Reducing Cycle Times of Refill Friction Stir Spot Welding in Automotive Aluminum Alloys 2020-01-0224
A major barrier, preventing RFSSW from use by manufacturers, is the long cycle time that has been historically associated with making a weld. In order for RFSSW to become a readily implementable welding solution, cycle times must be reduced to an acceptable level, similar to that of well developed, competing spot joining processes. In the present work, an investigation of the RFSSW process is conducted to evaluate factors that have traditionally prevented the process from achieving fast cycle times. Within this investigation, the relationship between cycle time and joint quality is explored, as is the meaning and measurement of cycle time in the RFSSW process. Claims and general sentiment found in prior literature are challenged regarding the potential for high-speed RFSSW joints to be made. The RFSSW weld design-as described by process parameters such as tool feed rate, tool rotational velocity, and plunge depth- is shown through experimentation to affect the loads and torques placed on RFSSW tooling and machines during the welding process. As cycle time is decreased, the load and torque on the toolset are shown to increase. Similarly, as tool rotational velocity is decreased, the load and torque on the toolset is shown to increase. The relationship between machine design limitations and cycle time is also explored. It is demonstrated that welds with cycle times below one second can be produced without compromising material properties, suggesting that high speed RFSSW can be enabled through informed efforts.