Re: [CAD_CAM_EDM_DRO] Re: Spindle motors

David G. LeVine wrote:

> At 08:55 AM 8/29/2007, you wrote:
>
>>This interesting but something in my engineer mind says to ask some
>>basic questions. Since 1 HP is 746 watts and the voltage is 30 to
>>40 volts to get the RPM the current has to be like 15 to 20 Amps at
>>that voltage! That is a sizable power supply.
>
>
> Yes, it is a big supply. I saw controllers up to 300 Amperes, that
> is significant overkill.
>
>
>>I suspect those motors are not designed to run continuously given
>>their application of running off batteries. I would also question
>>the lifespan in hours. RC stuff is designed for a different duty
>>cycle than running 8 hours a day.
>
>
> I suspect that ANYTHING running 60,000 RPM would have a longevity issue.
>

I have a Rockwell/Precise 54,000 RPM ball bearing spindle that
is intended for production work. It can mill or grind, and came
with a 1/8" carbide end mill in it. It is rated at 3/4 Hp.

I also have a Westwind air bearing spindle, designed for at
least that much speed. Due to the air bearings, it can run all
day for years.

>
>>As discussed I think heat removal will be a problem.
>

Both of these motors are air cooled. The Rockwell/Precise has a
filter on it, but I'm guessing that is to keep dirt out, it
seems positive pressure has to be a better solution. The
Westwind uses compressed air, which is easy to come by as it is
the same air used for the bearings, but it uses a LOT of air for
cooling - not too efficient. Newer Westwind motors are water
cooled.

I run the Westwind on a standard VFD with series inductors. It
is a traditional induction 3-phase motor, just very long and skinny.

The Rockwell/Precise is a 2-phase motor, and I haven't built up
a drive for it yet, although I have designed it.

Jon