Abstract:
The aim of this work was to develop an integration concept for using off-line
programming in robotic gas metal arc welding of thin sheet steel. Off line
-welding
parameter optimization and on-line monitoring and adaptive control of process
stability and torch-to-workpiece relative distance were used to ensure weld
consistency.
The concept developed included four main aspects: a) the use of a CAD
system to design the workpiece; b) the use of a welding off-line programming system
to design the welds, generate the welding parameters and to extract geometrical
information from the CAD models to generate a robot program; c) the use of a
graphical simulation system to simulate the robot movements; and d) the use of
monitoring and adaptive control for ensuring that the required weld quality is
delivered.
The CAD system was chosen to be the basis for the development of the
welding off-line programming system. The generation of optimized welding
parameters was based on empirical welding models and the robot program generation
was based on on-line programming experience.
A PC based monitoring and control system was developed to provide on-line
position and process control. The position control was carried out by pre-weld
adjusting the initial position of the workpiece using a wire touch sensor and on-line
adjusting the torch-to-workpiece distance by moving the workpiece based on the
information provided by a through-the-arc sensor. The process control was carried
out by automatically trimming the welding voltage such that the most stable process
could be obtained. The stability of the process was estimated by using previously
established monitoring indices. It was assumed that the off-line welding parameter
optimization would provide the deposition rate necessary to produce the required
weld quality.
Successful welding control trials were performed showing the effectiveness of
the adaptive control strategy.
An off-line programming system has been developed and the programs
generated have been tested by simulation. This showed that simulated positioning
errors, produced by deliberate wrong path data, were successfully compensated for by
the control system developed in this work.
