Need Help!- stepper questions

[scanboy]

I'm pretty new in CNC and currently, I'm looking for parts to start my 1st CNC. I've come across some step motor and wonder if they are suitable for my CNC (2' x 3').
The spec of the motor is as follow:
NEMA 23 with 277 oz.in holding torgue, step angle 1.8, 4 phase, 3.0A/phase and 3.6v
I'm not so sure if this is a good choice for CNC, cause I've seen most of the stepper with much high voltage (like 20+v), how would taking only 3.6v affect my project (good or bad)?

[doorknob]

In typical CNC applications, the driver uses a much higher voltage than the motor's "rated" voltage in order to optimize the speed of the motor. So I would not be concerned about the low voltage rating.

Do you have a link to specs for that motor?

[scanboy]

This seems to fit my price range. Do you know of any better deal out there?

[doorknob]

That seems to be a good price, however I have not been looking for motors recently, so maybe someone else can chime in and suggest other possibilities.

[Mad Welder]

Originally Posted by scanboy This seems to fit my price range. Do you know of any better deal out there?

Yep I agree as Doorknob says it looks like a reasonable price, but I have found unfortunately to my own expense that cheaper does not necessarily mean better. I looked at the link you posted Stepper Motor NEMA 23 (57BYGH405A) and if you look at the pdf’s specs too http://www.circuitspecialists.com/pr...57BYGH405A.pdf it states 1.8degree +/- 5% that’s not very reassuring for CNC usage as your 1.8degree has a 200 steps per revolution and if you have a plus or minus5% discrepancy and not including a compound discrepancy that results in up-to approx additional 18 steps per single revolution or a 32.4 degree extra rotation of the motor Clockwise or even Anti-Clockwise and as you suggest using a 2 foot by 3 foot table this could result in a considerable amount.

I have no commercial ties with Keling Stepper Motor, Stepper Motor Driver,CNC Router, Stepper Motor Power Supply, Stepper Motor Kit, DC Servo Motor, Stepper Motor, Stepper Motor Driver, CNC Router, Stepper Motor Power Supply, Stepper Motor Kit, DC Servo Motor, Keling Technology Inc, USA but for an approx extra $9 each you could purchase a similar stepper from them Stepper Motorwith similar specs. Look here in this forum under the Keling products to see all Advantages and disadvantages for their products and make up your own mind.

[Walky]

Mad Welder, no offense, but I think you got that one wrong.

If the steppers says 200 steps/rev, then it WILL be 200 steps/rev. Why? because the stepper's internal design makes it impossible for it to get more or less steps on a full revolution, since it's defined by the amount of different "magnet poles" on the center of the motor, which is an exact amount.

The 5% means that each 1.8º step can vary a max of +-5% each (1.71% - 1.89%). This is probably because of manufacturing tolerances regarding the size and distance of the internal magnets and coils.

Because of the stepper build structure it surely won't be accumulative to a noticeable point, or (if I'm right) not accumulative at all. I think it probably is 5% max error from the actual supposed position, so If you are at step 100 (180º absolute position), you could expect to be between 179.91º and 180.09º absolute position at worst. As an example to make the idea more clear: A ruler, with each mm (space between lines) having a tolerance of +- 10% (for example, ink displacement when manufactured), doesn't mean we'll have ten 0.9mm spaces and then a big 2mm space. And even so, the chances of getting ten spaces with max error in the same centimeter, and all of them negative, are so low you'll have to buy thousands of rulers to find one of those.

Since the tolerances will vary between steps and 5% is supposed to be the max allowed tolerance, it's not big deal really. I bet most steppers people use in this forum are close to those tolerances.

Anyone please correct me if I'm wrong.

[Mad Welder]

Originally Posted by Walky Mad Welder, no offense, but I think you got that one wrong. If the steppers says 200 steps/rev, then it WILL be 200 steps/rev. Why? because the stepper's internal design makes it impossible for it to get more or less steps on a full revolution, Anyone please correct me if I'm wrong.

Hey there Walky no offense taken, the specs which were quoted from Scanboy http://www.circuitspecialists.com/pr...57BYGH405A.pdfstated 1.8 degrees plus or minus 5% rotation "not 200 steps/rev" if you had looked it up.

