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  1. #131
    You could also try Fred at BST http://es.aliexpress.com/store/314742 email him direct for the best price

    Chia website is http://stores.ebay.com/linearmotionbearings
    Last edited by Clive S; 17-11-2015 at 06:09 PM.
    ..Clive

  2. #132
    Go with BST slightly better quality and great to deal with.

  3. #133
    Thanks guys!

    Quick question (I'll post an update later)....I'm going for HTD 5mm pitch pulleys (as suggested), what ratio should I start with for x and y axis? Also, I assume I want a larger diameter pulley for more teeth/belt contact as opposed to a smaller one?

  4. #134
    Quote Originally Posted by biketrialsdave View Post
    Thanks guys!

    Quick question (I'll post an update later)....I'm going for HTD 5mm pitch pulleys (as suggested), what ratio should I start with for x and y axis? Also, I assume I want a larger diameter pulley for more teeth/belt contact as opposed to a smaller one?
    If using typical router setup with 10mm pitch screws and steppers then you don't have a ratio so it's 1:1.
    Common pulley size is 20T. Don't go too small because there's not enough teeth engaged. Don't go too large because you increase screw inertia which affects acceleration and power required.

    The main reason for using pulleys is to lessen resonance which affects steppers. The abilty to apply a ratio is just a bonus.
    One advantage if usng say 10mm pitch is that you could apply 2:1 ratio and increase torque and resolution if ever required. Or go other way and apply ratio if you ever needed more speed but with 10mm pitch you won't anyway thats why 1:1 ratio is often used.

    Same with Z axis keep 1:1 ratio but use a 5mm pitch screw for better resolution/torque.
    Last edited by JAZZCNC; 18-11-2015 at 10:07 PM.

  5. The Following User Says Thank You to JAZZCNC For This Useful Post:


  6. #135
    Just the information I was after, all makes perfect sense. I can't thank you enough. Will have to send you something your way when I'm done!

  7. #136
    Quote Originally Posted by biketrialsdave View Post
    Just the information I was after, all makes perfect sense. I can't thank you enough. Will have to send you something your way when I'm done!
    Don't be daft it's what we do and why we are here to help each other.!. . . . just post pics and vids. .

  8. #137
    Still tons of work to go but a few pics of the latest design... I went back and reduced the overall size fairly substantially as I realised I didn't need it. I'm a lot happier with the general direction now.

    Click image for larger version. 

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  9. #138
    Coming together but . . .

    the spindle hangs a long way out in front of the gantry - what's happening with the Z axis? Can you show a side view of the Z axis ? Is it profile rails on Z - looks like they are very close together and possible you are not pocketing the ballscrew etc. therefore giving large overhang.

    Stiffness drops off significantly as you move out from the gantry so worth getting it more compact if possible.
    Building a CNC machine to make a better one since 2010 . . .
    MK1 (1st photo), MK2, MK3, MK4

  10. #139
    Dave drop that Linear stage for the Z axis it's massive weak spot on machine.

    I'd also look to beef those plates holding motors etc but other than those 2 things it's coming together nice. .

    Edit: didn't see Rout's post same thing really.

    One other thing regards the Drop bracket on the Y axis at rear it needs more support from a brace.
    Last edited by JAZZCNC; 19-11-2015 at 11:31 PM.

  11. #140
    I know what you're saying, that is a concern of mine. At the moment I'm using a thk kr33 assembly as I bought it a while back. However, I am planning to use the excess thk linear rail that I'll have left in the future. Perhaps I should design that in now...

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