Spindle motor to servo

[Robertspark]

Ok, non uccnc question, but I know I'll get an honest answer here.

Looking at changing a b14 flange motor with a 14mm motor shaft from a 1/2hp 3 phase 230v to a servo motor.

Why, it's a lathe spindle motor, and need to do some internal spline profile work , so was wondering at the viability of changing to a servo motor (or hybrid stepper with closed loop encoder drive)

The question is, should I be looking at 1hp servo motors?
The lathe spindle is suppose to be able to driven from 50rpm up to 2500rpm and I'd like to keep the same range (I'm not sure the 2500rpm from the lathe manufacturer is correct and not sales bull, given its a 4pole motor and it's pulley driven with a ~1.8:1 ratio)

The plan is to get something with a similar mounting flange size as I don't want to have to change too much on the lathe.

Never used servos before

Thanks

[Robertspark]

More noob questions

A 230v/50hz 4 pole motor rated at 1/2 hp (373W) runs at about 1480rpm
Am I correct that the torque would therefore be: 21.3 lb.in (2.41 n.m)

So if I was to use a constant torque VFD with this motor, then it could be considered equivalent to a 2.41 n.m servo motor?

So if I looked for a servo motor which delivered a bit more than this I'd be in the same ball park, and I can focus on frame and shaft size?

Thanks

[spumco]

I'm in a similar boat on my mill - time to change the spindle motor.

Not an expert, of course, but what I've found is that PM servos have a much better power density than 3ph induction motors - i.e. more power in a smaller package. And here's the important part when comparing AC servos to induction motors - the servos generally have quite a bit of reserve power/torque available, assuming you can supply the current.

Unlike most - not all - induction motor mfgrs just about every servo mfgr has the torque curves available.

You say it's a B14 IEC flange - the tables I pull up have different flange bolt hole dimensions. Need the IEC # in addition to the B14 designation to figure out a suitable motor. Post up the current motor nameplate and we'll pull the datasheet and find you an appropriate servo/drive combo.

Since your RPM limit is pretty low there is a huge selection of AC servos available in the sub-2HP, 2500RPM range.

[Robertspark]

I'll get the details shortly when I'm back at home, however it appears to be frame size 71 b14 flange as shown here

https://www.google.co.uk/url?sa=t&sourc ... u2bEBPmGmQ

From the manufacturers parts diagram the motor is an ASEA MT71 B14F 130-4

[spumco]

That helps.

For reference, a new Marathon induction motor:

https://dealerselectric.com/71T17FH5327.asp

There aren't a ton of direct-fit servos. If you're willing to make a fairly simple motor adapter that opens up quite a few options. NEMA34 and 80MM-class servos are available in the speed/power range you're looking for.

Have a look at the DMM Tech DST and DHT line.

http://www.dmm-tech.com/ac_servomotor_main_a1.html

Pretty close, and the DST-880 has a 14mm shaft. The 880 appears to have significantly more torque across the whole RPM range than your current motor. The matching drive can take 220v/50hz input directly (no power supply needed), and it has differntial encoder outputs to send to your motion controller to manage the threading. Set pulleys up, fiddle with the UCCNC spindle encoder settings and you don't need a separate spindle encoder.

If you're using a 1.8"1 pulley the drive index signal won't work (as Balazs & I discovered with my mill) so a single NPN proxy on the spindle will trigger the threading cycle.

Plenty more out there, but this is a start.

-Ralph

[ThreeDJ16]

I hate to just tack on to your thread, but you are in a similar boat as me. I'd previously purchase this Chinese servo deal (ended up being a POS and returned it) and have since switched to the DYN4 and their 750W nema 34/86mm servo. I've heard a lot of great things about it for spindle motors. In my case it's for a mill, so looking for 5K rpm at 220v and using timing pulleys for 10K.

My question is have any of your interfaced it with a UC300ETH and if so, what protocol method did you use? I've read for speed mode, the DYN4 prefers analog, but it's -10-0-+10v and none of my analog output cards will do anything other than 0-10v and use relays for switching. It does take step-direction and UCCNC will use that, but will my speed be limited? It also accepts RS485, but haven't seen any addon support for this servo motor.

