Preload Force Controlled Impact Wrench Tightening Using a Sensor-Integrating Bolt

Bolted joints typically require a defined preload. Conventional torque or angle control sets preload only indirectly. It is sensitive to friction and joint stiffness variation. Uncertainty is high, especially with impact wrenches. This paper presents a closed loop approach for impact tightening. A sensor-integrating M20 bolt is linked with an impact wrench, and preload is measured inside the bolt. The derivative of the measured preload force is used as the control variable. In lab runs, the system showed stable wireless operation, reliable motor control, and accurate preload measurement. Proof-of-concept tests show accurate setpoint attainment with low distribution and minimal overshoot, along with reproducible, automatic shut-off at the preload setpoint. The observed distribution of preload force remained within 3% of the setpoint. These results indicate lower assembly uncertainty and stronger quality assurance, while usability remains familiar, and no extra hardware is needed. They suggest less need for oversize bolted joints. Systematic studies are still needed to confirm robustness across operating conditions.