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### Author Topic: 4th Axis Calibration in Mach3  (Read 882 times)

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#### chriswalker

• 1
##### 4th Axis Calibration in Mach3
« on: June 26, 2017, 01:02:03 AM »
Hi guys,
Yes another newbie here.
I nned to know how to calibrate my 4th axis using the "A" axis. I can not find a useful how to video on youtube so i though i would try here. THe ONLY thing i know is that my Stepper motor is 1.8
Can anyone possibly help?

#### joeaverage

• 5,815
##### Re: 4th Axis Calibration in Mach3
« Reply #1 on: June 26, 2017, 04:28:21 AM »
Hi,
calculating the  'steps per' confuses a lot of people but really isn't that difficult if you break it down to simple ideas.

For a linear axis 'steps per' means steps per unit, whatever you think your standard unit should be... for most its inches or mm,
however if you were making semiconductors um or u inch might be more useful.

Lets say your 'natural' units are inches. The question is 'how many step pulses does the controller have to produce to make my axis go 1 inch?'
If we had some sort of pulse counter we could jog our axis 1 inch and write the counted  number of pulses as 'steps per', easy.

Another idea is to have the controller produce a certain number of pulses, 10,000 say, and then measure how far the axis moved. If for instance
the axis moved 0.871 inch then the 'steps per' is 10,000/0.871=11481 steps per inch, easy. You might ask 'so how do I get Mach to produce exactly
10,000 pulses?' As it turns out that's easy. On the Config/Motor Tuning page for the axis your trying to calibrate, say X to start with, set the 'steps
per' at 10,000 and save. We are almost bound to be wrong with our guess but we can now make Mach issue 10,000 pulses.
On the MDI screen issue:
G0 X1  <enter>
Mach will issue 10,000 pulses to the X axis driver, measure how far the axis moved with a dial gauge or similar, do the calculation and 'Bobs your Auntie'.

If you have accurate information about your machine you could calculate the answer without the experimentation above. You will need to know the
pitch of you lead screw/ballscrew, any gear/pulley reduction between your stepper and the screw and finally the number of microsteps per full step
your driver is set to. If you don't know these numbers EXACTLY then find out or devise an accurate way to measure them.
Lets take an example.... your leadscrew is 1/4 inch per rev, 2:1 pulley reduction, 8 microsteps per fullstep.
200 fullsteps is one revolution of the stepper, or 200x8=1600 microsteps per revolution. With 2:1 reduction your lead screw rotated 1/2 a rev ie 1/8 inch.
Therefore 1600/ (1/8) =12,800 microsteps per inch. Write this into the 'steps per' on your motor tuning page and your done. Clearly the numbers you
use must be spot on otherwise it will be inaccurate.

Your post is about your A axis. The question to be answered is 'how many pulses is required for my A axis to rotate 1 degree?' Is your A axis 'geared'
to your stepper and if so what gear ratio?. How many microsteps per fullstep is your drive set to?. Answer these and the calculation is easy.

Craig
My wife left with my best friend...
and I miss him!