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  1. #1
    hi everyone
    just thought i'd share an idea for a belt driven linear gantry on a large router table
    i was going with belts to keep cost down as the wife doesn't know what i am up to yet:naughty:
    just an idea running around in my head as i am trying to gather up parts just now
    has any one any thoughts on it?
    do you think there would be to much drag on the stepper motor
    sorry for the crappy autocad drawings!!
    Tom
    Attached Files Attached Files
    Last edited by dickieto; 19-01-2010 at 04:02 AM. Reason: forgot drawing!!

  2. That is a very good idea (wished I'd thought of it :)) Reminds me of Mike Everman's servo belt idea (worth reading for belt info)

    You'll probably need to gear down the drive from the stepper/servo to the drive belt to get the desired resolution. And, make sure the belt you choose has sufficient tooth strength to put up with the dynamic load.

    I like it .

    [edit] This is dickieto's idea for those of you without a dxf viewer:
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

Name:	belt drive-1.jpg 
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ID:	1485  
    Last edited by BillTodd; 19-01-2010 at 01:58 PM.

  3. The Following User Says Thank You to BillTodd For This Useful Post:


  4. #3
    Sweet. Thats so simple, unless I'm reading it wrong. Is that in plan with the belts running through the y axis?

  5. #4
    I like the look of your idea to, could possibly use chain and sprockets ?

  6. #5
    Quote Originally Posted by BillTodd View Post
    That is a very good idea (wished I'd thought of it :)) Reminds me of Mike Everman's servo belt idea (worth reading for belt info)

    You'll probably need to gear down the drive from the stepper/servo to the drive belt to get the desired resolution. And, make sure the belt you choose has sufficient tooth strength to put up with the dynamic load.

    I like it .

    [edit] This is dickieto's idea for those of you without a dxf viewer:
    thanks bill,how do you change autocad drawings into something everyone can see?
    i tried for ages to upload these drawings!

  7. its the same idea that was documented here to avoid racking when usiing one leadscrew offset from centre. The neat idea here is to make it the drive mechanism too... and I've not seen that before! The great thing about this is the pulleys at each end run in the same direction and in sync, so this works as a drive mechanism. 15 or 20mm belts can take some punishment, so it could work well....

  8. The Following User Says Thank You to irving2008 For This Useful Post:


  9. ,how do you change autocad drawings into something everyone can see?
    Export as bmp then use Serif PhotoPlus to convert to JPG

  10. The Following User Says Thank You to BillTodd For This Useful Post:


  11. #8
    Quote Originally Posted by Ross77 View Post
    Sweet. Thats so simple, unless I'm reading it wrong. Is that in plan with the belts running through the y axis?
    thanks ross
    my plan is to build router that can take 8x4 sheets so the belts would run full length of table crossing over gantry to other side,both being driven by toothed gear reduced down from stepper motor then the back of the belts would go round idler then down the other side of router. Hope that kind of makes sense:confused:
    I wish i could just draw a bit faster and better but am just learning autocad

  12. #9
    Quote Originally Posted by irving2008 View Post
    its the same idea that was documented here to avoid racking when usiing one leadscrew offset from centre. The neat idea here is to make it the drive mechanism too... and I've not seen that before! The great thing about this is the pulleys at each end run in the same direction and in sync, so this works as a drive mechanism. 15 or 20mm belts can take some punishment, so it could work well....
    thanks once again irving.
    I use to work on a machine years ago,that worked very similarly but with wire ropes, which pulled a sledge down a passage that feed cattle.
    great what you think of when looking for cheaper alternatives than racks or ballscrews:naughty:
    do you think that the belts would deflect(bounce) to much on travel over 8 ft?

  13. Some thoughts:
    big bed so want reasonable rapids, say 10m/min (traverse 8' in 15sec) and 3m/min cutting speed max.
    assume 25kg gantry

    Force(friction) = mass * g * friction coeef = 25 * 10 * .01 (skate bearings) = 2.5N

    Force(accel) = mass * acceleration. Assume acceleration time for rapids = 0.5sec = 0.5m/sec^2, cutting =0.1sec = 0.33m/sec^2 so take accel = 0.5m/s^2 then force = 25 * 0.5 = 12.5N

    Cutting force for wood, say 10N max

    Therefore force on belt = 2.5 + 12.5 + 10 = 25N, design for 50N cutting, 30N rapids (actually spilt equally between red and white belts)

    pitch of HTD belt = 5mm = 2000teeth/min rapids, for 10t pulley = 200rpm, 60rpm for cutting. 200rpm = 666 fullsteps/sec
    Requred resolution = 0.1mm, 1 turn of pulley=50mm so need 500steps/rev = 1/4step microstepping.

    design torque = 50N @ 7.5mm radius (10t pulley) = 0.38Nm @ 60rpm, 0.23Nm @ 200rpm... a 1Nm motor should acheive this.

    Peak torque on 25mm wide 5mm pitch HTD belt is 34N, but this is split between two belts so should be OK. If not will have to go to a wider belt.. Several suppliers, such as Gates-Europe, do HTD5 belts in open-ended style up to 150mm wide but you'd have to make your own pulleys above 25mm.

    Belt tension required is around 130kgf

    Belt data from gates-europe and spd. However open-ended belting is only available in 100m rolls, so this might not be as cheap as you might think!

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