Re: [CAD_CAM_EDM_DRO] Re: Stepper motors ( giants ) cheap.

True, I use a belt drive because with the Hi-Inductance causing a low speed
I had to maintain as direct a drive as possible. However, using a microstep
controller I built using the LMD18245 chip, I get at the end a 350 PPI
on my x-axis and at 4"/second I can snap a 3.5mm onsrud cutter if I go too
deep into hardwoord with it.
My Z-Axis is around 4000PPI with a worm gear and
could crush just about anything.
My Y-axis which is pushing a gantry weighing around
300lbs can accelerate to about 1"/sec quite smoothly. It
runs on a stainless steel 1/8" wire rope wrapped twice around a epoxy wheel
from one of my sailboats rope
pulleys. Due to the curved inside race of the epoxy wheel
the rope self-center's during movement. Seems to work well.


I guess the upshot is that if your willing to go microstep
and deal with the speed issues, Large AC-Sync motors work pretty good when
re-wired. Like anything else , however, there are always trade-offs.

----- Original Message -----
From: "Tim Goldstein" <timg@...>
To: <CAD_CAM_EDM_DRO@egroups.com>
Sent: Friday, August 18, 2000 8:35 PM
Subject: RE: [CAD_CAM_EDM_DRO] Re: Stepper motors ( giants ) cheap.


> >From my understanding there is nothing wrong with this approach other
than
> the fact that the high inductance will limit your maximum rpm. The 4"/sec
> figure will not equate on all systems with the 72 rpm limit that are
> mentioned. When you look at Art's machine you will notice he is using
belts
> to move the visible axis's. There are no lead screws that I can see. The
> point is Art would have far less steps per inch most likely than a machine
> with screws. On my Shoptask I have 5 tpi ballscrews and 2:1 reduction
belts.
> This means I need 10 motor turns for each inch of travel. At 72 rpm I
would
> only be getting a pokey 7.2 ipm or .120"/sec.
>
> Tim
> [Denver, CO]
>
> > -----Original Message-----
> > From: Terry May [mailto:tmay@...]
> > Sent: Friday, August 18, 2000 9:14 PM
> > To: CAD_CAM_EDM_DRO@egroups.com
> > Subject: [CAD_CAM_EDM_DRO] Re: Stepper motors ( giants ) cheap.
> >
> >
> > Ok everyone,
> >
> > Is there a down side to this other than the speed??
> >
> > I could sure live with 4"/sec. It would be about 1/10 the cost of
> > comparable torque steppers.
> > Terry May
> >
> >
>
>
>
>
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