Improvement of Accuracy by Decreasing the Fluctuation of Translation Speed in Automatic Length Measuring Machine

The purpose of the present study is to improve an accuracy by decreasing the fluctuation of translation speed of a moving carriage in an automatic laser interferometer for the calibration of standard scales up to 2 m. The translation system is analyzed of the carriage and a new device is introduced in order to decrease the speed fluctuation. Teflon slide bearings, which have a relatively low and velocity dependent coefficient of friction, are used as the device in place of the two of the eight roller bearings of the carriage. In consequence, the rate of the speed fluctuation obtained by the device is shown to become considerably smaller than the rate by only the roller bearings and the value to be less than 0.4% at the typical speed 100 mm/min. Decreasing the speed fluctuation, the standard deviation is experimentally estimated to be less than 0.04 μm in repeated measurements of a one millimeter line interval of a standard scale.