Itchy’s idler pulley

Today’s fun was making the head move on the gantry…

So, to make a CNC machine you need to make a thing, the cutter, move in X, Y, Z. There are a couple of ways you can do it – I am choosing to have the cutter moving, but I could also keep the cutter still and move the thing beneath it. My way is a moving gantry CNC cutter.

The X axis, or how far across the piece you are, is the gantry. It sits over the top of the piece. You mount it onto the Y axis, so it can run up and down. On top of the X axis, you mount the Z axis, or how high the cutter goes. In the door and up the stairs… and then turn left on the landing.

This gantry is made of an aluminium extrusion with very little variation, so I can run wheels straight along it. Those wheels are holding the blue plate on. The plate is attached to a toothed belt, and the belt goes around a pulley and around a motor with a pulley on, and back to the plate on the other side. When the motor goes one way or another, so does the plate.

The belt goes through the middle of the gantry here, where there is a hollow. Right now I’m pulling it by hand, but everything on the right is milled by me. Pleasingly, the mill I used is a manual one on which you keep the cutter still and the thing underneath it moves. It’s very satisfying.

Milled aluminium in a block with two screw holes and a hole for a bearing and boltThese brackets have big spaces in to fit bearings into. Those let the bar (currently an Allen key) turn freely. That lets the pulley turn freely too. The smaller holes are for mounting. Small bolts go through and attach to the gantry. There are various ways to do that. Magic happens. The step on each is so they both sit the same distance out from the end, and the bolts are forced into a line, so the pulley is vertical.

To make the making easier, I used a laser cutter to prototype the ends in 5mm acrylic. I tried to use the chop saw but it’s in a sad state and a hacksaw ws genuinely better. Next up in the yak shaving stakes: fixing the chop saw.