Re: [CAD_CAM_EDM_DRO] Re: Timing Belt Sizing

Wally K wrote:

> Doug Harrison" <prototype@c...> wrote:
> >
> > Most of the CNC knee mills I've looked at had 3/4" series L belts.
> This
> > size seems to give long life. However, the rotational inertia of
> series L
> > sprockets can have a substantial effect on acceleration - much more
> so than
> > table and load masses. Smaller belt/sprocket systems are
> preferable in
> > terms of performance.

The inertia of these sprockets (especially in aluminum) is negligible
compared to the mass of the machine tables, and probably the motors,
too. If it is a concern, you CAN drill holes in the sprockets and
hollow out the inner part, too. This would be standard on cast
sprocket blanks, but the extruded or milled versions are generally
just sliced off a long bar.

Unless you are accelerating a Sherline to 1000 IPM, I really doubt
the sprockets have any effect at all. Now, there may be high performance
motion systems with light weight components where it DOES make a big
difference, like pick and place robots.

I have worked with mag tape servo systems, with ironless rotor motors,
ceramic shafts, composite capstan rollers with beryllium spiders, etc.
These things accelerate from 0 to 2500 RPM in 1.5 mS or so, in closed-loop
servo control all the way.

Jon