Method for compensating milling cutter deflection

Patent metadata

Field	Value
Publication number	US-10788807-B2
Application number	US-201815960240-A
Country	US
Kind code	B2
Filing date	Apr 23, 2018
Priority date	Apr 25, 2017
Publication date	Sep 29, 2020
Grant date	Sep 29, 2020

Abstract

A method for compensating for the deflection of a milling cutter during the machining of a workpiece by a numerically controlled machine tool having a plurality of axes includes: executing a learning cut on a test workpiece having a known geometry by the milling cutter mounted on a tool spindle in a climb milling mode, and in doing so, ascertaining a correlation between a quantity that is proportional to the torque of the drive of the tool spindle and the deflection of the milling cutter normal to a surface of the test workpiece, the deflection being determined by comparing the actual contour of the test workpiece to a setpoint contour. This is followed by storing of the correlation for the milling cutter and machining of the workpiece by the milling cutter in a climb milling mode, while utilizing the stored correlation for compensating for the deflection of the milling cutter by applying a positional correction that is proportional to the quantity to a setpoint position of the axes of the machine tool.

First claim

What is claimed is:

1. A method for compensating for deflection of a milling cutter during processing of a workpiece by a numerically controlled machine tool having a plurality of axes, comprising:
performing a learning cut on a test workpiece having a known geometry using the milling cutter mounted on a tool spindle in a climb milling mode;
ascertaining a linear correlation between a quantity that is proportional to torque of a drive of the tool spindle and the deflection of the milling cutter normal to a surface of the test workpiece, the deflection being determined by comparing an actual contour of the test workpiece to a setpoint contour;
storing the linear correlation for the milling cutter; and
machining the workpiece by the milling cutter using the climb milling mode, and utilizing the stored linear correlation in order to compensate for the deflection of the milling cutter by applying a positional correction that is proportional to the quantity to a setpoint position of the axes of the machine tool.

2. The method according to claim 1 , wherein the performing of the learning cut and/or the ascertaining of the linear correlation includes measuring the test workpiece with the aid of a touch probe.

3. The method according to claim 1 , wherein the performing of the learning cut includes storing a rotational speed and/or a forward feed speed of the milling cutter used for the learning cut as a marginal condition, and wherein the machining of the workpiece includes monitoring the marginal condition.

4. The method according to claim 1 , further comprising detecting and/or forcing, in accordance with simulation and/or programming, a climb milling mode.

5. The method according to claim 1 , wherein the quantity that is proportional to the torque of the drive of the tool spindle includes a load current of the drive ascertained during the learning cut.

6. The method according to claim 5 , wherein a current flowing in the drive of the tool spindle during the learning cut, reduced by a no-load current and/or by a pilot-control current of the drive, is stored as the load current.

7. The method according to claim 5 , wherein, in a field-oriented control of the drive, a torque-forming current of the drive, reduced by a no-load current and/or by a pilot-control current of the drive, is stored as the load current.

8. The method according to claim 1 , further comprising filtering the quantity to reduce interfering frequency components.

9. The method according to claim 8 , wherein frequency components of the rotational speed of the milling cutter correspond to a tooth-engagement frequency and/or current noise.

10. The method according to claim 1 , wherein the linear correlation is stored in the storing step as a linear slope in a tool table of the machine tool.

11. The method according to claim 1 , wherein a pressure angle of the milling cutter during the machining of the workpiece is between 0° and 140°.

12. A system, comprising:
a numerical control for a machine tool having a plurality of axes, wherein the numerical control is adapted to perform a method for compensating for deflection of a milling cutter during processing of a workpiece, the method including:
performing a learning cut on a test workpiece having a known geometry using the milling cutter mounted on a tool spindle in a climb milling mode;
ascertaining a linear correlation between a quantity that is proportional to torque of a drive of the tool spindle and the deflection of the milling cutter normal to a surface of the test workpiece, the deflection being determined by comparing an actual contour of the test workpiece to a setpoint contour;
storing the linear correlation for the milling cutter; and
machining the workpiece by the milling cutter using the climb milling mode, and utilizing the stored linear correlation in order to compensate for the deflection of the milling cutter by applying a positional correction that is proportional to the quantity to a setpoint position of the axes of the machine tool.

13. The system according to claim 12 , wherein the performing of the learning cut and/or the ascertaining of the linear correlation includes measuring the test workpiece with the aid of a touch probe.

14. The system according to claim 12 , wherein the performing of the learning cut includes storing a rotational speed and/or a forward feed speed of the milling cutter used for the learning cut as a marginal condition, and wherein the machining of the workpiece includes monitoring the marginal condition.

15. The system according to claim 12 , wherein the method includes detecting and/or forcing, in accordance with simulation and/or programming, a climb milling mode.

16. The system according to claim 12 , wherein the quantity that is proportional to the torque of the drive of the tool spindle includes a load current of the drive ascertained during the learning cut.

17. The system according to claim 16 , wherein a current flowing in the drive of the tool spindle during the learning cut, reduced by a no-load current and/or by a pilot-control current of the drive, is stored as the load current.

18. The system according to claim 16 , wherein, in a field-oriented control of the drive, a torque-forming current of the drive, reduced by a no-load current and/or by a pilot-control current of the drive, is stored as the load current.

19. The system according to claim 12 , wherein the method includes filtering the quantity to reduce interfering frequency components.

20. The system according to claim 19 , wherein frequency components of the rotational speed of the milling cutter correspond to a tooth-engagement frequency and/or current noise.

21. The system according to claim 12 , wherein the linear correlation is stored in the storing step as a linear slope in a tool table of the machine tool.

22. The system according to claim 12 , wherein a pressure angle of the milling cutter during the machining of the workpiece is between 0° and 140°.

Assignees

• Heidenhain Gmbh Dr Johannes

Inventors

• Boye Tim

Classifications

• G05B2219/49174

  Compensate position by use of separate cmm · CPC title

• G05B2219/49173

  Compensation for sidewise deviation of machined workpiece · CPC title

• G05B2219/49181

  Calculation, estimation, creation of error model using measured error values · CPC title

• G05B2219/49186

  Deflection, bending of tool · CPC title

• B23C1/16

  specially designed for control by copying devices {(not used; see B23Q35/00)} · CPC title