Vacuum bag for laminating to a curved surfaces

[foamcutter]

Has anyone used a vacuum bag for this process?
Does the vacuum pump run continuously until the glue cures?............Or is it easier to use clamps and a former?
We have a project coming up that requires us to laminate plastic sheet to a number of polystyrene formers and thought this might be a quicker way to do the job.
I have seen a couple of UK sites selling these and made a few enquiries but they won't tell you any of the potential problems.
If it speed ups the process it maybe worth the investment for this and other projects.


TIA

[tim'll fix it]

we have a dyson, so no bag here

sorry no idea

[dewaltdisney]

Although I have no practical experience with vacuum bags I do not think that they will be any good for curves. The principal is to use air pressure to push surfaces together. From memory this is 14lb per square inch so it is an effective way of creating an even pressure, ideal for flat surface veneering.

Trying to do curve is different because there is resistance present. The natural spring in the material being formed will act against the plastic bag and I do not think that once the vacuum is present that it will contain the spring.

I would stick with a clamp method for this particular job.

DWD

[Scrit]

Hi foamcutter

Vac pumps are notmally fitted with a vacuum sensor so that they cut off when the required vacuum is reached and only cycle if/when air leaks into the bag during pressing (slight leakage is inevitable). It is much easier to use this technique than forms and cauls, but you have to be careful that the veneer doesn't move slightly as the pressure goes on. One tip if you do go to vac bag is to empty the bag out as far as possible with a shop/industrial vacuum cleaner before attaching the vacuum pump - it's much faster to clear out the bulk of the air this way

The UK sites you've seen must be Air Press and Bagpress. I'd also suggest taking a look at JoeWoodworker in the USA

Scrit

[foamcutter]

Thanks for the info.

DWD.
The plastic sheet is fairly flexible so I dont imagine that it will be a problem to follow the curves. I suppose you can only use materials for laminating that have a degree of flexibility.

Scrit.

The UK sites you've seen must be Air Press and Bagpress. I'd also suggest taking a look at JoeWoodworker in the USA

That's right, I couldn't find any other suppliers. I take it that you use this process yourself, do you have any preference with the suppliers?
Would you advise get different bag sizes or just get a large one and use it for all jobs?
Do you have a problem of glue seeping out and onto the bag or do you use a contact adhesive?
I will check out the other site. Cheers
Very useful information there. Thanks Scrit

Tim

a dyson

Over here thats slang for a high maintenance partner. Hoover is middle of the road and **************** better not go into that can of worms

[Scrit]

That's right, I couldn't find any other suppliers. I take it that you use this process yourself, do you have any preference with the suppliers?

Yes. I've bought some bags from Bagpress but I made the last three bags myself. Most of the fittings (elbows, manifolds, isolator valves, etc) I've used are either Festool or Enotts (IMI Norgren) push fittings in 8 and 10mm sizes. Tube is rigid poly and best cut with a special purpose cutter. Bag closers are scrap poly water pipe, the larger size is slit to slip over the smaller one, main thing is they have to be reasonably air-tight. My current pump is a Gast, 10cfm. See JoeWoodworker for the way to make bags - my home-made ones use oversize 2-part screw-together nylon sail eyelets drilled and tapped to take 1/8in BSP fittings. I don't like the American way of using valve fittings as I found that they tend to get blocked rather easily with debris from inside the bag.

Would you advise get different bag sizes or just get a large one and use it for all jobs?

Try to size the bag as near to the size of the work as you can. The bigger the bag the longer it takes to evacuate.

Do you have a problem of glue seeping out and onto the bag or do you use a contact adhesive?

I don't use contact adhesive as I'm doing true wood veneering. My normal glue is UF (urea formaldehyde). Any seepage is simply flexed/cracked off at the end of the process as UF doesn't adhere to the bags all that well.

Scrit

[foamcutter]

Thanks again for the info scrit.