Systematic quantitative investigation of the unscrewing process with regard to breakaway torque

Threaded connections make up the majority of separable connections used today. Their disassembly behaviour strongly depends on the conditions during the life-phase. With the trend towards circular economy, disassembly particularly for remanufacturing requires automation. For production systems this mandates a certain capability of adaptation towards different product conditions. In the regarded case of dismantling threaded connections, this is the automatic selection of appropriate robot tools. One important criterion for the tool-selection is the breakaway torque, which strongly depends on friction parameters within the threads and the head surface. Those are influenced by e.g. corrosion and head type. In this contribution, the results of a systematic experimental investigation of the breakaway torque of threaded connections is presented. The aim of the contribution is to determine the influence on the breakaway torque of typical factors appearing in automated disassembly systems. Therefore, a total of 90 experiments are conducted which include five factors: Nominal diameter; Screw head type; Corrosion; Plate material; Applied torque during assembly.