Re: [CAD_CAM_EDM_DRO] Does a VFD do the trick?

The 2 motors are inside the machine linked with belt or gear.
But when I have a stepper I still have a force to overcome cranking it
when the current is switched of. And as I understand if I crank a
switched off stepper it generates current that might kill the driver
(lets say a Gecko).
Right?
Sven Peter
----- Mensaje Original -----
De: juan gelt <juangelt@...>
Fecha: Viernes, Enero 6, 2006 9:15 am
Asunto: Re: [CAD_CAM_EDM_DRO] Does a VFD do the trick?

> you might reconsider steppers as they are cheap to
> control.
> you can get steppers with double shaft and put crank
> on it. my cnc mill is like that. no trouble to work it
> manually at all.
>
> --- Familia Peter Arce & TAD <peteryco@...>
> wrote:
>
> >
> > Hello friends,
> > I fell over my own words yesterday and have to make
> > the best out of it.
> >
> > A (2,5-3tons) beauty of surface grinder from 1957 I
> > have to get again to
> > work. Complete new electrics with a PLC.
> > What I thought were reduction motors are plain three
> > fase motors (1700
> > revs, 125W) inside 1 to 1 geared.
> > Out side reduction Y 1:3 makes 1,7mm per motor turn
> > and Z 1:7,5 makes 0,13mm per motor turn.
> > With solid state relays I will get the Y movement
> > reasonable well to work.
> > But for the Z movement not. I would like to have an
> > automatic down feed
> > graduable from 0,001 to 0,04mm until I am close to
> > the final measurement
> > and still be able to manage the machine by hand.
> > That makes me exclude steppers as option.
> >
> > Does a VFD on standard three fase motors do the
> > trick that I can turn it
> > just something like 2 degree or more per impuls and
> > later leave it free
> > spinning?
> >
> > As you know me, I work on all kind of machines, but
> > I hadn´t to convert
> > any with this kind of task and have no hands on
> > experience with VFD's.
> > The PLC has encoder inputs so if necesary I can hook
> > some on the motors,
> > screw or nut.
> >
> > The owner first of all needs the machine running,
> > keeping future options
> > open, but a automatic use and position feed back
> > will be greatly
> > apreciated. And tiny VFD's aren´t that much out of
> > financial reach.
> >
> > Who has played with VFD's and standard threefase
> > motors (240V Delta
> > generated with slave motor) and can give me a
> > reference if it is feasonable?
> >
> > Best regards from Costa Rica, where clocks work
> > diferent.
> >
> > Sven Peter
> >
> >
> >
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> OFF Topic POSTS: General Machining
> If you wish to post on unlimited OT subjects goto:
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> 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........
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> List Mom
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