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Agathon
17-11-2016, 01:16 PM
I'm replacing the old Superior Electric MO93-FD-301 stepper motors (see photo) on my Fehlmann Picomax 50 cnc. One is missing altogether and given the massive current requirement for the existing motor I'd like to buy a pair of new ones. Does anyone have any suggestion as to what sort of replacement would be suitable? The original motors are Nema34 but it's no problem to make up Nema23 adapters.

I was thinking of using closed loop steppers, but I can't get to the bottom of what would be suitable as a replacement and UK availability is limited.

Any help much appreciated.
19638

JAZZCNC
17-11-2016, 03:28 PM
Just about any Modern Nema 34 motor will beat those old round steppers so wouldn't worry too much.
Also I would consider replacing the drives with Modern Digital drives. Lead shine EM806 or AM882 drives are excellent drives and pair nicely with smaller Nema34 motors. There advanced resonance capabiltys are great for Mills which tend to be very stiff. It's Night and day difference in how the perform compared to old analog technology.

If you do want to go with Closed loop then On Ali express there are some good deals.
Also Consider Servos if buying from China because they don't cost much more money than closed loop.

If wanting from UK then you'll pay lot more money for closed loop or Servos.

Agathon
17-11-2016, 04:11 PM
Thanks for the reply. What do you think about using these - http://r.ebay.com/6XUOJV ? The holding torque is only the same as the nominal torque on the "old round things" but from what I know about closed loop motors they produce more torque relative to speed.

My other thought is for an integrated motor such as these - http://tinyurl.com/gprokbx None of these in Europe though.

m_c
17-11-2016, 04:32 PM
Without finding the datasheet for the original motors, 200 oz-in = 1.4Nm.
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The HSS57 closed loop servo will work well. Just remember you'll also need to get new couplers/pulleys, as I'd guess the shaft on the original stepper shaft will be a good bit bigger than a modern Nema 23 motor.
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Personally, I'd avoid the integrated stepper, not because it won't work, but because you need to run the step/dir wires to the motor. If you've not got differential (line driven) step/dir signals available, it makes things very prone to noise.

JAZZCNC
17-11-2016, 04:54 PM
Thanks for the reply. What do you think about using these - http://r.ebay.com/6XUOJV ? The holding torque is only the same as the nominal torque on the "old round things" but from what I know about closed loop motors they produce more torque relative to speed.

My other thought is for an integrated motor such as these - http://tinyurl.com/gprokbx None of these in Europe though.

Those are not what you think they are. They are closed loop but not to be confused with the Leadshine that they are copied from. The main difference is the motors are 2 phase not 3 phase and this makes big difference to how they perform.

Not fan of integrated motors in this application.

Agathon
17-11-2016, 05:01 PM
Thanks again. Yes, perhaps I'll avoid the integrated solution - a pain if the driver packs up too.

The nominal torque of the original motors is 300 oz in which is 2.1Nm - the machine's manual states the "maximum holding moment" as 3.2Nm.

I found this data sheet on line - https://drive.google.com/file/d/0Bxr59DtuJda_VDd6QXByMGdoLWc/view?usp=sharing

Thanks for the Leadshine observation. The Nema34 Leadshine motors are only two phase.

Agathon
17-11-2016, 05:17 PM
Just realised that it was your Youtube video of a Leadshine closed loop stepper that turned me on to the idea.

Maybe, as you've said in other threads, I'd be better off with conventional Nema34 steppers and digital drivers. Just like the idea of the smooth closed loop, but there's no point if the two phase motors aren't any smoother.

Thanks again for your help.

JAZZCNC
17-11-2016, 05:43 PM
Thanks for the Leadshine observation. The Nema34 Leadshine motors are only two phase.

Yes the 34's are but the smaller 2nm leadshine hs57 are 3 phase. Personally I wouldn't pay the extra for 2 phase closed loop over standard stepper with Digital drives.

JAZZCNC
17-11-2016, 05:53 PM
Just realised that it was your Youtube video of a Leadshine closed loop stepper that turned me on to the idea.

Maybe, as you've said in other threads, I'd be better off with conventional Nema34 steppers and digital drivers. Just like the idea of the smooth closed loop, but there's no point if the two phase motors aren't any smoother.

Thanks again for your help.

Yes that's me.!!

Standard 34's with Am882 will be perfect for Mill. When correctly setup there will be no difference between 2 phase Closed loop in performance terms.
If the machines loses position the closed loop will bring it back into line yes.!! . . But the damage will still have been done if it was machining at time. Again Correctly sized and setup stepper shouldn't lose position so it's not problem. I've built loads of routers using the AM882 and Em806 drives along with 34 and 23 steppers which travel high feeds where torque is lower and they don't lose position so on slower moving mill you won't have any trouble.

