Abstract
The pitch accuracy of the precise machine elements such as gear, screw and rack having periodic shapes, is very important in their performance. In order to measure the pitch accuracy, in this study, a non-contact measuring method is proposed for the screw pitch error utilizing thermoplastic hologram instead of silver-halide plate hologram, and then the possibility to realize this method is experimentally investigated. The experimental device is constructed by combining a thermoplastic recording system, a laser generator, an optical system, a laser length measuring system, a desk-top-computer, a carriage and so on. The thermoplastic hologram is made as follows : The thermoplastic plate is exposed with the reflected beam from the flank of the screw thread and the reference beam, and then developed by a electrifier. The pitch signal is obtained by illuminating the hologram with both signal and reference beam, and the positional pulse is obtained through the electric circuits. The obtained main conclusions are as follows : (1) The pitch signal can be detected not only at the flank where the hologram was recorded, but at the other flanks. (2) The non-contact measuring system for the screw pitch error was constructed based on this method. The repeatability for the measurement of the screw pitch error is 0.3 μm in standard deviation.
