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

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@...>
> To: <CAD_CAM_EDM_DRO@yahoogroups.com>
> 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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