Agathon
17-11-2016, 06:23 PM
It's a shame that the Leadshine Am882 doesn't appear to be available in the UK. Is there another driver worth considering?

Just a final thought on the closed loop steppers. Given the details of the original motors, do you think the Leadshine 3ph Nema23 2Nm motors would provide enough torque?

JAZZCNC
17-11-2016, 06:34 PM
Just a final thought on the closed loop steppers. Given the details of the original motors, do you think the Leadshine 3ph Nema23 2Nm motors would provide enough torque?

Difficult to answer without seeing machine etc but the fact the old where 34's and probably wired in series which gives more torque lower down Rpm then it will be close call and one I wouldn't take personaly.

AM882 and 34's would be safer bet.

m_c
17-11-2016, 09:08 PM
It's a shame that the Leadshine Am882 doesn't appear to be available in the UK. Is there another driver worth considering?

Just a final thought on the closed loop steppers. Given the details of the original motors, do you think the Leadshine 3ph Nema23 2Nm motors would provide enough torque?
The AM series has been replaced by the EM series. The new AM882 equivalent is an EM806.
The original HS closed loop stepper system has also been replaced with the Easy Servo range.

Agathon
17-11-2016, 10:17 PM
Ouch, those EM806 drivers are pricey - by the time I've bought a motor, I've exceeded the price of the Nema34 closed-loop units from Rattm motor in Germany (http://r.ebay.com/jCcjOw).

I notice these drivers claim to be digital - http://r.ebay.com/chJSF8

JAZZCNC
17-11-2016, 11:09 PM
Ouch, those EM806 drivers are pricey - by the time I've bought a motor, I've exceeded the price of the Nema34 closed-loop units from Rattm motor in Germany (http://r.ebay.com/jCcjOw).

Don't be fooled by the Germany part. They will come from China. You'll get message saying don't have stock in Germany and will be 6-8wks before re-stock and would you like them sent from china.

Don't be put off buying from china if you can afford to wait. You'll get AM882 cheap enough. I've used lots both EM and AM there's very little between them in performance terms.

Agathon
17-11-2016, 11:23 PM
Very good advice as usual. Many thanks.

Agathon
19-11-2016, 12:28 AM
Just to throw something else into the mix... I contacted Fehlmann (the makers of my mill) and asked them what they used on the modern equivalent of my machine. They now use Omron "Smartstep" servo motors (R88M-G40030h) with a nominal torque of 1.3Nm and a momentary torque of 3.6Nm. 2.6A mains (200v ac) powered driver.

I'm wondering again whether those Leadshine 3ph Nema23 2Nm closed loop steppers wouldn't do the job or is the torque characteristic for a servo very much different to a stepper?

JAZZCNC
19-11-2016, 04:08 PM
I'm wondering again whether those Leadshine 3ph Nema23 2Nm closed loop steppers wouldn't do the job or is the torque characteristic for a servo very much different to a stepper?

Very different.!!

The 1.3Nm is continous meaning thats what you'll get at full motor speed probably 3000rpm. The 3.6Nm is Peak torque which the drive/Motor can handle for limited period of seconds which is often enough to handle high enertia or heavy starting loads. Under heavy loads ie: cutting it will handle anywhere between 1.3nm & 3.6nm for limited periods depending on loads.
Throw into the Mix that because Rpm is often much more than required there will ratio applied so torque actually increases.

Stepper rating on the other hand measured at ZERO RPM and starts to drop as the Rpm's increase. Slowly at first up until point of the Speed curve where it starts to drop quickly untill full motors coils reach full saturation and motor stalls. On 34 motor the speed curve will be aprox 900rpm depending on inductance and voltage used. There'll be little to no torque at 1500rpm.

This is why inductance and Voltage is so important to the speed you get from steppers. Also you throw how stepper is wired into the mix and it can change again.?
If wired parallel you'll get torque higher up the rpm range but less lower down for set voltage. If wired series you'll get pretty much the opposite, Higher torque lower down rpm range but motor will reach saturation much sooner for the same voltage so lower RPM.

Most 34 motors are 4 wire series wound motors and to get any decent speed from them requires High Voltage. Often larger Nm 34's are run with mains voltage drives.
Now for mill you won't require high rpm's so series wound is often Ok. Nema 23 motors often come with 8 wires and can be wired series or parallel. But the same applies in that higher voltage is required for same rpm if series wound.

