CNC Machine Tool Accuracy and Repeatability Measurement Strategy: Analysis and Statistical Evaluation

Several factors can affect the accuracy and repeatability results of CNC machine tool positioning. One of the factors is to set up a measurement strategy for both linear and rotary axes based on standards such as ISO 230-2:2014 and VDI 3441. Measurement procedures (strategies) can be modified according to the purpose of the measurement, such as for a quick assessment of the current state of the linear axis, or a more time-consuming measurement to increase the accuracy of the linear axis. They can also be measurements designed for various diagnostic purposes and for better analysis of the measured data. This paper describes modern methods of measuring the accuracy and repeatability of the positioning of linear axes of CNC machine tools with statistical evaluation of the data obtained. In the next part of the paper, measurements are performed on small, medium and large CNC machine tools with defined set measurement strategies based on ISO 230-2:2014 standard. The results show that step size influences the measurement result by up to 54 %. The paper concludes by evaluating the results obtained and suggesting further research goals in this area with a focus on On-machine measurement.