Spindle Motor on PM-30MV Integration into Acorn

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firebrick43
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Re: Spindle Motor on PM-30MV Integration into Acorn

Post by firebrick43 »

suntravel wrote: Mon Jan 24, 2022 1:26 pm Well costs in Germany are different, but I compared new stuff. If I used chinese motor/vfd as well it would come much cheaper still, even new. I was using name brand drive and heavy duty American made motors.

2 pole 1.5kw 210€ Delta EL VFD 250€ SK30 Tapping holder 175€ collet 17€ each Tapping holder at maritool is about the same now(euro has really come down? collets would be a cost no matter if doing rigid tapping or with a floating tap holder

1.5kw JMC Servo with driver 559€

2 pole 1.5kw torque @2880 rpm 5 Nm 80% at 300 rpm
Servo 1.5kw torque 0-3000 rpm 5.73 Nm up to 14.33 Nm for short time

There are 4 different styles of 3 phase motor torque characteristics, two have high low speed torque. As does any inverter duty motor. I could cherry pick stats, it would be disingenuous as there are so many application differences and trade offs. Again, for the most part 1.5kw is 1.5 kw. AC servos are 3 phase motors. Its the encoder/drive thats the biggest difference. If I want more torque I can have belt reductions(or gear) as well with an encoder on the spindle shaft itself. With stepped poly v pulleys you could have more torque than a direct drive or cogged belts servo when wanted or more speed. In this instance the motor mounted encoder would not be a plus as it cant measure belt reduction (the motion controller can but not the drive itself) nor can it measure belt slip. So you would require a second spindle shaft encoder anyways.


Noise is better with servo also because they don't need a fan for cooling. TENV inverter rated motors have no fan either. Many larger servoes have fans. Inverter motors have class H insulation as does reputable ac servo. It allows for a max winding temp of 180 degrees C and a max temp rise of the whole motor of 125 degrees C

Rigid tapping or forming M3 / 2000rpm works with 0.2s deceleration time, never broke a tool It can be done with a 3 phase motor as well and good vfd/motion controller. It is easier with a direct drive servo but several manufactures such as fadal can rigid tap with belt reduction without issue, but a machine such as a robodrill can rigid tap like nothing else in speed. I will give credit to a servo where it has an advantage

For constant speed like a surface grinder there is no benefit for a servo IMHOThere can be advantages, especially in a production environment as a servo or vfd can match wheel speed to the work to get the highest production output but prevent burning. However the point I was making that the quality of components, not the type of drive/control is the main factor in surface finish as a whole. Your servo is a much higher quality component than what was originally installed on your mill.

All our 80 CNC machines in my day job have servos for the spindle also.Most have tool changers do they not? There fore its easier to orient.Also since many modern VMC/HMC use high speed spindles, and they are purpose built anyways for the speed. The drives are readily availible for this and and most vfd stop at 200 hertz so they would be have to be specially made. Most of the less that 30hp spindles at the Caterpillar large engine plant I used to work at were servos as well. But many of the big spindles(40 to 100hp), as they had selectable speed gear transmissions any way, had induction motors. Nothing is as fun as pulling a 100hp motor out of a waldrich coburg 40 feet up in the air! Fadals (not saying its a high class machine, they only had one) had a dual speed belt drive with air shifters and used induction motors.

None of the large turrent lathes at Cat had servos on C axis. The mazak mill turns had both induction motors for when pure turning and servo powered worm reduction would engage when indexing/mill turning.

All the junkers and shaundt cam grinders I now maintain have servos on the spindles but the small ones its sort of moot as they are belt drive (JB) to the wheel. They do it because its easier to intergrate as they already have a power section and a stack of siemens drives. The small DMG Mori/Boehringer have servos but also have live tooling.


Uwe
suntravel
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Re: Spindle Motor on PM-30MV Integration into Acorn

Post by suntravel »

Thats really a good discussion.

1.5kw is the rated consumption of motors

normaly 3 phase motors are asycronous and 3phase servos are syncronous in this range

The higher efficiency of syncronous drives is what makes the slight difference in torque on the drive shaft

For the combos with driver / VFD I found the short time boost was much higher in servos

My aim was to have 0-8000rpm without changing beltposition and good short time torque for tapping at low speeds and no fan cooling,
( my wife hates to much noise if i play at night with my machines :D )

Works like calculated and I have not found an example with asyncronous drive/VFD that could do the same thing

Uwe
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Re: Spindle Motor on PM-30MV Integration into Acorn

Post by firebrick43 »

1.5kw is almost 2hp exactly. So a Baldor IDNM3584T motor, which is a 145TC frame is a 1.5hp motor. It has a pull up torque(load it can accelerate from a dead stop) of 9.1 ftlbs(12.33nm) and and a pull down torque of 19ftlbs(25.7 nm) Even though this is a 1.5 hp motor instead of 2hp its pretty close to your servo. I am starting with this motor as I have 2 of them, one a powermatic planer and a powermatic belt sander is ran off of one vfd. They have a 6000 rpm limit, so yes, it could not do 8000 rpms with out a 1:1.5 belt ratio. If willing to have a dual speed polyv belt you can have your speed and even better low speed spindle torque.

