New spindle motor - Servo or Induction?

[Jim Dawson]

Here is something I just ran across, the 3 HP might be worth looking at https://www.automationtechnologiesin...or-and-driver/

[spumco]

Here is something I just ran across, the 3 HP might be worth looking at https://www.automationtechnologiesin...or-and-driver/

ARRGH!!! Not that thing again!

So... that's a "3HP" BLDC motor. Based on the original Sanmutung (out of business). Same motor/drive that killed the Mikini (out of business). The motor is fine, but the drives were utter garbage. A few drive updates were issued over the years but it's still suspect and there's no way it has 3HP.

Imagine a motor that takes 30 seconds to spin up to 5kRPM. Then imagine what happens to a cutter when the drive briefly shuts off during a cut - snap. Look through the Mikini forum here and learn what happened when a garbage spindle is combined with a jerk for a company owner.

I have one sitting in a box waiting for me to find a drive/amplifier that will power it - along with every other piece of Mikini electrical trash I stripped off my mill.

Adlee (Taiwan) has a drive for it I'd trust but it's ferociously expensive and they have no US distributor - Adleee wanted >$1000 for their motor/drive package.

There are a few AliExpress vendors selling similar or identical motor/drive combos, but none of them will sell me just a drive and I don't know if it would work anyway.

If anyone can point me to a drive I'd be happy to take a look. But that thing takes way more volts/amps than virtually every other BLDC motor drive I've been able to find. Mikini (as was typical of them) stripped off all motor nameplate info so there's no way to be certain about the specs.

The motor/drive Automation Tech is offering might be better than the original (or susequent revisions), but they'd have to deposit 2x the purchase price in escrow before I'd buy one. I absolutely LOVE the new steppers A-T sold me, but no way on the spindle motor.

[Jim Dawson]

Thanks for the heads up on that one.

[spumco]

UPDATE

So I finally found a new (used) spindle motor & drive that meets my requirements, more or less. Parker N0924JE motor and Parker GV6-U12E drive. Price was quite reasonable (less than a brand-new name-brand 2/3hp induction motor), and it only weighs 18 lbs.

Rated speed of 3750RPM, max of 7500RPM. I'll try to cobble up a 2:1 pulley setup and see how it works. Best part is that all the motor parameters are already in the drive software as the motor & drive are a recommended pair from Parker.

Downside is now I have to pay real industrial money for cables. Boo.

Thanks for everyone's input and advice.

[skrubol]

I thought you wanted a max speed of 7500 RPM. Why the 2:1 pulley?

[spumco]

I thought you wanted a max speed of 7500 RPM. Why the 2:1 pulley?

Because the rated speed -where torque falls off- is 3750.

[skrubol]

Because the rated speed -where torque falls off- is 3750.

But the 2:1 pulley will cut the torque in half..
I was thinking it was like an induction motor where field weakening enables roughly constant power from rated speed to max speed, but it looks like these drop off to 0 torque/power at max speed. Also, there's no extra overload torque even at 3750, so you're probably right.

[spumco]

True, the pulley will cut the torque in half, but I think this motor has plenty to spare.

My thinking is that if I can put the motor near it's rated speed at max spindle RPM I'll be in pretty good shape. Most of my machining time is at high RPM, and I'd rather trade some low-end torque for appropriate tool SFM in aluminum.

In addition to the motor/drive, I also bought a new BT30 spindle & PDB set with bearings good to 8k+RPM. I'm hoping to eventually build/buy an ATC, and I'll need spindle indexing/homing for that because of the drive dogs. I also need a spindle index trigger to start the rigid tapping cycle, but the same thing can be accomplished with my current setup (suitably modified for the new spindle).

It'll be a while before I'm ready to tear everything apart since I'll have to bore the head for the new spindle cartridge - in addition to fitting the new motor and drive. Right now I'm past paper-napkin stage but not much further. I am, of course, open to suggestions and advice.

Like:

Pulley ratio recommendations? (if 2:1 sounds inappropriate to somone)
Drive controlled with 0-10V or step & direction?
Alternate ways to home the spindle? (I've never fiddled with modbus stuff)

[raychar1234]

Hello Spumco and everyone

My required cutting performance spec. is quite similarly as yours. And I am quite confused some time about the case of using a servo motor that is for driving ballscrew to driving spindle.
if I can use Leadshine 1KW servo motor and its driver kit as my spindle motor? Will it survive long enough during the use?
It runs at 2500 ~ 3000rpm max. Will it perform similar as yours Parker motor?

[skrubol]

Most AC servos should work fine as a spindle. They don't have brushes to wear out, so should hold up quite well assuming the bearings aren't crap. Not sure how Leadshine is reliability wise vs the pricier brands, they've got a good rep as far as a Chinese manufacturer from what I've read though.
Leadshine has some conflicting info on their site, but it looks like the EL5-M1000-1-51 will be constant torque up to 2000 RPM and then constant power from 2000 to 3000 RPM.
Leadshine Technology Co., Ltd.

[spumco]

raychar,

Take this with a grain of salt as I'm no expert. The fundamental difference I can tell between dedicated spindle servos and 'normal' brushless AC servos is that the spindle servos have electrically driven cooling fans (and maybe cooling shrouds). They are intended to spin at nameplate loads for hours at a time. My little experience also indicates that 'spindle' servos are under-rated for power vs. a comparable size/frame/stack normal servo.

