Cross-Machine Comparison of the Usability of Internal Machine Control Data for Process Monitoring in Machining Applications

The use of machine control data for process monitoring has many advantages. It represents a cost-effective alternative to expensive external measurement devices and can be retrofitted to existing CNC machines. External sensors can be affected by the machining environment, require setup, and are costly to procure. Furthermore, they influence the process since they are part of the machining process because they replace either the workpiece clamping technology or the toolholder. Machine control data such as spindle currents are in proximity to the process without directly affecting it. Since these data are already known to the NC, they can be used for adaptive control applications. This paper focuses on investigating the differences in position control data on three different machine tools. Using the same reference process. Correlations between feed forces and motor currents are calculated and compared. Correlations of motor currents between different machine tools performing the same process are analysed.