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  1. #1
    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.
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  2. #2
    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.

  3. #3
    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.

  4. #4
    m_c's Avatar
    Lives in East Lothian, United Kingdom. Current Activity: Viewing Has been a member for 9-10 years. Has a total post count of 1,791. Received thanks 189 times, giving thanks to others 5 times.
    Without finding the datasheet for the original motors, 200 oz-in = 1.4Nm.
    .
    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.
    .
    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.
    Avoiding the rubbish customer service from AluminiumWarehouse since July '13.

  5. #5
    Quote Originally Posted by Agathon View Post
    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.

  6. #6
    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/0Bxr...ew?usp=sharing

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

  7. #7
    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.

  8. #8
    Quote Originally Posted by Agathon View Post
    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.

  9. #9
    Quote Originally Posted by Agathon View Post
    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.

  10. #10
    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?

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