Re: [CAD_CAM_EDM_DRO] Re: Bridgeport servo motors

braidmeister wrote:

>Jon,
>Which Ameteks are you talking about? From what I have been reading
>(and a lot has filtered thru my brain in the past week! ~ so forgive
>me if confused)...The Ameteks mentioned on here are only good for 60
>IPM when geared down to get the required torque. I will eventually be
>using the BOSS in a commercial capacity and want the added speed,
>especially for cutting AL.
>
>

The Ametek motors I've looked at have about a 4 Ohm armature resistance.
That is a real problem, as it drives the continuous torque rating way down.
The 900 RPM rating is one of those things I've been trying to convince
people
is not a maximum, but just a rating point at 36 V. I'm pretty confident you
can run this motor above 36 V and let it spin above 900 RPM. The motors,
on the whole, will be a lot happier with more voltage and belt
reduction, than
being forced to run the machine with direct drive.

To run through the numbers quickly, the peak current limit is 12 A. If you
try to push 12 A through a 4 Ohm motor, AT STANDSTILL, you need 48 V.
If the motor is spinning at 900 RPM, the back EMF is 36 V. To STILL get
full torque, you need 36 + 48 = 84 V. Now, you don't want to connect this
motor to a power supply greater than 48 V without electronic current
limiting,
as it will exceed the peak current limit.

But, on the whole, I would recommend a bigger motor on a BOSS machine.
Bridgeport uses those fantastic SEM motors, that make the Ameteks look
like toys! Even limited to 20 A, I think you'd get 3 or 4 times the
torque from
them. Also, the much lower armature resistance will end up heating the
motor
a lot less.

Jon