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

Peter,

The "42-Mod" consists of placing a 150K 0805 size resistor in
parallel with a 1MEG resistor that is on the standard drive. This is
done by soldering it on top of the existing resistor. The "mod" can
be reversed by removing this resistor.

My concern here is with potential damage to the drive if someone
tries to do it themselves without the correct SMT rework equipment or
techique. The component spacing is very tight, leaving little room
for error if it isn't done correctly.

The next revision (REV-5) of the G201 will have this "42-Mod" as a
jumperable option along with a few other minor improvements.

Mariss


--- In CAD_CAM_EDM_DRO@y..., "Paul R. Hvidston" <paul_hvidston@y...>
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