Anyway, apologize for not starting my own thread, but figured these are some questions that you either have or will be asking yourself if you go this route. FYI, I'm using a ConsewCSM1000 550w sewing machine BLDC right now, which has been fantastic on my Emco lathe and Taig mill. But they are very sketchy converting a linear signal to their very small linear rage of 2.7v to 4.8v and need to be isolated due to the above ground signal. I'll be glad that is gone using a DMM Tech servo. Just hoping others have used the DNY4 already and may have some input...LOL...on input.

Thanks,
Jasen

[Battwell]

ive just put a 1kw servo spindle in my mill. you can run step/direction to max speed no problem but if you have high encoder count you will need to divide the encoder output to uccnc.. and gear the steps in to a reasonable level. but step/direction gives perfect speed output without having to use the pid (servo drive manages this)
using 2500 line encoders i divided and geared 8;1 in the drive.
most servos under 500watts have 14mm shaft, then it jumps to 19mm for 750 watt etc.
a good make servo- eg mitsubishi, rated at 3000 rpm will be good to 4200 rpm max. ( i repair mitsubishi servos in the uk and keep loads on the shelf . superb servos for all cnc work)
for threading- use an npn sensor on the spindle shaft. the encoder z pulse out from the motor is too short unless gated and stretched.
shaft size isnt too important if you use taper lock pulleys- you just order the right size pulley and matching taper lock (strongest holding method anyway and not too expensive) just machine up an adapter plate from aluminium or even birch plywood and your almost ready to go!

[ThreeDJ16]

ive just put a 1kw servo spindle in my mill. you can run step/direction to max speed no problem but if you have high encoder count you will need to divide the encoder output to uccnc.. and gear the steps in to a reasonable level. but step/direction gives perfect speed output without having to use the pid (servo drive manages this)
using 2500 line encoders i divided and geared 8;1 in the drive.
most servos under 500watts have 14mm shaft, then it jumps to 19mm for 750 watt etc.
a good make servo- eg mitsubishi, rated at 3000 rpm will be good to 4200 rpm max. ( i repair mitsubishi servos in the uk and keep loads on the shelf . superb servos for all cnc work)
for threading- use an npn sensor on the spindle shaft. the encoder z pulse out from the motor is too short unless gated and stretched.
shaft size isnt too important if you use taper lock pulleys- you just order the right size pulley and matching taper lock (strongest holding method anyway and not too expensive) just machine up an adapter plate from aluminium or even birch plywood and your almost ready to go!

Hey, thanks so much for all the information. So you are saying that if I use the motor encoder, divider and pulley ratio that even with my timing belt setup I can't do rigid tapping without a spindle shaft encoder? My issue is I'm installing an R8 spindle and there is just no room for the spindle shaft encoder. I always get messed up with this encoder stuff. Right now I'm using one of those AMT203 encoders directly on the shaft, but just for PID feedback. But with the 1.2" R8 which is a custom made spindle we designed and built, there just wasn't room with the power draw bar to install another pulley to run the encoder from. I suppose I could run an idler pulley and dual sides belts, then instead of it being an idler pulley, couple it to the encoder. It's never easy, no matter the path I take....LOL...my luck.

Any suggestions on the encoder divider? Something premade from Amazon I suppose would be too easy and non-existent?

Lastly, I wish my shaft was 19mm as then I could reuse my pulleys already bored to 15mm for my Consew. But the CAD listed mine as 12.7mm which is wrong, actual measurements put mine at 14mm and it has a keyed shaft (which I won't use). There are a lot of discrepancies on DMM website, their ebay listing I purchased from and the CAD model they sent. Guess is just good ole fashioned caliper time...LOL. Then I know it's right.

Thanks,
Jasen

[ger21]

DMM makes two styles of 750w motors.
One with 1/2" shafts (12.7mm) that match Nema 34 steppers, and one made to standard servo sizing, with 19mm shafts.

As far as speed when using step direction, the DYN4 drives have electronic gearing available, so there's no limit to how fast you can go. As far as the step direction signals being a factor.

[ThreeDJ16]

DMM makes two styles of 750w motors.
One with 1/2" shafts (12.7mm) that match Nema 34 steppers, and one made to standard servo sizing, with 19mm shafts.

As far as speed when using step direction, the DYN4 drives have electronic gearing available, so there's no limit to how fast you can go. As far as the step direction signals being a factor.

Well I bought the 750w 86mm frame version and it's dead on 14mm shaft size. So there's another ebay auction from DMM tech currently with the exact same motor and DYN4. It states 1/2", but checked with two very trusted calipers and I can guarantee it's 14mm. LoL.