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Motor Acceleration between Master & Slave

SparWeb

SparWeb

Active Member
Hello,

I've been enjoying my CNC router table since getting it several months ago. The holidays have given me time to try some more ambitious projects, and get tighter tolerances on parts. I knew this is when limitations or problems would show up, but no disasters so far.
canadianhobbymetalworkers.com

Anybody still using Mach3?

I bought a CNC router! It's old! No it's not that bad, but it's a DIY project that the guy has picked at for almost 20 years. Still works, and tonight I have cut wood by jogging the cutter, just trying it out. Learning as I go. The CNC software is installed on a geriatric Windows XP computer...
canadianhobbymetalworkers.com canadianhobbymetalworkers.com
It's a CNC gantry router (42" x 30") with stepper motors. The gantry moves on belt-driven rack and-pinion, pretty typical.

I have run into a little mystery and I'd like to run it by the wise members here, before I change a setting I don't understand.
I set out to correct a scaling error, and I seem to have found a racking error at the same time. No big surprise, but as I investigated further, I found that the two motors driving the Y-axis have different parameters set. These 2 stepper motors are slaved together and I would assume that they should operate identically. Instead I find that only the velocity settings are the same. They are set to different accelerations. I don't understand why this would be.

Master:
Steps 1736.237
Velocity: 150 in/min
Accel: 30.669776 in/sec/sec
G's: 0.07944
Step Pulse: 2 microsec

Slave:
Steps 1736.237
Velocity: 150 in/min
Accel: 65.0 in/sec/sec
G's: 0.16836
Step Pulse: 2 microsec

Should I change them to match, or is there a reason for the two settings to be different?
 
Photos from Mach 3 so that you can see what I am seeing...
Motor_Config1-Y.jpg

Motor_Config1-A.jpg
 
I have a slaved motor on the Y axis of my router. You definitely want them to be the same. Also check the DIP switches on the drivers to make sure they are set the same.
 
i also have a slave on my router table, the parameters are set the same for both, drivers should also be set the same (the dip switches as @David_R8 mentioned)
 
OK fixed that.
Found another problem: The slave-motor's A-axis prox-sensor was 3/16" back from the stop compared to its counterpart Y-axis sensor.
I found this problem because re-referencing the Y-axis to home didn't zero-out the A-axis and its motor kept turning. Loud noises!
Shifted the prox sensor forward until the sensor's little light came on. Now when I reference the Y-axis, the A-axis comes into Home at the same time.
I had never noticed this wasn't happening before!

I'll do some more test measurements to see if the gantry has come back in line, yet.

Thank you guys!
 
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