Your 1kw servo might weigh about 4lbs - the Leadshine manual doesn't have exact weights - and the 2kw maybe 8lbs. The typical 'spindle' servos I ran across were about double that weight for the same Kw rating disregarding the added fan weight. I think this is all about thermal management.

'Normal' servos - at least as far as our CNC world goes - aren't spinning at max RPM all the time. There are plenty of times, even during a complicated program, when the servo is barely moving or is even idle.

Other than that, the differences are in pole count, windings, internal component quality, compromises on mechanical reliability vs. thermal management, ect.

The Leadshine servo will work as a spindle motor. If you rig up a separately-powered cooling fan and shroud I suspect it will work quite nicely for a good long time. I know there are a couple of threads in the DMM Tech sub-forum where some folks have reported success using their 130mm frame servos as spindles.

As to whether the Leadshine will perform similar to my Parker - who knows? Keeping in mind that the servo I bought is not a dedicated spindle servo, but I don't think so as the Parker has a much higher rated power & speed. The Parker's additional speed may be from better mechanical components, but it could also be a result of using higher-speed ($$$) inputs on the amplifier/drive so the servo encoder doesn't overload the drive at high RPM. One huge difference is that the Leadshine operates at 220V, while the Parker runs 340V. And I've seen spec sheets on some Fanucs & ABB's that operate at 480V.

I'm guessing here, if it isn't obvious.

Which makes me wonder why every single Chinese or low/middle-end servo I've seen has a max RPM of about 3000RPM. The 80mm frames seem to make it up to 4-5000RPM with a few vendors, but the larger 110/130mm servos all poop out at 3K. And yet Fanuc/Parker/ABB ($$$) seem to offer a much higher RPM in some of their larger servo models. Is it the higher voltages, rotor balancing, potted windings, or more expensive optos in the drive? All three?

Hope this helps,

-Ralph

[raychar1234]

Thanks for all guys valuable advice. Especially that I am now realized the importance of cooling fan that existed in the industrial spindle motor and of which it is not existed in axis-driven motors. BTW, just searched in web there is one cheap Chinese spindle motor (firstly I am not the one to advertise it ..https://item.taobao.com/item.htm?spm...d=567465461422 ). There is the smallest model of 2.2KW. But, still it is overwhelmed for me. Too heavy and too large for my machine bridge to support it. So, in the meantime, will continue to search. Which type of servos or just the common VFD spindle??

[mick41zxr]

That motor looks to be a Servo spindle driven by a VFD, doesn't appear to have complete closed loop control.
I have been testing a complete Spindle Servo with Driver that will accept a single phase supply. Quality is excellent & results so far are promising.
2.2kW, 8000rpm. Quick video of bench testing here;
Regards,
MB

[Azalin]

8000 RPM is amazing. I'm now converting a Schneider BMH0703 6000 RPM servo from Sinusodial encoder to incremental encoder. I will see how it works on a BF20.

[skrubol]

Purpose built spindle motors are typically induction motors, which are hard to make as compact as permanent magnet motors. One advantage they have is a wider constant(ish) horsepower range. It's not unusual for a spindle motor to have constant(ish) power from 1200-8000 RPM. Most motion control type servos this range is more like 3-5000 RPM or smaller of a range. As mentioned earlier, spindle motors usually are conservatively rated as well. Some are rated to run at 120% load for 30-60 minutes.

[mactec54]

That motor looks to be a Servo spindle driven by a VFD, doesn't appear to have complete closed loop control.
I have been testing a complete Spindle Servo with Driver that will accept a single phase supply. Quality is excellent & results so far are promising.
2.2kW, 8000rpm. Quick video of bench testing here;
Regards,
MB

That's a servo Drive not a VFD Drive, the plug under his hand is the encoder plug

[mick41zxr]

Mactec54 that's my hand, yes its a complete Spindle Servo with encoder feedback. I was referring to the driver in the link posted by Raychar1234.
Regards,
MB

[raychar1234]

Sorry guys, it has two versions, seems I posted a wrong link which is a VFD one and the following is the correct servo one.:
https://item.taobao.com/item.htm?spm...d=566048938033

[mactec54]

Mactec54 that's my hand, yes its a complete Spindle Servo with encoder feedback. I was referring to the driver in the link posted by Raychar1234.
Regards,
MB

Some of these motors are able to run up to 12,000 RPM 6,000 to 8,000 RPM is common, the first link with VFD has encoder feed back as well

[hatch789]

OK Please don't shoot me but I'm new to this topic but I would also like to remove my large 3-phase 2HP motor on my Tree Journeyman 200R machine and replace it with another servo motor or something where I could do rigid tapping and other fun things. My spindle currently runs at 3300 when in high gear so I was thinking I could remove the transmission and large old motor and just replace it with a nice new servo motor like this: https://www.teknic.com/model-info/CPM-MCVC-3426D-RLN/ and just drive the spindle directly from that 1:1 coupling. This servo will run at 5300 RPM which is nearly 2x the speed my existing system will do so that would be great but it would (should?) also give me the low end I need to do rigid tapping and similar things. -Am I crazy or am I on the right track? Please offer feedback with the understanding that this is my first go-around with even thinking of doing this. I would buy a 75v power supply to drive the motor and then just control it with LinuxCNC ...that's my plan as of right now in the infancy stage of development!