vacuum bagging bag material

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#1

Ive been having problems losing the vacuum in my bag after the vac is applied. Ive been using a vac bag tube that the seller says is nylon…looks like plastic to me…I wouldnt know the difference though. I went with a tube type bag from the manufacturer because then I only have to seal it on 2 sides with the mastic tape…reducing my potential sealing errors. Anyway, I am wondering if the bag material type only has the potential to hold a certain level of vacuum? Like polyethelene bag material can only hold X amount and nylon baggingmaterial only holds up to X amount. Is this the case? I believe my vac pump can apply 20+ inches of vac. but I havent measured. Ive checked endlessly for leaks in the bag to no avail. The part I am bagging is basically a box shape 6 inches by 6 inches.

What bagging material do the “big boys” use for autoclaving…whats the best?

THanks.

#2

Nylon is a Plastic…

I’d find the original manufacturer and ask them what you have or can you take a digital picture and post it and the roll here for us to help ID it?

I do have booklets on how to ID different types of plastics at the classroom too.

Try this little trick to find your leaks: dry bag up your mold with any type of cloth material, pull a vacuum on it, get a water sprayer and add some red food dye to it, spray it along any seams or suppected areas of leakage and you should see thru the clear (the vacuum bag is see thru isn’t it?) bag film and cloth will turn red.

Does your mold have any sharp edges? Or if inside of a box, did you use any pleats / Folds to help it conform to the shape of the mold?

You might also try getting a “seal a meal” or a heat sealer to melt a seal behind the bag sealant as a back up too.

For auto claving or even oven curing: Quality High Temp vacuum bagging.

In my classroom, we use Richmond Aircraft Products…but there’s many others like Airtech, …

#3

I also use a lot of the tube bags. The main thing that you have to be REALLY conscience of is that any sharp points on the back side of the mold will cause leaks. You can either sand down the back side to make sure there are no leaks each time before you use the mold or one thing I do is use a piece of breather cloth on the back side as padding. These tubes are really nice for smaller pieces and you cut down on material costs by not needing all the sealing tape. Another thing about using bags is that you don’t have to worry about making pleats as the extra bag space will fill the mold shapes. The ends seal with these plastic rods and C clips that go over the top of the rods pinching the bag , but not causing holes. That reminds me that another place for a leak is along these clips if you have a fold in the bag material. It needs to be flat across the top of the rods before pinching them. If you are using tape, then the standard tape sealing rules apply.

#4

Heres a pic and below is the info on the material:

[u][i]18124 - VACUUM BAGGING TUBE 2 mil,24"XYD.
$2.40

Nylon vacuum bagging tube, 2 mil, elongation at break 350+, max. use temp 350 deg F, excellent tensile strength. Sold by the lineal yard. [/i][/u]

#5

I wrap the entire 6x6 inch box in breather so I dont think sharp edges are causing leaks …not sure though. I dont use any pleats to aid the bag in hugging the part…it seems to do a good job without pleating.

I do use a Foodsaver food vacuum bagger to draw the vacuum and also one of their contaner lids as a vac hose/bag interface. There could be a leak there at the interface/ lid etc…but Ive checked a few times…removed the vac tube sealed the lid completely off etc and the bag still loses a bit of vac over time after the foodsaver is finished pulling.

For my other smaller parts Ive used the Foodsaver food vacuum bags …the ones that the Foodsaver appliance seals with heat after it pulls the vac…and those bags work awesome…seal and hold like no tomorrow. Works great for narrow smaller parts.

#6

Heres a pic of my other small part in a Foodsaver food vacuum bag…the appliance seals the bag with its heating strip after the vac is pulled. Works awesome and is very easy to use.

#7

I did a couple more layups on my box today and built a new tube bag. THe vacuum is now holding great…maybe the other bag was worn out or had small pin-hole leaks from being pulled around the corners of the box…dont know but the new bag is working great!

#8

good to hear!