Automatic estimation of weldgun size using section geometry

• US 7,974,733 B2
• Filed: 01/30/2009
• Issued: 07/05/2011
• Est. Priority Date: 01/30/2009
• Status: Expired due to Fees

• Current Assignee: GM Global Technology Operations LLC (General Motors Company)
• Original Assignee: GM Global Technology Operations LLC (General Motors Company)
• Inventors: Gupta, Ashish, Shastry, Gopalakrishna, Hunsur, Narahari K.
• Primary Examiner(s): BARNES-BULLOCK, CRYSTAL JOY
• Application Number:
  US12/363,244
• Publication Number:
  US 20100198384A1
• Time in Patent Office: 886 Days
• Field of Search: 700/117, 700/159, 700/179, 700/245, 700/262, 219/61.5, 219/86.1, 219/91.1, 219/121.45, 219/125.1, 219/136, 219/137.R, 219/137.31, 219/617
• US Class Current: 700/179
• CPC Class Codes: B23K 11/314 Spot welding guns, e.g. mounted on robots

Abstract

A method for estimating a plurality of geometrical parameters defining the size of a weld gun that has particular application for automatically selecting a weld gun for a welding operation. The method includes iteratively estimating a plurality of geometric parameters based on part section curves corresponding to a direction of approach of the weld gun to weld point of the plurality of weld points. Thereafter, a set of valid weld gun sizes are calculated based on the estimated plurality of geometric parameters. Similarly all the valid weld gun sizes are calculated corresponding to each of the weld gun approach direction. Further, each set of the valid gun sizes are estimated for each of the weld point for the welding operation. Finally, a weld gun for performing the welding operation is selected based on the set of weld gun sizes corresponding to the welding operation.

Claims

1. A method for estimating final values of a plurality of geometric parameters of a weld gun, wherein the plurality of geometric parameters define the size of the weld gun, wherein the weld gun performs a welding operation at a weld point, said method comprising:

a. generating part section curves corresponding to a direction of approach of the weld gun to the weld points, wherein the part section curves are generated by using a part section plane, and wherein the part section plane is a plane containing the weld gun approach direction and a normal to the weld point;

b. storing the part section curves as a link list of obstructions in an array of Y scan lines to analyze a given part geometry for available clearance space;

c. determining values of a first geometric parameter of the plurality of geometric parameters, wherein the value of the first geometric parameter is determined based on the presence of the part section curves in a pre-defined area;

d. estimating a first maximum and a first minimum limit for a second geometric parameter of the plurality of geometric parameters, wherein the first minimum limit for the second geometric parameter is determined based on the limit for the first geometric parameter, and wherein the first maximum limit of the second geometric parameter is determined based on the type of weld gun used;

e. estimating a maximum and a minimum limit for a third geometric parameter of the plurality of geometric parameters, wherein the maximum limit for the third geometric parameter is calculated based on the value of the first geometric parameter and the first maximum and the first minimum limit for the second geometric parameter, and wherein the minimum limit for the third geometric parameter is estimated based on the first maximum and the first minimum limit for the second geometric parameter, and wherein the maximum and the minimum limit for the third geometric parameter are calculated based on the part section curves;

f. estimating a valid maximum and a valid minimum limit for the third geometric parameter based on a value of the third geometric parameter for a first standard weld gun;

g. computing a second maximum and a second minimum limit for the second geometric parameter corresponding to the valid maximum and the valid minimum limit for the third geometric parameter, wherein the second maximum and the second minimum limit for the second geometric parameter are calculated based on the part section curves;

h. estimating a valid maximum and a valid minimum limit for the second geometric parameter based on a limit for the second geometric parameter of a second standard weld gun; and

i. repeating the steps e, f, g and h until each of the valid maximum and the valid minimum limit for the second geometric parameter converge and each of the valid maximum and the valid minimum limit for the third geometric parameter converge, wherein the first maximum and the first minimum limit for the second geometric parameter are replaced with the valid maximum and the valid minimum limits for the second geometric parameter, respectively, and wherein the limit for the first geometric parameter, the converged valid minimum limit for the second geometric parameter, the converged valid maximum limit for the second geometric parameter, the converged valid minimum limit for the third geometric parameter and the converged valid maximum limit for the third geometric parameter are the estimated final limits for the plurality of geometric parameters.

