Page 118 - Welding Robots Technology, System Issues, and Applications

4

Robotic Welding: System Issues

4.1 Introduction

Robotic welding research deals with the relevant technical and scientific aspects
involved in the task of reproducing the work of the experienced and skilled human
welder. Welding was for a long time a task performed only by humans, being a
craft that combines skill with art and science. Automating welding is therefore a
very difficult and demanding objective, because of the required adaptive behavior
of the automatic system.

It can be considered that any welding operation is constituted by three very
different phases [1],[2]:

1. Preparation phase: where the welding operator sets up the parts to be
welded, the welding apparatus (power source, robot, robot program, etc.)
and the welding parameters. The type of gas and the type of wire are also
selected in this phase. If any CAD/CAM or other offline programming
facility is used then a robot welding pre-program is available and should
be placed on-line. This aspect is very important since currently most of
the welding pieces are designed using CAD software. Consequently, that
software should be used to generate robot programs that could work as
starting points for the welding tasks, needing only minor tuning due to
calibration [3]. That may be done easily by the welding operator just by
performing selected on-line simulations of the process [1]-[3], calibrating
in this way the robot program that should then be ready for production.
2. Welding phase: considering a manual welding operation, the welder acts
by adjusting the process variables just by continuously observing the
welding operation and the correspondent results. If automatic equipment
is used to perform the welding operation, then the same capabilities must
be present, i.e., the system should be able to maintain the torch orientation
while following the desired trajectory (that may be different from the

105