[Gannz]

Frame is the beefiest 4060 Chinese kit I could find.

Spindle is a Gpenny 65mm 220V 1.5kW water cooled w/ Huanyang 220V 3kW VFD

Thought I had the steppers figured out (high torque, low inductance, high voltage) but then I found out about 3 phase steppers and now I don’t know how to compare the 3 phase driven at 50V to a 2 phase @ 80V. Here are my options…

1. Lichuan LC57H3100 3ph 3.0Nm 4A 3.0mH N23 motor w/ LCDA357H 50V driver & 45V PSU

2. Leadshine 57CME23 2ph 2.3Nm 5A 1.75mH N23 motor w/ CL86H 80V driver & 72V PSU

3. Leadshine 573HBM20 3ph 2.0Nm 5A N23 1.85mH motor w/ HBS507 50V driver & 45VPSU

4. Leadshine 86CME45 2ph 4.6Nm 6A 3.97mH N34 motor w/ CL86H 80V driver & 72V PSU

The frame is on order so I can’t confirm but the N34’s should fit the X & Z but the mounting brackets will overhang and look goofy. So option 5 is the 2 phase N23’s on the X & Z and the N34 on the Y.

Price is about the same for either option but 3 phase N34 is out of the budget.

I'm leaning toward option 3 because of the lower inductance motor vs the Lichuan and the Lichuan torque curve seems sketchy.

Torque curves attached:

Lichuan LC57H3100 3 phase (I don’t understand this… 1Khz = 60,000 RPM so this scale seems way off when compared to the Leadshines shown in RPM)

Leadshine 57CME23 2 phase (this is the torque curve for the Leadshine CS-M22323. It’s hard to find the torque curves for Leadshine because what they have on their website is not the same part numbers as what they’re selling on Cloudray and Aliexpress. On the website, they only have the 57CM23 which is an open loop or the CS-M22323 which is not close on the part number but the specs are identical to the 57CME23. So I assume this is the torque curve for the 57CME23/CS-M22323…)

Leadshine 573HBM20 3 phase (again, hard to find torque curves for retail leadshine models but this graph popped up on youtube when someone was discussing this model)

Leadshine 86CME45 2 phase N34 (can’t find the curve for this specific model either… only the 86CM45 which is open loop or this CS-M23445 which is identical but it's 4.5Nm vs 4.6Nm)

[joeavaerage]

Hi,
to be honest I don't really think the premium you pay for either closed loop or three phase steppers is worth the extra.

Good med torque, low inductance open loop two phase steppers with a high 80VDC min, ideally 110VDC) driver will perform every bit as well.

Closed loop steppers are still stepper. Closed loop does not make them any faster, any more powerful or anything else. If a closed lop stepper is marginally overloaded and misses a step
then the drive will insert an extra step to catch up....but guess what, the extra step is just as likely to be missed as a regular step.....its just plain overloaded, and no amount of closed loop
stuff changes that. Closed loop stepper allow much better microstepping interpolation and it will at least try to catch up if it misses a step, but will fault out if it cannot rather than carry on
and produce a misshapen part as a open loop stepper might....but you are paying quite a premium for slim advantage.

If you want close loop performance then get servos. The real advantage of servos is they have three to four times the rated torque as overload capacity, but good servos still are quite costly.

Craig

[Gannz]

Thanks, Craig. I have read the discussions between you and other knowledgeable members on this forum regarding closed vs open loop. I figured the slight differences would still benefit a noob like me and the cost is really not much different. Maybe I'm doing it wrong but I'm getting around $450 OTD +/- 10% for pretty much any combo. That has a lot to do with the offerings... there are closed loop motor/driver combos that cut costs vs purchasing the open loop motor & driver separately (there are open loop combos but if it's the motor I want, the driver is underpowered and if the driver is 110V they usually come packaged with a N34 or bigger).

One thing I failed to notice until now, and this was probably mentioned in the discussions but I glazed over it, is that the open loop motors have much lower inductance vs their closed loop counterparts. So one is actually sacrificing performance for communication when going closed loop, correct? That's enough to persuade me to go open loop.

So, open loop 2 phase vs 3 phase I think I already know your answer but I'll throw out the options anyway since I've done the research lol...

3 phase
3DM883 Driver 20-80VDC $100

573S20 N23 2N.M/2.4mH $45
863S42 N34 4.2N.M/4.5mH $80

2 phase
DMA860H Driver 24-110VDC $77
DMA882S Driver 24-110VDC $82
DM1182 Driver 113-212VDC $115

D57CM31 N23 3.1N.M/1.18mH $50
86CM45 N34 4.6N.M/2.95mH $65

2 phase DMA882S driver and D57CM31 motor the "best" (will do the job without overspending or overloading the gantry) combo for my application? I think I'll be happy with that D57CM31... I couldn't find a decent closed loop N23 around 3N.M with >2mH inductance. They were all around 2N.M w/ 2mH and the 3N.M motors are mostly around 4mH

For comparison, here are the OTD prices for 3 sets (X,Y,&Z) of the closed loop options in the OP...

1. Lichuan 3 phase $387
2. Leadshine 2 phase $450 (no kit)
3. Leadshine 3 phase $432

How about the N23 vs N34? N34's too heavy for my X & Z (they're about 2.5Kg vs 1.5Kg)? N34 a good idea for the Y at least?

[joeavaerage]

Hi,
without doing the calculations its not possible to know, but very commonly the inertia of an axis is not dominated by the weight of it, but by the rotating ballscrew.

As an example my mill has cast iron axis beds weighing 115kg. I guessed that the whole axis would weigh 150kg. The ballscrews are 32mm in diameter and 700m long being
direct driven by 750W Delta servos. The momentum of the axis is 80% in the ballscrew, 12.5% in the armature of the servo and only 7.5% the weight of the axis.
You read that correctly, the 150kg axis is a very small fraction, its the rotating ballscrew that dominates.

If you want to determine whether the weight of the stepper is significant in the momentum equation the do the calculation. At the moment you are guessing.

As a first guess I'd say the weight of a stepper is so small as to be insignificant. I still think the 1.18mH 23 size are the go.

Craig

[Gannz]

Copy. Thanks again.

So I'll need to go bigger on the toroidal transformer too. I think I can get by with the 1000W 95V 10A?

800W 48V 16.7A 17Lb $155 (enough to run the 50V drivers)

1000W 70V 14.3A 19Lb $158 (enough to run the 80V drivers)

1000W 95V 10A 20Lb $158 (the D57CM31 motors only draw 4A max so I can get by with this 10A… but if I add a 4th axis in the future I’ll be right up against it)

1500W 100V 15A 32Lb $230 (enough to handle everything comfortably but 32 lbs and $230!)

[Gannz]

*CORRECTION to post #3... the D57CM31 is 1.8mH inductance, not 1.18mH. Most of the retail sites have it listed at 1.18 but the Leadshine datasheet has it at 1.8. The torque curve posted is still correct.

[Gannz]

Have another correction... the 4A D57CM31 has a 2.8mH inductance. It's the 5A D57CM31 that has 1.8mH. So I'll need a minimum 1000W 95V 10A PSU for the 3 axis with no room for expansion.

12/1300W @ ~100V is a unicorn so it's either the 1000W 10A and add another PSU if I expand or go with the 32lb $230 1500W 15A. Looks like any savings by going open loop 110V vs closed loop 80V is eaten up by the monster PSU.