Voltage for Stepper Motor 0.9 degrees?

[jag2x]

Hi all,

Newbie here, I'm looking at building my first machine and looking to get a stepper motor that does 0.9 degree resolution wired to a Gecko G540.
I would like resolution to be the key here, as I will be doing very detailed work(jewelery cutting).

The Gecko G540 accepts a 18VDC to 50VDC supply voltage, 0 to 3.5A rated phase current.

The stepper motors i'm looking at have these details (cost US $20):
Current phase (A) : 2.8
Holding Torque (oz-in): 208.3
Resistance (Ohm/Phase): 1.13
Inductance (mH/Phase): 5
Inertia (oz-in2): 2.624
Number of leads : 4
The part I dont get??
--->
Insulation Resistance 100 mΩ Min. 500V
DC Dielectric Strength 500 VAC 1 minute
<----
I'm unsure what 500 VAC means?

Will this stepper motor work with the G540? Phase current is fine, its the just voltage part that i'm unsure off?

Would anyone know of another 0.9 stepper motor with the equivalent or greater torque that will work with the G540?

Thanks
jag2x

[pfred2]

I guess if you're dumb enough to run more than 500 VAC into your motors you have a good minute before it blows up in your face? Its the motor insulation dielectric breakdown voltage. Its a safety thing. No one pays any attention to stepper motor running voltage anyways so some companies don't even give the rating anymore. Most stepper motors run on DC.

Gecko has the formula on their website to calculate maximum motor voltage based on the inductance I believe it is. You may just want to head on over there and check it out? IIRC its in their FAQ section. if I were you I'd read everything on the site, twice. Then whatever didn't make total sense to you read again!

I would think if you wanted high resolution you'd want a fine pitch lead screw, but I suppose a .9 motor can't hurt you either. Anyhow, they sound like nice motors to me for $20. Are they Vextas?

BTW you're looking for more than 208 oz/in to cut jewelery with? Who are you making jeweleries for King Kong? It sure doesn't sound to me like you're going to need long fast rapids with your application otherwise.

Anyhow go over to gecko.com look in the FAQ there is a simple formula there to determine maximum voltage for top performance.

[jag2x]

Thanks for the info, will check the Gecko faq.

The motor is from imttusa.com Model Number : 2S23HM-604 infact its $40.

Not sure about Vextas, do you have a link somewhere?

I'm going to be using C7 rolled ballscrews.
I'm looking to do jewelery amongst other things, can't hurt to have high torque

[Mariss Freimanis]

One specification step motor manufacturers don't list is motor linearity. Motor linearity determines how evenly microsteps are spaced over the span of 1 full step. An ideal 0.9 degree motor would move precisely 0.09 degrees for every microstep when using an accurate 10 microstep drive. No real motor can do that but a few come very close.

Many say you cannot depend on microstep accuracy but that isn't entirely true. At 10 microsteps, an ideal motor can deliver 15.6% of its rated holding torque while keeping a 1 microstep accuracy (accurate torque = holding torque * sine (microsteps / 90 degrees)). For a 200 in-oz motor this equals 31 in-oz.

Say you are using a 5 TPI screw. 31 in-oz into that screw gives 61 lbs of thrust (lbs = in-oz * TPI * pi / 8). In other words, it would take 61 lbs of workload to move the motor off-position by 0.09 degrees. This translates into a 0.00005" (0.0013 mm) linear error when using a 5TPI (~5mm pitch) leadscrew.

Microstepping eliminates low-speed vibrations and its increased resolution is usable as well so long as one understands the underlying limitations.

Mariss

[pfred2]

Mariss you always have the most interesting equations. I haven't seen that one about microstep torque before. But math was never my strong suit, so its all Greek to me. Do you have a link to a resource that might more fully explain how to calculate that holding torque value like you did?

It looks like something that'd be useful for me to be able to do. I'm doing my best to try to understand. Thanks!

I think I am beginning to see why people need such huge oz/in stepping motors if we're all taking this kind of a torque beating when mictostepping. And do we really have any choice when it comes to step sequencing?

[Mariss Freimanis]

You don't take any kind of torque beating. Like any step motor, your motor will develop 208 in-oz of holding torque when it's displaced 1 full step from its rest position. For you that is +/-0.9 degrees.

Motor torque is the sine of angular displacement.