Re: [CAD_CAM_EDM_DRO] Servo motor selection

jbordens wrote:

> First, an introduction...
>
> I'm Jake, and I'm new to the group. I'm currently waiting for my new
> Grizzly G3012 mill to arrive. Its backordered, so I've got a few
> weeks till it arrives.
>
> I'd like to do a motion control setup for it. I'm pretty handy with
> electronics, and I understand most of how this works. However, as
> for chosing motors I'm at a loss.
>
> I'd like to thank Mariss for the wonderful top 10 list. Its helped
> me greatly. To quote:
>
> "7. Bewildering choice of motors, encoders, servodrives"
>
> I'm offcially bewildered. I'm deathly afraid of taking all this time
> (and money) and having underpowered motors.
>
> The camtronics people sell peak-600oz/in motors 50oz/in per amp for a
> price I can afford. My question is: is this a good way to go? Will
> these be strong enough to handle a mill this size? Should I go with
> a direct drive, or timing belts? Is there a good conversion factor
> from stepper to servo oz-in ratings?

With a 2:1 belt reduction and 5 TPI ballscrews, it will probably have
enough force to break any tool you can put in the spindle. Stepper to
servo is meaningless. Steppers have a fall-off in torque with rising speed
that depends on the power supply and motor inductance, mostly. Servos
generally have full torque up to the max speed limited by the power
supply. So, a 100 Oz-In servo may be able to outperform a 600 Oz-In
stepper at moderate speeds like 600 RPM! These motors should be
quite adequate.

> Any help is appreciated, and I do appologize for the post. I haven't
> seen a "guide to chosing motors", other than a really confusing bit
> about coiled ropes and such that I found in this forum. Maybe I'll
> put something together with all my notes once I've gained some
> experience.

I've got a calculation here http://206.19.206.56/motor.htm
I'm running a Bridgeport with 73 Oz-In (cont) motors, which gives about
300 Oz-In peak. It is fine for me, and I can deliver about 1000 Lbs
linear force to the table.

Jon