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IndustryArena Forum > CNC Electronics > Servo Motors / Drives > Leblond tape turn electro-craft permanent magnet servo motor-tach
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  1. #1
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    Leblond tape turn electro-craft permanent magnet servo motor-tach

    Looking to add “modern” nc to my old tape turn. It does not have any no on it now. The servos run by some hand dials that have either a tach or resolver on them that go back to the amplifiers. These dials also have motors on them that run by using the joystick. I want to replace the amps with ones that have step / direction input. The lathe also has resolvers / encoders that are gear driven off the lead screw pulleys. So the questions I have are:

    1) what voltage would these servos run at? The nameplates are wore off so I can tell but suspect 90V or 110V maybe??? The amps run off of 110V

    2) where to fit new encoders? It will be a lot easier to replace the resolvers that are driven by the lead screw pulley, but that gear seems to be about 3:2 ratio to the motor. Plus there is a bit of lash between the gears which I suspect would result in some jitter. The tach on the back of the motor doesn’t have a shaft sticking out that I can attach to. I suppose I could remove the tach brush holders and see about fixing an encoder in its place. Is it feasible to run the encoder on a driven gear rather than the motor shaft?

  2. #2
    Community Moderator Al_The_Man's Avatar
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    Re: Leblond tape turn electro-craft permanent magnet servo motor-tach

    It has been eons since I retrofitted one of these, but I used a Mitsubishi system, the existing Electronic H.W. method is by a resolver on the H.W for the command, I cannot recall the motor details, but modern motor drives do not require a tach, these can be removed, if possible replace the tach with an encoder, using an encoder on the B.Screws if there is back lash is going to present problems. if you leave the tach in place, remove the tach brushes.
    I once had all the documentation for the TapeTurn but it was scrapped along time ago!
    Al.
    CNC, Mechatronics Integration and Custom Machine Design

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

  3. #3
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    Re: Leblond tape turn electro-craft permanent magnet servo motor-tach

    Thanks for the reply. Any thoughts on encoder resolutions? I have some 200 ppr and some 1000 ppr. Also unsure of voltage. I have a 70VDC supply and a G340 gecko drive that I was going to try testing an axis with.

  4. #4
    Community Moderator Al_The_Man's Avatar
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    Re: Leblond tape turn electro-craft permanent magnet servo motor-tach

    I would go with the 1000p/rev, which will give you 4k pulse/rev after x4.
    That drive/voltage should be fine to test the axis with.
    Al.
    CNC, Mechatronics Integration and Custom Machine Design

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

  5. #5
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    Re: Leblond tape turn electro-craft permanent magnet servo motor-tach

    I'd be curious to hear how you resolve the driver issue. As to your question 2, that should work just fine.
    James hosts the single best wiki page about steppers for CNC hobbyists on the net:
    http://www.piclist.com/techref/io/steppers.htm Disagree? Tell him what's missing! ,o)

  6. #6
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    Re: Leblond tape turn electro-craft permanent magnet servo motor-tach

    So I hooked up the power supply and gecko, but the servo seems really weak. I played with the PID trim pots over and over and got it as stiff as I could without oscillating. I am able to twist the rotor by hand when stopped until the drive faults. I also ran it to 30 rpm and 200rpm and could grab the hub and stop the motor. Maybe 70vdc is too little or perhaps the motor is wore out. It “seemed” to work fine however with the old amplifier. I say seemed because I didn’t do any machining with it and didn’t try stopping the motor like I am now. The motor doesn’t “sing” at idle like it did with the old amp. It also looks like someone opened up the motors as they scribed witness marks on the case for re-aligning. I don’t know if these demagnetize like steppers if you take them apart. Should I just get some new motors? Not sure what power would be sufficient? I think NEMA 34 225oz cont / 1100oz peak are the biggest I can use with the electronics I have.

    Edit: motors on machine are electro craft 0703-05-007

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