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Author Topic: motor tuning: aim for max speed??  (Read 3964 times)

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Offline jaja

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motor tuning: aim for max speed??
« on: June 15, 2009, 05:58:01 PM »
What would be wise,,,,, go for the maximum x-axis and z-axis speed? Or set things a bit slower to get a more relaxed lathe?
Lathe: -between centers 600 mm (23 Inch)
          -3 fase stepper motors 3,7 newton meter on the x- and z axis
          - powerfull computer 100 kHz kernel speed is possible

A motorvelocity of 4400 mm's per min is possible (higher is not possible for the steppermotor, it vibrates and does not turn), but is it clever/wise  to have this speed?

gr jaja

Offline Hood

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Re: motor tuning: aim for max speed??
« Reply #1 on: June 15, 2009, 06:07:33 PM »
Depends on what you are happy with and feel comfortable at.
 My lathe is big, over 3 tonne and I have servos on it. I can and have had it at 20,000mm/min during testing but it scared me too much :D Have it set now at 10,000mm/min and that seems fast enough to me.

Hood

Offline jaja

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Re: motor tuning: aim for max speed??
« Reply #2 on: June 16, 2009, 05:50:44 PM »
Thanks for your reaction Hood,

But is a high speed necessary for certain turning jobs?
Or can all parts be made with a much slower speed? (keep in mind that I'm an absolute beginner)
Re: motor tuning: aim for max speed??
« Reply #3 on: June 16, 2009, 06:07:00 PM »
Thanks for your reaction Hood,

But is a high speed necessary for certain turning jobs?
Or can all parts be made with a much slower speed? (keep in mind that I'm an absolute beginner)

If you're an "absolute beginner", then tune everything WAY down, or you'll waste a lot of money replacing broken tools (or broken machines) until you learn how to operate it properly.  It is VERY easy with CNC to make a simple mistake (like type + instead or - or X instead of Y), and causing the machine to do something stupid.  The faster the machine, the less chance you have to say "Oh, s**t!", and stop it before it crashes.

Regards,
Ray L.
Regards,
Ray L.

Offline Hood

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Re: motor tuning: aim for max speed??
« Reply #4 on: June 16, 2009, 06:11:14 PM »
You wont realistically be anywhere your rapid speed when machining, where rapids will come into there own is travelling back for the next pass or toolchanges etc. Whether that would make much difference to you would depend on the size of parts you turn and suppose really whether you were in a hurry or not.
 Best bet is probably to set at 2m/min or there abouts until you get used to the lathe then if you feel the need you can then speed things up. Acceleration may however be more important than rapids, especially for threading so you might find it is better to have the slower rapids.
Hood

Offline Hood

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Re: motor tuning: aim for max speed??
« Reply #5 on: June 16, 2009, 06:15:15 PM »
Oh meant to say its normal  to use feed per rev when turning, it will depend on materials but  normally I am  in the region of 0.2 to 0.3 mm/rev for roughing and maybe 0.1 to 0.15mm/rev for finish pass.

Hood

Offline jaja

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Re: motor tuning: aim for max speed??
« Reply #6 on: June 16, 2009, 06:30:13 PM »
Oke, thanks for your replies.
The picture is getting clear now, especially about the difference in speed and acceleration, while doing a job.
I red about it, but only now i realise the real difference
Just want to say that Mach3 is so much better then my previous cnc lathe program, but because everything can, and must be tuned, one must realise the theory behind it.

gr jaja
Re: motor tuning: aim for max speed??
« Reply #7 on: June 23, 2009, 06:21:54 PM »
insufficient accelleration can slow down complex work dramatically. Then, too much and it can lose steps or trip over itself. Disable the auto-zeroing when homing the system, send it in a series of full-speed movements and return home; check for discrepancies. Or move it to a programmed position near a gauge block on the bed before and after a spot of dancing and check with slip gauges before and after. Gradually raise the acceleration until you get errors, then back off until you don't.

Offline jaja

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Re: motor tuning: aim for max speed??
« Reply #8 on: June 24, 2009, 07:45:08 AM »
BluePinnacle,

Thanks for your reply.
I was just experimenting with the method you suggest (it is also suggested in the manual of mach3).
But then I found that my ballscrews have 0,05 mm backlash.
Nasty, perhaps I have to buy new ones.

gr jaja