Re: [CAD_CAM_EDM_DRO] Re: GeckoDrives.. Can anyone Help?

>
>
> I thought that a servo motor was just a stepper with an encoder on it.
> Are you telling me they are different? I have not purchased my
> steppers or servo motors yet.

No, a servo and a stepper motor are very different animals.
A servo motor is basically a quality DC brush type motor.(there
are brushless and AC servos also but they are not supported
by Gecko drives so we won't get into that) An encoder is required
for feedback to tell the drive how far the motor has moved.


A stepper motor does not require any feedback. It has a specific
number of steps, usually 200, per revolution. If you need to move
a stepper one revolution the drive must power the different windings
of the motor in a specific sequence 200 times. The big problem with
stepper motors is a limit on speed due to the inductance of the
windings. Also they tend to resonate at certain speeds. This can
cause stalling and missed steps. Microstepping the motor can
help with this. I believe the Gecko drives will microstep. For a
good lesson on stepper motors see the following link
http://www.cs.uiowa.edu/~jones/step/

>
>
> >
> > I bought 1 Gecko G340 and use it on my Z axis. The difference between
> that
> > and
> > the stepper motor that was previously there is amazing. I would
> never go
> > back to
> > stepper motors. I can't wait to get two more for the X and Y axis'.
> IMHO get
> > the
> > G340 drives if you can.
>
>
> Are you saying that if I purchase the G340 I have to use servo type
> motors? The only thing that I have from my first project that I will
> use here is "CNC-PRO" software. Will CNC-Pro work with the G340?

Yes to both questions. The Gecko drive will take step and direction
inputs just like a stepper motor drive. Most large type servo systems
do not take step and direction inputs, but the Gecko drives are kind
of a cross between steppers and servos. Stepper motor input and
servo motor motor output. This allows you to use servos with most
all of the lower priced software out there.

>
> Also what size servo motors should I be looking at to power a
> Drill/Mill on all three axis? Do you also suggest a pulley system or
> to hook them straight to the lead screw? If a pulley system is best,
> what ratio do you use? 1/1, 2/1, etc.
>
>

I am now using 1:1 pulleys on the stepper motors on my CNC router
but will be going to direct drive servo motors as soon as I buy 2 more
G340's. I got the ballscrews from some sort of very high precision
machine that weighed about 6 tons, made of granite. The ballscrews
came with motor mounts, couplings and servo motors all together,
all perfectly aligned. If you are adding motors to a machine I would
suggest using belts and pulleys. Easy to align and setup. Easy to
change the ratio if you don't like what you have. By the way, that
granite machine would have made a great mill with tons of travel
and no deflection or vibration. If only I could have fit it in the back
of my car. Someone on the list will be better able to suggest a size
and ratio for your application

Are you changing out the screws on your mill/drill? No matter what
motor you use the backlash will need to be reduced if it's anything
like some of the mill/drills I've seen.

Bill