Machsupport Forum

Mach Discussion => General Mach Discussion => Topic started by: Peter. on October 05, 2012, 04:13:25 PM

Title: Microsteps - can less be more or is more always, well, more?
Post by: Peter. on October 05, 2012, 04:13:25 PM

I'm looking to drive a 10mm pitch ballscrew directly with my 750w servo motor, which is run as a stepper. I have two of these to drive my x and y axes on my mill conversion. For stepping I have options of 200, 400, 500, 1000 steps per rev and 10x microstepping. Clearly, 10k microsteps gives a resolution of 0.001mm per step which is miles finer than this old chinese mill can manage anyway, but it does sound nice and smooth when travelling slow whereas 2000 step/rev which gives me a resolution of 0.01mm/step seems more sensible and gives me faster rapids but it hums quite loudly when moving at slow speeds.

What would you do in my situation?

Title: Re: Microsteps - can less be more or is more always, well, more?
Post by: Chaoticone on October 05, 2012, 04:37:03 PM

If the steps per can be divided equally into your desired resolution is the first thing I would shoot for (with in reason).   Sounds like your fine there.  I like them as smooth as possible but if it is slowing you down too much at the finer res. you may want to run it at fewer steps per.  I think in your case you would be fine either way but that's totally up to you.  If the noise and coarser resolution are a fair trade to you for the speed you should be fine. 

Brett

Title: Re: Microsteps - can less be more or is more always, well, more?
Post by: Peter. on October 06, 2012, 08:29:23 AM

Ok that's great - thanks for the reply. I last tested it on 5000steps/rev and it gave me a max speed of 3m/min on motor tuning, which gives me 6 seconds end-to-end on the x-axis. I'll hook up another axis and see if that changes.

Pete.

Title: Re: Microsteps - can less be more or is more always, well, more?
Post by: rrc1962 on October 06, 2012, 09:00:44 AM

10 microsteps in optimal.  Anything more doesn't gain you anything in terms of resolution.  Here is a good explanation.....

http://www.geckodrive.com/support/step-motor-basics/accuracy-and-resolution.html

Title: Re: Microsteps - can less be more or is more always, well, more?
Post by: Peter. on October 06, 2012, 09:41:24 AM

Hmm, interesting read. These are not ordinary drives and motors though, they are industrial drives that do up to 1000 normal steps per revolution.

Title: Re: Microsteps - can less be more or is more always, well, more?
Post by: Hood on October 06, 2012, 01:17:39 PM

Interesting, never heard of using a servo as a stepper before.
Few questions, why would you want to use a servo as a stepper and not as a servo?
Do you have a link to the drives you are using?

Hood

Title: Re: Microsteps - can less be more or is more always, well, more?
Post by: Peter. on October 06, 2012, 02:23:37 PM

Sure, this is what I am using for x and y axis control, and I'm hoping to get a third one for Z.

Title: Re: Microsteps - can less be more or is more always, well, more?
Post by: Hood on October 06, 2012, 02:32:32 PM

Ok seems they are steppers, or according to Berger Lahr anyway.
Hood

Title: Re: Microsteps - can less be more or is more always, well, more?
Post by: Hood on October 06, 2012, 02:45:34 PM

Having a quick look at the manual and they are weird beasts, kind of cross between stepper and servo from first glance.
I would say  your higher res will give you better results but as you have found lower rapids. That is unless you go to an external controller such as SmoothStepper, CSMIOIP-S or amy of the others that are capable of pulsing up to 4MHz.
Hood

Title: Re: Microsteps - can less be more or is more always, well, more?
Post by: rrc1962 on October 06, 2012, 02:50:20 PM

Sounds like the hybrid system Automation Technology (Keling) is selling now.  Basically a stepper with encoder feedback.

http://www.automationtechnologiesinc.com/products-page/nema34-closed-loop-stepper-motor-system-hybrid-servo-kit

Title: Re: Microsteps - can less be more or is more always, well, more?
Post by: Peter. on October 06, 2012, 02:52:01 PM

Aah ok, someone told me it was a servo acting as a stepper. Pretty new to these things.

rrc1962 - yeah there is room for encoder feedback but it's an option that sadly isn't fitted.

Title: Re: Microsteps - can less be more or is more always, well, more?
Post by: Hood on October 06, 2012, 02:54:39 PM

They seem to be a kind of cross between stepper and servo, 3 phase but they have 50 pole pairs.
Hood