Development of a robot for orbital welding

This work demonstrates the development of a robot, which was designed for the orbital welding of pipes.

The robot consists of a small car pressed against the pipe by means of chains, which are used by the robot to move around it. To provide all necessary torch movements, the robot must have four degrees of freedom: torch travel speed, stick‐out, torch angle and lateral motion. Thus, using a look‐up table‐which was specially designed to this application‐it is possible to follow the optimal parameters (voltage, current, welding speed, torch angle and stick‐out) for each welding position (flat, vertical and overhead).

The robotization of the orbital welding process brings enhancement in the final product quality, considerable increase of repeatability, reduction of rework and reduction of the weld execution time. At the very least, the robot is capable to reproduce the weld bead of the best human welder, through the use of the same paramenters contained in a table.

The use of this robot in welding with GMAW proved to be extremely viable. It was shown that the bead shape did not suffer great variations from one welding postion to another, thanks to the use of a gradual change of parameters.

Although, by RIA definition the devices for the orbital welding shown in literature up to now are not robots, the developed device can be called a robot due to its capability of being completely programmable and automatically carrying through all welding activities.