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IndustryArena Forum > Mechanical Engineering > Linear and Rotary Motion > Designing a cycloidal gear for 4th axis
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  1. #21
    Join Date
    Mar 2014
    Posts
    1131

    Re: Designing a cycloidal gear for 4th axis

    Hi,
    Actually a strain wave gear was my first choice but Turkey has a EUR 150 limit per order. If one goes over that amount the cost almost tripples because the customs import sh*t. So I need to build one myself.

    Craig, the one you got looks very nice. Good find.

  2. #22
    Join Date
    Nov 2013
    Posts
    4282

    Re: Designing a cycloidal gear for 4th axis

    Hi Azalin,
    I think the harmonic drive or strain wave has too greater reduction. If you look on-line you'll find 50: and 100:1 are common with only a few of 30:1.

    If you have a rotating axis like mine that would mean then even with a 3000rpm servo the best you could get is 100rpm at the chuck. I can promise you that many rotary toolpaths
    require some thousands of rotations and it will take an age at only 100rpm.

    My fourth axis has a reduction of 19.5:1 for an output speed of 150rpm, and its useful but I sure as hell do not want it to go any slower.
    For a rotary axis I would guess around 10:1 is the sweet spot, that would give me an output speed of 300rpm, and that would make my cycle times
    less.

    In the next few weeks my rotating fourth axis will become a trunnion table, and then 50:1 or 100:1 would be fine as the axis only rotates +90 to -90 degrees.

    New Zealand has a Goods and Services tax that should and usually does apply to all imports of 15%. Some low value items (<$400NZD) come in without GST
    but most other items do. For instance I had to pay GST on the servo reducer I pictured. The cost was $180USD, but the shipping cost was nearly the same and with GST
    it cost me $635NZD landed at my door. So $180USD sounds pretty good, but the reality is not quite so attractive, but still I'm happy, it is a truly superb piece of
    engineering and will serve me well, and that's what I paid for.

    Just as a matter of interest while my fourth axis will become a trunnion my C axis will be a B axis if the trunnion is rotated 90 degrees, and that would mean I have
    a 6.75:1 reduction between the 'B axis' servo and the chuck for a rotational output speed of 444 rpm, a useful increase which I look forward to to reduce the cycle times
    of my 4 axis rotary toolpaths.

    Craig

  3. #23
    Join Date
    Jun 2015
    Posts
    4131

    Re: Designing a cycloidal gear for 4th axis

    In the next few weeks my rotating fourth axis will become a trunnion table
    please, when you get close to it, share an image

    geometry wasn't perfect because the backlash in the X and Y axes.
    each machine has backlash, more or less, and for that part is important that inside holes are as true as possible to outside wavy shape, thus it requires a single fixture for both operations

    besides that, for a true indexing, is needed a rotary axis (in good condition), and not only linear axis, so, for example, a lathe with c axis will get it done, with phase identical devations, while a vmc can not do that; expected accuracy can be known, if you know your machine

    in the end, is what is available there
    Ladyhawke - My Delirium, https://www.youtube.com/watch?v=X_bFO1SNRZg

  4. #24
    Join Date
    Mar 2014
    Posts
    1131

    Re: Designing a cycloidal gear for 4th axis

    @deadlykitten, are you really in Antarctica?

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