Vacumn Boxes

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Ron Bontz

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I am not sure where to post this. So moderators feel free to relocate.
I am needing/ wanting to build a vacuum box for infusing wood panels, etc. using "cactus juice" and other acrylic stabilizers/and or epoxies. So I can not use acrylic chambers. This brings me to using aluminum or stainless for the box. I was thinking along the lines of a box 24" long x 18" wide x 8" to 12" deep. To infuse multiple panels at once.
Most of the smaller vacuum systems I have seen were designed for pen makers and other smaller pieces of wood. The vacuum pumps are generally around 5 to 9 CFM and some are listed as creating a vacuum of 5 or 6 Pascals. So not much it seems. I am looking for a pump to go with 25"Hg at the moment. My question is what thickness should I use to avoid any collapse breaking the seal of the box. I was thinking 0.25" of either 5052 or 6061 for the sides and .375" for the bottom and top.
Is this over kill? The top will have the gauges, inlets and outlets tapped into it, but I wouldn't think would affect strength. Thanks in advance. :)
 
At a company that I worked for some twenty years ago we used vacuum boxes for mixing epoxy. The boxes were constructed from 1/2" aluminum plate and welded construction. When a vacuum was applied, there was a very noticeable deflection at the center of each panel. At 14 psi differential pressure and 900 sq. in. per panel that works out to a total force of more than 6 tons on each panel. The doors were made from acrylic, around an inch thick as I recall. An O ring seal in a captive gland should do the job. McMaster sell O ring material by the foot. The door was a plain flat panel, the groove was in the box. They were used five or six times a day , five days a week for decades.

Bob
 
So it sounds like if I went with .375 on the sides and 0.5" on the lid and bottom, I should be ok. Expensive little box. Thank you.
 
I have seen a vacuum box of similar size and thickness in aluminum, it did not hold up to vacuum. The panels flexed and quickly leaked.

I would suggest an internal/external reinforcement system and using the thickest plate everywhere.

I would really look into vacume bag systems/resin transfer as an alternative. Best of luck.
 
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I would be using .5" on all surfaces with 1.5-2" reinforcements on edge welded longitudinal on the surfaces.
 
Hi Ron,

You did not mention your panel size, but this vacuum press bag kit:
http://www.leevalley.com/en/wood/page.aspx?p=51167&cat=1,250,43298,43314,51167

advertises two bag sizes (26x28" and 14x48") and 12 psi vacuum using a small hand pump.

It might work with dies/stabilizers, but I doubt you could peel the bag off with epoxy....

I have never used it, but they do typically sell decent quality tools.

-brino
 
Flat side vessels will not hold up to that kind of negative pressure, that's why most vaccuum chambers are cylindrical or tank like. I use a stainless steel cooking pot to vac out air in silicone mold resin. I use a lid made from 1/2" lexan and a rubber gasket. The vaccuum pump was easy, I just hooked an inlet to my pancake air compressor and it will pull 27-28"hg. I have also use a piece of 6" pvc pipe for larger items like gun stocks.
 
Thanks, guys. the welded ribs sounds like a good idea. I wanted to be able to infuse several panels, about 2' long, at once with color additives, etc.. Some 10/4 wood as well.
 
Ron I would use 1-1/2 to 2 inch pieces of the same 1/2 inch material used on the walls spaced about 3 inches apart.
 
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