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General Mach Discussion / Re: Spindle calibration, how I manage to get it working

« on: November 29, 2020, 10:30:20 PM »

I recently changed drives from a Gecko G540 to a Leadshine MX4660 and later realized it has a 1.1V drop in its PWM to analog circuitry so the 0-10V output is actually 0-9V. As a result my spindle speed no longer tracked with S commands.

After searching found some threads about Linearity.dat, including this one. Unfortunately, I didn't have a copy of excel on my computer so I wasn't able to use the macro to generate the Linearity.dat file. I ended up writing a small python script to take a csv of measurements and output the dat file. Referencing it here in case someone else finds it useful: https://github.com/modbog/mach3linearity

it does some interpolation so I didn't have to take that many measurements to get a pretty accurate result. Here's the input from my test. Left column is the requested RPM, right column is the observed value using a digital tach:

Code: [Select]

0,0
1000,0
2000,1456
3000,2480
4000,4095
5000,5419
6000,6745
7000,8076
8000,9411
9000,10745
10000,12080
11000,13416
12000,14748
13000,16088
14000,17416
15000,18756
16000,20100
17000,21443
18000,21555
19000,21555
20000,21555
21000,21555
21555,21555

After calibration I got pretty accurate measurements.

Code: [Select]

0,0
1000,0
1500,1505
2000,2006
3000,2998
4000,3993
5000,4991
6000,5999
7000,7003
8000,7992
9000,8998
10000,9993
11000,10992
12000,11993
13000,12998
14000,13998
15000,14992
16000,15998
17000,17000
18000,17998
19000,18990
20000,19996
21000,21299
21561,21584