Leadscrew stops and starts? Answered
I'm trying to make a cnc plotter similar to this: http://hackaday.com/2013/10/17/unorthodox-home-made-cnc-machine/
I have changed some things though: I'm using aluminum rod with washers super glued to the end, another washer, and two nuts instead of flange bearings (brushings) and two nuts, I'm using 3/8 rod, pololu steppers (#1209), and slightly different conduit clamps. I'm using a wooden dowel with a half-inch hole, and aluminum and nylon spacers tapped and with a setscrew to act as a motor coupler. The problem I'm having is that as the motors rotate, even continuously in one direction, the gantry stops and starts moving. It moves 1/16th of an inch per rotation, as it should, but within each rotation it moves quickly, probably 5/6 of the way within the first 180 degrees, then moves just the remainder in the last 180. The motors do not stall, miss steps, or change speed, but the gantry does. There is almost no backlash, and little play. Any ideas whats wrong?