Re: sherline and Gecko's

--- In CAD_CAM_EDM_DRO@y..., "John" <johnhe-uk@s...> wrote:

> I remember asking whether it'd be worth putting Gecko's on a

Sherline a good

> long while back and someone said it'd be quite pointless

considering the

> size of the travel and the screw properties. Like 'Going first

class on a

> second class machine'. I understand a lot more about CNC now but

could

> someone be helpful and remind me why this is the case?
>
> Thanks,
> John H.
>
> P.S. I'm talking steppers here! : )

It would not seem pointless as the gecko is a nice looking drive.
The problem is the screw pitch (.050) per revolution and the backlash
needed on the sherline machine (.003) I believe. With a 200 step
motor your full step increment is already a low .00025. If you used a
201 at 10 microsteps that's .000025 per step.

You get into a range where the step frequency from the computer
needs to be quite high for any speed. That and you really can't use
the extream resolution, it takes 120 steps just to take up the screw
backlash. You would be likely better with the 210 running the rate
multiplier.

I believe most of the folks would say the same since you are not
moving much inertia, the screw is highly geared and full of friction
you will not benefit as much from the advanced microstepping. You
could get good performance from a simple drive. You do still have the
advantages of the drive quality, excess capacity (7amps) good support
and all that.

If you like smooth quiet operation the microstepping can be an great
plus. I run a very small machine with 1mm pitch screws and have no
problems but at slow feeds there is so little load on the motors they
snap to position quite fast. This does create considerable noise and
vibration.

It's all a give and take on where you have the funds. You don't need
the capacity but some days the quality is just nice. My opinion the
210 is the better choice simply due to the fine pitch screw so you
get the microstep smoothing without the painfully slow max rates.

Brian
BSP