Opportunistic electrode replacement in a robotic spot welding system

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.