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Change gt3 timing belts for something else??

Discussion in 'Concepts and Ideas' started by Steve hope, Oct 17, 2015.

  1. Steve hope

    Steve hope Well-Known
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    hello community,

    I built from scratch what I can only describe as a routy Ox giant.
    My bed measures approx 1500 x 3m long.

    I opted to use gt3 timing belt when I started which has been ok, drives smooth enough but....
    Has a tendency to bind if it catches anything and looses steps.

    I have been know to accidentally stick something in its path on occasion.

    So my belt runs inside the groove of the aluminium extrusion with steppers and cogs running horizontal to the aluminium.

    What I would like to do now is convert it to rack and pinion or something with similar rigidity to make the operation smoother/run better.
    Although in fairness to my build, it doesn't happen that often and I do ponder if I am being an arse for thinking this way, major upheaval = down time cutting, if it ain't broke.......!!

    Can anyone give me suggestions as to how to convert my machine, I feel like I am at a loss as the steppers run off Ox plates with delrin wheels so obviously can't squeeze it in between the profile like the belt.

    I did try a previous suggestion from a member of using an extra bit of belt run on top of the X belt tooth to tooth, but could not get it to work as effectively as I would have hoped.


    Has anyone converted their machine like this.

    Do I need to change to whole system to linear rail, trying not to spend thousands but hundreds.

    Any help and advice would be greatly appreciated.

    Kind regards


    Steve
     

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  2. Rick 2.0

    Rick 2.0 OpenBuilds Team
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    How are you driving/controlling this system? How many volts is your power supply? Are your wires properly sized for the length? Losing steps is not a belt problem but an oomph problem. Skipping/slipping is a belt problem.
     
  3. Steve hope

    Steve hope Well-Known
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    Hi Rick,

    I may have not explained myself properly, if my X hits something it does not like, the cog moves over the belt and doesn't travel along it, ergo I lose steps on my bed.
    It kind of skips rather than traveling, so not losing steps just missing part of the g code which in turn screws up my whole job, especially on a large piece, the last time was my Hoover hose, didn't connect it properly, next thing I know, X has run into it and missed a beat, enough to mess the job up which was a lot of pocketing.

    You are probably gonna say make sure everything is attached correctly! Operator error, just thinking I would rather drive through it and cut the hose than lose the steps/code/movement. Hence the thought of rack or linear rails or????
     
  4. Rick 2.0

    Rick 2.0 OpenBuilds Team
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    There are a number of solutions for slipping belts. Wider belts and belts with coarser teeth come to mind. Check the belt and pulley selection on sdp/si to get a better idea of what your options are. The other option is dual belting but you need the proper thickness of double stick tape filler below the lower belt for that to work properly. You also need to apply glue/sealant to the back of the belt to get the belt to stick to the double stick tape filler.
     
  5. Hytech2k

    Hytech2k Master
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    There's also that mod to drill a extra hole in the plate to mount a idler pulley to get more belt wrap on the stepper pulley... That's probably what I would try first. More belt wrap = less chance of it skipping... But IMHO, for a machine that large your really pushing the limits of the GT3 belt. If the idler pulley mod doesn't help then probably the next best thing would be to upsize the belts to a XL .375" or .5" wide and redesign the side plates so the belt goes above the wheels, instead of under them. That would be much cheaper than doing a major redesign for R&P...

    Hope this helps a bit...
     
    #5 Hytech2k, Oct 18, 2015
    Last edited: Oct 18, 2015
  6. Steve hope

    Steve hope Well-Known
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    Hi Rick2.0 and Hyteck2k,

    Thank you for your advice, I did previously try the duel belt system however did not have the right tape to secure it to the extrusion and sort of gave up on it.

    I think I will revisit that as my primary fix initially, using the links you sent me Rick.

    I am not sure if I understand the idler pulley correctly, do you have a better instruction, photo or details on this please.
     
  7. Hytech2k

    Hytech2k Master
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    Here's is a link to the thread where we were discussing this problem before..

    Longest x axis | OpenBuilds

    Some thing like figure 3 in the picture of the first post, or you could try with 1 idler like figure 1B, please excuse my crude drawing. Just add 1 idler pulley if space permits. I haven't tried or tested either so i'm not sure if there's even space to do this without redesigning and making the plates taller or moving the stepper up...

    PullyScetches.jpg
     
  8. Steve hope

    Steve hope Well-Known
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    Cool.

    Thank you for the explanation and images. I think if I put in the dual belt system that should get around my problems. I think I should be able to find something to sit into the slot prior to fitting my lower belt. I think with both belts pushed right up in the slot to the wheel that should eliminate any slipping.
     
  9. Rob Taylor

    Rob Taylor Veteran
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    If it's really large and requires a decent amount of torque to move around... Have you considered chain drive? Similar TPI/rev figures, but, well, can't skip. You can get smaller sized chains for robotics, but a normal size one would probably do it.

    Seems a reasonable drop-in solution unless anyone's aware of an issue with chain (backlash in the pins, or something?).
     
  10. Steve hope

    Steve hope Well-Known
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    Hi all.

    I bought idler pulley wheels, belt tensioners. Some 3m tape and some new belt to do a double belt system.
    I figure between the 3 options I must be able to cure the problem. Thanks for all your advice.
     

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