MAXNC 10 with nema 17 stepper motors and Sainsmart Prover GRBL contoller

[707offroad]

My friend gave me an old MAXNC 10 and I've retrofitted some small nema 17 steppers and a Sainsmart prover grbl controller.
I'm trying to get the stepper motors calibrated and I really have no idea what i'm doing.
I've tried changing the values for $100, $101, and $102. but I don't fully understand what i'm doing.
my stepper motors have a 1.8 step angle
leadscrews are 1/4-20 allthread

What values should i be changing?

Thank you in advance

707

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[awerby]

You should be changing the motors. NEMA 17 steppers won't have enough torque to run that machine. All the MaxNCs were originally equipped with NEMA 23s; I'd suggest looking for some of those, or if they came with it, finding a controller to run them (not sure if the grbl is up to it).

[707offroad]

You should be changing the motors. NEMA 17 steppers won't have enough torque to run that machine. All the MaxNCs were originally equipped with NEMA 23s; I'd suggest looking for some of those, or if they came with it, finding a controller to run them (not sure if the grbl is up to it).

Thank you, i agree this is not the ideal controller or steppers. I'm trying to learn how to get this machine running as I've got a Harbor freight Central machinery 44142 mill/drill/lathe i would like to convert to cnc when i'm done with this machine.

I must be doing something wrong. If i set my $100, $101 and $102 values to 3000 it gives me about .98" movement when jogging the machine one inch.
When i use the formulas to calculate these values I come up with a $100, $101 and $102 value of 1259.84252. that value gives me about .38" movement when jogging the machine 1 inch.

I will be going out to the garage momentarily to test these values again

[awerby]

"I must be doing something wrong. If i set my $100, $101 and $102 values to 3000 it gives me about .98" movement when jogging the machine one inch."

That's probably as accurate as you're going to get. One problem with that machine is that the screws are directly coupled to the motor shafts and float with the motor armature, which isn't rigidly constrained - there's no bearing fixing them in place. So if they're .02" out, that's totally understandable.

[peteeng]

Hi 707 - Due to mechanical and electronic issues as Awerby says the theoretical value and real value are never the same. So you do the motion and measurement a couple of times and if commanded 1" is actually 0.98" then you multiply the 1259.84 value by 1/0.98 to give 1285.55 to correct the difference. Each axis will be slightly different so you calibrate each separately. So update the value, redo the test and maybe correct again to get it as close as poss to correct. Use as big a distance that you can measure accurately with as well. Say 125mm on a 150mm vernier...or imperial if thats what you have...Peter

[hfjbuis]

You could have measured some backlash in your result. Move 1", zero the dial and than move another 1" in the same direction. Repeat the last step and gather some measurements. It will tell something about the steps/inch and the repeatability.

200 steps/stepper revolution, 20 TPI leadscrew you need 200x20=4000 full steps/inch. According to your 1259.84 value, you use a micro stepping of 8. Your 3000 steps/mm setting seems pretty much OK (0.98") so there must be something wrong.
You can turn the leadscrew by hand (20 turns) and check the movement.
You can set GRBL to report in inches, but you have to setup grbl in mm settings.
My assumptions are based on that you use a grbl version 0.9 or higher.
https://diymachining.com/grbl-settin...-how-to-guide/