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IndustryArena Forum > CNC Electronics > Spindles / VFD > 8.1kw 380v brushed DC spindle driver replacement?
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  1. #1
    Join Date
    Dec 2006
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    112

    8.1kw 380v brushed DC spindle driver replacement?

    Hello!
    I´m retrofiting an old Modig MD5000 with an 8.1kw 380v 5000rpm brused dc spindle, the old drive is broken so I´m considering if I want to use the old brushed dc spindle or pay quite a lot of money more for a new ac spindle servo motor.

    Are there any big dc spindle drivers out there for a reasonable price or is it better to suck it up and replace the hole package?

  2. #2
    Join Date
    Dec 2006
    Posts
    112

    Re: 8.1kw 380v brushed DC spindle driver replacement?

    Another option is to use a conventional ac induction motor with or without added encoder for closed loop control but I would probably loose some rpm in that way, I know I can run a small 1-2kw motor at 5000rpm but I havent tried it with a 7.5kw motor yet.

  3. #3
    Join Date
    Dec 2003
    Posts
    24216

    Re: 8.1kw 380v brushed DC spindle driver replacement?

    Is there any opportunity of getting the original repaired?
    Large DC motor controllers are very expensive. You also have to consider the condition of the motor, brushes and comm wear etc.
    Also ensure it is not just the field power registering a field loss of its power supply,
    Do you intend to run on 380 3ph supply?
    Al.
    CNC, Mechatronics Integration and Custom Machine Design

    “Logic will get you from A to B. Imagination will take you everywhere.”
    Albert E.

  4. #4
    Join Date
    Dec 2006
    Posts
    112

    Re: 8.1kw 380v brushed DC spindle driver replacement?

    Well actually I dont really want to use the old one, I replace all other electronics, motors and drivers so I would rather replace at least the spindle drive with a new one but as you say and as I have found when searching for them a new driver cost almost as much as a new ac spindle motor with driver.
    So I have to choose between a ac spindle servo with driver or a conventional ac induction motor that I have to fit an encoder to get the spindle orientation working and use a closed loop vfd to drive it.

  5. #5
    Join Date
    Dec 2003
    Posts
    24216

    Re: 8.1kw 380v brushed DC spindle driver replacement?

    Do you need C axis control for the T.C. etc? or just velocity control?
    Most ordinary VFD's use a encoder for precise revolution control but not positioning.
    One method is to use an aux C servo axis motor which is just engaged at C axis time to position.
    Al.
    CNC, Mechatronics Integration and Custom Machine Design

    “Logic will get you from A to B. Imagination will take you everywhere.”
    Albert E.

  6. #6
    Join Date
    Dec 2006
    Posts
    112

    Re: 8.1kw 380v brushed DC spindle driver replacement?

    I need it to position for toolchange and its always nice with rigid tapping.
    Its some kind of strange "poles" on the side of the spindle, or between the spindle and motor, maybe its for some electromagnetic orientation or clutches for gears, I have no documentation what so ever. Have to take it apart so see whats what.
    Its aslo quite limited with space, only max 185x185mm so a ac induction motor wont fit easily.

  7. #7
    Join Date
    Aug 2006
    Posts
    17

    Re: 8.1kw 380v brushed DC spindle driver replacement?

    How did you go with this conversion?

    I have all the documentation from this machine and have recently repaired the spindle drive on my MD5000, I could scan parts of it if there are some specifics you need.

    The "poles" you've found on the gear box are isolators for the 24V coils inside the gearbox used to select high or low gear.
    Do it by the book.. but be the author!

  8. #8
    Join Date
    Dec 2006
    Posts
    112

    Re: 8.1kw 380v brushed DC spindle driver replacement?

    Well, I removed the original spindle and motor and bought a new special made BT40 spindle and AC spindle servo motor but before we had time to mount it we sold the machine to a customer to mill in saw blades, so now we are going to fit an 18000rpm water cooled BT30 atc spindle instead

  9. #9
    Quote Originally Posted by the_ball View Post
    How did you go with this conversion?

    I have all the documentation from this machine and have recently repaired the spindle drive on my MD5000, I could scan parts of it if there are some specifics you need.

    The "poles" you've found on the gear box are isolators for the 24V coils inside the gearbox used to select high or low gear.
    Hi
    We have a MODIG MD6000 with Heidenhain TNC350 control. Would it be possible for you to send me any documents you have for your machine? I'm trying to solve a spindle orientation and tool change problem and I don't have a single piece of document on this machine.
    Best regards

  10. #10
    Join Date
    Dec 2006
    Posts
    112

    Re: 8.1kw 380v brushed DC spindle driver replacement?

    I dont have any docemtation left unfortunately, we changed all the electronics and sold it.

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