Shop made vacuum bag seals - anyone?

[Dengue]

Hello, I am looking to make a good leak proof clamp for a vacuum bag used in a veneer press, one that can be fitted quickly and one that is very efficient and does not allow leaking of the vacuum in the bag.

I find that the sealing tape that came with the Roarrockit bag I purchased is messy and time consuming to apply and maintain correctly, as shown in this youTube video (https://www.youtube.com/watch?v=lGOP90vNps8). I have a couple of the Quik Loc ones on order, but the suppliers advise against them say that after a few uses they start to leak.

I have looked at the ones shown here (http://www.joewoodworker.com/veneering/clamps.htm) . The dowel one (Method 3) looks good, but would be quite time consuming to apply and get right with all those clamps.

I was thinking more along the lines of something that folded down and latched quickly and securely the full length of the bag opening width.

Can anyone share their designs of a successful home made clamp please?

[Dengue]

Hello, I had a think about it and decided to build a prototype as shown below and see how tight it is.

I have a 12.7mm cove bit, and some 12mm dowel. Spraying water along the seal is supposed to be a good test, as the water appears on the workpiece, or in the test case, a sheet of butchers paper in the bag.

In the prototype, it will initially be held down by 4 clamps along its 360mm length, 120mm apart. The bag will be firmly clamped on the top of the dowel, where the dowel has deliberately been made 0.7mm smaller than the cove diameter to allow the bag of 0.8 thickness to fit neatly on top of the dowel with the top piece clamped down. In addition, the bag will be clamped along the flat surfaces on either side of the dowel by these 4 clamps. So it should really be a good efficient clamp. Hopefully.

If that works OK, the next step will be to see how it can be implemented faster than the time taken to fit 4 clamps.

Please feel free to add any suggestions and ideas

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[rob streeper]

I think you're idea would work.

What about this:

Two flat boards each face covered with some of this http://www.homedepot.com/p/Armacell-2-in-x-30-ft-R-1-Foam-Insulation-Tape-TAP18230/100539553 on both opposed faces followed by clamping as you suggest?

Cheers,
Rob

[soundman]

sorry but if you thnk you will pull a good vaccuum between any pair of plain flat surfaces clamped togther, you are dreaming.

if you are not using some sort of sealer. you'll need to fold the bag over several times and then clamp it..and you will need either a lot of clamps to keep the pressure up or a very strong clamping beam.

There have been a number of devices published over the years with varying sucess

Fine wood working had a table top of thick MDF with a tortouraous path routed each end and a matching clamping beam..it ised a lot of clamps and the bad needed to be doubled over from memory.

I remember a method that used a flat lath....like a big thick ruler...that the end of the bag was rolled over several times and then clamped with many spring clamps

remember the incomming air pressure..about 15psi.... is persistent, insistent and everywhere..it takes a fair bit of keeping out.

cheers

[rob streeper]

sorry but if you thnk you will pull a good vaccuum between any pair of plain flat surfaces clamped togther, you are dreaming.



That's why I speculated about using the boards with some of the self adhesive foam applied to the opposed faces - the foam should conform to the bag and form a pretty effective seal. If you got some nice warped boards and a hinge you could make up a single clamp vac bag closer. Why not think outside the box?

Cheers,
Rob

[Dengue]

I made a timber vacuum bag seal as per the sketch I made above, complete with locating dowels.

The seal was a success with no leakage over 8 hours of curing time for the Techniglue epoxy. I started with a vacuum cleaner, then finished it off with the manual vacuum pump supplied, with only about 20 strokes needed before it started clicking, indicating maximum vacuum.

The seal design was so successful that after the valve on the bag was released and air allowed back in after 8 hours, and the metal clamps removed, the seal would not open - I could not get the two halves apart (any suggestions as to why?). It needed a chisel to crack the two timber halves apart at one end before they separated freely.

The trick in establishing the vacuum is to make sure the open end of the bag is uniformly flat across the rod in the bottom half of the timber seal, and then put the top part on, and then put the first metal G clamp in the middle of the timber seal. The next clamps are applied either side of this centre clamp, working their way out to the sides of the bag.

Vacuum press setup

331781Vinyl vacuum bag and seal. Wedges used to keep bag apart when sliding workpiece in position. Long white masonite inserted inside the length of bag, makes it easier to slide the taped up workpiece into position

331779The workpiece consists of veneer glued with Techniglue epoxy to either side of a moisture resistant MDF panel, then nonstick paper between the veneer and the top and bottom cauls. the whole lot was taped together to prevent the veneers sliding out of position.

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Timber bag seal

331785 331782Left and right ends of the seal


331783 331784
Need to clamp the outer edges of the bags well, as this is where most leaks occur

[Dengue]

Here are the pics of the timber seal for the vacuum bag, as per the drawing above.

Made with radiata pine, a 1/2" round nose router bit, a 1/2" x 400mm rod, and two 8mm x 40mm locating dowels

331787
Dowels and rod glued to the bottom half



331786



331788