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Thread: Looking to build more stable table

  1. #21
    Join Date
    Jan 2004
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    Novato CA
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    210

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    Quote Originally Posted by Chuck Keysor View Post
    Not only would GFRC be far cheaper than granite, and lighter depending on the ingredients, you could route a form in which to cast the plenum layer. For that matter, one could integrate the base and the plenum layer as one cast piece.
    I like this idea, although if you should happen to accidently send the bit through the spoil board (which I've never done... NOT LOL), there'd be hell to pay.

  2. #22
    Join Date
    Dec 2007
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    2,341

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    Quote Originally Posted by EricSchimel View Post
    Surely that would be stable, but there'd be no reasonable way to cut a plenum into it.
    If you used a wet saw you could cut the plenum and a hole saw for the vac hook ups. or just have a counter top maker cut them for you.

  3. #23
    Join Date
    Jun 2013
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    Pasadena, CA
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    986

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    One thing I have not seen mentioned is the stiffness of the thin table, given the 8x4' dimensions and the different expension coefficients (by temperature and humidity) vs. the steel frame. I think there is no way to make a thin slab that would not move a little with environmental changes. From all the earlier proposals I think most promising would be the granite (but hard to get in 4x8 and impossibly heavy), a thick and ground MIC-6 cast aluminum plate (really expensive) or the epoxy glass concrete (would probably need some surface grinding to be flat and be super heavy as well). At the end you may effectively be looking at building a new machine.

    One low cost compromise may be to look for a sandwich torsion table design. That means lightweight rigid plates (e.g. good quality plywood) spaced apart (let's say 4 inches) by a grid of stringers. This hollow symmetrical sandwich could serve as vacuum plenum as well when sealed well. It would probably not be totally flat as constructed but the spoilboard surfacing could compensate for that. For that matter, if you glue a spoilboard on the top I would glue the same board to the bottom of the sandwich.

    Now, I have no idea if that could be fitted to your machine and you may lose some z-travel. Just talking theoretically....

    FWIW, my 3x4' machine has an 80/20 extrusion table. Works pretty well but it is just a bunch of extruded aluminum sticks. To make flat table that does not flex, I bolted them to a rigid sandwich table as mentioned above.

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