Re: [CAD_CAM_EDM_DRO] suggestions for router lead

Graham Stabler wrote:

>(snip)
>
>Anyway, I'm looking into leadscrews. I am considering acme screws
>with Delrin nuts but am having a hard time deciding on the lead I
>should go for. Obviously more lead gives greater speed but
>resolution suffers.
>

Oh ya... Can be confusing.

Without doing incredible amounts of sophisticated math ( and I am lousy
at that), considering your machines size, and Assuming you are going to
use NEMA 23 in your case,
I'd shoot for either .200 (5 turns per inch) or .25 (4 turns per inch)

Here is how resolutions stack up with the .200:
Full Step > .001
Half Step > .0005
1/4 step > .00025
1/8 Step > .000125
and, the very popular 10 step > .0001

Here is how resolutions stack up with the .250:
Full Step > .00125
Half Step > .000625
1/4 step > .0003125
1/8 Step > .00015625
and, the very popular 10 step > .000125

In either case, resolutions are pretty low. Applying Microstepping of
any sort will make the resolution finer, but likely it is not that you
NEED finer resolution. The real trade off is that if you go much larger
( more travel per turn) you may suffer Power Capability. Seeing that
this size machine likely does not need 300ipm rapids, those larger Leads
are not a good bet. IF you are using NEMA 34's, I'd choose something
larger in "Lead".

So, I'd shoot for that ".2" neighborhood. With most software packages
available, and some good motors, That combination should be able to run
at least at 100ipm rapids, (I know of some similar hitting 160ipm
easily) and still give you more than adequate resolutions. Some of this
all comes down to what you DO with the machine, what software you are
going to use what drivers/settings you have as an option AND what
voltage the whole thing runs at.

One last consideration that I've seen creep up, IF you do run the .200
leads with Big motors and you want to run really fast ? I have seen
issues in engraving applications where a typical rolled leadscrew and
anti-backlash nut can develop lots of heat between nut and screw on
numerous really short moves. That "heat" can give you grief. I know from
experience that running at 160ipm on a .200 in very short (engraving
type) moves is less than optimal.

But I think that gets close......... Someone correct me if I am wrong.

Chris L