Re: [CAD_CAM_EDM_DRO] Values for Calulating Motor Sizing

natchamp_87 wrote:

>I "think" (bad, I know) I have an idea of the motor size I need for a
>BP retrofit but would like to calc it out to see. I have read
>numerous archives, especially the infamous # 45509 from Mariss. That
>is very useful. However, I don't have a good feeling for the input
>values of IPM and Lbs.
>
>What would be a low/med/high IPM for a CNC milling operation?
>

For actual milling, 30 IPM is about the highest I've done with a
Bridgeport. But, you also
want a decent rapid feed, at least 60 IPM, to move around from place to
place, or when setting
up, etc. Even 120 IPM would be nice. Unless you are doing serious
production, anything over
120 IPM is not likely to be needed.

> I will
>be mosting doing aluminum with some steel. What IPM is slow, fast,
>etc. I'm shooting in the dark at this point.
>
>

Heavy milling in steel might be more in the 6-10 IPM range, depending on
whether you are
using HSS or carbide cutters. Flycutting in steel might be down near 1 IPM.

>What is a good Lbs value? Is this suppose to represent the weight of
>the table or force required to move the table while cutting, or
>both?
>

This is the linear force required to move the work into the cutter on
the worst cut you can
think of. Obviously, if your motors stall out on a practical cut, it
can be a big problem.

I did some VERY back of the envelope type calculations, once, for a 1/2"
end mill at fairly
low speed, cutting something hard. I figured that the cutting forces to
stall my 1 Hp spindle
motor would amount to something like 500 Lbs of linear force. To
provide some safety margin,
I figured I wanted 1000 Lbs of linear force, to accomodate losses,
friction, etc.

Jon