On-machine form measurement of high precision ceramics parts by using a laser displacement sensor

Ceramics materials have excellent mechanical characteristics such as high-stiffness, low-thermal expansion, wear resistance and light weight. Owing to those characteristics, the ceramics parts have been used for the sliding part of the precision positioning stages. However, it is difficult for the ceramics workpieces to achieve the desired form accuracy in once machining process because of the brittleness of the ceramics materials. The compensation of the form error is processed by the manual procedures in general, so it requires a skill of the operator and a great deal of time. In order to realize the automation of the error compensation, it is necessary to measure the workpiece form on the machine tool. In this study, an on-machine form measurement system using a laser displacement sensor having nanometric accuracy is introduced for the surface form measurement of the precision ceramics workpieces. The laser displacement sensor is mounted on the tool post of the ultra-precision polishing machine to realize the on-machine measurement of the ceramics workpieces. By using two horizontal linear slides of the machine tool, the laser displacement sensor can scan the surface of the workpiece with sub-micrometric motion accuracy. Consequently, three-dimensional continuous surface form of the precisely machined ceramics workpiece can be obtained in non-contact condition. In order to evaluate the measurement accuracy of the constructed system, the experiments to investigate stability and motion accuracy were conducted, and then the form measurement of the precision ceramics parts is carried out by using the proposed measurement system.