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Thread: Flattening my CNC's table top (finally!)

  1. #1
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    Flattening my CNC's table top (finally!)

    Well after futzing around with my dust shoe and a few other distractions, I finally got around to flattening my top... Here's a video I shot of the dry run and the first pass ...



    I built the router mount with some intentional play for this very thing. I knew it'd have to be done and was prepared. I'm kinda surprised it was as close as it was, actually. The mount has slightly oversized holes which allow me to wiggle it around a bit. I still need to play a little bit with the same adjustment in the X plane but I don't think it's too bad as I ran a couple cross passes earlier that didn't seem to have any trouble at all.

    Anywho - after a .005" second pass, all the pencil marks were gone which was nice - i figure i was out only .010" total across the entire surface. Not bad for an MDF torsion box without actually TRYING to get it very flat!

    With it now flat, I've begun the fun task of coating it with poly. My reasoning is that MDF is not uniform in density - the top surface is much denser than the inner stuff and machining off that top "skin" has exposed a much less durable surface. By thinning down poly and flooding it on till it quits soaking in, my hope is that this surface will be very durable and should accept double stick tape really well.

    I first put a 15-20% mixture of poly on, it soaked WAY in - used a whole pint jar on the first pass. The 2nd coat was a bit thicker, about 30% and soaked in another pint jar's worth. The 3rd pass today was about 50% and I had to work to get it to soak in all of that pint jar. I'll let this dry a couple days then lay down a full thickness coat and probably run a very light skimming cut to knock down any swelling - probably another couple coats of poly after that and it should be a finished surface that I can use for years.

    Thanks for lookin!
    Jason Beam
    Sacramento, CA

  2. #2
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    Dave, you should put a long string with a rubber band on it to attach to the middle of your vacuum hose, keep it off the table and out of the way, but have lots of play in it too!
    Great job!
    The pessimist complains about the wind; the optimist expects it to change; the realist adjusts the sails.
    William Arthur Ward

  3. #3
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    Stu - yeah i'm working on that very thing ... i was pleased with how well it behaved for the most part except for the dragging ... I'll be working out something for that - I was considering something like a curtain rod with a few sliding clips that would carry the weight but allow it to move fore and aft yet ...

    Still doing some headscratchin' on that one
    Jason Beam
    Sacramento, CA

  4. #4
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    Looks great, Jason. Are you planning on using it enough to warrant the space dedication, or just to see if you could? While I would love to have something like that, I don't think I'd do enough with it to justify the space required. But wew all do different things and I can't wait to see what you do with it!
    Billy B.

    "It has been said that politics is the second oldest profession. I have learned that it bears a striking resemblance to the first." - Ronald Reagan

  5. #5
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    Quote Originally Posted by Billy Burt View Post
    Looks great, Jason. Are you planning on using it enough to warrant the space dedication, or just to see if you could? While I would love to have something like that, I don't think I'd do enough with it to justify the space required. But wew all do different things and I can't wait to see what you do with it!
    That's exactly what my secret decoder ring said when I ran my wife's questions through it!

    I do plan, eventually, to use it for hire to some extent. My near term plans are to play and learn as much of it as I can and probably won't try selling anything for the first year or so. I figure it'd be unfair to charge anyone right now as I'm not sure what realistic costs are yet. Once I have a few of my own projects under my belt, I'll have a better sense of that and can start doing some business with it.

    And for my shop, this really wasn't an additional use of space. It sits where I used to have a cabinet for outfeed support. In that cabinet was a lot of air because I never got around to organizing it. There's actually a good deal of space on the shelf below and I'll likely put together some boxes or drawers for down there. In the end, I look at it more of a refinement of previously used space. That cabinet was really more about outfeed support and the CNC table is perfectly level with the TS so it's now outfeed support. By sending the gantry all the way to the side, I can still rip ply just as before.

    But I think this is the last "air" I'll be able to refine in this space - it's getting tight these days. If my brain latches on to some other obsession, I'm gonna have to add onto the building! :P
    Jason Beam
    Sacramento, CA

  6. #6
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    That's a great idea of using the table for outfeed.

    There are dozens of things that you can do with it, just need to decide if you've got time to do manufacturing or just want to have it for your own use. I had started to do zero clearance plates with mine just before I sold the last house. Found I could make them repeatedly without standing around and watching the machine. I was listing them on ebay and making a little money to pay for barley pop. However, as you said, you need to determine your cost for running the machine + wear/tear; then decide what your bottom line is for doing projects to make it worth the effort.
    Darren

    To a small child, the perfect granddad is unafraid of big dogs and fierce storms but absolutely terrified of the word “boo.” – Robert Brault

  7. #7
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    Oh ZCIs are a great idea. I like that!

    I was also casually considering the idea of designing a smaller benchtop CNC machine that I could cut parts out on for and let the buyer assemble. Like a little 18x18 or something ... or 18x24. I have a good source for aluminum and thought that might be a fun project.

    Then again - repetition doesn't sound much fun - once I've figured something out, i make one or two and then move on to the next challenge. Maybe custom signs are a better fit for my brain.
    Jason Beam
    Sacramento, CA

  8. #8
    I hope you're planning on a masonite/hardboard cover for the CNC table for its second job as an outfeed table. It'd be a shame to do all that flattening work then damage it.... in machine shops, guys get FIRED for using surface plates for anything but measurement related work.

  9. #9
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    Quote Originally Posted by David Agnew View Post
    I hope you're planning on a masonite/hardboard cover for the CNC table for its second job as an outfeed table. It'd be a shame to do all that flattening work then damage it.... in machine shops, guys get FIRED for using surface plates for anything but measurement related work.
    I'm not - i don't have the clearance, actually - maybe a formica scrap would fit - but honestly, I'm not too worried about damage from outfeed. My previous cabinet's outfeed was never damaged so i'm not terribly concerned that anything i feed through the saw would hurt the CNC. Maybe I'm having a failure of imagination here... but it doesn't seem that high a risk to me?
    Jason Beam
    Sacramento, CA

  10. #10
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    Quote Originally Posted by Jason Beam View Post
    .......But I think this is the last "air" I'll be able to refine in this space - it's getting tight these days. If my brain latches on to some other obsession, I'm gonna have to add onto the building! :P
    Come on Jason, be real here, you have a TON of unused space in your workshop, from what I've seen on your videos, TRUST ME, on this one, LOTS of under utilized space, heck, I can see bare wall all over the place
    The pessimist complains about the wind; the optimist expects it to change; the realist adjusts the sails.
    William Arthur Ward

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