Towards developing a control of grinding processes using a combination of grinding power evaluation and Barkhausen noise analysis

After grinding of hardened workpieces, especially in case of safety-relevant components, usually non-destructive testing is carried out to detect thermo-mechanical damages in the surface layer. In-process detection methods allow a fast reaction to negative changes before producing a large amount of rejects and open the possibility to save additional time for post-process inspection. However, these are not industrially used yet, since boundary conditions and application limits are not defined so far. This study shows the potential of a grinding process control based on a soft sensor combining a thermal limit in a Pc′′- Δt-diagram and magnetic Barkhausen noise analysis applied in-situ during grinding (BN). The specific grinding power Pc′′ in dependence of the contact time Δt allows to identify/avoid grinding burn starting from light tempering zones. Furthermore, the BN is well suited for the detection of detrimental residual stress changes (tensile) occurring even before tempering zones are generated. The developed process control based on this combination optimizes the process parameters to prevent negative thermo-mechanical surface changes while keeping the productivity of the process as high as possible. The applicability is demonstrated for external cylindrical and non-circular grinding processes. Due to the radius varying over the workpiece circumference, the latter ones require special demands on signal evaluation, resolution and control speed.