Abstract
A Constant speed feeding mechanism which is driven by the lead screw is constructed in order to make the “magnetic scale” type position encoder. The uniformity of the feeding speed at the “writing” head, which is fixed on the feeded carriage, is disturbed by undesirable motion of the carriage due to 1) inaccuracy of the restraint mechanism, 2) pitch error of the driving screw and 3) variation of rotating speed of the driving motor. The experimental procedure to examine these influences is set up and the results show that the influences of the restraint mechanism and the rotating speed variation are negligiblebut the pitch error gives rise to irregular feed-rate (defined as the displacement of the table per revolution of the driving screw). Therefore, the range of uniform feed-rate is estimated by the t-inspection method and then the feeding speed is measured in the range. The variance of the feeding speed measurement is compared with that of the feed-rate measurement by the F-inspection method. The results show that the variation of the feeding speed is mainly due to the pitch error of the driving screw. The numerical results are as follows:
Mean feed-rate4.9967mm/rev.
Standard deviation of feed-rate1.8μ/rev.
Mean feed-speed4.9962mm/sec.;Standard deviation of feed-speed2μ/sec.
