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