Re: [CAD_CAM_EDM_DRO] More on servo motor selection

Drew Rogge wrote:

> Jon Elson wrote:
> > But, we're really going around in circles, here. Let's start from the
> > beginning. You want to use 1/2 Hp with up to 1/2" end mills, at what
> > RPM? In aluminum, 600 SFPM is recommended, so that comes out to about
> > 4300 RPM. A dirty worst case cutting force calculation would show that
> > the torque to turn the tool was .5 Hp x 550 Ft-Lb/Sec = 275 ft-Lb/sec
> > A 1/2" end mill has a circumference of .5 X Pi = 1.571" or .131 Ft, and
> > is turning 4300 times a minute, or 71.7 times a second. So, the peripheral
> > velocity is 71.7 x .131 = 9.388 Ft/Sec. To get equivalent torque under these
> > circumstances, (275 Ft-Lb/Sec) / (9.388 Ft/Sec) = 29.3 Lbs.
>
> Jon,
>
> Sorry for being so dense but this is all new to me. Is the part
> of your mail I've referenced above the "worst case cutting force
> calculation" you mentioned?

Yes, that is the first part. If an end mill is used to take a very thin side cut,

then i think the calculation would be pretty accurate. When plowing
the bottom of a slot, I suspect the force may be much higher. My experience
with manual machining tells me it is a lot higher.

> Also did you base the initial .5 Hp requirement on my calculation of
> removing 1.5 cu. in. of al. per minute?

Yes, essentially.

>
> I also wanted to mention that I found a page on your web site that
> also helps to explain some of this. The URL is:
>
> http://206.19.206.56/motor.htm

Ah, yes. I know I'd gone through this, but didn't remember where it was.

Jon