I’ve been printing out a few models and calibration cubes, and my z height seems consistently off. Since i don’t have an endstop I manually set it, but what seems to happen is that my prints are always nearly 1mm too short, whether it’s a 10mm cube or 40mm.
Right now I am using a m6 leadscrew for the z, so my steps are set to 3600. (1mm pitch at 16u steps). And im just using vinyl tubing with zip ties to connect the motor shaft to the leadscrew.
Until i get the leadscrew mounts printed, is there anything else that can cause this?
On the z homing back down before a print, it is off too so i have to re-level it. I checked the current of my motors by turning them down until they stopped and then turned them back up (i kinda go by ear), it seemed too much current and they wouldn’t move either.
Are you using a heated bed?
Do the bottom few layers “look squished”? What printer design?
Have you done some G0 z100 calibration to confirm your steps/mm are bang on? If its always 1 mm off then it could be mechanical, maybe some play in the lead screw nut trap, or loose z motor mounts… I guess you’ve probably checked those out already though 
Are the calibration prints coming out with smooth walls, any sign of inconsistencies that could be a result of lost z steps? Sorry if this is all stuff you’ve checked already.
If it’s consistent 1 mm regardless of height that suggest Z steps are correct (in that it means that the 30 mm from 9 to 39 are spot on). So we have to be looking at something that consistently happens in the first couple of millimeters.
@Jasper_Janssen Yes agree, under usual circumstance I’d say it was a z homing issue but that should show as some really messy, squished out bottom layers that Stephanie didn’t mention. One way to confirm this would be to print one of those stepped pyramid type calibration pieces and then measure each tier, if only the bottom tier is off, its a z homing issue, if they are all a consistent fraction off then its a steps/mm or missing steps problem. Could also be bed mounts being to springy/loose or thermal expansion of heat bed.
M6 (1mm pitch) with a 200 steps/rev motor at 1/16 microstepping should be 3200 steps/mm, not 3600.
@Whosa_whatsis you’re absolutely right, but shouldn’t a steps/mm value that’s too high result in a printed object that’s too tall?
I had very a similar problem, every object I printed was 0.5mm shorter than expected. Turned out it was due to using a flexible coupling. The first bit of movement was being absorbed by the coupling. A temporary fix was to preload then coupling to remove all the flex. I will eventually replaced it with a solid coupling.
I have weird z homing issues as well before starting a print it will home fine, then immediately jump up a few mm after warming the hot end. it then goes back down about Half the height it moved up then Starts to print, it’s annoying when you think you have your z homing just right go to print and realize the z went to high…
What electronics do you have? I had a similar issue but in my case it was that the z stepper motors where not getting enough current and would miss steps. It was just a case of increasing the pot on the stepper driver board on the Ramps and it fixed the problem.
I’m using my teensylu board. I’ll check the steps/mm i think that was my typo here.
The heat bed is always warmed up before I start so i dont think it’s a thermal expansion issue. I’ll check the springs, I did use some relatively stiff ones, but the board the y bearings are mounted too seems to flex rather easily.