A few days ago I changed my X and Y axis pulse/rev from 1000 to 3200. I calculated and fine tuned the steps/per to where the table moves 6.000" (within .0003") when commanded to move this amount. My issue is at low feed rates (10 IPM and lower) the motors are setting up a harmonics that sounds like vibrating sheet metal. It's more pronounced when both axis are moving at the same time, i.e. cutting a radius. At feed rates higher than 10 IPM the motors run smooth. I've played with acceleration but it doesn't have any effect. Surface finish is good so the harmonics are not affecting that. For info velocity is set at 135 in/min and acceleration is 15 in/sec. As long as the harmonics aren't doing any harm to my mill I can live with it but it sure is annoying.