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  1. #1
    Join Date
    Sep 2006
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    Australind , WA
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    Default Better choice for Couplings?

    Hi Guys,
    I wonder if there is a better choice for couplings I can use on my machine?

    The machine came with ( what I think ) are quite ridged couplings. I think they would not be very forgiving in regards to ball screw to motor misalignment ( binding )and generating noise.
    old.PNG

    I thought a better option may be this flexible type:
    new.PNG


    What do you guys think? Am I on the right track?
    Any good aussie suppliers?
    Need 8 mm x 8mm holes.

    PS: I found some light machine oil and it seems to do the job.
    Have also found a dodgy bearing and some corrosion inside the Z axis stepper, so I have ordered some bearings...(lol)
    Have to run out of things to fix soon...

    Corrosion is probably my fault. Water cooling lines were leaking a while before I could find a fix...doh.

    Steve

  2. #2
    Join Date
    May 2011
    Location
    Murray Bridge S Aust.
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    66
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    3,438

    Default

    Hi Steve,
    At a guess I'd say that the OE ones would be better than the AM's. The reasoning for my thoughts are that it looks like the OE have a urethane cross in between the metal drivers, so that would allow it more flexibility.
    The aftermarket ones that you show, I've not seen before, so I can't comment on.
    Kryn
    To grow old is mandatory, growing up is optional.

  3. #3
    Join Date
    Nov 2011
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    Sutherland Shire, Sydney
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    Default

    Have a look at 'power transmission suppliers' in the yellow pages, or call in to a bearing supplier such as BSC Motion Technology. See Couplings | BSC. There is a brand of couplings called 'Lovejoy' that have quite a range.

    Hope this is of some help.

    Alan...

  4. #4
    Join Date
    Aug 2008
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    near Rockhampton
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    5,645

    Default

    Wouldn't flexible couplings be a big no no on a CNC machine? You want the ball screw to turn with the stepper, not the coupling joint flex and then the controller thinking the machine has moved when it hasn't.
    Gold, the colour of choice for the discerning person.

  5. #5
    Join Date
    Sep 2006
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    Australind , WA
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    Default

    Thanks guys....

    RC: They allow axial offset but do not flex radially, as, like you said, they would introduce errors, if they did.
    Steve

  6. #6
    Join Date
    Jun 2013
    Location
    Tasmania
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    207

    Default

    The urethane component of the couplings it actually surprisingly hard and rigid. Certainly more than I thought they would be.

    I have these same couplers, but have yet to use them in a build but I don't think I would have any issues using them. Good alignment is probably best no matter which coupler you use.

  7. #7
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    Default

    Thanks Hornetb,
    The alignment has been cast in stone by the 'factory'. 😕
    Im just trying to allow for any misalignment.

  8. #8
    Join Date
    Oct 2004
    Location
    Southern Highlands NSW
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    1,282

    Default

    A classic device to cater for axial misalignment is the Oldham coupling.
    These don't rely on flexing, but a sliding motion. Google images for animation demo.
    They are 3 piece. The centre element can be solid metal, or to add some flexibility or shock absorption can be plastic.
    I've seen these on many things including car radios, where they are used so the knobs could be placed in various positions, to overhead camshaft bevel drives on racing motorcycles. I have one on my old Panther motorbike for the magneto drive.

  9. #9
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    Sep 2006
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    Australind , WA
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    Default

    Thanks Jordan,
    I watched a few you tube vids. Would they be prone to having backlash?

    Maybe I should just stick with the OE couplings.

  10. #10
    Join Date
    Oct 2004
    Location
    Southern Highlands NSW
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    Default

    In theory no. In practice, for an all metal type it probably should be constantly oiled. For one that is not enclosed within a lubricated system, the centre element could be a self-lubricating material.
    Talk to a rep. These are not new tech. There are many makers of various types. If you are really worried about axial misalignment, they could be a good solution.

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