Reducing Cycle Times of Refill Friction Stir Spot Welding in Automotive Aluminum Alloys 2020-01-0224
Refill friction stir spot welding (RFSSW) is an emerging welding process that has shown great potential in joining automotive and aerospace aluminum alloys. Though the process has been in development for nearly a decade, RFSSW has yet to see wide-scale implementation in the automotive industry. 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 RFSSW 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, torques, and heat placed on RFSSW tooling and machines during the welding process. The relationship between machine design limitations and cycle time is explored, along with the effect of other process variables relevant to RFSSW on both joint quality and cycle time. It is shown through experimentation that RFSSW cycle times can be reduced, and that high speed RFSSW can be enabled through informed efforts.