Vacuum chamber ideas

RS at work · 2010-10-13T21:41:34+00:00

I am going to build a chamber type vacuum sealer.Unlike the Food-saver Seal-a-Meal machines that pull a weak vacuum, donot seal really well and use expensive special bags, a chamber stylehas an impulse sealer inside the chamber and the product is bagged,set inside the chamber, and sealed after you have drawn a vacuum.The reason I am going to build this is that prices for the commercialmodels start around $1,500 and you have to repack a whole lot of foodto recoup that kind of money.I think I have most of the design figured out, but I am unsure how tofabricate the chamber itself. My first thought was to use a stainlesssteel steam table pan, but I am worried that this might crush in undervacuum, as the thickest one made is only 20 gauge.My first thought was to make a tubular frame and epoxy some supportsthat could then be wired to the frame to give some support to the panto prevent it from crushing.My next thought was to layer a 1/4 inch of fiberglass on the outsideof the steam table pan using epoxy resin.Then I wondered if the pan was necessary at all or if I could justmold a fiberglass chamber over a chunk of foam or plywood and end upwith a chamber that would hold up to the pressure and the cycling.So I figured that before I went to a bunch of work and watched afailure because it was not quite strong enough, or wasted a whole lotof money overbuilding, I figured I would run it by you guys for yourthoughts.Roger Shoaf

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DoN. Nichols 15 years ago

[ ... my post snipped ... ]

O.K.

:-)

I think that the centers of some of the bumpers are support columns distributed over the top, so I'm not sure what this proves without knowing precisely where the weight was applied, and where the support columns were relative to that.

That is somewhat more meaningful.

We don't know what other support members may be present hidden from view.

O.K. They will certainly err on the conservative side.

Hmm ... I don't know the ID of your "6?" (which I presume to be

6 inch) pipe, so calculating from the OD, I come up with 28.27 square inches, or 145.6 pounds total force.

Again -- I don't trust the bonded principle. There are a lot of things which can go wrong in the bonding. And -- if you are going to try solvent bonding over a large area -- expect the solvent to be trapped in the center areas, weakening them.

And -- add to that the fact that acryllic tends to form cracks from exposure to oil (from the machine tool which fabricated the parts, unless you worked with totally clean new tools dipped in acetone to wash off the oil before cutting. Also -- all clamping surfaces will similarly need to be cleaned of oil totally.

Until I see evidence to the contrary, I am reluctant to consider two layers of Plexiglas bonded together to be any stronger than the thicker of the two individual layers.

This looks a lot smaller than what you originally wanted in volume.

Maybe -- but consider that the walls are undergong lateral force which could weaken them. Consider a pipe 20' tall supporting a load something like 80% of the calculated safe load. Then apply 20% of that force sideways to the center of the pipe. What would happen?

This -- I don't trust. Especially with the surface area being solvent glued together. How long would it take the solvent to dry in the center of the glued surface?

Well ... I tend to be rather conservative when it comes to vacuum containers.

And for the tempered glass -- what happens with that if a scratch is applied to the surface -- especially on the center of the inside, so it becomes a stress riser.

I would feel more comfortable with Lexan. It is not as brittle as Plexiglas. (Have you ever used the scribe and bend method of cutting Plexiglas?)

You're welcome.

Best of luck, DoN.

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DoN. Nichols 15 years ago

Not here! You must have created your ASCII graphics in a proportional pitch font -- which gets drastically distorted when viewed with a fixed pitch font. (The width of different characters, including spaces) is different in a proportional pitch font. If you had used a fixed pitch font, like (courier), you would have produced an easier to read image.

Just as an example, I will do a simple ASCII graphics square with multiples of various width characters in it, and you can see how well the right margin lines up on your system. Then switch to Courier (or some other fixed pitch font) and see what it looks like.

+----------------------------------------+ | | | ___________________________________ | | MMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMM | | ''''''''''''''''''''''''''''''''''' | | nnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnn | | 11111111111111111111111111111111111 | | | | QQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQ | | | | jjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjj | | | | ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, | | | | ----------------------------------- | | | | !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! | +----------------------------------------+

Now -- since I can't switch to a proportional spaced font in my newsreader, and since proportional space fonts vary somewhat even with the supposedly same font on different machines, I'll just wait.

I wish that I had an easy way to show you what it looks like on my system. :-)

At least, you didn't use tabs, which adds yet another problem, as different systems have different tab settings. :-)

Good Luck, DoN.

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Califbill 15 years ago