An important problem in the tool and mould industry is faster and more automatic process to
repair and re-engineer moulds through welding.  In this paper we consider the problems with
robotically TIG welding large volumes of material on moulds.  For robotic systems, defining the path
the robot will take is rigorously tested before production takes place.  We will focus on the
problem of creating a robotic path generator that will fill in a given volume with quality weld in a
time-saving manner and the modifications throughout the welding process due to inevitable
deviations from the generated path.
    The goal is to create solid 3-D objects robotically from a flat plane, where current practice of
mould modifications in the industry is to manually deposit material on the surface by a skilled
welder.  Given that an industry standard is to preheat the mould to approximately 700°F to
eliminate the stress and possible cracks the welding process may produce, this manual procedure
can be very time consuming and labour intensive for the welder.  A difference model has been
constructed to define the appropriate volume to be welded from CAD data.  Extensive
experiments and designing have been undertaken to apprehend the appropriate welding
parameters to produce a quality weld.  A path generator is proposed to create the trajectory best
fit to complete the proposed 3-D object.  A feedback controller to the robot has been
implemented to monitor the position of the torch using through-the-arc-sensing to guarantee
conditions of the welding are being kept within the appropriate parameters.