Analysis of the FSW force footprint and its relationship with process parameters to optimise weld performance and tool design

Advanced process automation is essential to ensure consistent and reliable friction stir welds. This paper illustrates the potential for a better understanding of the influence of certain process parameters on weld properties, through their monitoring and feedback into process control during the welding process. To accomplish this, the force footprint and temperature profile need to be accurately monitored and controlled during welding. In particular, the reaction forces of the tool can be described through a "force footprint" and related to weld quality and dynamic performance. This requires the integration of reliable and accurate sensor output into a computerised control program. Such an instrumented friction stir welding (FSW) set-up has been created. These parameters include tool torque, tool temperature, vertical force of the tool shoulder on the material and the horizontal force profile around the tool during its revolution. Future work will include more complete determination of the temperature profile associated with the thermomechanically affected zone (TMAZ) weld region. The system monitors these parameters during welding and can modify tool speed, feed and forces in response to changing weld conditions.