Re: mill servo conversion ?'s

This response has really created a lot of questions for me. Hopefully,
someone can answer them, or point me to somewhere I can find the
answers for myself.

Are the the Ametek motors from Camtronics really a bad deal? I don't
mean in terms of the high resistance. I mean in terms of what you get
for the money. If they are, where is there a better deal? And why
isn't it more widely publicized? Also, why do you recommend a 80-120V
power supply for the Ameteks when camtronics only sells a 36V for them?

I am part of a student organization that currently has a stepper
powered benchtop mill. We are, for the most part, satisfied with it,
but I would like to get a servo motor setup on the benchtop, with a
view towards replacing the benchtop mill with a 9x42 knee mill later.
As a student organization we don't have a lot of money, and we're also
not in a position to "save up;" we have to spend our budget each year,
also the budget is firmly set, so any money we spend, is money we
can't spend on something else. However, we are guaranteed a certain
amount of money each year.

In terms of requirements, we don't do that much heavy machining and
the reason we want a knee mill is to increase the maximum volume size
of parts we can machine. My understanding is that our steppers (230in
oz) would be grossly underpowered.

So, all that is in way of asking, what would be a better deal than
Camtronics complete setup? I'm not asking how Bridgeport's or your
setup is better; I'm sure they both are. I'm asking if I have ~$1250
to spend on a servo system, what should I get?

For instance, how do the motors offered in this auction:
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&rd=1&item=3831771088&ssPageName=STRK:MEWA:IT
compare to the ones from Camtronics. Are they better, worse, or the
same and why? Yes, to us, $30 matters.

We are not afraid of some work, such as building our own servos to
save some money, but we really don't know how to choose or find motors
and a power supply.

thanks,

-carlos

> I thought the Ametek motors at Camtronics were a bad deal due to the

4-5 Ohm

> resistance. They are still more powerful motors than the

EC/Reliance E660,

> which has an 11 Ohm resistance. This SEVERELY limits the power, and
> especially
> the peak ratings of the motor. (For comparison, my 75 V, 1/8 Hp cont.
> rated motors
> have 1.5 Ohm resistance. But, they are much bigger and heavier than
> either of the
> motors being discussed.)
>
> >what sort of power supply would they require, and where would one
> >acquire such a power supply.
> >
> >
> All these motors are different. You'd want a 120 - 160 V supply for

the

> E660
> with the -05 winding as those have, and probably 80-120 V for the

Ametek.

> The E660 would need a large belt reduction, while the Ametek could be
> used direct drive or with a smaller reduction ratio. A power supply
> with 15 A
> average current rating should be sufficient for a milling machine.
>
> >I suppose I'm not really interested in the latter questions if the
> >motors don't compare favorably with the servos from camtronics.
> >
> Well, I would recommend a larger motor than EITHER of those for a

Bridgeport

> Series I -sized machine. Note that Bridgeport uses a motor from

SEM, with

> a peak current rating of 24 A at 120 V (Or is it 42 A?). That is

2880 W or

> 3.8 HP!
>
> Jon