Laser-CCD based 6 degree-of-freedom machine error measuring system

Machine error measurement and compensation is very important for enhancing machining accuracy. Although the compensation based on indirect measurement or off-line calibration has been developed and used, real-time compensation based on direct error measurement is the most effective and accurate method to improve machining accuracy. Especially, the measurement method that can be used in an actual machining operation in a regular manufacturing environment is most preferred.; Taking above mentioned background into consideration, the concept of direct and simultaneous measurement of 6 degree-of-freedom (DOF) machine errors has been proposed for real-time machine error measurement and compensation in regular manufacturing environments. Based on this concept, a novel measuring system, which is referred to as the Laser-CCD Based 6 Degree-of-Freedom Machine Error Measuring System (LC6DMS), has been developed. LC6DMS consists of a laser module, a CCD measuring module, and a computer system for data processing. The unique design of the laser and CCD measuring modules enables LC6DMS to measure, simultaneously, 6 components of machine errors and keep a minimum size so that it can be attached to a machine tool for real-time application.; The theoretical basis for simultaneously measuring 6 DOF machine errors has been established. Forward solutions that show how machine error changes the positions of law beams on each CCD camera have been derived based on the law of reflection of optics and homogeneous coordinate transformation techniques. Reverse solutions have been formulated based on the forward solutions to determine 6 components of machine errors using beam center coordinates detected by the CCD cameras.; Some important laser and CCD characteristics and their influences on the measurement performance of LC6DMS have been addressed. Computer simulation has been conducted to optimize structural parameters of the laser module and CCD measuring module. A prototype of LC6DMS has been made based on the results of structural parameter optimization.; One of the biggest concerns in using a laser beam as a metrology basis is laser beam center drift. Statistical characteristics of beam center drift have been investigated; a digital method to reduce beam center drift has been developed.; In order to evaluate measurement performance of LC6DMS, a testing platform has also been built. The measurement results of LC6DMS were checked by some other high-accuracy measuring systems, and the comparison showed a good agreement.