RE: [CAD_CAM_EDM_DRO] Musings on screw pitches

Iv'e been toying with the idea of changing my belt pulleys on my 3-in-1.
The way the machine came from the manufacturer, there are larger pulleys
on the screws than on the motors. This means the motors must spin faster
for a given screw speed. This seems to me as if it is a setup designed
for servos, not the steppers that I am using.

I have thought about just getting the same size pulleys, but putting the
larger one on the motor, and the smaller one on the screw, thereby
letting my steppers turn more slowly.

Seeing your messages has given me a bit more of a reason to try it.
Unfortunately, the shaft sizes are different. So I can't just swap the
pulleys around.

Thanks,

________________________________________
Andy Wander |


-----Original Message-----
From: CAD_CAM_EDM_DRO@yahoogroups.com
[mailto:CAD_CAM_EDM_DRO@yahoogroups.com] On Behalf Of Paul Kelly
Sent: Friday, June 02, 2006 10:59 AM
To: CAD_CAM_EDM_DRO@yahoogroups.com
Subject: RE: [CAD_CAM_EDM_DRO] Musings on screw pitches

> >
> > Well it went 6 times faster.
> http://www.caswa.com/nobott_on_speed.wmv
> > (cutting the road runner)
> > Not only that, it accelerated 6 times faster. Same drives, same
> > motors.
> >
> > The acceleration is the clincher. It's clear that, on
> machines of this
> > size, that the mechanical advantage of the ballscrew
> reduces the mass
> > that the motor "sees" to a point well bellow the inertia of
> the motor+
> > screw.
>
> Where did he get the ballscrews with that pitch?

Ebay, unable to cope emotionally with having the slowest router in town.
I
immediately went looking for some 20mm pitch screws (yes I drive a big
car
too). Found 'em pretty quick.

>
> My XY system for programming a panel of processors ended up
> being so slow with a 20TPI thread that it was faster to do it
> by hand. My next approach was going to be to use belts. But
> 20mm ball screws sounds like a good idea.

Yeah, this is the sort of thing I'm talking about, using a coarser pitch
screw to improve speed with steppers just doesn't seem to be a strategy
that's in the public domain... Seems strange that..

> >
>
>

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