Re: [CAD_CAM_EDM_DRO] Re: Stepper Motor or Servo Motor Requirements for my Van Norman #12 mill?

Thanks to all of you for the responses. John Kasunich, you are of course
correct that the knee must be used, but I didn't necessarily see that as a
show stopper, although the motor driving it must of course be pretty strong
:-)
The Van Norman is indeed sturdier than the bridgeport, and without a quill
it has a slight disadvantage from the BP's and BP clones, but I felt the
horizontal mode capability offsets that. Besides, it was cheap too! :-) I
was able to get all the collets and will be able to machine the other couple
accessories like shell mill holders from "soft" chinese R8 tooling, so
that's no problem. I understand the lack of tooling is the only reason
these units aren't as popular with machine shops.

At any rate, if I install a big 1200 oz-in servo, even a 1/4 to 1/2hp servo
on the knee, and smaller servose or even steppers on the x,y, and possibly
later, A axis(rotary table) shouldn't I be "in business" with this setup?
Additional thoughts are welcome.

Bill Kichman
R. William Kichman, P.E.
Kichman Engineering Associates
103 Old Furnace Road
Cornwall, PA 17016-0643
tel/fax 717/270-0714

----- Original Message -----
From: "jmkasunich" <jmkasunich@...>
To: <CAD_CAM_EDM_DRO@yahoogroups.com>
Sent: Friday, May 02, 2003 8:50 AM
Subject: [CAD_CAM_EDM_DRO] Re: Stepper Motor or Servo Motor Requirements for
my Van Norman #12 mill?


> --- In CAD_CAM_EDM_DRO@yahoogroups.com, Jon Elson <elson@p...> wrote:
> >
> >
> > Bill Kichman wrote:
> >
> >> Can anyone tell me what size minimum motor I will need to add
> >> CNC to my full size Van Norman Model 12 milling machine? Can
> >> I use a 150 oz-in stepper and gear it down or will this be too
> >> slow or just too small? (Can you tell I have these already in
> >> stock?) I suspect I will need a much larger servo motor?
> >> Thanks for any input....
> >
> > I used 200 Oz-In (holding torque) motors on a mini-mill at
> > a 1:1 drive ratio (this is with 16 TPI screws.
> >
> > If "full size" means similar to a Series I Bridgeport,
> > ie. 9 x 42" table or larger, I would forget 150 Oz-In
> > steppers. You might be restricted to 10 IPM or less
> > before the motors bog down. In fact, if the machine is
> > somewhat stiff, it might not be able to move at all!
> > Most people use 600 Oz-In or larger motors on machines
> > this size.
> >
> > Jon
>
> Jon:
>
> You are right that 150oz-in is way too small.
>
> The Van Norman #12 is almost BP sized. There's a
> picture of mine at:
> http://home.att.net/~JEKasunich/vannorman/VN_Home.htm
> It weighs about 1800 lbs and the table is 9" x 37".
>
> They are great manual machines, pound for pound they
> are more rigid than Bridgeports. X axis power feed
> is standard. But I don't consider it a great CNC
> candidate for the following reasons:
>
> 1) No quill - you would have to use the knee for Z.
> 2) ACME screws all around. Conversion to ballscrews
> is possible, but a lot of work.
>
> On the other hand, a CNC'ed Van Norman in horizontal
> mode with the work on an angle plate would be great
> for pocketing, etc, because the chips fall clear
> instead of piling up.
>
> John Kasunich
>
>
>
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