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

    Hi,

    I wanted to open my own thread for this one. Like the title says I'm designing a cycloidal gear to use in 4th axis on my mill. I'm not after high gear ratios but what I want is low backlash as possible so kept the pin number as high as I could.

    This is the first version of the design:

    - Diameter of the wheel is 100mm
    - Pins are 5mm hardened and ground steel
    - Number of pins: 40
    - Eccentricity of the wheel is 1mm
    - Thickness of the wheel is 10mm (or maybe 15mm. I don't know yet)

    Notes:
    - I'll be using a Nema 34 stepper motor to drive this gearbox.
    - I think I'll use 2 wheels.

    I'm in the beginning of this so I'm sure I'm missing some important details. I welcome your thoughts and recommendations.
    Attached Thumbnails Attached Thumbnails 2.PNG  

  2. #2
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    Re: Designing a cycloidal gear for 4th axis

    By the way I guess having the wheel 100mm diameter is a little too big.

  3. #3
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    Re: Designing a cycloidal gear for 4th axis

    New version. To make it a little smaller I reduced the pins to 30. That gives me 67mm diameter on the wheel. So the diameter of the housing will be roughly 80-90mm. Considering the 4th axis will have a 125mm chuck, is the design good? What do you think?


  4. #4
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    Re: Designing a cycloidal gear for 4th axis

    Photos of progress, please!
    I think 10 mm thick should be plenty.
    For two reduction, the first could be even a bit thinner imho.

    Cheers
    Roger

  5. #5
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    Re: Designing a cycloidal gear for 4th axis

    It's a single stage reduction. The second wheel is just for the balance.

  6. #6
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    Re: Designing a cycloidal gear for 4th axis

    Anyone knows what this bearing is? Some kind of needle roller? Looks like a good one for the eccentric.


  7. #7
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    Re: Designing a cycloidal gear for 4th axis

    The output bearing is a CSF-32. It is specifically made for harmonic drive but I already have it so I decided to use it.

  8. #8
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    Re: Designing a cycloidal gear for 4th axis

    Quote Originally Posted by Azalin View Post
    Anyone knows what this bearing is? Some kind of needle roller? Looks like a good one for the eccentric.

    That is just a custom made Roller Bearing, a regular Roller Bearing would be fine in your design
    Mactec54

  9. #9
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    Re: Designing a cycloidal gear for 4th axis

    Quote Originally Posted by Azalin View Post
    Anyone knows what this bearing is? Some kind of needle roller? Looks like a good one for the eccentric.

    These bearings are now standard bearings you can buy from a few suppliers.
    I found them on AliExpress from many sellers already, but from brands/sellers of unknown quality.

    https://www.aliexpress.com/item/4000...rch-mainSearch

    Also, they trend to be bigger than I would like. I believe they are made as spare parts to commercial eccentric cicloida lreducers from sumitomo and others.

  10. #10
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    Re: Designing a cycloidal gear for 4th axis

    Quote Originally Posted by mbello View Post
    These bearings are now standard bearings you can buy from a few suppliers.
    I found them on AliExpress from many sellers already, but from brands/sellers of unknown quality.

    https://www.aliexpress.com/item/4000...rch-mainSearch

    Also, they trend to be bigger than I would like. I believe they are made as spare parts to commercial eccentric cicloida lreducers from sumitomo and others.
    Yes, the only problem would be the eccentric would have to match the design that is being made, the problem with what you can buy would be the offset.

    This one would be better if the offset would match, https://www.aliexpress.com/item/4000...mend-recommend
    Mactec54

  11. #11
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    Re: Designing a cycloidal gear for 4th axis

    Hi,

    I cut the first disc from mild steel. It is also the first job of my mill. I used a 6mm 4 flute end mill and lost a flute during the cut but looks like the rest 3 flutes did the job well. Surface finish looks good and measurements are correct. I think I can use it.
    Attached Thumbnails Attached Thumbnails IMG_20220330_234317.jpg   IMG_20220330_234432.jpg  

  12. #12
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    Re: Designing a cycloidal gear for 4th axis

    Lost a flute?
    What sort of cutter?
    I have broken a few cutters, but I've never lost a flute.

    Cheers
    Roger

  13. #13
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    Re: Designing a cycloidal gear for 4th axis

    An ordinary 4 flute end mill. The cutting tip of the flute got broke about 1mm.

  14. #14
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    Re: Designing a cycloidal gear for 4th axis

    Hi,
    I made new discs but this time I added ten 10mm roller holes and a much larger eccentricity hole. Thickness is 6.5mm.

    Sent from my MI 5s Plus using Tapatalk

  15. #15
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    Re: Designing a cycloidal gear for 4th axis

    Quote Originally Posted by Azalin View Post
    Hi,
    I made new discs but this time I added ten 10mm roller holes and a much larger eccentricity hole. Thickness is 6.5mm.

    Sent from my MI 5s Plus using Tapatalk
    Looks Good
    Mactec54

  16. #16
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    Re: Designing a cycloidal gear for 4th axis

    Quote Originally Posted by Azalin View Post
    Hi,
    I made new discs but this time I added ten 10mm roller holes and a much larger eccentricity hole. Thickness is 6.5mm.

    Sent from my MI 5s Plus using Tapatalk

    Hi Azalin, any progress on this project?

    I'm working in a custom cycloidal gear for my project,

    I'm studying a lot, the concepts, reading a lot of articles and drawing and drawing for days... it would be nice to have someone to talk and exchange insights


    I have a Spark Erosion and Wire Erosion

  17. #17
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    Re: Designing a cycloidal gear for 4th axis

    Hi,

    I nearly finished it but the geometry wasn't perfect because the backlash in the X and Y axes. So I stopped there and started to upgrade my mill. I installed DFU ball nuts thus backlash minimized. I also changed my cycloidal design a bit. Will start on machining this week.

  18. #18
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    Re: Designing a cycloidal gear for 4th axis

    Hi Azlin,
    great thread, looking forward to how it goes.

    I considered doing the same but I came to a different conclusion to you, I thought I could buy an acceptable solution for very much less than I could make something.

    I bought this off Ebay. It has a 6.75:1 reduction, <1 arc min backlash and up to 10hp input, for $180USD new-old stock.

    Craig

  19. #19
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    Jun 2015
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    4131

    Re: Designing a cycloidal gear for 4th axis

    hello only now i had time to look over this; can i help with something ?

    the gear is simple ... trials may be needed to get it to right size, so to fit into existing reducer with low play

    as for excentric bearings, if you can't find proper ones, you could modify a standard one and adapt design

    last but not least, what joe did with 180$ seems a good deal, especially on time saved ... depends if you allready have the reducer and only need the gears, or you have to craft the entire reducer / kindly
    Ladyhawke - My Delirium, https://www.youtube.com/watch?v=X_bFO1SNRZg

  20. #20
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    Re: Designing a cycloidal gear for 4th axis

    Hi,

    what joe did with 180$ seems a good deal, especially on time saved
    That was what swayed me this way. It would be good to make a cycloidal gear reducer as Azalin is, a lot of fun and great learning opportunity, but I wanted something
    in fairly short time frame. I already have another servo reducer from the same company, Atlanta Drives, it is the next size up, (63mm cf 50mm) and has <2 arc min lash and 19.5:1
    reduction. I use it for my fourth axis. Its great and that experience led me to seek something the same for my fifth axis.

    The reducer I've got already has all the bearings and seals and all of that. I can install my fifth axis platter directly in its output bore and rely on the bearings of the reducer.

    Craig

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