Re: Stepper size recomendation.....

Hello,
The deal with steppers is that they are very accurate, open loop,
devices so long as you NEVER exceed their torque rating so that they
lose steps. That said, if you could put an exact number on what you
would need for machining power for say a .100" depth of cut in 3"
stainless steel bar etc... then you would want to double that number
for 'overhead'. So, within realistic size limitations on actually
mounting the motors to the lathe, you can't really ever have to much
power.

I highly recommend you get in touch with Dan Mauch at Camtronics.
He knows all about steppers, and has quite a few larger steppers for
sale at very decent prices.

http://www.seanet.com/~dmauch/

I see some 762 in-oz and 1303 in-oz for $159 and $195 respectively
that would make for excellent prospects.

That may be more than you want to spend up front, but I don't
think you would ever regret it if you got some nice/powerful motors,
with a big power supply and Geckos.



--- In CAD_CAM_EDM_DRO@yahoogroups.com, "lcdpublishing"
<lcdpublishing@y...> wrote:

>
> Thanks Jan,
>
> I was kidding about the nema 17s - I just pulled four of em out of
> some old printers. They are cut little things, might find a use for
> them somewhere, but not on this lathe.
>
> I will be using ball screws, and depending on the pitch, I will

work

> out the best belt drive ratio for speed and torque on this little
> machine. When I was teaching CNC, one of my customers had some PC
> Turn 50 machines from Emco Maier that were I believe the original 9
> x 20 machines (the iron part, not the CNC part).
>
> Any way, those machine didn't really have enough power to cut

steel,

> even aluminum was a bit of trouble at times. It's been a long time
> since I have seen those machines, but I believe they probably had
> Nema 23s on them.
>
> Based on the stepper suggestions you offered, it looks as though I
> should be looking in the 300 Oz in range?
>
> Thanks for the input.
>
> Chris
>
>
>
>
>
>
>
>
> --- In CAD_CAM_EDM_DRO@yahoogroups.com, JanRwl@A... wrote:
> > In a message dated 3/14/2005 3:53:23 P.M. Central Standard Time,
> > lcdpublishing@y... writes:
> >
> > So I am trying to determine the best size motors (in oz./in) I
> should be
> > looking for. My "More power" side of me wants to bolt on some
> 600 oz/in motors,
> > but my wallet says nema 17s ;-)<<
> > I assume you are JOSHING about "NEMA 17" for a 9x20! I would go
> for
> > something like the Superior Electric KML092-F07 Bipolar

steppers,

> using GECKO 210
> > drives and a decently-built UN-regulated supply with about 70
> volts UNloaded,
> > and capable of five amps load. The "chopper high-voltage"

design

> is vastly
> > more efficient than the old "LR system" with energy-wasting

power-

> resistors in
> > series with the motor's +common leads. OH: This kind of
> stepper is
> > commonly known as the new "Square NEMA 34, two-stack" size.
> >
> > NEMA 23, even triple-stack, would be a bit shy for some work the
> 9x20 size
> > lathe can do.
> >
> > Back in '99, before I knew about the Gecko drives, I built two
> lathes (see
> > photo: "Homebre...") using these motors and Superior

Electric's

> proprietary
> > bipolar-chopper dual-drive with power-supply in one box, and

that

> worked
> > very, very well. A similar lathe built in '84 used "round NEMA
> 34" unipolar
> > steppers, and it is sometimes "borderline" and can NOT be
> expected to display
> > "brute force". And it's DC motor-supply is 24 volt/15 amp.
> >
> > I assume you realize you must (better!) replace the lead-screws
> with
> > preloaded ball-screws, or at least (second choice:) fine ACME
> screws with preloaded
> > Turcite nuts. If you leave the screws and nuts as-is from the
> manufacturer,
> > you MIGHT eliminate some backlash by tweaking the half-nut on

the

> Z axis, but
> > for the X axis, you'd be kinda "on your own".
> >
> > Lotsa luck! Jan Rowland
> >
> >
> >
> >
> >
> >
> >
> >
> > [Non-text portions of this message have been removed]