Re: Microstepping thru the Tulips

Based on what I am seeing it sure appears as though there is a very
high potential for having positional problems at these higher step
rates too then.

Perhaps Maris could shed some light on the relationship between the
torque/speed curves and the transitional point where chopping ceases
to perform completely.


--- In CAD_CAM_EDM_DRO@yahoogroups.com, "Phil Mattison"
<mattison20@...> wrote:

>
> Again, these traces illustrate my point, which is that when the

step rate

> gets to the point where the inductive phase shift of the motor

winding

> dominates the period during which the winding is energized, the

chopper

> simply turns off once during that phase, in effect acting like a

single-step

> driver. It doesn't matter at that point how many microsteps are

processed,

> the motor never sees them.
> --
> Phil Mattison
> http://www.ohmikron.com/
>
> ----- Original Message -----
> From: Mariss Freimanis <mariss92705@...>
> To: <CAD_CAM_EDM_DRO@yahoogroups.com>
> Sent: Monday, August 14, 2006 5:39 PM
> Subject: [CAD_CAM_EDM_DRO] Re: Microstepping thru the Tulips
>
>
> > Hi,
> >
> > For everyone who is interested in this thread, I took 8 scope

pics of

> > winding currents for a 3.9A/phase motor operated at 24VDC.
> >
> > The motor pics were taken at 3.75 RPM, 15 RPM, 150 RPM, 375 RPM,

750

> > RPM, 1500 RPM, 3750 RPM and 7500 RPM.
> >
> > Yes, that's right, 7,500 RPM at 24VDC for a 3.9A NEMA-23 motor.
> > That's 250,000 microsteps per second. That step pulse frequency

IS

> > 12.5 times higher than the 20kHz PWM switching of the drive. See

how

> > it all works, makes sense and doesn't violate any known law of
> > physics.
> >
> > Please go to the Geckodrive Yahoo Group, Files section and see:
> > Files > G203V step motor drive > MOTOR CURRENT WAVEFORMS
> >
> > The accompanying .pdf file by the same name describes the 8 gif

scope

> > pictures.
> >
> > Mariss
> >
> >
> >
> > --- In CAD_CAM_EDM_DRO@yahoogroups.com, "turbulatordude"
> > <dave_mucha@> wrote:
> > >
> > > --- In CAD_CAM_EDM_DRO@yahoogroups.com, "Steve Stallings"
> > > <stevesng@> wrote:
> > > >
> > > > violent agreement indeed, except for your assumption
> > > > of what most folks consider high speed.
> > > >
> > > > If we assume Gecko drives microstepping at 10 micro-
> > > > steps per full step and the known appx. 20KHz PWM
> > > > rate, then we get a possible 10 rev. per second or
> > > > 600 RPM with microstepping still nominally functioning.
> > > >
> > > > Apply this to a Bridgeport with 5 TPI screws and
> > > > 2:1 gearing (typical of Boss series) and you get
> > > > 60 inches per minute. Not blindingly fast, but a
> > > > long ways from slow.
> > > >
> > > > Cheers,
> > > > Steve Stallings
> > > > www.PMDX.com
> > > >
> > >
> > > <HUGE snip>
> > >
> > > My understanding is that microstepping shows it's best face on

slow

> > > speeds and acceleration, and that at *some* point, becomes
> > > inconsequential.
> > >
> > > but,
> > >
> > > those useful speeds are the most common to actually use the

motor.

> > > not rapids, but cutting speeds.
> > >
> > > Personally, I could care less of the smootheness of a rapid,

as long

> > > as there were no missed steps.
> > >
> > > It seems the question what speed is considdered slow enough to
> > benifit
> > > from microstepping and what is too fast to need it ? And that
> > appears
> > > to be dependant on power supply voltage, motor inductance and

maybe

> > > some other factors ?
> > >
> > >
> > >
> > > Dave
> > >
> >
> >
> >
> >
> >
> >
> >
> > Addresses:
> > FAQ: http://www.ktmarketing.com/faq.html
> > FILES: http://groups.yahoo.com/group/CAD_CAM_EDM_DRO/files/
> > Post Messages: CAD_CAM_EDM_DRO@yahoogroups.com
> >
> > Subscribe: CAD_CAM_EDM_DRO-subscribe@yahoogroups.com
> > Unsubscribe: CAD_CAM_EDM_DRO-unsubscribe@yahoogroups.com
> > List owner: CAD_CAM_EDM_DRO-owner@yahoogroups.com,

wanliker@...,

> timg@...
> > Moderator: pentam@... indigo_red@... davemucha@...
> [Moderators]
> > URL to this group: http://groups.yahoo.com/group/CAD_CAM_EDM_DRO
> >
> > OFF Topic POSTS: General Machining
> > If you wish to post on unlimited OT subjects goto:
> aol://5863:126/rec.crafts.metalworking or go thru Google.com to

reach it if

> you have trouble.
> > http://www.metalworking.com/news_servers.html
> >
> > http://groups.yahoo.com/group/jobshophomeshop I consider this

to be a

> sister site to the CCED group, as many of the same members are

there, for OT

> subjects, that are not allowed on the CCED list.
> >
> > NOTICE: ALL POSTINGS TO THIS GROUP BECOME PUBLIC DOMAIN BY

POSTING THEM.

> DON'T POST IF YOU CAN NOT ACCEPT THIS.....NO EXCEPTIONS........
> > bill
> > List Mom
> > List Owner
> >
> >
> > Yahoo! Groups Links
> >
> >
> >
> >
> >
> >
>