So in nut shell if they Fit 1.3nm Servos then 2Nm Nema 23 Stepper isn't going to cut it really.

Agathon
19-11-2016, 05:26 PM
Very clear reply - thanks.

OK, so just to confuse myself more I've tried to fill out the Excel motor calculator here - http://www.mycncuk.com/threads/1524-What-size-stepper-motor-do-I-need

I've attached the calculation with what I think are generous values using the Leadshine 3ph 2Nm motors 19666
This seems to look OK, but have I missed something - are my estimates as to load mass and table speed too low? The 3ph 2Nm Leadshine motors have an encouragingly flat torque curve at less than 360rpm - 19667

If I go for conventional steppers I'll go with the AM822 drivers, but what size motor? The old steppers have a surprisingly small shaft (3/8") so Nema34s with 14mm shaft are a bit of nuisance. I see Nema23 3Nm motors with 10mm shafts - http://r.ebay.com/KuT9Ez - Are these big enough though?

Sorry for all the questions.

Just to give some idea of the sort of machine - here's a (bad) photo:19670

As you can see, it's a kind of mill-drill. But don't be fooled, this thing is a beast weighing in at about a tonne. The table weighs around 150kg - hence my 100kg load per axis estimate. The motors drive the ball-screws directly.

m_c
20-11-2016, 10:36 AM
My gut instinct for a machine like that with direct drive steppers, would be something in the 4Nm range to give plenty safety margin.

I think personally I'd consider altering things to use a belt drive with some Nema23 steppers, which should give you better performance. With big Nema34 motors, for best performance you've really got to use high voltage drivers, but you're then still limited at torque drops of quite quickly with big steppers.

Agathon
20-11-2016, 10:43 AM
My gut instinct for a machine like that with direct drive steppers, would be something in the 4Nm range to give plenty safety margin.

I think personally I'd consider altering things to use a belt drive with some Nema23 steppers, which should give you better performance. With big Nema34 motors, for best performance you've really got to use high voltage drivers, but you're then still limited at torque drops of quite quickly with big steppers.

Thanks. I had considered driving via a belt just in order to make the machine more compact. Would you gear up in order to increase the speed of the ball-screw relative to the stepper?

m_c
20-11-2016, 11:04 AM
Opposite way!
You want to decrease speed of the ballscrew in relation to the stepper, so you get more torque at the screw. Somewhere around a 2:1 ratio would be a good starting point.

Try running some figures through the spreadsheet to see what kind of speeds you can get with different ratios, while still having usable torque to handle the cutting forces.

JAZZCNC
20-11-2016, 11:06 AM
If I go for conventional steppers I'll go with the AM822 drivers, but what size motor? The old steppers have a surprisingly small shaft (3/8") so Nema34s with 14mm shaft are a bit of nuisance. I see Nema23 3Nm motors with 10mm shafts - http://r.ebay.com/KuT9Ez - Are these big enough though?

Ok well first need to check if the machine is fitted with Ballscrews not just lead screws which you are calling Ballscrews.?

If ballscrews then 3 or 4Nm Nema 23 motors will probably work. I've fitted loads of Both 3 & 4nm motors and to be honest see very little difference between them in performance terms so wouldn't stress over which to use. The Key is buying ones with Low inductance. No higher than 4mh ideally closer to 3mh.
These are better motor and will fit your needs.
https://www.cnc4you.co.uk/Stepper-Motor/Nema23-4Nm/Stepper-Motor-4Nm-60BYGH401-03-Nema23

If you speak to them Don't Let them Bullshit you into believeing there drives are as good or better than Leadshine AM or EM they are not.!

Agathon
20-11-2016, 11:28 AM
Opposite way!
You want to decrease speed of the ballscrew in relation to the stepper, so you get more torque at the screw. Somewhere around a 2:1 ratio would be a good starting point.

Try running some figures through the spreadsheet to see what kind of speeds you can get with different ratios, while still having usable torque to handle the cutting forces.

OK, that's certainly how I would have dealt with torque issues with a conventional motor, but I thought the whole point was that torque went down as speed increases. I see that gearing down, by say 1:2 would give twice the torque, but getting the speed up to 1800 mm/min (900rpm for the motor) for rapids will mean that the motor is well outside it's optimum torque region. Or is it the case that in practice this wouldn't be an issue?

JAZZCNC
20-11-2016, 11:32 AM
This maybe your Lucky day my friend.?