It was I who suggested that..... as the specs stated 1.8 degrees that would mean a normal 200 steps per revolution stepper motor, so YUP I stand corrected......

and as I had previously looked at Keling's hybrid motors and didn't see reference to a 5% differential in step rotation before... but yup as I said I stand corrected I DID come accross http://www.kelinginc.net/KL23H276-30-4AM.pdf with a step angle of 0.09 degrees and accuracy +/- 5 % and
http://www.kelinginc.net/KL23H76-30-4A.pdf step angle 1.8 degrees and accuracy +/- 5 %.

[louieatienza]

Originally Posted by Mad Welder Hey there Walky no offense taken, the specs which were quoted from Scanboy http://www.circuitspecialists.com/pr...57BYGH405A.pdfstated 1.8 degrees plus or minus 5% rotation "not 200 steps/rev" if you had looked it up. It was I who suggested that..... as the specs stated 1.8 degrees that would mean a normal 200 steps per revolution stepper motor, so YUP I stand corrected...... and as I had previously looked at Keling's hybrid motors and didn't see reference to a 5% differential in rotation before... but yup as I said I stand corrected I DID come accross http://www.kelinginc.net/KL23H276-30-4AM.pdf with a step angle of 0.09 degrees and accuracy +/- 5 degrees and http://www.kelinginc.net/KL23H76-30-4A.pdf step angle 1.8 degrees and accuracy +/- 5 degrees.

You can even find steppers with a .72 degree/step as well...

[Mad Welder]

Originally Posted by louieatienza You can even find steppers with a .72 degree/step as well...

Yup that's true

[scanboy]

Originally Posted by Mad Welder Hey there Walky no offense taken, the specs which were quoted from Scanboy http://www.circuitspecialists.com/pr...57BYGH405A.pdfstated 1.8 degrees plus or minus 5% rotation "not 200 steps/rev" if you had looked it up. It was I who suggested that..... as the specs stated 1.8 degrees that would mean a normal 200 steps per revolution stepper motor, so YUP I stand corrected...... and as I had previously looked at Keling's hybrid motors and didn't see reference to a 5% differential in rotation before... but yup as I said I stand corrected I DID come accross http://www.kelinginc.net/KL23H276-30-4AM.pdf with a step angle of 0.09 degrees and accuracy +/- 5 degrees and http://www.kelinginc.net/KL23H76-30-4A.pdf step angle 1.8 degrees and accuracy +/- 5 degrees.

Thanks for all the reply, but I think I'm even more confused now.
Mad Welder, the 4A motor spec stated that the step angle is 1.8 but also with a position accuracy of +-5%, is that better than the one I provided? What is the difference? Also, looking at keling's motor, there's single and dual shaft, what's the diff? and 2 and 4 phase, which one is better? I didn't expect I'd need a PhD in stepper motor to make a purchase

[Walky]

Originally Posted by scanboy Thanks for all the reply, but I think I'm even more confused now. Mad Welder, the 4A motor spec stated that the step angle is 1.8 but also with a position accuracy of +-5%, is that better than the one I provided? What is the difference? Also, looking at keling's motor, there's single and dual shaft, what's the diff? and 2 and 4 phase, which one is better? I didn't expect I'd need a PhD in stepper motor to make a purchase

They're possibly pretty much the same accuracy-wise, that 5% isn't really something to care about. It seems Mad Welder made a typo in his last post and he really meant "1.8 degrees and accuracy +/- 5%" instead of "1.8 degrees and accuracy +/- 5 degrees" when referring to the Kelings.

Those motors will not have a 5% (18º) error in its movement, not even 1º. Read my previous post for a more complete explanation about where does that 5% come from and why it's not a big deal.

[doorknob]

Originally Posted by scanboy Also, looking at keling's motor, there's single and dual shaft, what's the diff? and 2 and 4 phase, which one is better?

A "dual-shaft" motor will have the shaft sticking out from both the front and the rear of the motor housing. A dual-shaft motor may make it easier to attach things such as shaft encoders (which are not often used with steppers) and anti-resonance dampers, without getting in the way of the shaft coupler that drives the axis position.

As far as 2-phase vs. 4-phase, the typical stepper motor driver that you will get will work just fine with either one. You can use external wiring to treat a 4-phase motor as a 2-phase motor.