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Z calibration

Posted by tony woollacott 
Z calibration
March 01, 2012 01:01PM
I have got the build of my Prusa completedrinking smiley, now for the calibration! The Z axis when set on 10mm step moves about 30mm. I have had a look at the preferences and cannot find any reference to the stepper/screw relationshipconfused smiley. Am I in the right place, or am I missing something? I have'nt checked the X and Y, but presume that they would be adjusted in the same place as the Z.
Any help would be much appreciated.
Tony
Re: Z calibration
March 01, 2012 01:11PM
You will need to set the steps per mm for each axis somewhere in your firmware. For Sprinter and Marlin (perhaps others too, but I've never used them), they are in configuration.h in an array declaration.

The three calibration formula at the bottom of this page were extremely valuable. I found measuring the hobbed bolt to calibrate the extrusion to be quite difficult and wound up with a wildly different value than what it actually turned out to be, so this handy calculator and some post-it flags came to the rescue.
Re: Z calibration
March 01, 2012 01:21PM
Thanks that looks great, and very handy.
So what you are saying is that I need to make changes to the firmware loaded on the chip? If this is the case would it be possible to get a copy of the correct firmware and load it up? This is all new to me, as I am a mechanical guy with very limited electrical knowledge.eye rolling smiley
Re: Z calibration
March 01, 2012 01:34PM
tony woollacott Wrote:
-------------------------------------------------------
> Thanks that looks great, and very handy.
> So what you are saying is that I need to make
> changes to the firmware loaded on the chip? If
> this is the case would it be possible to get a
> copy of the correct firmware and load it up? This
> is all new to me, as I am a mechanical guy with
> very limited electrical knowledge.eye rolling smiley

I'm pretty new myself. spinning smiley sticking its tongue out

Thing is, all the numbers depend on what's on YOUR machine. For example, I'm using GT2 belts on pullies with 32 teeth each, on 200 step motors (1.8d) at 1/16 microstepping, so my magic steps_per_mm are 50 for X and Y. If you were to use that number with printed pullies featuring 8 teeth and T5 belts on 1.8d motors microstepping at 1/8, you're going to be very disappointed.

The calculator page is super easy to use to calculate steps per mm. The only thing I had to do more than once is the E calibration.

It would be awesome if you could define them at runtime with an M code so you can have a golden-master firmware, but I don't know if that's possible.
Re: Z calibration
March 01, 2012 01:41PM
Okee dokee, so in a nutshell, no quick easy fix for Tony! I guess I will have to knuckle down and do some experimenting. Thanks for the input Mazawsmileys with beer
Re: Z calibration
March 01, 2012 03:49PM
If you are setting it to move 100mm and it doesn't you need to find the value that is set in your firmware and this calculation.

Lets say the value is 456 and you get a movement of 87mm

you would need to use this formula works every time is is quite simple

456*100/87

where 456 is the current firmware setting 100 is the movement you want and 87 is what you actually got.

This formula works an all axis and also works on the extruder


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Experimenting in 3D in New Zealand
Re: Z calibration
March 02, 2012 03:28AM
Thanks, it's the whole firmware thing that scares meconfused smiley. I have never touched it before and quite honestly don't know where to start.
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