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Torsion Boxes!

Discussion in 'CNC Mills/Routers' started by Sage, Feb 2, 2014.

  1. Sage

    Sage Journeyman
    Builder

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    Thought I would start a thread dedicated to building/improving Torsion Boxes. Torsion Boxes are awesome and everyone should have one or two... here is a great video of an all wood build:
    http://www.thewoodwhisperer.com/videos/episode-18-assembly-table-torsion-box/

    Being super flat, and super strong they make great work spaces, but more importantly they make a great platform to build your CNC machine on!

    Since late last year, I've been kicking around a design for a CNC. I was already planning on using V-Slot, so Marks OX build was perfectly timed. Eventually I want to take this design to much a much larger size (~1500x1500mm), and according to my research that means one of the better designs is a fully supported X axis. And that means building a large support structure, and/or a Torsion Box...

    So I made one. Since I didn't have the woodworking tools to create perfectly flat lumber, and because I love aluminum extrusion, I made mine using V-Slot! Probably not the cheapest option, but I knew it would be super strong and flat. Here is what I used:
    • ~4 1500mm 20x40 V-Slot extrusions, cut down to ~750mm lengths
    • M5 Hardware all around (10mm and cut down 90mm)
      • Some standard M5 T-Nuts
      • Some 5mm wood T-nuts (these were a ***** to find)
    • 2x Metal brackets in the corners, and then printed versions on the interior to save a bit of cash.
    • 1/2 inch MDF for the bottom skin
    • 1/4 sanded plywood for the top skin
    Cutting down the extrusion was easy because I went out a picked up a chop saw. Obviously it's critical that you get all your external lengths identical so you end up with a nice square box. I had the skins rough cut at the local hardware, and then used a flush cut router bit to get them perfect after bolting the whole thing together.

    If I had to do it over again I would work on a jig to help line up and drill the vertical holes in the extrusion (I don't have a drill press so this was done by hand). I did use a printed template to space the holes correctly, but it still required quite a bit mucking about to get everything squared up. Now that its done, and I've drilled what feels like 5000 holes in some 3/4 angle iron so I can bolt my 20x60 to the new Torsion Box (more on this later) Now I've got a great base for my upcoming CNC machine!

    What do people think? How can we make this easier to build, cheaper, better, and/or stronger? PS - the reason I went with different upper and lower skins was so that I could eventually embed 2 20x20 V-Slot extrusions as hold down rails for the table. It will make more sense later I promise.
     

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    Mark Carew likes this.
  2. CutAboveZ

    CutAboveZ Well-Known
    Builder

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    Looks good to me!

    I thought about doing the same, and priced it out. It became apparent a big chunk of the price of setting up a CNC is going to be the table. I don't have a flat spot in the shop, and dead flat by using aluminum extrusion looks appealing.

    To save costs I was looking at using aluminum box levels or screeds. The i-beam levels I looked at weren't very stable I could twist them. Online I found 3/4" x 4" x 48" aluminum screeds for $12 each. The screeds have handles so air flow could happen and this could be used for ribs in a vacuum table. Gluing the screeds down to the skins. If I could find some waterproof skins I could have a wet table. Maybe some boat building composite.

    I think I'd have the MDF or spoil on top and use the CNC to flatten it. After it spoiled, flatten it again. After a few times, flatten then glue on a fresh top.

    If I made a wooden table, I'd be tempted to level the ribs with the cnc before gluing down the top.

    With the v-slot, you open up a section of the table to clamp boards vertical to route the ends of boards if needed.

    So many choices - the v-slot makes sense as the table can be changed again and again :)
     

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