Opportunistic electrode replacement in a robotic spot welding system

Abstract

This paper addresses the electrode replacement and general maintenance optimization problems for a robotic resistance spot welding system consisting of k non-identical guns. The electrode tip wear compensation methodology is introduced. Using the modelling results based on field data, a tip wear trend as well as high and low limits for tip usage are established. The expected failure time or replacement time for a specific tip is then predicted. Three kinds of replacement policies (corrective replacement, preventive replacement and opportunistic replacement) are described. Through a careful cost investigation, a simulation model for electrode opportunistic replacement in a 17-robot resistance welding system has been developed. An optimum electrode opportunistic replacement interval is then predicted, which achieves a maximum cost saving based on some simple operational assumptions. The total expected cost, number of tips replaced, production line stoppage times and the next replacement time can also be obtained.

Keywords:

• Opportunistic maintenance
• Robotic spot welding
• Optimization
• Empirical modelling
• Simulation

Acknowledgements

Thanks are extended to our industrial partner for their great support on this project. We further thank Dr K. Farkas, J. Liaw and B. Morris for their valuable information and help in the experimental work.