Optimizing robot programs for longer gripper lifetime

Abstract

Modern production is challenging in many ways. Competition is high and the costs need to be reduced continuously to be competitive. This is often achieved with a production system that runs smoothly and is in balance. However, the unforeseen breakdowns of machines and processes stops the production and impose big costs to the company. Company Volvo Cars is having issues with robots’ gripping mechanisms in welding and assembly processes at their factories. The robots’ gripping mechanisms get fatigued and fail, which stops the processes until the grippers are fixed and this is bad for the company’s productivity. This project investigated the possibility of measuring vibrations and accelerations occurring on robot grippers in order to minimize cyclic stress occurring. The study is limited to one failure mode and is based on the data generated by one robot at one department. It gives enough data to explore and test the fundamental concepts of a method that can be applied and verified on other robots. Project resulted in a method for measuring accelerations on robot grippers. The method helps to find imbalances in robot movements due to unideal programming of the robot. Further, lowered cyclic stresses on gripper were achieved using the developed method. Reduced stresses in grippers prolong gripper lifetime and reduces production stops. Volvo Cars want to use the method for verifying all new robot programs before putting them into production. The company also considers using the method for doing controls on existing grippers in production to find and eliminate imbalances in robot processes.