I’ve got an SV08 and have realized I need to calibrate my Z Steps. I printed a 100mm test that came out at 98.8. The math said to change my “rotation_distance” from 40 to 40.486. I saved, restarted and reprinted and it’s shorter not taller.
rotation_distance 40 pink 98.8
rotation_distance 40.486 orange 97.79
What the heck is going on?
100 mm @ 40mm/turn = 2.5 turns of the screw
100 mm @ 40.5 mm/turn = 2.47 turns of the screw → shorter model.
To get a taller model you need a shorter rotation distance to get Klipper to turn the screw further.
BUT the lead screw pitch is quite precise. Your rotation distance probably isn’t the reason for a short print. A thin first layer (low Z offset) and a low flow rate will result in a short print. Also the bed mesh (with stock settings) causes thin layers over high spots and thick over low spots until the layers end up flat.
It’s usually best to act elsewhere when steppers aren’t being properly maintained. The motors are new, everything is pretty reliable on that side, and modifying the stepper can accidentally resolve a problem that’s elsewhere… What said by Cardoc is true :
And BTW, this calibrations tests (and the one related to the extrusion factor) are good to execute to know if there is a gap (and if that change for different size, with time, after slicing changes…) but to fix it, that is probably just one very simple change. Under extrusion if probably the issue here… and 98.8 is “about” 100 (yes, i know, that is more than 1mm… but for industrial quality, does not use a plastic printer).
Did you account for shrinkage in the filament after cooling ?
this is a setting in your slicing filament profile
Lol, NVM. My model needs a little more bed contact surface, It was lifting from the bed and measuring shorter.
A tip for beginners:
Except for the extruder the rotation distance (or steps/mm in Marlin) is the LAST thing to change to “fix” a model. The lead screw pitch and the tooth pitch on belt sprockets are probably the most precise components on your machine.
