The influence of tool control in non-linear friction stir welding (FSW) on mechanical
properties of joints was investigated. FSW is widely applied to linear joints. It is impossible for five
axis FSW machines, however, to keep all the FSW parameters in optimum conditions at non-linear
welding. Non-linear FSW joints should be made by compromise with the order of priority for FSW
parameters. The tensile test results of butt joints with rectangular change in welding direction on plate
plane (L-shaped butt joints) with various welding parameter change. It was found that turn to the
retreating side is encouraged when welding direction change. And the method of zero inclination tool
angle is effective at non-linear and plane welding.