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  1. #1
    looking at doing a complete over hall of the 6 station atc on my triac.

    I want to change the 6 tool holders to 10 and replace the slow motor that only spins one way with a decent stepper that can go both ways.

    all the designing is done and ive hit a stumbling block which I need some help on - a pulley system.
    the shaft of the nema isnt long enough to stick out the bottom of the mounting part.

    so not sure how im going to get a toothed pulley system to do the job.
    but that's all I need is 2x toothed pulleys and a belt of the right length.
    as you can see from the drawing two centres are 47.5mm apart



    green = part of existing atc arm
    blue = new nema
    black = new 10 station tool holder
    red = dimensions

    see through -




    solid version



    you can just see the atc to the left here



    sorry got the white cover on

    Last edited by andy_con; 07-02-2016 at 09:32 PM.

  2. #2
    So basically you are saying you have place for <20mm wide pulleys with say both diameters no bigger than 20mm

    so at least the belt width is clear, it could be 15mm or 10mm.

    Now the big disc seems to have 20mm shaft. question is could the shaft itself be machined as a pulley or it has to be 20mm diameter and pulley over it?
    project 1 , 2, Dust Shoe ...

  3. #3
    correct, 20mm or less would be fine.

    heres another photos to explain a bit more



    you have the long steel rod with 3 holes which slides into the ally disk which holds the tools, then the cog goes on top of the ally disk. the dia of that steel rod is not changeable and will be used on the new setup. that steel rod fits perfectly into the rest of the arms and bearings etc...

    Quote Originally Posted by Boyan Silyavski View Post
    So basically you are saying you have place for <20mm wide pulleys with say both diameters no bigger than 20mm

    so at least the belt width is clear, it could be 15mm or 10mm.

    Now the big disc seems to have 20mm shaft. question is could the shaft itself be machined as a pulley or it has to be 20mm diameter and pulley over it?

  4. #4
    current setup



    so these are the bits that will remain that I have to work with
    green cast iron arm and steel rod insert which the new ally disk will mount to


  5. #5
    just been speaking to a friend with a lathe whos going to make me a little shaft extender to go on the nema so I can attached a pulley to the other end to solve the height issue.

    so I just need some recommendations on two toothed pulleys with matching belt to fit a centre distance of 47.5mm

  6. #6
    Quote Originally Posted by andy_con View Post
    so I just need some recommendations on two toothed pulleys with matching belt to fit a centre distance of 47.5mm
    simply Google "toothed belt pulley calculator" and plug in your numbers, all the major suppliers seem to have one,

    - Nick

  7. #7
    So then you are stuck with min size pulley HTD 5m 20 teeth having in mind 20mm bore:

    Click image for larger version. 

Name:	pulley.PNG 
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ID:	17543


    Then we go to the belt calculator, play a little with it and find that voilaa, if i am not wrong you have a hit.

    Click image for larger version. 

Name:	Capture.PNG 
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ID:	17544

    we search the web for the 180mm HTD 5m belt and find that indeed there is one existing in this size:

    Click image for larger version. 

Name:	the belt.PNG 
Views:	58 
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ID:	17545


    So more or less problem solved. Pulleys from belting online, contact them if they have the belt if not search and buy. its a good idea to pay them to bore the pulley as they do it well and wall thickness will be alright at 3mm as per drawing above.


    So problem solved? Right? if you want to mill them or to do them i could pass you a dxf drawing of any tooth count you need for HTD5 pulleys
    Last edited by Boyan Silyavski; 08-02-2016 at 12:51 AM.
    project 1 , 2, Dust Shoe ...

  8. #8
    So are thinking to do away with the Geneva wheel.? If so then I'd re-think it because with such large diameter disc and lot of weight then stepper may struggle to hold position good enough, esp with higher rotating speed with more weight. You'll certainly need fair ratio on it.!
    Last edited by JAZZCNC; 08-02-2016 at 01:32 AM.

  9. #9
    Quote Originally Posted by JAZZCNC View Post
    So are thinking to do away with the Geneva wheel.? If so then I'd re-think it because with such large diameter disc and lot of weight then stepper may struggle to hold position good enough, esp with higher rotating speed with more weight. You'll certainly need fair ratio on it.!
    What i wanted to say was that a stepper with a gear could do the job.
    Last edited by Boyan Silyavski; 08-02-2016 at 12:48 PM.
    project 1 , 2, Dust Shoe ...

  10. #10
    So then you are stuck with min size pulley HTD 5m 20 teeth having in mind 20mm bore:




    Then we go to the belt calculator, play a little with it and find that voilaa, if i am not wrong you have a hit.



    we search the web for the 180mm HTD 5m belt and find that indeed there is one existing in this size:




    So more or less problem solved. Pulleys from belting online, contact them if they have the belt if not search and buy. its a good idea to pay them to bore the pulley as they do it well and wall thickness will be alright at 3mm as per drawing above.


    So problem solved? Right? if you want to mill them or to do them i could pass you a dxf drawing of any tooth count you need for HTD5 pulleys


    that is perfect, thank you very much.not sure I understand it all but I will contact them with this detail and buy a bits.many many thanks
    Last edited by andy_con; 08-02-2016 at 01:47 PM.

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