Re: Motor size calculation HELP

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "Laurence Casey"
<lcasey@l...> wrote:

>
> > >The above calculation would say I need a 116 in-oz motor (40%

reserve).

> > >Not sure how much reserve is needed. Did I miss something?
> > >
> > >
>
> I am using steppers.
>
> > >
> > 60 IPM is QUITE a lot. I suspect you might have been able to do

more,

> > but you
> > need to turn the cutter faster. As the feed rate increases, the

cutting

> > tooth has
> > to take a thicker chip off the work, and at some point the

advancing

> > workpiece
> > rams into the BACK of the cutting tooth. When this occurs, you

can see

> > smashed
> > metal on the back of the cuting flute. Assuming a 2-flute end

mill at

> > 2300 RPM,
> > that is 4600 cutting teeth per minute. At 60 IPM, each tooth is

taking

> > a cut of
> > 60/4600 = 0.013", which is enormous for a 1/4" end mill. If you

look, I

> > suspect
> > you'll find that smeared metal on the back of the tooth. There

is a way

> > to grind
> > the flutes to allow feedrates like this on aluminum, but

standard end

> mills
> > won't handle it.
>
>
> Yes, the back of the tooth is smeared with metal. I was not under

the

> impression that IPM really meant rapid speed. That's why I didn't

understand

> how people where getting such high cut rates. Don't know much

about it, back

> to the books.

Well both cutting and rapid speeds are measured in IPM. IPM does not
mean one or the other. For example my mill is set to do rapids at
100 IPM, but I've never cut anything faster than 15 IPM.

Mark