After last time's success with calibrating, I was hoping to get at least to primitive printing, but no luck. First I had to slice a piece off the plate under the extruder to not have it stuck on the edge of the Z frame. That's bother enough to take on and off. Then I made some little cardboard pieces to hold the roller skater bearing under the Z rod in place, but they still move back and forth. I think the rod is warped.
Most worrisomely, when I tested the Z stage with these new bearing holders, it moved erratically, as if it was skipping half the steps randomly. At first, I though it was a problem with the new holders, but it persisted when I took them out again. And when I tried on the Y stage. And the X stage. And when I unplugged everything but the X stage. And when I swapped out the power supply. And when I tried a different driver, or no driver.
Only when I took off my homemade shield and connected directly with little bits of wire did it work nicely again. While trying to set that slightly differently, I accidentally removed the ground connection, and it did the jerking skipping motion again. Aha! It's caused by not being properly connected to ground. As opposed to the simply switching rapidly back and forth in place, which is caused by wiring Step and Dir wrong. Luckily, FabLab has a set of small but high-quality wires compatible with the Arduino, instead of the random little bits I've been using that keep falling out. So until I get a properly constructed shield from Fritzing, I will have to make do with setting up wires every time I want to use it. So, in the end, I got very little progress today.