Re: Treadmill motors as Servos

Hi Les,

I see the math now. Posts crossed paths I guess.
Yow! 150 IPM, that almost scares me. I'm used to 35 IPM.
Whatever it takes to get rid of missed steps!

I guess you saw the pictures of the thing I'm going to try
to run.

John



--- In CAD_CAM_EDM_DRO@yahoogroups.com, Leslie Newell <lesnewell@...>
wrote:

>
> Hi John,
>
> I would aim a bit higher than 80 IPM. 80IPM is rather low for wood. I
> would go for something like 150IPM. With ballscrews you could probably
> go to twice that.
>
> At 150IPM the screw will be doing 150 * 10 = 1500RPM.
> At 35kHz (Mach3's middle kernel speed setting) with a 200 CPR encoder
> the motor will do 35000/(200 * 4) = 43.75 RPS = 2626RPM
> The ideal reduction ratio would be 2625/1500 = 1.75:1.
>
> Your screws are quite small diameter so you will be very close to the
> critical speed where they start to whip. Go here
> <http://www.nookindustries.com/ball/BallCalculators.cfm> and look at

the

> inch ball critical speed calculator. It looks like your 32" axis will
> probably have to be run a bit slower to keep under the critical speed.
>
> Les
>
>
> John Hansford wrote:
> > Hi Les,
> >
> > I'm not sure HOW to calculate it on this machine I'm making.
> > I'm not after great speed...80 IPM would be plenty good.
> > It's only about half done. That's why I got interested
> > in using servos before I made all the brackets & hardware.
> >
> > It uses 1/2-10 acme for a screw. I want it to cut 3/4" thick MDF
> > shapes. It'll have a cutting area of 28" x 32".
> >
> > I'll rig it it to use a router or an R8 spindle, so the speeds
> > will vary between 1000 to 30,000 rpm. The reason for that is the
> > spindle is quieter and generates much less airborn dust. It's
> > an experimental thing to try out before welding up a good single
> > purpose production machine.
> >
> > John
> >
> >
> >
> >
> >
> > --- In CAD_CAM_EDM_DRO@yahoogroups.com, Leslie Newell <lesnewell@>
> > wrote:
> >
> >> Those pulleys are a lot cheaper than I can get them here in the UK.
> >> Shaftloc or other taper fittings are good. Apart from being a

pain to

> >> make, traditional keyways have a tendency to come loose and wear.

One

> >> machine I repaired a while back had a key that had worn nearly

round.

> >> The keyway was a horrible mess as well.
> >>
> >> Have you actually calculated the reduction ratio you need? My mill
> >> worked out 4:1 but your machine may be different. What type of

machine

> >> have you got and what materials are you cutting? What is the maximum
> >> rapid speed you want? Also what is your ballscrew pitch?
> >>
> >> Les
> >>
> >>
> >> kz1927 wrote:
> >>
> >>> Hi Les,
> >>>
> >>> Your consideration and experience is Greatly simplifying what
> >>> could be an expensive and frustrating, trial & error experience
> >>> for me.
> >>>
> >>> I am as grateful as a person can be.
> >>>
> >>> I'll go with the surpluscenter encoders...they're proven to work
> >>> on your setup. Plus I'll have a few spare motors for (something)?
> >>>
> >>> I'm looking at these pulleys
> >>>
> >>> http://www.sdp-si.com/estore/CoverPg/Shaftloc/HTD5_Pulley.htm
> >>>
> >>> I'd get a 20 and an 80 for 4:1 reduction.
> >>> I think I've got that right.
> >>>
> >>> John
> >>>
> >>>
> >>>
> >
> >
> >
> >
> >
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