A preliminary design of a portable friction stir welding (FSW) machine for use in space has been developed. The in-space FSW machine takes the form of a handheld router tool that is historically used in woodworking applications. With the design of the in-space FSW machine, the FSW tool is directly connected to the motor shaft while the motor is mounted to a small frame that supports the tool. The frame has handlebars that allow the operator to grasp the welder and maneuver it along a desired weld path. The key enabler of the in-space FSW machine is an innovative FSW tool design. The FSW tool is a fixed shoulder-to-shoulder bobbin tool that self-aligns and adjusts to the workpiece. The self-aligning and adjusting FSW (SAA-FSW) tool floats freely in the vertical direction, thereby eliminating any external axial load on the machine or operator. The total weight of the in-space FSW machine is 73 lb (≈33 kg), and it only requires one operator. The machine is capable of butt-welding aluminum 1,100 workpieces 1/8 in. (≈3 mm) thick.
The operator will grasp the welder by its handlebars and turn on the machine. The machine with its electric motor will begin to spin the SAA-FSW tool. The FSW machine will then be maneuvered such that the rotating tool will be placed into contact with the two pieces of aluminum to be joined together. The rotating tool will deform and then forge together the two pieces of aluminum. The operator will manually, with the use of the handlebars, maneuver the machine along the desired weld path.
The SAA-FSW tool floats freely in the vertical direction, thereby eliminating any external axial load on the machine and operator. The elimination of the historically large axial load allows for the creation of a small, portable welder. The tool consists of two shoulders connected via a central pin. Each shoulder contains features such as tapers and scrolls that assist in the deformation of the two pieces of material to be joined. In addition, the shoulders that are connected by the central pin create forging pressure required to join the deformed material into a single workpiece.