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Help needed
« on: December 18, 2010, 04:24:18 PM »
Hi -

I am not new to CNC but I am new to setting up some of these settings in Mach3. How do I calculate steps per inch in Mach3? I am not getting accurate when I use the setup wizard thing.

I have a DIY cnc machine

My board is set to FULL step

1/2" 10 tpi ACME screw rods.
Direct drive
Kelling KL23H276 bipolar stepper motor
NEMA 23
Dual Shaft  Front shaft=1/4" x 7/8"  Back shaft= 1/4" x 5/8"
200 steps per revolution
1.8 degrees per step
No. of wires=8
Bipolar series Volts=3.86,  Amps=2.1, Ohms=1.84, Holding torque=2.0 Nm. 0r 282 oz-in
Bipolar parallel Volts=1.93, Amps=4.2, Ohms=.0.46 Holding torque= 2.0 Nm. or 282 oz-in


THANKS
« Last Edit: December 18, 2010, 04:27:48 PM by studysession »

Offline Hood

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Re: Help needed
« Reply #1 on: December 18, 2010, 04:42:18 PM »
Ok, one bit of info missing is what the microstepping is that you have the drives set to.

How it works is this
200 steps to turn the motor one turn in full step but as you will have some microstepping you need to multiply by that to get the amount of steps to turn the motor one turn. Say you have the drive set at 8 microsteps (sometimes written as 1/8 or also sometimes 1600 on the Chinese drives) That would mean to turn your motor 1 turn it would require 200 x 8 = 1,600 steps. Because you are direct drive that rotates your screw one turn but as you need to turn it ten times for 1 inch (10TPI) it means 1,600 x 10 = 16,000 is your steps per inch.
Hood

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Re: Help needed
« Reply #2 on: December 18, 2010, 04:44:23 PM »
OOPS I need to learn to read, I see you have it in bold that it is full step, so 2,000 is your steps per.
Suggest however you set to 8 or 10 microsteps as you will get much better motion.
Hood
« Last Edit: December 18, 2010, 04:46:22 PM by Hood »
Re: Help needed
« Reply #3 on: December 18, 2010, 04:46:47 PM »
I have it set to 1 FULL step -
I have options for 1/8 or 1/2 and something else, but left at 1 FULL step.

What is better - Should I change it 1/8 or something else? Is one better than the other?
Re: Help needed
« Reply #4 on: December 18, 2010, 04:47:26 PM »
Thanks Hood -

This helps a lot.

Offline Hood

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Re: Help needed
« Reply #5 on: December 18, 2010, 04:49:13 PM »
1/8 is probably your best bet and should give you smoothest motion, Geckos say 10 is the optimum if I recall.
So if you set to 1/8 your steps per will be 16,000
If 1/4 it will be 8,000
If 1/2 it will be 4000
If full it will be 2000
Hood
Re: Help needed
« Reply #6 on: December 18, 2010, 04:50:59 PM »
Thanks!!!!

How does velocity and acceleration affect steps or does it even matter?

Offline Hood

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Re: Help needed
« Reply #7 on: December 18, 2010, 04:59:46 PM »
It doesnt really, obviously if you have either the velocity or the Accel set too high your motor will stall and you may actually get higher on both of them with 1/8 stepping than you would with full stepping.

What the steps per do affect is the max velocity you can run at a certain kernel frequency in Mach.
For example if your steps per were 10,000 and the kernel was 25KHz you could theoretically get a max rapid speed(Velocity)  of 25000/10000=2.5 inch per second or 150IPM
If your steps per were 25,000 and kernel was 25KHz that would mean 1 inch per second or 60 per min.

Dont however set the kernel higher than you need as it may impact on your computers stability.
Hood
Re: Help needed
« Reply #8 on: December 18, 2010, 05:02:29 PM »
I have always left it at the default because I never knew what to change or what I can change things to.
Re: Help needed
« Reply #9 on: December 18, 2010, 05:03:35 PM »
Thanks again!!!