Difference between two stepper motors

[qwertysimo]

Hi,

I would like to build a CNC router and found two 425 oz-in stepper motors with similiar specs. They are both from China's Longs Motor company and these are differences:

23HS9430, rated voltage 4.8 V, rated current 3.0 A, inductance 6.8 mH, resistance 1.6 Ω
23HS9442, rated voltage 3.78 V, rated current 4.2 A, inductance 3.8 mH, resistance 0.9 Ω

I think it does not matter that much which one to use for router. Low IPM should not be an issue.


My idea is to reuse these stepper motors for laser engraver as well and in this situation high IPM is needed.

Can you confirm that the lower inductance motor will be more suitable in respect of getting higher RPM? Low torque is OK in this application. And of course, this application would use timing belt to get higher IPM.

425 oz-in steppers are probably overkill for moving lightweight laser head, but I dont want to buy other smaller ones if not absolutely neccessary.

Which one of these two steppers would you use? Please comment. Thanks.

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[H500]

Lower inductance is almost always better. The motor will maintain torque at higher speeds. 3.8mH is actually quite high. Have you looked at these:
NEMA 23 | Automation Technology Inc

[qwertysimo]

Thank you. On linked page, these two are best match (dual shafted only):

381 oz-in (KL23H2100-35-4B), 4 wires, Inductance: 2.8 mH, 3.5 A
570 oz-in (KL23H2100-50-4B), 4 wires, Inductance: 2.5 mH, 5.0 A

Both these have basicaly the same physical specs and price difference is minimal.
As both have max voltage of from 50 to 53 V, 48 V power supply should be fine.
The latter one limited to 3.5 A would give holding torque close to 381 oz-in.

I like more that 570 oz-in motor. Using 5 A stepper driver would enable extra torque if neccessary.

Anything else to consider or other candidates? Thanks a lot.

[ger21]

If you run both of those at 3.5 amps, I think that the 381 oz motor will perform much better.

I've only seen two people using the 570oz motors. Both were running at 5 amps, and imo, both didn't seem to be performing as well as I'd have expected.

If you need to spin the motors faster, then the 381oz are a much better choice. Smaller steppers will almost always spin faster than larger ones. Those 381oz motors paired with a Gecko G540 have been used by a lot of members here, and have proven to provide plenty of power and speed.

[qwertysimo]

Looking at G450 max specs (50 V, 3.5 A), it looks like natural choice for that 381 oz-in motor. I will consider this controller...

I am just curious, what makes that 570 oz-in motor a not-so-good performer? Is it a specific motor parameter or combination of many factors in real applications you have seen?

Putting 381 oz-in to the first position in list so far. Thanks.

[ger21]

I don't know the specifics, but it's a pretty good rule that the larger the motor, the slower it's max usable speed will be.
With the same drive and voltage, a 200oz motor will spin much faster than the 381oz motor will.
I've heard of people using 200-250oz motors on small mills at up to 2500rpm with a G540. For a 381 oz motor, your max rpm will probably be around 1000 rpm. The 570oz motor will be slower still.
Using steppers for high speed applications can be problematic. Because steppers have the most torque when they are not spinning, you need to keep them spinning slower to get the maximum power out of them. This limits your resolution. When you need to slow the stepper down to move the machine faster, speed becomes inversely proportional to resolution.

[qwertysimo]

H500, Gerry, thanks for your comments. Decided to go with 381 oz for the router. After evaluating finished build I will decide if I need smaller motor to satisfy my idea from the first post.

[qwertysimo]

Hi,

I am back chasing my dreams... I took a step forward - those discussed 381 oz-in, 2.8 mH, 3.5 A steppers (KL23H2100-35-4B) will arrive within a few days. This brings me to a driver selection and I would like to ask you for opinion and advice.

I did not go for G540 for reason I cannot reasonably explain. Anyway my list ended up with these two Leadshine's drivers: EM503 (user guide) and EM705 (user guide). I am not sure about about two things...


The voltage.

I want to use 48 V power supply with motors in order to achieve higher RPM when needed. While EM503 max spec is 50 V, user guide says

20-45VDC recommended, leaving rooms for voltage fluctuation and back-EMF

And similiar for EM705 with max spec 70 V:

24-63VDC recommended, leaving rooms for voltage fluctuation and back-EMF

Other thing, while EM503 typical voltage is 36 V, EM705 is 48 V.


The current.

Motor needs 3.5 A (RMS) to provide rated torque. EM503 allows to set 4.2 A peak/3.0 RMS - this is the highest possible driver setting. EM705 provides also 5.1 A peak/3.6 A RMS.


Is correct to say that EM705 is a better match for this specific combination of stepper motor and power supply? I might not need full torque but definitely want have option to use it. Thanks.

[H500]

The em705 is better, since you want to use 48v. There's less chance of damage due to high voltage.

[qwertysimo]

Thank you.