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

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....
>
>

Oh, I see you also mention servos. That is a different story, as servo
motors can deliver full rated torque up to the maximum speed. Also,
steppers are rated at zero speed, where they produce no power. Servo
motors are rated for continuous torque, and have a peak torque rating
4 - 10 times higher! So, a motor rated for 150 Oz-In continuous
could deliver 600 Oz-In or more for a few seconds, and do it while
moving the table at 120 IPM, too, which a stepper never could do.

Servos also don't suffer from belt reduction, as long as they are not
required to turn so fast that their back EMF equals the DC power supply
voltage. So, if you don't get enough torque (within the ratings of the
motor and servo drive) then you can put in more reduction until you
have a limit on the top speed.

Jon