Wednesday, October 01, 2025
V0.05 Z Axis Driver - Superbly Stable, New Features
Many mods and great results from the Z Axis Driver. I'm unable to see any lateral movement at all (with USB microscopes anyway) as the probe goes up and down. So far I've driven it from the Stage all the way up to 3.5mm, and it is such a relief to have a usable range that does not require me to manually position the probe tip to within a mm of the stage and tighten a clamp without shaking. I have no probe holder yet, it's literally just bolted on. Looks like this:
A lot of the holes are going away now I know where I want to mount things. This should result in a more rigid structure that prints faster and is less confusing to assemble. I'm happy enough to put a "V0.05" stamp on it and prepare for an interim release.
New features
From the left: In black you see a U-shaped bracket bolted to the end of the framework. This is an easily adjustable Limit Switch, enabling maximum usable range and simple realignment of the contacts in the event of a mishap.
Two holes right, you will see a couple of blue vertical cylinders; "Nut Bars." These are clamped to the frame with two M3 x 50mm screws, which add rigidity. The crossbeams above and below hold M3 nuts drilled out to 3mm which significantly limit the wobble of the drive screw and make the thing much less finicky to assemble (more on that later).
One hole right there are 3-hole long lugs that more or less allow mounting to V0.04 frame parts. Not perfect, needs a bit of shim, but functional.
Next we see the rectangular pair of complementary flexures. These constrain the moving end so that it can only move up and down. Coupled with the Nut Bars, these give the probe excellent stability and repeatability.
Completely missing off the right end is any kind of adjustable probe holder. You can see the small shiny probe tip, bottom right, and for now it's just held there with a bit of Metriccano and an M3 x 40mm screw. Unfortunately the increased length of the Axis Driver means the old mount no longer holds the probe tip near the centre of the Stage, so I've had to pull the slide out and examine it with a proper microscope. The dreaded "Hello World" (I swear I will do something else shortly):
Nut Bar Advantage
On that micrograph you'll see two obvious things: Smaller dots on the top image, and random displacement on the Y axis.
Y axis error is large because the Y Axis Driver lacks the lower Nut Bar. I'm replacing that driver with one that has a Lower Nut Bar right now.
Dots are much more consistent in size because the probe no longer oscillates. The dots are smaller at the top (approx 10μm dia) because I was able to position the probe more accurately. This was done using the new video workbench. If I push too hard on the surface with the probe tip, it starts sliding off to the left and the dots get elongated.
Video Workbench Height Determination
I've switched to using vlc to mpv. The latter is better supported and allows me to assign keys to move around the image and zoom in and out easily (plus it doesn't use the accursed Flatpak). By zooming in on the one pixel at the very tip of the (now stable) probe, I can discern a brightness change in that pixel that is caused when the probe tip hits the glass slide and thus get a really good indicator of zero height.
As the Stage isn't optimally positioned, figuring that out that was tricky. But it should get easier once I've fixed the Z Axis Driver support structure.
So, get that Lower Nut Bar on the Y Axis Driver, Relocate the Z Axis Driver so the probe fits on the Stage, and we're back on track. I'll do a release then, unless anyone contacts me asking for files.