Unfortunately the 145c frame 2 hp motor specs are not showing up right now for me. But undoubtably would exceed the numbers above and I would surmise would at least equal/slightly exceed the 1.5kw servo numbers. IDNM3587T.

The IDNM3669T is an 182 frame motor, much bigger physically. It has 12.12ftlbs of pull up torque (16.4nm) and 24.5lbs (33nm) of pull down torque. It is also rated at 6000 rpm. Now this is a large motor, I would not put it on a mini mill but I have put some (3) 3hp versions of the same frame on the three bridgeports at work, getting rid of the blasted reeves drives on them with an even better range of speeds. Surface finishes improved as well as the vibration of the reeves drives was eliminated as well as the rattling noise so prevalent.
suntravel
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Re: Spindle Motor on PM-30MV Integration into Acorn

Post by suntravel »

This Baldor is 1470€ in Germany....

https://www.raptorsupplies.de/pd/baldor ... ewQAvD_BwE

Uwe
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Re: Spindle Motor on PM-30MV Integration into Acorn

Post by rk9268vc »

IMPORTANT

Be aware that the bearings in the PM-30MV are only rated for just over 3000 rpms. If you replace the motor with intentions of higher rpm or much higher HP you MUST replace the bearings in the spindle.

Battle resistant outfitters (now called MP Machining) on youtube did a bearing upgrade to his PM-30 and the cost for the bearings to run 6krpm was around 1000$ so be aware of that.

also thought, you may be able to just get a better driver for the 2HP brushless DC motor that is already on the PM-30. I am looking into that for my PM-30

good luck
suntravel
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Re: Spindle Motor on PM-30MV Integration into Acorn

Post by suntravel »

My mill was outfitted with spindle bearings, not tapert roller Bearings as usual.

But i replaced the chinese stuff with good quality FAG bearings an Klüber ISOFLEX NBU 15 spindle grease.

No need to by a 1000$ kit.

But you can also get roller bearings which work up to 12000 rpm with NBU 15

Uwe
suntravel
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Re: Spindle Motor on PM-30MV Integration into Acorn

Post by suntravel »

Short video about thread forming with the servo drive



Uwe
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Re: Spindle Motor on PM-30MV Integration into Acorn

Post by firebrick43 »

suntravel wrote: Tue Jan 25, 2022 12:52 pm This Baldor is 1470€ in Germany....

https://www.raptorsupplies.de/pd/baldor ... ewQAvD_BwE

Uwe
I don't doubt it. They are expensive here new except for some reason I have been able to pick them up dirt cheap on ebay for 100 dollars or less in really nice shape. Baldor just happens to have very good documention so I was showing that induction motors have/can have similar torque numbers.

I have two 1.5hp and three .75hp on different machines with ac lenze or teco vfd. I roll a set of skf/ntn/nsk bearings into them as a precaution but all but one felt fine and all had very good runout on the shaft. I power tap with them on my drill press all the time, although I wouldn't do an m3 or 6-32 tap. I normally start them with the drill press and the chuck lightly clamped when that small and then finish by hand
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Re: Spindle Motor on PM-30MV Integration into Acorn

Post by suntravel »

They draw nearly 19A at startup, do you need a 20A VFD to run them?

Uwe
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Re: Spindle Motor on PM-30MV Integration into Acorn

Post by firebrick43 »

suntravel wrote: Wed Jan 26, 2022 1:20 am They draw nearly 19A at startup, do you need a 20A VFD to run them?

Uwe
No. VFDs are typically rated by horse power. You actually enter the numbers right off the motor plate into the vfd with "limits" its output to the motor itself. I had to look it up but a 2 hp vfd is putting out around 9-9.5 amps at 230V.

Remember, the vfd had acceleration values and is not trying to go from 0-1800 instantly. You can program acceleration and deceleration rates, although depending on how fast you want to bring it to a stop you may need to add an additional braking resistor. \

My jointer specifically but since I share a vfd with the belt sander, its very nice to have them accel slowly and come to a stop briskly. I have been contemplating getting a 3 phase motor and vfd for my 3hp unisaw as it thumps something fierce when the contacts pull in but I would have to buy a another vfd and it already has some braking on stopping.
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