Science of and Advanced Technology for Cost-Effective Manufacture of High Precision Engineering Products. Volume 6. Accuracy Improvement of a CNC Machining Center by Using a Touch Probe and a Metrology Pallet

摘要

Errors in the position of the tool in the work space of a machine tool are a major problem in precision engineering. The problem of determining these errors in a convenient and acceptable way for a certain thermal condition of a given machine tool has not yet been fully solved, for the unmanned manufacturing environment. To determine the errors in the position of the tool with a touch probe, a metrology pallet was used. The error model for touch probe application has been constructed using actual error measurements. An error calculation procedure, including the calibration of the metrology pallet on a machine tool, is formulated. Two approaches to obtaining error regression functions at a tool tip position have been formulated using one or two touch probes and the metrology pallet. A procedure for the decomposition of the probed errors into error components is set-up using the regression analysis. It establishes the relative contribution of each error component to the change in the resultant errors in the work space. A dynamic method of compensating the backlash is proposed using ANOVA (Analysis of Variance) analysis to determine the important factors affecting the backlash. Determination of probing intervals for the metrology pallet is done dynamically according to the thermal change of the machine tool using the drift error model obtained by General Method of Data Handling (GMDH) technique at Ivakhnenko.