POSITION-DEPENDENT COMPLIANCE COMPENSATION IN A MACHINE TOOL

• US 20100121478A1
• Filed: 07/28/2006
• Published: 05/13/2010
• Est. Priority Date: 07/28/2006
• Status: Active Grant

• Current Assignee: Siemens AG
• Original Assignee: Siemens AG
• Inventors: Jahn, Dirk, Vitr, Mirco, Meidlinger, Rouven
• Granted Patent: US 8,150,545 B2
• Time in Patent Office: Days
• US Class Current: 700/173
• 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: G05B 2219/49095 Of rigidity of workpiece
• CPC Class Codes: G05B 2219/49177 Runout, eccentricity, unbalance of tool or workpiece

Abstract

The invention relates to a method and a device for position-dependent compliance compensation in a machine tool. To permit the lowest possible machining time or greatest possible contour fidelity in the machining of a workpiece with a machine tool, the following method steps are proposed:—deriving the compliance (2) of the machine tool (1) at a position of a tool of the machine tool (1) from machine data (3) stored in a memory,—determining a machining force (4) acting on the tool during a machining process at said position,—modification of at least one machining parameter (5) that has an influence on the machining process for the said position in dependence on the derived compliance (2) and the machining force (4) in such a way that a displacement (6) of the tool with respect to a desired position that is caused by the compliance (2) of the machine tool (1); and the machining force (4) is counteracted.

Claims

1-28. -28. (canceled)

29. A method for compensating a position-dependent compliance of a machine tool, comprising the steps of:

deriving from stored machine data the position-dependent compliance of the machine tool at a tool position of a tool of the machine tool,

determining a machining force acting upon the tool during a machining process at the tool position, and

modifying, depending the derived compliance and the determined machining force, at least one machining parameter affecting the machining process at the tool position so as to counteract a displacement of the tool from a desired tool position caused by the compliance of the machine tool and the machining force.

30. The method of claim 29, wherein the machine tool is provided for cutting operations.

31. The method of claim 29, wherein the at least one machining parameter is a value of the desired tool position specified in a control program.

32. The method of claim 31, wherein the control program is a NC program.

33. The method of claim 29, wherein the at least one machining parameter is a feed rate value or a cutting depth or a spindle speed.

34. The method of claim 29, wherein the machine data is determined from a simulation of a rigidity characteristic of the machine tool.

35. The method of claim 29, wherein the machine data are determined from a measurement.

36. The method of claim 29, wherein the machine data include discrete compliance values at discrete locations within a workspace of the machine tool.

37. The method of claim 36, wherein the compliance of the machine tool at an arbitrary location is derived by interpolating between the discrete compliance values.

38. The method of claim 29, wherein the machining force is measured with a force sensor.

39. The method of claim 29, further comprising the steps of:

measuring drive currents of the machine tool, and determining the machining force from the measured drive currents.

40. The method of claim 29, further comprising the steps of:

performing a process simulation of the machining process, and determining the machining force from the simulation.

41. The method of claim 29, wherein the at least one machining parameter is modified before machining of a workpiece.

42. The method of claim 29, wherein the at least one machining parameter is modified during machining of a workpiece.

43. A device for compensating a position-dependent compliance of a machine tool, comprising:

a memory storing machine data,

deriving means for deriving from stored machine data the position-dependent compliance of the machine tool at a tool position of a tool of the machine tool,

determining means for determining a machining force acting upon the tool during a machining process at the tool position, and

modifying means for modifying, depending the derived compliance and the determined machining force, at least one machining parameter affecting the machining process at the tool position so as to counteract a displacement of the tool from a desired tool position caused by the compliance of the machine tool and the machining force.

44. The device of claim 43, wherein the machine tool is a cutting machine tool.

45. The device of claim 43, wherein the at least one machining parameter is a value of the desired tool position specified in a control program.

46. The method of claim 45, wherein the control program is a NC program.

47. The device of claim 43, wherein the at least one machining parameter is a feed rate value or a cutting depth or a spindle speed.

48. The device of claim 43, wherein the machine data is determined from a simulation of a rigidity characteristic of the machine tool.

49. The device of claim 43, wherein the machine data are determined from a measurement.

50. The device of claim 43, wherein the machine data include discrete compliance values at discrete locations within a workspace of the machine tool.

51. The device of claim 50, wherein the deriving means are configured to derive the compliance of the machine tool at an arbitrary location by interpolating between the discrete compliance values.

52. The device of claim 43, wherein the determining means include a force sensor for measuring the machining force.

53. The device of claim 43, wherein the determining means comprise a current sensor measuring a drive current of the machine tool and a calculating unit calculating the machining force from the measured drive current.

54. The device of claim 43, further comprising a simulator performing a process simulation of the machining process, wherein the determining means determine the machining force from the process simulation.

55. The device of claim 43, wherein the modifying means modify the at least one machining parameter before machining a workpiece.

56. The device of claim 43, wherein the modifying means modify the at least one machining parameter during machining a workpiece.

57. A machine tool comprising a device for compensating a position-dependent compliance, the device comprising:

a memory storing machine data,

deriving means for deriving from stored machine data the position-dependent compliance of the machine tool at a tool position of a tool of the machine tool,

determining means for determining a machining force acting upon the tool during a machining process at the tool position, and

modifying means for modifying, depending the derived compliance and the determined machining force, at least one machining parameter affecting the machining process at the tool position so as to counteract a displacement of the tool from a desired tool position caused by the compliance of the machine tool and the machining force.

58. A computer program which enables a computer, after the computer program is loaded into a memory of the computer, to execute a method for compensating a position-dependent compliance of a machine tool, the method comprising the steps of:

deriving from stored machine data the position-dependent compliance of the machine tool at a tool position of a tool of the machine tool,

determining a machining force acting upon the tool during a machining process at the tool position, and

modifying, depending the derived compliance and the determined machining force, at least one machining parameter affecting the machining process at the tool position so as to counteract a displacement of the tool from a desired tool position caused by the compliance of the machine tool and the machining force.