Re: shaft torsion ?

If you are talking about a well designed machine with ball slides,
frictional forces will be insignficant. If the machine is dovetail
or box/gib slides, then friction might be a consideration. The
easiest thing to do is to measure frictional resistance using a
spring force gage and then decide if there will be a problem or not.

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "Philip Burman"
<philip.burman@...> wrote:

>
> Sorry I guess my terminology is incorrect. I assumed frictional
> forces were included in machining forces. What about F = Mu.N, no

A

> some F. I understand that frictional forces are low in this kind

of

> machine, I was just interested to know if it has any practical
> influence in the design and the selection of motor size.
>
> Phil
>
> --- In CAD_CAM_EDM_DRO@yahoogroups.com, "carbonsteelsam"
> <corryharper@> wrote:
> >
> > Don't understand your view of "windup". At constant velocity

there

> > are no "loads" (F=MA; no A, no F). In a trued-up machine, at
> > constant velocity, there would'nt even be a need for the cross
> shaft
> > (ignoring friction).
> >
> > --- In CAD_CAM_EDM_DRO@yahoogroups.com, "Philip Burman"
> > <philip.burman@> wrote:
> > >
> > > My point was that there are "machining" loads, even at

constant

> > > velocity, that may cause "windup of the shaft. I was just
> > interested
> > > why this was not a problem in practice. I assumed it is due to
> the
> > > relatively low level of precision required with this type of
> > machine.
> > >
> > > Phil
> > >
> > > --- In CAD_CAM_EDM_DRO@yahoogroups.com, "carbonsteelsam"
> > > <corryharper@> wrote:
> > > >
> > > > Not unless they're overpowering your motors or there is an
> > > extremely
> > > > biased friction load from one rail to the other. With good
> setup
> > &
> > > > alignment the rails should perform pretty much the same and

the

> > > > pinions would easily handle minor side-to-side fluctuations.
> > > >
> > > > --- In CAD_CAM_EDM_DRO@yahoogroups.com, "Philip Burman"
> > > > <philip.burman@> wrote:
> > > > >
> > > > > Are frictional loads at constant velociy not an issue.
> > > > >
> > > > > Phil
> > > > >
> > > > > --- In CAD_CAM_EDM_DRO@yahoogroups.com, Kevin Martin
> > <kpmartin@>
> > > > > wrote:
> > > > > >
> > > > > > In the original message the system was described as "5

foot

> > > wide
> > > > > gantry on a plasma cutter" so there are essentially no
> > machining
> > > > loads
> > > > > (unless you count the recoil from the plasma jet).
> > > > > > -Kevin Martin
> > > > > >
> > > > > > -----Original Message-----
> > > > > > From: CAD_CAM_EDM_DRO@yahoogroups.com
> > > > > [mailto:CAD_CAM_EDM_DRO@yahoogroups.com] On Behalf Of
> > > > carbonsteelsam
> > > > > > [...]The real differential loads will result when the
> router
> > is
> > > > to
> > > > > the extreme end of its travel and is under heavy cutting

load.

> > > [...]
> > > > > >
> > > > >
> > > >
> > >
> >
>