wear amount per unit cuffing length used for the estimation so that the detected wear amount and the estimated wear amount coincide with each other.