Hmm, getting an issue I’m not familiar with on a custom oversized bukobot. What’s your diagnosis?
I suspect it’s the z motors not raising or lowering appropriately, I have my doubts that extrusion is the issue as that’s pretty standardized by now. I use a Teflon tube to relieve the pull of the filament so I can rule that out.
One question: I’m not sure who the supplier of the motors is so are there variations in the steps for motors listed as Nema 17?
It seems that the distance between waves is the same than the size of metric screw threads of z axis. Could be?
Could there be a bend in the Z axis? Does one ripple occur per revolution of the motor?
The most likely problem is overconstraint of the the z threaded rod. Add a z isolator and remove anything that fixes the rod rigidly in place. It should “float” a little bit. It’s OK if the rod wobbles, better the rod wobble than force it to be straight and distort your other mechanisms in the process.
I forgot, another possibility is using inch threaded rod on a millimeter machine.
Your Z sliders are probably loose, making the axis under-constrained. Add some layers of tape to the backs of the sliders to tighten it up. With the printed sliders, this is usually caused by over-compressing the first layer when printing them, which is easy to do and is part of the reason we switched away from printing those parts.
Check to see if the bands are like a corkscrew (a wobble) or a stack of pancakes (ribbing/banding). If wobbling, watching the z rods during a long homing travel should help you spot the source of the motion.
Excuse me, are your use cura? Or what slicer did you use?
Another source of ribbing is letting the Z motors sleep, or using a layer height that doesn’t divide evenly into full steps. For a Z threaded rod with 0.8mm pitch (and 16x micro-stepping), layer heights should always be even multiples of 0.004mm. For 1mm pitch, even multiples of 0.005mm. Etc.
