Mini Kossel Z Calibration Issue

I have been through calibration a few times now and I can't seem to dial in the Z Height on my prints. My calibration print is 20X20X5. The print is printing 20..1X20.1X5.5. I have my steps per mm @100 for all 3. It passes a paper test across the entire bed and if I measure Z movements of 10mm(across the entire bed) they are measuring perfect. I'm really at a loss as to what could be going on. Any input would be greatly appreciated.

Thanks!

Edited 1 time(s). Last edit at 07/24/2014 11:56PM by Radair.

As a note, I have been through all of the other threads related to this issue. I guess the part I may be missing is. How do you properly calibrate steps per mm on a delta? I figured since @ X0 Y0 Z should be a linear move on all 3 towers that measuring the movement of the effector should be a valid check of steps per mm. If this assumption is incorrect then I am sure that is my root issue.

Thanks again!

You can measure Z movement on any of the carriages. Presuming you have the same belts and pulleys on all three they will all move the same amount. Repetier Host has a belt calculator on its top menu. Tell it your belt type, microstep value and pulley size and it will give you the correct value to feed into Marlin

@AndyCart

Thanks. The calc actually confirmed the 100. I'll have to keep playing and see if I can figure out what is going on. Really banging my head against the wall on this one.

It may be a stupid question but ...

Did you actually count the teeth on your pulleys?

Someone mentioned some errors with delta calculations with 20 tooth pulleys on marling firmware. I have the 20 tooth pulleys on my printer, so far no issues. Keep in mind two things however, 1 plastic just like any material expands and contracts with heat, and 2 it could depend on the slicing software. I had ok luck with kisslicer, better luck with cura. Almost no luck with slicer itself. The joys of tuning a printer.

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I verier the pulleys and they are proper 16. I think i'm going to start calibration all over again and see if I missed something. I will give cura a try also. I have been using slicer. Thanks for the ideas all!