The aerostatic guide in the traditional three-coordinate measuring machine and profilometer generally use metal or ceramics material. Limited by the guide processing precision, the measurement accuracy of these traditional instruments is around micro-meter level. By selection of optical materials as guide material, optical processing method and laser interference measurement can be introduced to the traditional aerostatic bearings manufacturing field. By using the large aperture wave-front interference measuring equipment , the shape and position error of the glass guide can be obtained in high accuracy and then it can be processed to 0.1μm or even better with the aid of Magnetorheological Finishing(MRF) and Computer Controlled Optical Surfacing (CCOS) process and other modern optical processing method, so the accuracy of aerostatic bearings can be fundamentally improved and ultra high precision coordinate measuring can be achieved. This paper introduces the fabrication and measurement process of the glass guide by K9 with 300mm measuring range, and its working surface accuracy is up to 0.1μm PV, the verticality and parallelism error between the two guide rail face is better than 2μm, and the straightness of the aerostatic bearings by this K9 glass guide is up to 40nm after error compensation.
The precision of traditional squareness measurement on ultra-precision motion stage is mostly determined by the standard component, such as bare L-square and optical pentaprism, and the measurement precision is lower than the precision of the standard component. Based on the error separation, this paper presents a novel method of squareness measurement with an optical square brick. The angles between the guide and the four lines of the section of the brick are measured, and the squareness error distraction is achieved by the truth that the internal angle sum of a tetragon is 360°. A squareness measurement test is carried out on the coordinate measuring machine (CMM) by using an optical square brick with the squareness error of 0.3°. The results show that the local squareness and uncertainties between the X axis and Y axis of the CMM are 2.5arcsec and 0.5arcsec respectively. The measurement precision is higher than the precision of the brick and the feasibility and accuracy of the method are validated.