Building a Vacuum Chamber

[BJohn]

Maybe it is just because I like building as much of my stuff as I can.

But has anyone built their own vacuum chamber? If so can you advise me on your thoughts like in what wall thickness is adequate? Plan on using a clear acrylic is 1/4" thick enough or would it be best to jump up to the 3/8" or 1/2"?

What is best to use for the lid?

 

[ed4copies]

I suspect it will be helpful if you mention the dimensions you have in mind. Acrylic will flex, so the longer it is, the more this could be a problem.

FWIW,
Ed

 

[BJohn]

Not large at all, maybe 8"X8" or like a sheet of paper 8"X12"

 

[Chasper]

I built one using a thick glass cake cover as a bell jar. The sucking end of the vacuum was a tube that came up from the bottom through a heavy factory finished piece of plywood. I really liked the way it worked in that being transparent I could see what was going on with the cup of resin or mold that was being vacuumed. The problem was with getting it to seal properly. I put a sheet of semi-soft rubber on the base platform, that helped. I used a wide piece of sand paper to smooth out the rim of the cake cover, that helped. But the only way I could get it to consistently work was to run hot water over the 1/8 inch rubber sheet so it was flexible enough to accommodate the imperfections in the cake cover.

Ultimately I threw it away and just use my paint pot for a vacuum. I think it would have worked if I had the patience to get the cake cover more smooth and even. There was no issue about the cake cover being strong enough. Other than the pump it cost about $15 to make it,

 

[BJohn]

How is it working out with the pressure pot? I would think that not being able to see the stabilization process in the works would be an issue?

 

[Janster]

..using a plastic or plexiglass lid would take care of the visual issue. .Jan

 

[MesquiteMan]

John,

For 8x8, you would need 1/2" acrylic. For much larger, you would need 3/4" acrylic. Anything less WILL fail! I would probably duplicate some that you see on e-bay and use a metal cooking pan with a clear lid. It is not as good as having a chamber that you can actually see through, though.

 

[BJohn]

Hi Curtis, no I don't like the idea of the cooking pan with clear lid. I kind of thought the 1/2" would be best. It's all over ebay at what looks like reasonable prices. Just have to plan it out.

Do you bring any parts/inventory to SWAT or just take orders then ship when you return? If so if I let you know a week or so ahead of time could you bring something there for me?

 

[BJohn]

Hey Curtis by the way how's your wife doing, still getting better I hope.

 

[William Menard]

I use a food saver machine with the clear acrylic storage containers from foodsaver

 

[KenV]

John

If you are headed to stabilization, you will be creating a bit shy of 15 pounds force per square inch on every square inch of surface.

To save some mess, be a bit conservative. Note that few pressure vessels have rectalinier shapes.

 

[BJohn]

William Really that sounds interesting and you get enough vacuum to get the air out of the wood.

 

[Bocere1]

Second Curtis' post. I've built two that size using 1/2, thinner would not have worked, built one bigger using 3/4.

Know what type of plexi you have, cell cast or extruded, they use a different adhesive, I found out that straight away.

Make sure your pieces are square and your assembly is square!

Building your lid will be a challenge and if the top of your chamber is not flat, level and square it will be an even bigger challenge.

I used a soft temper 1/8 Nitrile rubber for the gasket.

Good Luck.

BTW, I think with my trial and error and time I didn't really save much over buying from Curtis, which I would have done but I'm just not a real patient person

 

[BJohn]

Mark I thought I was the only one that has the patience problem. That plus I just like to build some things, can't buy everything already built

Not sure which type of plexiglass I will use yet just started looking, other then the different adhesive is there any other difference?

 

[Kendallqn]

Make sure to wait at least 24 hours for the welds to set when you make your chamber as well. I learned first hand how strong a vacuum can be if you don't. also you can buy closed cell hobby foam at micheals or hobby lobby which makes excellent gaskets.

 

[MesquiteMan]

No, a foodsaver will not produce a deep enough vacuum for the best results. It will do a fair job at best. The best foodsaver produces around a 23" vacuum at sea level. That is a 76.8% vacuum. Remember, the higher the vacuum, the more air you can remove and thus, the more resin you can get back in. A 76.8% vacuum will only remove a maximum of 76.8% of the air in the wood. Some folks think they can just let it run longer and get the same results. This is absolutely false. If your pump can only remove 76% of the air, that is all it can remove even if you let it run forever.

A rotary vane, oil filled pump as I recommend will remove as much as 99+% of the air IF the chamber is close to perfect. One word of advice on that part...foam gaskets are not completely air tight, at least none that I have tried. I used to use hobby foam for my gaskets. Then I switched to industrial neoprene foam gasket material. Both leak air. One way to verify is to put water in the chamber and pull full vac. Then tip the chamber up so the gasket area is submerged. With any of the foam materials, I was getting lots of bubbles. A better gasket material, IMO, is buna n or butyl rubber. An easy source is the local tire shop and a large innertube. Cut a gasket to fit and you will have a better seal, assuming the top of the chamber is perfectly flat and the lid is perfectly flat!

There is more that goes into building a vacuum chamber that is capable of deep vacuum than most folks realize!

As for materials to use...if you are going to try to do an acrylic chamber, make sure you use acrylic. Polycarbonate will not work well with Cactus Juice or similar copycat resins. It is likely to turn a milk jug white color. Then again, I am phasing out my acrylic chambers all together. Just too much maintenance needing to wash it out after every use.

 

[BJohn]

Ok Curtis now your killing me, what are you switching too?

