PROBE TYPE SHAPE MEASUREMENT SENSOR, AND NC MACHINING DEVICE AND SHAPE MEASURING METHOD USING THE SENSOR

摘要

A probe head 10 and a laser interferometric displacement meter 20 are provided. The probe head supports a probe 2 that is capable of contacting a workpiece 1, that is free to move in the direction of the workpiece, and drives the probe towards the workpiece. The displacement meter measures the displacement of the probe with a high accuracy without contact. The probe head 10 is also provided with a probe shaft 12 with steps 11a, 11b at intermediate portions thereof and air bearings 14a, 14b that support the probe shaft on each side of the steps. The air bearings have a high stiffness in the radial direction, and the probe shaft is made to float by using compressed air, thus the resistance of the shaft to sliding is reduced. In addition, another compressed air is supplied to the location of the step and produces a driving force in the direction of the workpiece due to the difference of cross sectional areas on each side of the step, that provides a very small load within a predetermined range. Thereby, the measuring pressure can be adjusted to a constant very small load without reducing the stiffness of the bearings of the probe, and the measuring pressures can be varied freely. Therefore, a sub-micron accuracy of about 0.1 µm can be obtained, and the equipment can be made compact and is easily applied to on-machine measurements.