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. : Ceramics, On-machine measurement, Non-contact measurement, Laser displacement sensor, Ultra-precision machining tool, Ultra-precision grinding IntroductionUltra-precision positioning stages are utilized in various instruments such as ultra-precision machine tools, semiconductor manufacturing equipments, optical apparatus, and precision measurement instruments (Nakamoto, 2006). With the high density and miniaturization of the devices, the precision positioning stages have been required both of nanometric positioning accuracy and travel range of several hundred millimeters. The positioning accuracy and motion accuracy of the positioning stages are relied on the form accuracy of the sliding surface. In general, the sliding part of the positioning stage is made of the metallic material. However, the form accuracy of the metallic sliding part is not enough for the ultra-precision positioning with nanometric accuracy because of thermal expansion, wear of the sliding surface and its own weight (Ostuka, 2009). Therefore, in the recent years, the sliding parts made of the ceramics materials are employed for the ultra-precision positioning stages. Ceramics materials have the excellent mechanical characteristics such as high-stiffness, low thermal expansion, wear resistance, and light weight (Sugawara, 2013).In order to realize the nanometric positioning accuracy, the form accuracy of sub-...

In this paper, a four-probe measurement system is implemented and verified for the carriage slide motion error measurement of a large-scale roll lathe used in hybrid manufacturing where a laser machining probe and a diamond cutting tool are placed on two sides of a roll workpiece for manufacturing. The motion error of the carriage slide of the roll lathe is composed of two straightness motion error components and two parallelism motion error components in the vertical and horizontal planes. Four displacement measurement probes, which are mounted on the carriage slide with respect to four opposing sides of the roll workpiece, are employed for the measurement. Firstly, based on the reversal technique, the four probes are moved by the carriage slide to scan the roll workpiece before and after a 180-degree rotation of the roll workpiece. Taking into consideration the fact that the machining accuracy of the lathe is influenced by not only the carriage slide motion error but also the gravity deformation of the large-scale roll workpiece due to its heavy weight, the vertical motion error is thus characterized relating to the deformed axis of the roll workpiece. The horizontal straightness motion error can also be synchronously obtained based on the reversal technique. In addition, based on an error separation algorithm, the vertical and horizontal parallelism motion error components are identified by scanning the rotating roll workpiece at the start and the end positions of the carriage slide, respectively. The feasibility and reliability of the proposed motion error measurement system are demonstrated by the experimental results and the measurement uncertainty analysis.

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