Re: Gecko 2xx "Nema 42 modification"???

well, them ignore my original question, now that i've read this exact
message... hehehe, that was a little amusing...

> When I said direct coupled, I should have made it clear that the

motor

> is connected to the leadscrew via a Heli-Cal brand helical motor
> coupler. This is a zero backlash "spring" that allows for a bit of
> alignment error. They're not cheap but they work great.
>
> I just posted 3 pics in the main Photos folder which show the

motors

> mounted (the X-axis photo best shows the coupling) and one showing

the

> Geckos. Files are named NEMA42... and Gecko Drive...
>
> Cheers, Peter
>
>
>
> Paul R. Hvidston wrote:
>
> > Peter,
> >
> > Interesting you're running 1870oz-in NEMA42's with stock(?)

210's. Maybe you

> > just got lucky and the direct connection (no belts) damps any

instability

> > for you. I've got the original CNC conversion articles in

HSM's "Projects

> > Seven", and am eagerly reading the new series in HSM.
> >
> > In response to my query to Geckodrives, I got a couple of speedy

(but

> > non-technical) replies:
> >
> > ---
> > Dear Mr. Hvidston,
> >
> > The G210 drive can be modified at the factory to run a size 42

motor. After

> > the modification, it would be unsuitable for small size 23

steppers.

> >
> > Dear Mr. Hvidston,
> >
> > The size 42 modification is not considered reversible, unless you

have

> > surface mount technology available.
> >
> > To purchase the G210's with this modification, you need only

specify "42

> > modification". There is no charge.
> > ---
> >
> > The Gecko folks seem very responsive, and the products sound

great. I'll be

> > ordering some 210's to run these motors. I was hoping to get a

little more

> > technical info out of them on the mod since I might want to un-

modify them

> > down the road, and I do have SMT rework capability.
> >
> > I got the big motors to use in various test-beds. First use may

be on an

> > RF-31 "play-pen", then use them on a 3-axis wood carver using a

3HP router.

> > Ultimately, the RF-31 will use servos and ball-screws, but for

now it's

> > play-time.
> >
> > Thanks for the input.
> >
> > Paul R. Hvidston, N6MGN
> > ACKSYS Engineering
> > Upland, CA
> > ----- Original Message -----
> > From: "Peter" <prenolds@s...>
> > To: <CAD_CAM_EDM_DRO@y...>
> > Sent: Wednesday, February 27, 2002 8:31 AM
> > Subject: Re: [CAD_CAM_EDM_DRO] Gecko 2xx "Nema 42 modification"???
> >
> >
> >
> >>I'd be interested if Mariss can answer this one on-list. My

experience

> >>with G210's running 1870oz-in NEMA42's has been extremely

positive. My

> >>motors are direct coupled (no belts) to the three axes of a BP-

clone and

> >>I have not experienced any motor growl. Only problem I had was

that I

> >>was losing position accuracy due to a bug in the step rate

multiplier

> >>PCB when set to 5 step/microstep i.e. X2. Once the step mult.

board was

> >>replaced n/c under warranty, they have performed flawlessly.
> >>
> >>You do have to be careful about your acceleration rates - if you

try to

> >>accelerate too fast, the stepper will "spit the dummy" (an Aussie
> >>expression - U.S. translation: "spit the pacifier"... anyone

who's had a

> >>baby will know what I mean) and just sit there buzzing. I have

my big

> >>machine (runs a Flashcut controller) set at 7500 steps per second

per

> >>second acceleration. I have set top speed rapid at 2.2 meters per
> >>minute (U.S. translation: 86 IPM) I can go faster (110 IPM) but

the

> >>motor has very little torque at such high speed.
> >>
> >>Your motors should be fine for the RF31 . I also have a Busy Bee

Mill

> >>Drill with ~500oz-in servo motors direct driven and get acceptable
> >>performance although things get a little tight at the ends of the

table

> >>travel. This (busy bee) machine still has the original acme

leadscrew

> >>threads rather than ball screws (on the big machine) which I do
> >>recommend you consider fitting. The last two issues of HSM

discuss this.

> >>
> >>Cheers, Peter
> >>
> >>
> >>Paul R. Hvidston wrote:
> >>
> >>
> >>>Question for the group:
> >>>
> >>>I Fired off a question to Geckodrives, but users on the list

might also

> >>>
> > have
> >
> >>>had experience with this one and I could use all the input I can

get.

> >>>
> >>>I purchased three large steppers on eBay recently (SIGMA
> >>>
> > 20-4247TD200-F1.3,
> >
> >>>and hopefully I didn't make a real bad purchase) so I could start
> >>>
> > playing
> >
> >>>around CNC-ing my RF31. The seller said that a previous customer

used

> >>>
> > Geckos
> >
> >>>with a NEMA 42 modification. The explanation I received was:
> >>>
> >>>"These steppers work FLAWLESSLY with gecko stepperdrivers with

the nema

> >>>
> > 42
> >
> >>>modification.
> >>>I had a lot of trouble with intermitent stalling with drivers

purchased

> >>>without the nema 42 modification."
> >>>
> >>>"as it was "explained" to me, the nema 42 motor's are designed

to run in

> >>>
> > a
> >
> >>>different RPM / torque range. the Mid band stabilization

circuit on

> >>>standard gecko drivers can get "saturated" causing that annoying

motor

> >>>
> > growl
> >
> >>>(phase lock) and subsequent positioning error. since replacing

the

> >>>
> > standard
> >
> >>>gecko driver with the modified drivers all my axis (especially

the Y

> >>>
> > axis
> >
> >>>which carries the beam) run perfectly. the Modified drivers

cost the

> >>>
> > same
> >
> >>>as the standard, but they do have a distinct label engraved on

them.

> >>>
> > The
> >
> >>>guy who developed the gecko driver is the guy I spoke with, and

he was

> >>>
> > very
> >
> >>>helpful"
> >>>
> >>>The published ratings for the motors are:
> >>>
> >>>200 step
> >>>540 oz-in @ 50 sps
> >>>635 oz-in holding
> >>>22.6 oz-in detent torque
> >>>5.0 Amp phase current
> >>>1.29 ohms phase resistance
> >>>2.2 mH phase inductance
> >>>17.4 oz-in^2 rotor inertia
> >>>10 lbs. weight, 30 watts dissipation, 8-wire
> >>>
> >>>Anybody know about this?
> >>>
> >>>Thanks all,
> >>>
> >>>Paul R. Hvidston, N6MGN
> >>>ACKSYS Engineering
> >>>Upland, CA
> >>>
> >
> >
> >
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