looking for a FAST stepper...

i need a fast stepper (>500rpm, preferably >1000rpm...) to drive a really light load.

is it true that this is really hard to achieve with bipolar steppers? are nema17 are better for the job than nema23?
as most stepper would not provide a torque/speed curves, what parameters should I look for -- what kind of size/current/holding-torque would be suitable for high speeds?

or better yet - could you recommend any particular stepper?

thanks in advance !!

You need a low voltage, low inductance motor and drive it with high voltage constant current drive. Most low voltage motors will do 5000 steps per second at 24V with a reasonable amount of torque left. That is 1500 rpm. It wont start at the speed though, so will need acceleration.

NEMA17 will probably accelerate faster than NEMA23 due to lower rotor inertia but will have similar top speed and lower torque.

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[www.hydraraptor.blogspot.com]

thanks for the tips!
so something like that: [www.pololu.com] - ?

also, for choosing the power supply: i understand that the higher voltage the better for going high-speed (assuming current limiting driver). how about the current specification of the psi -- any reason to go higher than the max-rated-amps of the motor?

That only shows the torque up to 4000 half steps per second, which is only 600 rpm. For 1000 rpm you need torque at 6667 half steps per second. 4V is not particularly low voltage. I was forgetting that the curves are normally half steps, so you do need a particularly low inductance motor.

You don't need more current than the motor rating, in fact you need less average current with a high voltage supply.

I

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[www.hydraraptor.blogspot.com]

thanks!

doing some more reading, it seems that 'unipolar' stepper are 'faster' as the current direction doesn't change in the coils.
however, i couldn't find any low-cost unipolar driver (with current limiting) around. it seems like everybody switched to 'bipolar' stepper and drivers.. any ideas?

anyway, the best bipolar stepper i could find was 42BYGHW811: 3.1V, 2.5A, 1.25Ohm, 1.8mH, 15$. couldn't find any torque/speed curve though.

anyone knows what kind of steppers are used in those fast ink-jet printers?

... in most modern inkjet printers my sons and i disassembled we found DC-motors with optical encoder stripes as position sensors, not steppers.

The possible speed of a stepper is depending on low inductance motors, as nophead mentioned, but you need some good high microstep drivers with really high max. clocking speeds too.

I have some drivers from IMT which are capable of 1/256 microstepping and max 10MHz clocking speed - this will with a 'normal' 1.8°/200step-motor give a resolution of 51200 steps per rev. and (with acceleration) a maximal possible rotating speed of 11718 rpm!

I hadn't tested the higher values (no controller fast enough), but this drivers would be a bit owerwhelming for a normal reprap

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Viktor
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Aufruf zum Projekt "Müll-freie Meere" - [reprap.org] -- Deutsche Facebook-Gruppe - [www.facebook.com]

Call for the project "garbage-free seas" - [reprap.org]

thanks for the tip Victor.
I didn't understand why should I use microstepping -- does it help in achieving higher speeds?

... it makes the step-motion of the mothor smoother because of smaller steps, and the motor won't vibrate so much as with coarser steps.

When a 200step-motor runs with 1/256 microstepping instead of full- or halfstepping then you barely will hear any noise - it's a really low hiss instead of an audible buzzing.

But as microstepping reduces the step-angle, you have to rise the clocking speed too or you'll get lesser rpm's.

And most it's not really that easy - i have some other big 3-phase steppers and corresponding drivers that runs with 325Volts and selectable steps per revolution from 200 to 1000 ... and selctable none or 1/10 microstepping

With 1000 steps per rev. i have a max. step rate of 10 kHz, so i'll receive 600 rpms.

With 1/10 microstepping i'll have 10000 steps per rev and tested a max. step rate of around 100kHz, what's results in the same 600rpms!

So you need the right motors too to get the max. out of your drivers ...

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Viktor
--------
Aufruf zum Projekt "Müll-freie Meere" - [reprap.org] -- Deutsche Facebook-Gruppe - [www.facebook.com]

Call for the project "garbage-free seas" - [reprap.org]

Did we ask rubin what he wants to achieve with these fast stepper motors? For printing fast, the ordinary ones are perfectly well, limitations are currently elsewhere (firmware, mechanics, extruder).

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Generation 7 Electronics	Teacup Firmware	RepRap DIY

no, i'm actually building some linear slider that needs to move fast (with hardly any load).
thanks again for all the tips!