Z axis upgrade

3D printing as a hobby brings with it plenty of tinkering. I noticed an effect in my printed parts that looks like z wobble from my old cupcake, but the openbeam printer should be better constrained in the xy axes to prevent that.
Basically there are 8mm guide shafts that keep everything aligned and a pair of z motors with misalignment couplings and a threaded rod and M8 nut to actually impart the force in the z direction with minimal x and you components. I had used some spare M8 threaded rods that I bought from makerbot when they were clearing out old cupcake parts.


What I noticed was that the ridges on my parts changed size as a function of layer height. This meant that some layers were being squished more than others. The pattern was the exact same pitch as the threaded rod, which meant the z didn’t move a consistent amount up for each part of the rotation of the motor turning it.
I got some new motors with integrated threaded rods from pololu for cyber Monday and printed up some new mounting hardware and brackets.


The new motor have a pitch of 8mm per rev, and has 4 intertwined threads (2mm apart each), which can help with evening out pitch variations. The nuts are also much nicer too, and came with mounting holes already tapped for M3.
I also moved the old z motors into place as the second x axis and second extruder, though those aren’t wired yet.

I discovered a new problem as well. I thought I could get more z height by moving the motors up (to take full advantage of the threads going all the way down into the motors), and had to move them up enough to clear the wooden platform of the year axis.

I homed the newly configured machine and got a grinding noise as the z finished homing.


The motor on the first extruder hits the z motor when the x axis has just been homed. I’ll probably add a spacer to the x home switch, but for now I am very careful about homing things in the right order and making sure everything clears.
It was too late to print that night, so I had to wait a day to see if things improved. Here’s the first print after the upgrade compared to a print from a few days before the upgrade.


All in all, a simple and worthwhile upgrade.

In the same order I got a raspberry pi b+, which is now installed with octopi, WiFi, and a webcam for time lapse printing. I still haven’t printed via the pi, but it’s ready to test when I have time.

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