Hi, I am working on a DIY router / mill which will run from a stepper motor + belt drive system. I know the normal route is a precision ball screw + nut combo, but I would like to attempt this method, after all, it is a hobby, so I can play a bit.
I have identified stepper motors with very little shaft play and reasonable radial load capability with a nominal 1/2 in shaft. This will (hopefully) allow mounting the timing belt pulley directly to the shaft of the stepper motor. Micro stepping will be used to obtain the small precise steps, and special high tolerance belt will be used to help minimize issues there.
The challenge I have is this:
- No matter what I do, there will be at least a small amount of eccentricity in the stepper motor shaft, pulley center hole, and teeth.
- How do I "reduce this to a minimum ?
So far, I am thinking:
- Buy high quality Al toothed pulleys
- Have them lathe bored (I don't have machining tools yet) to 0.005 under size for the shaft and shrink fit them on + set screws
- Use the stepper motor to drive the "assembly and have someone take a "finishing cut" on the pulley teeth to true it up to the last 0.001 or maybe less.
I am pushing a bit on this aspect, as any errors in the eccentricity are amplified X pi in the linear motion, at least the way I am thinking about it.
Any suggestions ?