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please need advice for long cnc router

Discussion in 'Concepts and Ideas' started by abdusalam, Jul 18, 2017.

  1. abdusalam

    abdusalam New
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    HI TEAM ...
    i have good experience in build cnc with sizes (1m*1.5m)....but now !!!!
    i want to build cnc with ( 4m*2m working area ) ,to cut wood and plastic and some aluminum .
    the speed i want for rapid is about (7000mm/min)
    maximum fade rate about (5000/min)
    so i want good accuracy and rigidity
    my spindle is 24000 RPM
    i knew that is long travel on Y axis (4m)
    do i need long ball screw ? or other like rack and pinion ? what description i want ?
    what stepper or servo motor need? what description i want ?
    because i know some problems with long ball screw ....
    no problem with cost ($) ....all i need the rigidity and accuracy
    does Rotating Ballnut design good idea ?
    any advice please
     
    #1 abdusalam, Jul 18, 2017
    Last edited: Jul 18, 2017
  2. Rob Taylor

    Rob Taylor Master
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    Rack and pinion isn't a terrible plan, as long as you don't need ultra-accuracy. Really long screws can start to get whippy without support, it's a tricky proposition.

    You might end up needing NEMA 34 motors depending on your final weight. Rotating ballnut is pretty much always a good plan- if you need the accuracy over rack and pinion, go that route.

    I'd go fixed gantry for rigidity and build a fully supported 8m long bed under it for the table to go on. I'd build it primarily from steel rectangle tube with some aluminum parts and backfill all the hollow bits with at least sand, maybe concrete. Then add your V-Slot or other rail on top of that.
     
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  3. Gary Caruso

    Gary Caruso OpenBuilds Volunteer
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    find me a 4m ball screw....? for under $1k
     
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  4. Rob Taylor

    Rob Taylor Master
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    Hey, he said cost is no object! :D
     
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  5. Jonathon Duerig

    Jonathon Duerig Journeyman
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    I would use Rack and Pinion here. It is plenty accurate enough for almost any purpose, especially with a belt reduction. Not only would ballscrews be extremely expensive at that length, you will never be able to get the speeds you want with them at that length. I switched from a lead screw to rack and pinion for my 1m x 1m system and am extremely happy with the results. Take a look at the CNC Router Parts rack and pinion system. That is the one I used and it integrated pretty well with C-Beam V-slot rails.
     
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  6. abdusalam

    abdusalam New
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    thanks for advice ....
    i think r&p is good plan
     
  7. abdusalam

    abdusalam New
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    thanks for your replay team ....
    my question
    what is the specification for rack and pinion i want for my long cnc ?
     

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