Abstract—In this work, we study the piping manufacturing technology wherein two flange surfaces are connected by pipes using industry robots. This system can aid the manufacture of pipes, as it enables the precise measurement of piping through the use of industrial robots. However, the system demands high precision in terms of position and posture. Therefore, in this work, we attempt to study the precision of large industrial robots involved in the construction of the system. We describe the equations that govern the positioning of the robot. Then, we calculate the link length in the equations using the least squares method. Consequently, we arrive at the link length that is similar to the catalog value. However, there are differences of less than 3.4%, and the calculated link length exceeds the posture, which seems more forward than the value indicated by the robot. In addition, we focused on the torque applied at these joints from the servomotor and we obtained the diameter of circular orbit using a double ball bar. As a result, the torque value changed along the change of joint angle and error changed along the change of torque value. In addition, the torque of the internal information tends to influence the motion accuracy, and the possibility that the method of performing the correction when the torque value is large is effective is clarified. 
 

Index Terms— pipe production system, large industrial robots, double ball bar, laser tracker, servomotor information