Can a stepper motor be too big?

[Mackle]

What are the disadvantages to having an oversized stepper?

In a recent thread "Sparky NY" said: "NEMA42 steppers are not used much in this hobby because they have problems unique to the larger frame."

Confessing my ignorance, I have no idea of the size of NEMA42. The step motors I have are nearly the size of a football, heavy as a bowling ball, 3v, 6 amp, 1390 oz/in holding torque. The drives for them can microstep up to 25,000 steps/rev, and have "reduced current" and "windings off" modes to save power (at the expense of start-up speed). I'm guessing this equipment is overkill for my needs: hobby wood working.

So in that context, back to the question: what are the "problems unique to the larger frame"?

Thanks,
Mike

P.S. - Be easy on me, this is my first post here and I'm just coming up to speed on acronyms, company names, lingo, and such.

[Karl_T]

I guess I don't know either. Alll the earlier Bridgeport Boss CNC machines used steppers on size 42 frame. Many folks have refit these to Mach 3. I bought 2400 OZ-IN size 42 steppers for my Excello, worked great. I could have fit the size 34 on but they were more expensive.

I personnally don't believe everything i read here.

Karl

[cowpoke]

What drives are being used for these size steppers?

[Crevice Reamer]

Hi Mike. Welcome to the Zone!

All things considered, it is better to increase power by increasing frame size than by adding to length of smaller frame size.

Here's some info for you:

What is between....

CR.

[Mackle]

What drives are being used for these size steppers?

(My guess is your question was directed at Karl, but just in case it was sent my way...)

The drive is a Superior Electric, a.k.a, Danaher Motion, a.k.a. Slo-Syn, SS2000D6, which is being controlled by their S2000I controller. They were all designed for each other, so it's making it all a really painless introduction to CNC for me. Plug it into 120v, connect a terminal program to the controller's RS232 port, type in some G code, and motion results. Sweet.

The motors are now mine, but the owner and I haven't figured out what a proper price for the drive and controller should be (Ebay prices are all over the map; anybody have suggestions?). I'm sure I want the drive, but not so sure about the controller. I want to run all this stuff off of LinuxCNC/emc2, and I don't know how the controller would fit in there... but that's a topic for another thread once I learn a little more about all this stuff.

Mike

[dertsap]

I'm guessing this equipment is overkill for my needs: hobby wood working.

.

not overkill but room to grow

i cant say much for the drivers but if they dont work out then gecko's will drive them motors nicely , ive got slo-syn steppers on my setup ( 1 nema 42 , 2 nema 34) and ive got nothing but good to say about them and i wouldnt trade them for anything , if i were you i'd be all over them motors

[Mackle]

Here's some info for you:

What is between....
CR.

Thanks for the welcome and the link. It filled in some holes in my understanding. For instance I now know that these big honkin' (110mm) things are indeed NEMA42's. A small step on the road to enlightenment, for sure.

The discussion there about power supplies was interesting. Until reading that I had assumed (incorrectly) that drives always took 120/220 as input, and that the only head scratching required was finding a drive whose output matched the motors' needs. I never thought about the power needs of the drive itself.

As I just mentioned in my post to cowpoke, the pieces I have to work with so far were all made to work with each other (120v in, rotation out), so up to this point it has all been embarassingly easy. Too easy, I fear. I have a worrisome feeling it's now going to get pretty complicated pretty quickly.

Mike

[Mariss Freimanis]

Depends on what the motor is attached to. A turbocharged 454 V8 is a tad large if it's on a lawnmower. It's about right if it's in a Corvette.:-)

About 'round' NEMA-42 motors: Times have changed since they were popular. Today, a lot of modern 'square' NEMA-34 motors develop the same holding torque as the old, round NEMA-42s but deliver more power (torque times RPM) than the NEMA-42 ever could.

Mariss