Low-Cost Wireless Force Sensor Design with Applications in Friction Stir Welding

Measuring Friction Stir Welding (FSW) process forces can be important in both research and industrial applications.  Force data can provide insight into weld quality, resulting mechanical properties, and even tool wear.  Implementation of force control increases the applicability of FSW, and some research suggests that weld characteristics can be manipulated using force control.

A rotating multi-axial wireless force sensor was developed for use in FSW.  A special emphasis was placed on developing a system that was both low-cost and robust in terms of handling the loads and thermal environment of FSW.  The system was designed and built in-house at Vanderbilt University and was shown to be lower in cost than any commercially available load cell that could be utilized in FSW.  Torque (M_z) measurement was demonstrated in the first stage of development and the capabilities are currently being expanded to measure the traversing (F_x) and side (F_y) forces in FSW.

Forces are measured with strain gages that are mounted on an elastic member and powered by lightweight, rechargeable lithium polymer batteries.  The electronics enclosure was rapid-prototyped from ABS plastic.  The elastic member transmits loads to a standard NMTB 50 taper, allowing this device to be installed in a variety of machines.  XBee radios are used to transmit voltage data from the rotating spindle to a stationary receiver, and a custom incremental encoder using optical interrupters will be utilized for resolving traversing and side forces into fixed directions.