Impact of hybrid workpieces on statistical process monitoring of machining operations

ThispaperexaminestheinfluenceofmaterialtransitiononaprocessmonitoringapproachbasedonconfidencelimitsforfrictionweldedEN-AW6082/20MnCr5 shafts. Process error sensitivity was investigatedfor differentcontrol and accelerationsignals as well as for the first principal component during slot milling. To that end, three material defects were applied by a hole, stainless steel rod, and high-speed steel drill. The signal changes caused by these defects were characterized by amplitude, duration, and shape.Basedonthe information,errorsweresimulatedfor eachsignal, whichwereusedtoevaluatethe confidencelimitsandto comparethedetectiontimefortheentiremachiningprocess.Anewmethodologywasdevelopedtoevaluateprocessmonitoring systems with regard to error sensitivity. It was determined that errors were not detected during the entire process due to the material transition. By combining features with the first principal component analysis, the sensitivity of process monitoring had been improved by more than 50%.