Re: [CAD_CAM_EDM_DRO] Gecko 2xx "Nema 42 modification"???

Peter,
I assume you have replaced the Opto's in the FlashCut Black box with The correct
transistors ?

I think the Geckos run the best with the transistors........ After changing mine
out, I noticed a huge improvement running a set of MicroKinetics 4050's.
Especially in regards step loss when abusing the accel/decel settings. My set of
MK DR3535's don't seem to mind either way. I'm gonna get me some of them there
Gecko's someday !

Also, you are aware of the "Chip" upgrade to increase your step rates to above 30k
per axis? Big difference let me tell ya.

Chris L

Peter wrote:

> 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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