Just remembered somewhere in box I've got some motors and sure enough there was.!! And guess what they are 2 x Brand New 34's with 10mm shaft 8 wire motors model number FL86STH65-2808A-H. Think about 3.5Nm but would need to dig out motor data sheet.

Also got another 34 4 wire motor with 12mm shaft which is around 4Nm I think. SY85STH65-5904B.

Drop me PM if your interested.

Agathon
20-11-2016, 11:46 AM
Ok well first need to check if the machine is fitted with Ballscrews not just lead screws which you are calling Ballscrews.?

If ballscrews then 3 or 4Nm Nema 23 motors will probably work. I've fitted loads of Both 3 & 4nm motors and to be honest see very little difference between them in performance terms so wouldn't stress over which to use. The Key is buying ones with Low inductance. No higher than 4mh ideally closer to 3mh.
These are better motor and will fit your needs.
https://www.cnc4you.co.uk/Stepper-Motor/Nema23-4Nm/Stepper-Motor-4Nm-60BYGH401-03-Nema23

If you speak to them Don't Let them Bullshit you into believeing there drives are as good or better than Leadshine AM or EM they are not.!

Yes, definitely ball-screws. This is a very high-class bit of kit and would have cost many tens of thousands when new in 1980. The slides are conventional dovetails but have low friction inserts and are automatically pressure lubricated.

Thanks for the link and recommendation - will look into it.

Sorry to keep harping on about closed loop, but what do you think about using the Leadshine Nema23 kits?

Agathon
20-11-2016, 11:47 AM
This maybe your Lucky day my friend.?

Just remembered somewhere in box I've got some motors and sure enough there was.!! And guess what they are 2 x Brand New 34's with 10mm shaft 8 wire motors model number FL86STH65-2808A-H. Think about 3.5Nm but would need to dig out motor data sheet.

Also got another 34 4 wire motor with 12mm shaft which is around 4Nm I think. SY85STH65-5904B.

Drop me PM if your interested.


Great, I'll pm you.

m_c
20-11-2016, 11:48 AM
OK, that's certainly how I would have dealt with torque issues with a conventional motor, but I thought the whole point was that torque went down as speed increases. I see that gearing down, by say 1:2 would give twice the torque, but getting the speed up to 1800 mm/min (900rpm for the motor) for rapids will mean that the motor is well outside it's optimum torque region. Or is it the case that in practice this wouldn't be an issue?

I'm about to head out, so this is a very brief explanation.
Generally smaller motors the torque doesn't drop off as quick, especially on relatively lower voltage power supplies. Larger motors can maintain a similar torque drop, however you're into high voltage drivers, which carry an additional cost. So you can quite often get better performance from a smaller motor spun faster from a lower voltage, than you can with a large motor run from a less than ideal voltage.

And that is probably as clear as mud, but I've got to go!

Agathon
20-11-2016, 11:52 AM
I'm about to head out, so this is a very brief explanation.
Generally smaller motors the torque doesn't drop off as quick, especially on relatively lower voltage power supplies. Larger motors can maintain a similar torque drop, however you're into high voltage drivers, which carry an additional cost. So you can quite often get better performance from a smaller motor spun faster from a lower voltage, than you can with a large motor run from a less than ideal voltage.

And that is probably as clear as mud, but I've got to go!

Thanks again - I think I get it. I thought I was good on electrics and motors until I started reading up on steppers!

JAZZCNC
20-11-2016, 12:18 PM
Sorry to keep harping on about closed loop, but what do you think about using the Leadshine Nema23 kits?

The 2Nm won't be enough IMO.

This machine sounds too nice to be skimping on motor so don't spoil it just for sake of feature that won't give anything more than well setup Stepper would.

For me it would boil down to 2 options. Conventional steppers with Good drives like AM/EM or Servos. Wouldn't waste money on Closed loop Steppers.

Agathon
20-11-2016, 03:56 PM
The 2Nm won't be enough IMO.

This machine sounds too nice to be skimping on motor so don't spoil it just for sake of feature that won't give anything more than well setup Stepper would.

For me it would boil down to 2 options. Conventional steppers with Good drives like AM/EM or Servos. Wouldn't waste money on Closed loop Steppers.

I certainly don't want to "spoil the ship for a ha'p'orth of tar". Ironically, that's why I was thinking of closed loop. My initial thoughts were to fit Leadshine Nema34 4Nm hybrid servos, but they are only available from China - or at twice the price from the UK. Of course, I'd love to spend hundreds on quality servos, but as a first foray into CNC I need to keep the costs down.