Monday, March 10, 2008


Hooked up the electronics. Just the comms and 3 stepper drivers. Left the extruder board out of the loop for now. Don't seem to have any PCB mounts and the diagonals I would've mounted them on aren't installed, so I just left them hanging in a rat's nest arrangement while I did a systems check.

Fired up the host app and opened the stepper exerciser. First thing I noticed was that the Y axis kept moving in the same direction no matter where I moved the slider. Turned out to be a mechanical problem with the Y opto. It was reading "home" even when not blocked. Once I fixed that, I noticed that both the X and Y axes were running backwards. When I moved the slider in the positive direction, the stepper would move the head away from the corresponding opto. I reversed the order of the wires on both motor connectors and that seemed to fix it.

This is very odd because, at the time, the instructions indicated that the Y and Z motors should be wired one way and the X should be wired opposite. As it sits now, I've got the X and Z wired one way and the Y opposite. The instructions have since been edited and there's now only a single note indicating that the X stepper is the odd one out. There used to be a table showing the wiring of the Y and Z versus the X but it's no longer in the wiki. I managed to find an archived version of the table and I've edited it to the wiring arrangement I'm currently using:

Pin (X & Z axes) Pin (Y axis) Colour
1 4 Red
2 3 Black
3 2 Green
4 1 Yellow

Note: The above is the wiring for the Nanotec motors.

The good news is that the Z axis worked perfectly the first time. I had made three mods to it:
1. Used a metal motor coupler
2. Added a belt tension idler
3. Removed the backlash springs and screws

The end result is a Z axis that moves smoothly with very little strain on the motor. As far as I can tell, the weight of the bed is more than enough to prevent backlash.

After a bit of fiddling, I worked out that I'm getting roughly 10 steps per mm on X and Y and 300 steps per mm on Z. Total travel on X and Y is about 230 mm and Z is at least 90, depending on where the nozzle ends up.

No comments: