A new methodology for identifying location errors in 5-axis machine tools using a single ballbar set-up

Abstract

Ballbar testing of rotary axes in 5-axis machine tools can be time-consuming and requires high levels of operator expertise; especially in the set-up process. Faster tests reduce down-time and encourage frequent updates to compensation parameters to reflect the current state of the machine. A virtual machine tool (VMT) is developed to emulate the machine tool, its geometric errors and the testing procedures. This was used to develop a new single set-up testing method to identify all rotary axis locations errors, whilst remaining robust in the presence of set-up error and linear axis squareness errors. New testing and data processing techniques remove the requirement for fine-adjustment of the tool-cup and permit full automation of necessary toolpaths, including transitions. Using the VMT, error identification residuals were found to be 2.7 % or less. Experiments and statistical analysis then showed that all errors can be measured using a single set-up, and values are sufficiently close to the values measured using conventional multi-set-up procedures to be used in error compensation. This method will significantly reduce set-up durations and removes the need for any modified testing hardware.