Real-time measurement of tool forces and machining process model parameters

• US 20050154488A1
• Filed: 01/07/2005
• Published: 07/14/2005
• Est. Priority Date: 01/09/2004
• Status: Active Grant

• Current Assignee: University of New Hampshire, Vulcancraft LLC
• Original Assignee: Vulcancraft LLC
• Inventors: Esterling, Donald M.
• Granted Patent: US 7,206,657 B2
• Time in Patent Office: Days
• US Class Current: 700/175
• CPC Class Codes: G05B 19/4065 Monitoring tool breakage, life or condition

Abstract

A system and method are provided for real-time measurement of tool forces. A relationship between a motor characteristic and tool forces is determined by first directly measuring tool forces for a standard tool, work piece, and part program in a central facility. A force profile indicative of the tool forces and the standard tool, work piece, and part program are provided to a user at a user facility. The motor characteristic for a CNC machine at the user facility is then measured for the standard tool, work piece, and part program. Based on the force profile determined at the central facility, the relationship between the motor characteristic and tool forces is determined. Thereafter, the motor characteristic of the CNC machine is measured for a desired tool, work piece, and part program and converted to tool forces using the relationship between the motor characteristic and tool forces.

Claims

1. A method for measuring tool forces comprising:

determining a force profile for a standard tool, work piece, and part program on a first Computer Numerical Control (CNC) machine based on direct measurement of tool forces;

providing the standard tool, work piece, and part program to a user facility;

measuring a motor characteristic of a second CNC machine at the user facility for the standard tool, work piece, and part program;

determining a relationship between the motor characteristic and tool forces based on the motor characteristic for the standard tool, work piece, and part program and a force profile determined for the standard tool, work piece, and part program on the first CNC machine; and

determining tool forces for a desired tool, work piece, and part program on the second CNC machine at the user facility based on the motor characteristic for the desired tool, work piece, and part program and the relationship between the motor characteristic and tool forces.

2. The method of claim 1 wherein determining the tool forces for the desired tool, work piece, and part program comprises:

measuring the motor characteristic for the desired tool, work piece, and part program; and

converting the motor characteristic for the desired tool, work piece, and part program to the tool forces for the desired tool, work piece, and part program using the relationship between the motor characteristic and tool forces.

3. The method of claim 1 wherein determining the force profile for the standard tool, work piece, and part program on the first CNC machine based on direct measurement of tool forces comprises determining the force profile for the standard tool, work piece, and part program on the first CNC machine based on direct measurement of tool forces in a central facility at a first geographic location, wherein the user facility is at a second geographic location.

4. The method of claim 1 further comprising repeating the steps of measuring the motor characteristic of the second CNC machine at the user facility for the standard tool, work piece, and part program and determining the relationship between the motor characteristic and tool forces for cool and warm motor conditions of the second CNC machine.

5. The method of claim 1 further comprising periodically repeating the steps of measuring the motor characteristic of the second CNC machine at the user facility for the standard tool, work piece, and part program and determining the relationship between the motor characteristic and tool forces such that the relationship between the motor characteristic and tool forces is periodically updated to account for wear of the second CNC machine.

6. The method of claim 1 wherein the motor characteristic is motor power.

7. The method of claim 1 further comprising determining process model parameters based on a process model and a geometric model and the tool forces for the desired tool, work piece, and part program.

8. The method of claim 7 wherein the process model parameters comprise cutting energies.

9. The method of claim 7 further comprising predicting tool forces for the desired tool and work piece based on the process model and the process model parameters.

10. The method of claim 9 further comprising performing Numerical Control (NC) optimization based on the predicted tool forces.

11. The method of claim 9 further comprising performing tool condition monitoring for the desired tool based on the predicted tool forces.

12. The method of claim 11 wherein performing tool condition monitoring for the desired tool comprises:

measuring the motor characteristic for subsequent cutting processes on the second CNC machine for the desired tool and work piece;

converting the motor characteristic for the subsequent cutting processes to tool forces based on the relationship between the motor characteristic and tool forces; and

monitoring the condition of the desired tool based on a comparison of the tool forces for the subsequent cutting processes and the predicted tool forces.

13. The method of claim 7 further comprising performing tool condition monitoring for the desired tool based on the process model parameters.

14. The method of claim 13 wherein performing tool condition monitoring comprises:

determining second process model parameters for subsequent cutting processes on the second CNC machine for the desired tool and work piece; and

monitoring the condition of the desired tool based on a comparison of the process model parameters for the desired tool, work piece, and part program and the second process model parameters for the subsequent cutting processes.

15. The method of claim 1 wherein determining the relationship between the motor characteristic and tool forces comprises determining a transfer function for converting the motor characteristic to tool forces.

16. A method for measuring tool forces comprising:

receiving a standard tool, work piece, and part program from a central facility at a user facility;

measuring a motor characteristic of a first Computer Numerical Control (CNC) machine at the user facility for the standard tool, work piece, and part program;

determining a relationship between the motor characteristic and tool forces based on the motor characteristic for the standard tool, work piece, and part program and a force profile determined on a second CNC machine at a central facility for the standard tool, work piece, and part program; and

determining tool forces for a desired tool, work piece, and part program on the first CNC machine at the user facility based on the motor characteristic for the desired tool, work piece, and part program and the relationship between the motor characteristic and tool forces.

17. The method of claim 16 wherein determining the tool forces for the desired tool, work piece, and part program comprises:

measuring the motor characteristic for the desired tool, work piece, and part program; and

converting the motor characteristic for the desired tool, work piece, and part program to the tool forces for the desired tool, work piece, and part program using the relationship between the motor characteristic and tool forces.

18. The method of claim 16 wherein receiving the standard tool, work piece, and part program further comprises receiving the standard tool, work piece, and part program from the central facility at a first geographic location, wherein the user facility is at a second geographic location.

19. A computer readable media comprising software for instructing a computer to:

measure a motor characteristic of a first CNC machine at a user facility for a standard tool, work piece, and part program, the standard tool and work piece provided from a central facility;

determine a relationship between the motor characteristic and tool forces based on the motor characteristic for the standard tool, work piece, and part program and a force profile determined on a second CNC machine at the central facility for the standard tool, work piece, and part program; and

determine tool forces for a desired tool, work piece, and part program on the first CNC machine at the user facility based on the motor characteristic for the desired tool, work piece, and part program and the relationship between the motor characteristic and tool forces.

20. The computer readable media of claim 19 wherein to determine tool forces for the desired tool, work piece, and part program, the computer readable media further instructs the computer to:

obtain measurements of the motor characteristic for the desired tool, work piece, and part program; and

convert the motor characteristic for the desired tool, work piece, and part program to the tool forces for the desired tool, work piece, and part program using the relationship between the motor characteristic and tool forces.