I always thought the alignment was slightly out on my k8400. But it was producing parts with good a surface finish and dimensions etc. So I left it…
The other day I was blighted by a massive mid print layer shift ~9hours into a 12hr print 😡
So I decided it was time to sort it out. I loosened all pulleys and belts & had the rods out. I adjusted the distance between the iglidur bearings on the x & y carriages as mentioned in the wiki page (I didn’t use a hammer!) just a twist and wiggle etc did it. I won’t sugar coat it, it took ages. Possibly due to my prior negligence of the missalignment issues there was slight play in either the iglidur bearings or the central brass bearing. As such it was difficult to know if it was the perfect distance was achieved. When printer was tilted at ~45 degrees, a slight touch of the carriage would send it sliding to the bottom. At that point I determined it was acceptable. Certainly much better than it was before!
My advice deviates from the wiki at this point. For each axis:
- With the belts and pulleys lose, fiddle with the pulleys so the grub screws are accessible, then tension the belts.
- Move the carriage back and forth to distribute the tension throughout the belt (allowing the pulleys to swivel)
- Attach the alignment tools to the axis
- Tighten the pulley grub screws
It turns out, that the most significant reason for this later shift was actually due to the stepper motor pulley grub screw coming lose 😞. Anyway, the printer has performed admirably since this re-alignment.