[CAD_CAM_EDM_DRO] Mill Conversion - Please check my calcs (thanks)

> I wish to finalize the gear ratio calcs for the 3 axes on my Van Norman

mill conversion, and would greatly appreciate some "eyes on" here to be sure
I don't make a serious calculation error.

> My calcs assume for the 3 xyz axes, I will be using inefficient acme

screws, and a servo for the 800 pound knee, and 2 steppers hopefully for the
xy axes,

> First, the x,y axes...I desire 2 inches per second maximum travel and

assume a 500# force is required...therefore for (watts) power required I
calculate 113 watts. Since this falls in between 100 and 200, I am in the
no man's land between steppers and servos.

>
> For the z axis, I assume 1 inch per minute travel and 1000# force required

(heavy mill) and calculate the identical 113 watts, since my speed is halved
but my force is doubled.

> 113 watts again required.
>
> Now into torque...in-0z = 2.55 x lbf/(tpi x screw eff)
>
> For the x and y axes: torque required = 2.55 x 500 / (5 x 0.3) = 850

oz-in.

> For the z: torque = 2.55 x 1000 / (5 x 0.3) = 1700 oz-in, double that of

the others.

>
> So now I should divide the required torque by the available motor torque,

asI have understood. I have available some NEMA 34 150 oz-in holding torque
steppers (4 total) with 1.7V.phase, 4.7A/phase....

> Additionally I have a small servo with ratings: 32v, 250w, 10.5A, 250W,

2200 rpm,

> and finally (2 total) 1/2hp servos rated as follows: 90v, 4.7A, 1/2HP,

10.5A.

>
> Which would you recommend that I use? I hesitate to determine out loud,

as I am unsure whether these steppers are even worth considering, given the
large load required. I understand that stepper rotational torque is about
70% of holding, leving these steppers at about 105 in-oz, not a large
amount.

> What are your recommendations based on these ratings?
> Thanks for your insight...
>
> Bill Kichman
> 103 Old Furnace Road
> Cornwall, PA 17016-0643
> tel/fax 717/270-0714
>
>