2. The method according to claim 1 wherein the first maximum limit for the second geometrical parameter is taken as a sum of a minimum limit for the second geometrical parameter for the type of weld gun used, length of the gun frame for the type of weld gun used, and a value of tolerance for the type of weld gun used.

3. The method according to claim 1 wherein the method is carried out in a UG-NX design software.

4. The method according to claim 1 wherein the type of weld gun is selected from a group comprising a P type weld gun, a C type weld gun, an X type weld gun and an S type weld gun.

5. The method according to claim 1 wherein the first geometric parameter is a tip angle of shanks for stationary and moving arms of the weld gun.

6. The method according to claim 5 wherein the second geometric parameter is an arm stick-out of the weld gun.

7. The method according to claim 6 wherein the third geometric parameter is an arm offset corresponding to a moving arm and stationary arm of the weld gun.

8. The method according to claim 1 wherein a number of weld gun approach directions to the weld point is defined by a user.

9. A method for estimating a set of valid weld gun sizes for an approach direction of a weld gun to a weld point, wherein final values of a plurality of geometric parameters define the weld gun size, and wherein the plurality of geometric parameters include a tip angle of a shank for moving and stationary arms of the weld gun, an arm stick-out of the weld gun, and arm offset of moving and stationary arms of the weld gun, and wherein the weld gun performs a welding operation at the weld point, said method comprising:

a. generating part section curves corresponding to the weld gun approach direction to the weld point, wherein the part section curve is generated by using a part section plane, and wherein the part section plane is the plane containing the weld gun approach direction and a normal to the weld point;

b. storing the part section curves as a link list of obstructions in an array of Y scan lines to analyze a given part geometry for available clearance space;

c. determining a value of the tip angle of the shank for moving and stationary arms of the weld gun, wherein the value of the tip angle of the shank is determined based on the presence of the part section curve in a three-dimensional cylindrical zone around the weld point;

d. estimating a first maximum and a first minimum limit for the arm stick-out, wherein the first minimum limit for the arm stick-out is determined based on the value of the tip angle of the shank of the weld gun and the first maximum limit for the arm stick-out is determined based on the type of weld gun used;

e. estimating a maximum and a minimum limit for the arm offset, wherein the maximum limit for the arm offset is calculated based on the limit for the tip angle of the shank of the weld gun and the first maximum and the first minimum limit for the arm stick-out, and wherein the minimum limit for the arm offset is estimated based on the first maximum and the first minimum limit for the arm stick-out, and wherein the maximum and the minimum limit for the arm offset are calculated based on the part section curves;

f. estimating a valid maximum and a valid minimum limit for the arm offset on the basis of a value of the arm offset for a first standard weld gun;

g. computing a second maximum and a second minimum limit for the arm stick-out based on the valid maximum and the valid minimum limit for the arm offset, wherein the second maximum and the second minimum limit for the arm stick-out are calculated on the part section curves;

h. estimating a valid maximum and a valid minimum limit for the arm stick-out based on the a limit for the arm stick-out for a second standard weld gun;

i. repeating the steps e, f, g and h until each of the valid maximum and the valid minimum values of the arm stick-out converge and each of the valid maximum and the valid minimum values of the arm offset converge, wherein the first maximum and the first minimum values of the arm stick-out are replaced with the valid maximum and the valid minimum values of the arm stick-out, respectively, and wherein the limit for the tip angle of the shank, the converged valid minimum limit for the arm stick-out, the converged valid maximum value of the arm stick-out, the converged valid minimum value of the arm offset and the converged valid maximum limit for the arm offset are the final limits for the plurality of geometric parameters; and

j. estimating the set valid weld gun sizes for the approach direction of the weld gun to the weld point, wherein the set of valid weld gun sizes is estimated by mapping the final values of the plurality of geometric parameters onto a set of standard weld guns of the type of weld gun used.

10. The method according to claim 9 wherein the first maximum value of the arm stick-out is taken as a sum of a minimum limit for the arm stick-out for the type of weld gun used, length of a weld gun frame for the type of weld gun used and a limit for tolerance for the type of weld gun used.

11. The method according to claim 9 wherein the method is carried out in a UG-NX design software.

12. The method according to claim 9 wherein the type of weld gun is selected from a group comprising a P type weld gun, a C type weld gun, an X type weld gun and an S type weld gun.

13. The method according to claim 9 wherein a number of weld gun approach directions to the weld point is defined by a user.

