An innovative device for enlarging the allowable misalignment for screwing tasks

Abstract. To ensure the repeatability in a screwing task, the robot manipulators have to be calibrated regularly. If the allowable position error of the manipulator is increased, then the frequency of stopping a production line and calibrating the manipulators can be lower; therefore, the cost can be also decreased. This paper presents an innovative device for enlarging the allowable misalignment (DEAM) with five mechanisms, namely detecting, trigger, positioning, pin-and-stopper, and screwing mechanisms. By scanning around the target threaded hole, the screw can be precisely positioned at the location where the hole is detected by the probe. The motion and force analysis are carried out and verified through computer-aided simulation, and the sensitivity of the linkage tolerance is analyzed to ensure that the output position error of the mechanism does not affect the function of the device. Finally, the performance of the innovative device is verified by prototype testing, and the allowable misalignment is enlarged by about 6 times for an M6 screw.