Re: Going home / more stepper speed!

Hi Ian,

Your motor drivers are L278/279? I know a little about L297/298
drivers; They are usually wired to be a chopper drivers. In that case,
you can use 5X voltage or more, and get some acceleration out of them!
What voltage do you use? Are you running half step or full step? I
think the 3:1 reduction is probably what's getting in the way! the
steppers have to turn 3X faster then the 1:1 setup commonly used on the
Sherline. But if 'ya got 'em, might as well use 'em! Don't know what
the oz/in are of your motors, probably low? If you wanted faster moves,
then bigger motors that could run without the 3:1 reductions would be in
order. Or if you have excess resolution, shifting to full step from
half step would give you a higher top end. What's your final
resolution?

More information on your setup would be interesting to me. I'm still
hedging on buying new bipolar steppers and new drivers. BUT, I finally
got and OK and got an air compressor (wives love "ON SALE") from Sears,
so that killed my CNC budget! NOW I have to find hoses and a "tire
inflator" end. 6HP, 30gal, should be fine for a hobby shop. And I can
charge up my portable tank for steam engines!

Best regards,

Alan KM6VV


Ian Wright wrote:

>
> Thanks everyone,
>
> Even if there are varying views in positioning of the home switch (as I
> really expected), I (and hopefully others) now have some very useful
> information on setting tool lengths etc. I quite like Smoke's idea of having
> a moving home switch but quite how I could implement that I'm not sure -
> I'll go and find my thinking cap!
>
> Jon, the motor driver are fairly basic L278/279 combinations with current
> setback and running in half step mode. The motors are surplus and, as near
> as I can tell they are about 5volt, 1.5 amp. At the moment it seems that the
> best speed I can get out of them without losing steps is 210 r.p.m. In my
> case this is taken through a 3:1 reduction to a 1mm pitch leadscrew which
> therefore gives me 70mm / min or 2.75" / min! Not particularly fast and
> that's on a G0 command. Speed doesn't really worry me too much as the parts
> I will be working on are unlikely to exceed an inch or so in size but a bit
> more on the rapid would be nice. Maybe there's something I'm overlooking
> and, if I knew where to look, I could change something to get more speed but
> I don't know where to look. I don't think it is the motors themselves as I
> have three different types which all behave similarly so that only leaves
> the drivers and the computer. Any thoughts?
>
> Ian
> --
> Ian W. Wright
> Sheffield UK
> www.iw63.freeserve.co.uk
> ----- Original Message -----
> From: "Jon Elson" <jmelson@...>
>
> > It is likely due to the motor/driver combination, as EMC should do OK
> > on a P266.