Study on Pre-travel Behaviour of Touch Trigger Probe under Actual Measuring Conditions

In order to increase the accuracy of On-Machine Measurement, it is very necessary to develop a methodology to calibrate and compensate checking errors resulted from the pre-travel behaviour of touch trigger probe under actual measuring conditions accurately. The some factors impacting on the pre-travel behaviour under various measuring situations are investigated in this paper thoroughly. Based on analyzing the probe's triggering mechanism and working procedure, the influencing law of main metrological parameters including measuring speed, the approaching direction, stylus length, material and geometrical characteristics of the detected objects on the pre-travel behaviour has been implemented. A novel measuring-task-oriented calibration method is presented, by which several main factors lessening calibration accuracy such as errors of machine tools and manufacturing errors of artifact are eliminated. By means of this method, the pre-travel behaviours affected by several combinations of the above-mentioned parameters for different measuring task have been obtained. The correctness and efficiency of the theoretical analysis and the calibration method has been verified by a compensation experiment. The experimental results show that the On-Machine Measurement accuracy could be improved obviously.