A new sub-nanometre error separation technique

The accuracy of roundness measurement is limited by the repeatability of measurement machines. For commercial roundness measurement machines, this limitation can be reduced by means of complex solutions to control the parameters' influence and thus limit the non-repeatable effects. The LNE-CNAM developed a cylindricity measuring machine with a particular architecture to overshoot the repeatability limitation. The working principle consists in comparing the form of the measured part with a reference form. This architecture offers the possibility of overcoming the spindle defects and consequently getting rid of the non-repeatable and random spindle error motion. The present work is about the development of an error separation technique based on the particular architecture of the new cylindricity measuring machine. In this case the separation technique consists in separating the defect of the reference form from that of the measured part. In addition, through the introduction of a one-step measurement with two sets of probes or two measurements with a set of probes, the method described here is also concerned with the minimisation of the number of operations necessary for a complete separation of errors. The effectiveness of the introduced method for a sub-nanometre error separation is proved by simulation.