14. A method for selecting a weld gun corresponding to a welding operation, wherein the weld gun is selected based on the final values of a plurality of geometric parameters of the weld gun, and wherein the plurality of geometric parameters define the size of the weld gun, and wherein the plurality of geometric parameters comprises a tip angle of a shank of moving and stationary arms of the weld gun, an arm stick-out of the weld gun, and an arm offset of the stationary and moving arms of the weld gun, and wherein a welding operation comprises a plurality of weld points, said method comprising:

a. generating part section curves corresponding to a direction of approach of the weld gun to a weld point of the plurality of weld points, wherein the part section curve is generated by using a part section plane, and wherein the part section plane is a plane containing the weld gun approach direction and a normal to the weld point;

b. storing the part section curves as a link list of obstructions in an array of Y scan lines to analyze a given part geometry for available clearance space;

c. determining values of the tip angle of the shank of stationary and moving arms of the weldgun, wherein the values of the tip angle of the shank are determined based on the presence of the part section curves in a three-dimensional cylindrical zone around the weld point;

d. estimating a first maximum and a first minimum limit for the arm stick-out, wherein the first minimum limit for the arm stick-out is determined based on the limit for the tip angle of the shank of the weld gun and wherein the first maximum value of the arm stick-out is determined based on the type of weld gun used;

e. estimating a maximum and a minimum limit for the arm offset wherein the maximum limit for the arm offset is calculated based on the limit for the tip angle of the shank of the weld gun and the first maximum and the first minimum value of the arm stick-out, and wherein the minimum limit for the arm offset is estimated based on the first maximum and the first minimum limit for the arm stick-out, wherein the maximum and the minimum limit for the arm offset are calculated based on the part section curves;

f. estimating the valid maximum and valid minimum limit for the arm offset based on a value of the arm offset for a first standard weld gun;

g. computing a second maximum and a second minimum limit for the arm stick-out based on the valid maximum and the valid minimum limit for the arm offset, wherein the second maximum and the second minimum limit for the arm stick-out are calculated based on the part section curves;

h. estimating a valid maximum and a valid minimum limit for the arm stick-out based on a value of the arm stick-out of a second standard weld gun;

i. repeating the steps e, f, g and h until each of the valid maximum and the valid minimum values of the arm stick-out converge and each of the valid maximum and the valid minimum values of the arm offset converge, wherein the first maximum and the first minimum values of the arm stick-out are replaced with the valid maximum and the valid minimum values of the arm stick-out, respectively, and wherein the value of the tip angles of the shank, the converged valid minimum limit for the arm stick-out, the converged valid maximum limit for the arm stick-out, the converged valid minimum limit for the arm offset and the converged valid maximum limit for the arm offset are the final values of the plurality of geometric parameters;

j. selecting a set of valid weld gun sizes corresponding to a weld gun approach direction to the weld point, wherein the set of valid weld gun sizes is estimated by mapping the final values of the plurality of geometric parameters onto a set of standard weld guns of the type of weld gun used;

k. performing the steps of a, b, c, d, e, f, g, h, i and j for each of the weld gun approach direction to the weld point of the plurality of weld points;

l. obtaining a set of weld gun sizes corresponding to the weld point based on the set of valid gun sizes corresponding to each of the weld approach direction to the weld point;

m. performing the steps of a, b, c, d, e, f, g, h, i, j, k and l for each of the plurality of welding points of the welding operation;

n. obtaining a set of weld gun sizes corresponding to the welding operation based on the set of valid gun sizes corresponding to each of the weld point; and

o. selecting a weld gun for performing the weld operation, wherein the weld gun is selected based on the set of weld gun sizes corresponding to the welding operation.

15. The method according to claim 14 wherein the first maximum limit for the arm stick-out is taken as a sum of a minimum limit for the arm stick-out for the type of weld gun used, length of a weld gun frame for the type of weld gun used and a value of tolerance for the type of weld gun used.

16. The method according to claim 14 wherein the method is carried out in a UG-NX design software.

17. The method according to claim 14 wherein the type of weld gun used is selected from a group comprising a P type weld gun, a C type weld gun, an X type weld gun and an S type weld gun.

18. The method according to claim 14 wherein a number of weld gun approach directions to the weld point is defined by a user.

19. The method according to claim 14 wherein selecting a weld gun for performing the welding operation is done on the basis of a plurality of user defined parameters.

20. The method according to claim 19 wherein the user defined parameters are selected from a group comprising a weld gun cost, a weld gun size and a list of available weld guns.