Re: [CAD_CAM_EDM_DRO] What variable speed motor to use?

Lee <amylknight2000@...> wrote:

>
>
> I have recently purchased a Harbor freight 3 in 1 machine tool,
> and I'm pretty happy with it, it's more than I expected of a low
> priced asian import.
>
> One problem with this one (it's the lathe mill drill, no power feed,
> and metric feed screws)is the lack of speed choices for the lathe
> spindle. it has only has 3 speeds, fast, fast, and faster.I'd like
> some lower speeds and more speed choices ,and from looking at all the
> options so far, seems to me a variable speed DC motor would be the
> simplest way to accomplish this. The motor pushing it now is a 1/2 hp
> single phase AC motor.
>
> So what DC motor/speed controller would be suitable for this
> application?
>

I had talked about this before (see message #31712 )

http://groups.yahoo.com/group/CAD_CAM_EDM_DRO/message/31712

I am planning to use a Leeson 90V 10A 1HP 2500rpm (cat#108020
Model: C4D28FK5D Price $490) motor under my 1KW 75V power supply,
a 1000 line (4000 count/rev) rotary encoder from USDigital.com and
a Gecko G340 DC servo driver.

Although the 75V is less than the 90V, the 1 HP rating comes
from its 'SCR/Thyristor' rating, and a motor driven by PWM
(pulse width modulation) as in the G340, has a higher HP rating
(I got this from http://www.leeson.com catalog page 71).
So the HP you'd end up with is still around 1 HP.

With the G320, you could theoretically use any motor up to
80V and 20A (approx 2.0 HP), but I haven't been able to find
any higher than 1 HP as the bigger motors skip to 160V at
lower current ratings..... let me know if you come across any
motors 90V and greater than 10 amps.....

It goes without saying, this technique is a bit 'overkill',
but it handily solves the 'lathe threading problem' on S&D
output only controllers. Also, two more G340's will be
powering the Z and X lathe axes...

One last thing - beware of chucks threaded on the spindle
(like with a 1.5-8 type thread) under CNC control, because
under rapid deceleration (or reverse direction), the chuck
can come flying off. You really want a D1-4 Camlock type
spindle for safety.

- - -

It is interesting to note that some versions of the Smitty 'Granite'
3-in-1 machine already have a 1 HP DC motor installed at the
factory....

- - -

Doug Fortune
http://www.cncKITS.com