I built my first CNC router over the past few weeks.

So far all I've tried to do is draw some things with a pencil I mounted to it until I'm more confident with the software.

I've hit a roadblock that I want to get over before I move on to anything else. While the machine is running, it will randomly shoot off in a straight line, sometimes that line is bigger than the entire drawing, and then it will go back to drawing as if nothing happened. The glitches sometimes are in the X and sometimes in the Y. I've not seen them in the Z but since I'm only doing pencil drawings, I only have the 2 Z commands; I'm sure if I was doing some 3d carving it would show up in the z direction as well.

I've got the speeds dialed down really far to eliminate any missed step issues but it still has these random glitches. They are always in different spots on the same drawing.

I'm running mach3 to a hobbycnc 3 axis board. the power supply is 36V from a chinese supplier. the pc is an old Dell with windows XP. The parallel port is 3.3V. I've got 3/8" x 16 threaded rod for leadscrews and am only running the thing between 10 and 20 inches per minute.


Any ideas? I'm thinking its probably the computer...