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Thread: clamp or vacuum bent lamination???

  1. #1
    Join Date
    Sep 2007
    St. Louis, MO

    clamp or vacuum bent lamination???

    Apparently, my newly found free time is too torturous, so i'm cued up for the next project. I pulled out one of my older sketches that i've been mulling over for a while and have decided to build it. It's a shallow wall hung table about 5' wide and about 14" deep at the center. The front edge is radiused and returns back to the wall on either side. The top is supported by a radiused apron with an arched front. It's about 20" tall at each end (where it mounts to the wall) and about 3" tall at the center.

    The top, i'm not concerned with. It will be solid stock with a radiused dado to receive the top of the apron. The apron is the issue. It will be 3/8" or 1/2" thick, made of 1/8" layers laminated together to hold the curve. The outside radius of the apron is a hair under 30 inches. I am building a "mold" or die with the proper radius to use as my base. On that, i can either laminate the layers and clamp them over each other using a "blanket" of slats (think beefy roll top desk top) and nylon strapping, OR i can build a vacuum bag and clamp it that way. I've done the straps / slat blanket process before. It works fine, but you need to work quickly. I've got a vacuum pump, and i've read up on making vacuum bags with thick plastic sheathing such as shower curtains.

    Anyone out there with any experience with both processes willing to chime in with bits of wisdom???

    Paul Hubbman

  2. #2
    Join Date
    Oct 2006
    i`d advise against using "home made" bags.......i`ve ruined some pretty nice wood when my (multiple) attempts failed
    but a good vacuum bag is really the way to go! absolutely perfect joints with minimal fuss.
    [SIZE="1"] associated with several importers and manufacturers.[/SIZE]

  3. #3
    I gave up on the bags after several failed attempts, could not maintain the necessary vacuum till the glue dried. When I got the vacuum to hold then the bent pieces tried to poke through the vinyl, wouldn't hold the shape. (I was bending 4' long pieces. I reverted back to what I know and that is clamping to a mold. Works every time for me. But that is my experience, I know others are sworn to using vacuum bags but Knot Eye... but perhaps another time and different project.

  4. #4
    Join Date
    Oct 2006
    i`ve used the same 30mil polyurethane bag for literally thousands of laminations without fail.
    it`s kinda like trying to rip 8/4 oak with a saw you can carry......if the tool is not up to the job it`s only a matter of time before it fails.
    as far as mechanical clamps vs a vacuum bag......the failure rate in my shop is much greater for mechanical than vacuum and the labor is more than tripple when using mechanical clamps.
    i just don`t clamp laminated curves with clamps unless i can`t figure out a way to shove the assembly in a bag.
    [SIZE="1"] associated with several importers and manufacturers.[/SIZE]

  5. #5
    I've been using a vacuum bag recently; I agree with Todd; totally the way to go IMHO. As for what Pete said about the end of curved pieces not wanting to lay down we had that problem as well. We placed a wider caul strip across the end (inside the bag) to add some extra force to that area, and it worked OK. I think the best solution is to use thinner plys in your laminate so they will conture with your form easier.

  6. #6
    Sorry Bill! I called you Pete in my post

  7. #7
    Maybe, If I had more success with my attempts I would be more inclined to agree but (Just as you are doing) I go with what works for me.

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