Home Built Vacuum Chamber Box

[Dick Mahany]

I want to try my hand at stabilizing some punky and void filled Maple and Buckeye Burl pieces for pen blanks. I watched MesquiteMan's excellent video on stabilizing and decided to make a vacuum chamber box. I was lucky to find some 1/2" polycarbonate cut offs at my local plastics supplier for about $12 and made the box below. Inside dimensions are 5-1/4L x 4-5/8W x 4-1/4H. I would have liked to make it a little taller for the outgassing foam, but was limited by the size of the cutoffs. The top is baltic birch ply with adhesive backed closed cell foam from the local hobby/craft store. I used Weldon #4 fast set adhesive and had no leaks when I pulled the first vac to 26" :biggrin: I think I'd like to make the top clear as well, but this will be fine for now.

I used it to de-air some silicon RTV for a mold and I am now anxiously awaiting for the Cactus Juice to arrive so that I can turn these blanks into something useful.

 

[MesquiteMan]

Dick,

Be careful if you decide to make a clear lid. I advise against it but some folks have had some luck. The problem is that once you drill holes in the lid, you have compromised the strength of the material and it prone to cracking and failure. Also, you will likely find that polycarbonate turns milky white when used directly with Cactus Juice. That is why I don't use it myself. You may want to consider putting something on the inside of the plywood as vacuum will pull air right through it and you will not be able to achieve the best vacuum. Looks good though. Just thought I would toss out those suggestions for your consideration!

 

[Dick Mahany]

I was wondering about whether an acrylic top might be compromised by drilling / tapping. Thanks for the feedback and I'll just stay with the top as is. I was able to pull and maintain >26 inches with the 3/4 multi ply top, but I like your suggestion for improving it. I think I'll look at an MDF or hardened hardboard liner and laminate it to the underside of the top.

As far as the turning milky white, I'll just live with for as long as I can and build another one eventually. I couldn't help myself this time as the price was right. Many thanks.

 

[MesquiteMan]

Don't use MDF or hardboard as a laminate. Use a piece of plastic laminate otherwise know as the brand name Formica! MDF is just as bad, if not worse, than plywood. As a matter of fact, CNC routers frequently use MDF as their vacuum spoilboard. They apply vacuum to the bottom side of the MDF and it sucks right thorough, sucking the piece down and very firmly in place.

Based on the location in your profile and Wikipedia, it appears you are about 350' above sea level. With a good vacuum pump, you should be pulling over 29" Hg on the gauge. The maximum theoretical vacuum at your elevation on a standard atmospheric day is 29.538" Hg. At 26", you are only achieving an 88% vacuum. Assuming you are running an oil filled rotary vane pump, you should easily go over 29".

 

[Dick Mahany]

Laminate (as he slaps head !). Perfect solution. I'm in the hills here at 1000 ft above sea level. I'm running a Gast oilless rotary vane pump that I use for vacuum chucking, and it is rated for continuous duty and should be capable.

Thanks again and this place is a Gem.

 

[MesquiteMan]

Even at 1,000' asl, your max theoretical vacuum is 28.844" Hg. However, with a Gast oil-less, you will not get any better than the 26" you are currently getting. They make GREAT pumps for their intended use but that does not include deep vacuum like you can get with an oil filled rotary vane pump. It will work fine, though, just maybe not quite a good as you could potentially get.

 

[MesquiteMan]

Another suggestion...I zoomed in on your pictures and it appears you are using 4 pieces of the foam for the gasket. I suggest you cut the gasket out of one piece, like a picture frame. That way you don't have any seams to leak. If the picture is correct, you are most certainly leaking at your joints in the gasket.

 

[Dick Mahany]

4 pcs not as good as a single gasket.....agreed. The closed cell foam is inexpensive enough (as in my wife won't miss a sheet from her scrap booking supplies ) that this is a welcome suggestion. Again, thanks so much and do you think my stabilization efforts with my set up would be compromised if I only add the Formica and seamless gasket?

I'm very interested in doing the best job possible within my limitations.

 

[Kenny Durrant]

What do you use to glue or weld the chamber together? Looks good from here. I recieved my C.J. for Christmas and I love the stuff. My problem is I'm using mason jars for a chamber and it takes too much liquid to fill the empty spaces in the jar. I recieved a quart from my wife and it's already half gone. I would like something more space effecent so I don't have to use so much liquid each time I stabilize.

 

[Dick Mahany]

I used Weldon # 4 fast set (water thin) adhesive, and have also used SCI Grip #3 Very fast set adhesive with excellent results. Both work on acrylic or poycrbonate, styrene, and are water thin. I have used a plastic bottle with syringe type applicator and it works great.

There may be better alternatives since the VOC restrictions in CA may be limiting adhesive choices.

Both glues (more like solvents) are made by the same company... iPS.

 

[MesquiteMan]

Weldon #4 is what I use. It is not an adhesive but rather a solvent weld. It melts the material together and the joint is as strong as the material itself. It is mostly methylene chloride which is the same stuff in a lot of the harsh paint strippers. However, paint strippers will not work in its place, I have tried! Weldon #3 is the same thing except it is faster. Epoxy WILL NOT work, neither will CA. Remember, vacuum is a very powerful animal so please, if you don't know what you are doing, don't do it! You can have a failure that could hurt you.

 

[MesquiteMan]

My problem is I'm using mason jars for a chamber and it takes too much liquid to fill the empty spaces in the jar. I recieved a quart from my wife and it's already half gone. I would like something more space effecent so I don't have to use so much liquid each time I stabilize.

Kenny, you are aware that any unabsorbed resin is re-usable, right?

 

[MesquiteMan]

Again, thanks so much and do you think my stabilization efforts with my set up would be compromised if I only add the Formica and seamless gasket?

You are most welcome! Your efforts will be fine with just those two changes. Your limiting factor is your vacuum pump but even then, you should still get good results on most material.

 

[Kenny Durrant]

Yes Curtis I'm aware that it can be reused. It's just with the mason jar there is a lot of open space that has to be filled to submerge the blanks. Since I mainly do just pens your chamber would be by far the best way to go just not the right time. I also realize buy the time I screw up extra material and time trying to figure out how to make one it would be cheaper and SAFER to buy one from you. That way I could treat a few blanks without having to have a half gallon of C.J. Kenny