Study on performance of passive flexible device based on tube-piercing machine of tubular heat exchanger

Abstract

Abstract This article analyzes the conditions for the assembly of pipes through rough inner walls of axial holes without jamming and designs a passive-compliant device based on repulsive magnetic forces to solve the jamming issue encountered during the assembly of copper pipes and axial holes. In the passive-compliant device, two repulsive magnetic forces are placed internally. During the assembly process, the end effector is separated from the axial hole, and the torque generated by the rotational push-pull of the passive compliant device is used to overcome the jamming point and quickly return to its original position. By measuring the magnitude of the force using a force sensor at the end of the axial hole, experiments were conducted on axial holes with different offset angles and clearances. The results indicate that there is a gap between the copper pipe and the inner wall of the axial hole. When the offset angle is less than 15° and the axial hole clearance is smaller than 5.5mm, the copper pipe can effectively and quickly pass through the axial hole. With the damping coefficient k set to 0.1, the assembly time can be effectively shortened to no more than 7.2 seconds without affecting the ability of the copper pipe to overcome the jamming phenomenon. This article conducted numerical simulations of the piercing process and analyzed that the controlled range of offset angles is between 15° and 21°, while the controlled range of the clearance within the axial hole is between 5mm and 14mm. These parameters enable overcoming the jamming phenomenon and facilitate effective pipe insertion.