y axis

With the x-axis working (at least, without load) on to the y-axis. Having two working axes is a big deal as you can then use it as a point locator. So you can zero to a known reference point, translate to the desired location then perform an operation (for instance, drill a hole) and get well-dimensioned parts even if not fully automated. 

The y axis is slightly more involved than the x axis. The motor is cantilevered ~100mm away from the mill requiring a solid print (with reinforcement). The x-axis has built in thrust bearings, whereas the y axis does not (the handwheel has a rubbing surface). Finally there's a keyway involved! 

The design will be similar to the x-axis in that we will be using an oldham coupler to link the motor to the leadscrew. A printed part will suspend the motor out ~100mm, leaving ~10mm gap between the motor shaft and the leadscrew shaft. 

First I designed the print. I cribbed off of this design. Reyer was nice enough to tweak that model for my x-axis (his mill had a different bolt pattern), but I decided to do the x-axis on the opposite side. I borrowed the idea for the y-axis but made several improvements, the biggest being I ran 4 M5x100mm bolts through the print to provide compressive force to the print. My issue with Reyer's design is he had about 15mm of bite on the nuts, and then the nuts ate up a good chunk of the cross-sectional area of the print - and I'd hate to see my stepper fall to the floor mid-print! 

You can see the model on thingiverse. It wraps around the y axis pedistal and bolts it to the mill, while bolting the stepper through the print. 100% infill, layers normal to the bolt direction. 15 hour print! 

Next: I bought a cheap thrust bearing off Amazon.  Pack of 3, I'll need the other 2 for the Z conversion. This allows me to tighten the print down to the Y axis and reduce the drag between the print and the pedistal.

I have two printed parts for the coupler, but only used the stepper side print. Clean it up and use a mallet to tap it onto the axis nice and tight, then tighten down with a washer and two nuts. 

I had to machine the inner coupler and the motor side. I don't have a drawing I more or less eyeball and test-fitted it. Kind of frusturating without the handwheel in place - I need to come up with drawings so other people can make the parts a priori. 

Here's the print bolted to the stepper with the motor-side coupler. The coupler is basically a 1" aluminum rod 25mm long with a slot and a hole in it, and 3 tapped holes to secure it to the shaft.

All mounted up. this took several iterations as the middle part to the oldham coupler was too long. Better than too short (easier to remove material than it is to add it) but still frustrating.

It looks a little funky because the top side and bottom angles are all different but the motor is flat relative to the mill. There is almost no play in the coupler - I put a dial indicator on the y axis and I could move it +/-10mm within 0.01mm after getting the steps per mm put in correctly.

Here's a look at that inner coupler. the other side looks the same except I didn't have to core out the middle. This side needed clearance for the nuts, the other side needs no clearance as it fits in the slot on the motor side coupler.

All assembled. Here's a video of jogging both the x and y axes. Very pleased to be here in 2 weeks of effort.