And if I still go with the Acrylic what do you wash it out with when done?

Actually you can answer if you want but I think I am going to wait a month and talk with you at SWAT. So when the FAt Guy with the shaved head comes up to your booth you will know whats going on. LOL

 

[Bocere1]

John the only reason I mention the different types is that there are some sellers on ebay selling pcs at a decent price but don't mention that it is "cross-linked acrylic" (Lucite and some other brands). There are differences such as opacity, thickness variations but for the purposes of what we are building the main difference in the types are cost, cast is more, but cross linked also requires a adhesive cement like IPS #40 where extruded uses a solvent cement like #4, 3 or 16. Cast built with #40 is the best, but extruded (more common, less expensive) using #4 works. Just know which you've got.

Also, while we may not be patient, you'll need some after glue up before using, these cements may fixture at 1 or 2 hours but gain their strength over WEEKS. Mine sat 3 weeks each before I used them.

 

[Kendallqn]

Curtis is right as usual. I just tested the hobby foam with water as suggested and it does bubble. I show 29 bars at full vacuum yet with the gasket bubbling I'm guessing I'm not getting as much air as I could out of the wood. Time to switch to rubber.

 

[Bocere1]

......
There is more that goes into building a vacuum chamber that is capable of deep vacuum than most folks realize!

As for materials to use...if you are going to try to do an acrylic chamber, make sure you use acrylic. Polycarbonate will not work well with Cactus Juice or similar copycat resins. It is likely to turn a milk jug white color. Then again, I am phasing out my acrylic chambers all together. Just too much maintenance needing to wash it out after every use.

Yep, love that pvc. Now if Curtis had a couple units say 16-24" just laying around,ready to ship, NOW, I would be buying.

 

[Kendallqn]

I agree I built mine only because I'm too impatient to wait eight weeks for one. If there were a say eighteen inch one ready to ship I'd buy it as well.

 

[BJohn]

Thanks Mark for the information, yup while this project looks kinda easy, one needs to do a little research and ask questions.

Appreciate the information on the different types of glass and their adhesives. Got that noted.

I am evaluating the costs here and as much as I don't like to say, it actually maybe more cost effective to buy one from Curtis.

Now if I can develop some patience I will see him at SWAT in Six weeks, I can either get more information or just by one.

Hmmmmm patience John patience.

 

[BJohn]

Got the chamber built, as far as I know it appears to be working ok. Tested it last night, using a vacuum generator it pulls about 22 in and held it for about 30 minutes without loosing any vacuum.

Any one know of another test I can run?

 

[MesquiteMan]

Yes, fill it partially with water and pull vacuum. Tilt the chamber to move the water around the seams to see if there are any leaks. Also move the water to the junction of the lid and chamber to see how your gasket is fairing.

 

[BJohn]

Yeah you mentioned the water awhile back to some one.

For now I am using a vacuum generator not a pump. 22in while is pretty good, can I get better with an actual pump? Or is what I should expect for about 500ft above sea level in the humid Arkansas air?

 

[MesquiteMan]

You can do MUCH better with a real vacuum pump. A 22" Hg vacuum at your elevation is only a 74.8% vacuum. You will only be able to remove 74.8% of the air from the wood at best. The more air you remove, the more Juice you can get back in the wood. Your maximum theoretical vacuum is 29.38" Hg so I would expect you to be able to get closer to 29" Hg with a good pump.

 

[BJohn]

Ok I had this small unit, So i will be on the look out for an actual pump. But in the mean time I will finish the testing the chamber, at this point small leaks could be keeping it from that magic 29Hg goal. Or at least closer.

Thanks Curtis

 

[MesquiteMan]

Some vacuum generators will reach close to 29" but most won't. If it is one sold by StickFast for vacuum chucking (and they claim for stabilizing!), it will only pull 25" Hg.

 

[BJohn]

Ok good to know, If I have time this evening I will finish testing and see what I can get.

It is a slow day here at work was pondering the fittings. Is there a way to check the fittings or relief valve for leakage? I can not think of any.

 

[MesquiteMan]

You can check for vacuum leaks with shaving cream. Spray the joint with shaving cream and if there is a leak, it will get sucked in. Works great.

 

[rblakemore]

JB Eliminator Vacuum Pump

Based on Curtis's advice, I was able to find a JB Eliminator vacuum pump, I have used it several times and can pull 29" hg. I am very pleased so far, I also have one of Curtis's new vacuum chambers and it has been great so far also. I also considered making an acrylic chamber, mainly for making something larger than pen blanks. I may still do so later this year.

 

[BJohn]

Ok looking at getting an actual vacuum pump, that Piece of *&^% vacuum generator from HF. Say's it will get 28.3" IMHO B.S.

So is a single stage 2.5CFM rotary vane going to cut the mustard. Or do I need to go a little bigger. Chamber is 10" X 6"

 

[MesquiteMan]

Yes. A 2.5 cfm single stage is fine. If you are thinking of the Harbor Freight one, I would suggest skipping it and going with a Robinaire 15310 for similar money. Both are still made in China but at least the Robinaire is from a company that makes vacuum pumps.

Here it is on Amazon.com for $115 delivered. I have one of these as my backup pump and my "carry to shows" pump. I also use it on my CNC router vac jig and it has been great for over a year now.

Amazon.com: Robinair 15310 VacuMaster 3 CFM Single Stage Pump: Automotive

 

[BJohn]

Thanks for all your help. I just purchased one it is not a Robinaire, but it is not a HF either 3cfm single stage. bought it off a guy locally. We'll see what happens.