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Author Topic: OK, I give up. How do I tune my motors? I've just spent hours trying!  (Read 5431 times)

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Hi All,
Most people on this group probably use inch measurements, but how do I set the steps per unit for my motors when I'm using millimetres as my unit? I'm running Mach3.

Here's the set up:
Xylotex driver running in 1/8 microstep mode, 200 step steppers and my X axis moves 1.5mm for one turn of the handwheel.

Maths was never my strong point and I'm stumped here :'(. If someone one can give the applicable formula for metric units I'd be very grateful. ;D

Thanks,
Dave.
Re: OK, I give up. How do I tune my motors? I've just spent hours trying!
« Reply #1 on: January 21, 2007, 12:39:54 PM »
This is what I came up with

200 * 8 = 1600 steps per motor revolution (1.5mm)

1600 * 2/3 = 1066.6666666666666666666666666667 steps per mm

Darek

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Re: OK, I give up. How do I tune my motors? I've just spent hours trying!
« Reply #2 on: January 21, 2007, 10:52:02 PM »
Hey Dave, here is an example.

Here is how you do the math. I will give you mine as an example. What we need to know is, How many pulses from Mach will it take to move the machine 1 of your units? (inch,mm) Mine is in inches. 1 inch = 10,000 pulses on mine. This is how I came up with the number.
My steppers have 200 pulses per revolution. ( 360 degrees divided by 1.8 degrees = 200 )
Micro stepping = 10. So 200 X 10=2,000
Motor to screw gearing is 1-1. So 2,000 X 1=2,000
Screw lead is .200 of an inch. My screw will have to turn 5 rounds to move the nut 1". 1.0 divided by 0.200=5. So 2,000 X 5=10,000.

Brett
;D If you could see the things I have in my head, you would be laughing too. ;D

My guard dog is not what you need to worry about!
Re: OK, I give up. How do I tune my motors? I've just spent hours trying!
« Reply #3 on: January 22, 2007, 06:57:52 AM »
Hey Dave, here is an example.

Here is how you do the math. I will give you mine as an example. What we need to know is, How many pulses from Mach will it take to move the machine 1 of your units? (inch,mm) Mine is in inches. 1 inch = 10,000 pulses on mine. This is how I came up with the number.
My steppers have 200 pulses per revolution. ( 360 degrees divided by 1.8 degrees = 200 )
Micro stepping = 10. So 200 X 10=2,000
Motor to screw gearing is 1-1. So 2,000 X 1=2,000
Screw lead is .200 of an inch. My screw will have to turn 5 rounds to move the nut 1". 1.0 divided by 0.200=5. So 2,000 X 5=10,000.

Brett

Thanks Brett,
I had seen (your?) post about this to someone else and used it as a basis - took me a while to figure out the conversion to mm's and also my microstepping is 1/8th but I ended up with a figure that didn't work so I thought I had it wrong. See the reply post to HillBilly.
Thanks,
Dave.
Re: OK, I give up. How do I tune my motors? I've just spent hours trying!
« Reply #4 on: January 22, 2007, 07:09:20 AM »
This is what I came up with

200 * 8 = 1600 steps per motor revolution (1.5mm)

1600 * 2/3 = 1066.6666666666666666666666666667 steps per mm

Darek
Hi Darek,
Thanks - I came up with the same figure but it didn't work. Has me stumped, what I also found was that after a while of changing the steps per unit (a LONG while), Mach3 seemed to be losing the plot, e.g., I'd tell it to move 25mm and I got it tuned to that (but the figure I had to enter was very very small!) and, still using that figure when I moved back to the zero point, the table only moved somewhere around 1 to 2 mm! I gave up after that.

Methinks I'll rebuild my PC and do a clean install of Mach2, I just got my licence key from Art and he says that the early version of Mach2 runs well on slower PC's - mine is a PIII running at 600MHz - so maybe that has something to do with it.
Probably won't get to doing that for a coupla days but I'll repost when I have done it and entered the steps we both calculated. Wish me luck! :D

Cheers,
Dave.

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Re: OK, I give up. How do I tune my motors? I've just spent hours trying!
« Reply #5 on: January 22, 2007, 09:50:03 AM »
Hello Dave, I have sent you a PM.

Brett
;D If you could see the things I have in my head, you would be laughing too. ;D

My guard dog is not what you need to worry about!
Re: OK, I give up. How do I tune my motors? I've just spent hours trying!
« Reply #6 on: January 30, 2007, 06:53:44 AM »
Hi All,
I have Mach3 running my steppers successfully! ;D

The calculations I did, and that others confirmed, were pretty darned close but I had to fiddle a bit to get the steppers to move the table the required X distance. X axis was pretty easy to do - it's direct drive, but Y axis still needs some fine tuning (it's geared 2:1, i.e., two turns of motor for one turn of leadscrew). I spent hours the other night and couldn't figure out why I could not get Y axis correct - until I disovered that the gibs were loose! Tightened them up and now I'm in the ball park - just a little way to go now. Funnily enough it is not an exact two times the number of steps I use for the X axis! Weird. Anyway... I'm pretty confident I'll get it nailed next time I play with it.

Incidentally, I started with Mach2 but after playing with Mach3 a few months back (simulations) I didn't like Mach2 so tried Mach3, since I am only usinga PIII running at 600MHz I was expecting trouble but it runs as sweet as a nut when I run any of the G Code examples (road runner etc). I am mighty impressed, and have learned a heck of a lot about motor tuning!  :D

Cheers,
Dave.
PS - Brett, thanks for your off-line help.

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Re: OK, I give up. How do I tune my motors? I've just spent hours trying!
« Reply #7 on: January 30, 2007, 08:21:31 AM »
Your welcome Dave,
    Glad you are narrowing things down. I don't understand why your y is not exactly 2x the x though.


Brett
;D If you could see the things I have in my head, you would be laughing too. ;D

My guard dog is not what you need to worry about!
Re: OK, I give up. How do I tune my motors? I've just spent hours trying!
« Reply #8 on: January 31, 2007, 05:58:13 AM »
Your welcome Dave,
    Glad you are narrowing things down. I don't understand why your y is not exactly 2x the x though.


Brett
Yep, it's weird all right  ??? - however, I've decided to put that on the back burner for a while as I need to machine the bits for the Z axis conversion. When I get that done (and I have read up on the inner workings of Mach3!) i'll get back to it and post my findings.

Cheers,
Dave.