Measurement of geometric errors in a miniaturized machine tool using capacitance sensors

Many studies have been carried out to produce 3D features in the size range between 10 μm and 10,000 μm, called meso-scale using material removal process by mechanical force. In addition, the concern with miniaturization of manufacturing system has been growing as the required size of parts becomes smaller. At present, several prototypes of miniaturized mechanical manufacturing system were developed including a miniaturized lathe. If these miniaturized systems have high relative accuracy and good volumetric utilization, it is possible to manufacture more complex and accurate shapes with various materials as well as there are advantages of reducing energy, space and resources. Due to imperfect components and misalignment in assembly, even though these systems are small, it is necessary to assess the accuracy of the miniaturized system itself to obtain high relative accuracy. Laser interferometers are widely used to measure geometric errors called as quasi-static errors. For miniaturized system, however it is difficult to install the required accessories such as optics and the measuring range is limited because of the size of the system and also this method is very expensive. Moreover, it is impossible to measure each error component simultaneously. A new system to measure simultaneously multiple geometric errors is proposed using capacitance sensors, providing quick and easy process. Similarly to the measurement of accuracy in a spindle, each error was measured using capacitance sensors and a measurement algorithm was mathematically derived. The experiments show that the proposed measurement system can be used effectively to assess the accuracy of miniaturized system at a low cost.