1985 Volume 51 Issue 6 Pages 1257-1263
In order to evaluate straight motion accuracy of precision machinery, two kinds of errors i. e. positional errors and angular errors, have to be considered. Angular errors are so far measured by using precision levels or autocollimators and positional errors, by using straight edges or steel wires. Recently, laser interferometers become available for positional error measurement. A method what is called the inclination method for straightness evaluation of forms, is often applied to measurement of straight motion accuracy. In the method, the angular change of a moving table measured by an autocollimator is integrated and converted into the positional change. But it has been experienced that a positional error by the method does not coincide with that by the laser interferometer. In this report, it is shown that this disagreement occurs even if each measurement is carried out correctly. The reasons for the disagreement are ; (1) parallel motion of a moving table without an angular change of it. (2) difference between the distance of the table feet and that of the measuring intervals. It is concluded that the application of the inclination method to measurement of position errors is unreasonable.
