Case Study of the Influence of Linearity Uncertainty on the Applicability and Capability of CNC Machine Tools

Evaluation the capability of a CNC machine tool as a measuring device and the determination of TOLmin according to ISO 22514-7:2021 is influenced by a number of factors. One of the important factors that enters into the calculation of TOLmin is the root mean square deviation of linearity based on the Analysis of Variance (ANOVA). The present paper describes possible ways of evaluating the root mean square error of linearity obtained from measured data of accuracy and repeatability positioning a linear axis of a CNC machine tool according to ISO 230-2:2014. The evaluation of the accuracy and repeatability positioning is further implemented according to a modified measurement strategy and subsequent compensation of the linear axis of the machine. It is shown that the newly proposed modified measurement and compensation strategy of the CNC machine tool can lead to a reduction in the root mean square error of linearity and thus further contribute to increasing the capability and applicability of the CNC machine tool as a measuring device.

I. Introduction

The issue of On Machine Measurement (OMM - Traceable on machine coordinate measurement) is aimed at more efficient use of CNC machine tools (MT), expanding their technological capabilities and a higher degree of automation and digitalization in the spirit of Industry 4.0[1] [2].