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

Bill,

It may not be quite that simple. Unlike steppers, servo motors
generate their rated power at about 80% of their no-load RPM.

Figure out what is the fastest speed (IPM) you need the Z-axis to
move at. Knowing your leadscrew pitch (10 TPI?) calculate how many
RPM it has to turn at that speed.

Divide that into 80% of your motor's no-load RPM.

The answer will be your gear reduction ratio and the motor will need
reduction gearing.

You won't find a 1,200 in-oz continuous rated torque motor. If it's a
big one it may be 1,200 in-oz when stalled but its continuous torque
will be about 200 in-oz in that case. Run it at the bigger number and
you will burn it up.

Let's say it is 200 in-oz at 1,500 RPM (1,800 RPM no-load). That's
3/10 of a HP. Let's also say you want 60 IPM on the z-axis. At 10 TPI
the screw would turn at 600 RPM while the motor is turning 1,500 RPM.
The ratio is 2.5:1, being your reduction ratio.

The motor, reduction gearing and screw would generate 1962 lbs
of "lift". Figure on 1/2 that when you take the screw efficiency into
account.

Mariss

--- In CAD_CAM_EDM_DRO@yahoogroups.com, Bill Kichman
<billkichman@c...> wrote:

>
> 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