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TOOL TIME - Restoring a Vacuum table -"Done"

Heavens Eagle

Well-known member
I ran across this as one of my co-workers dad used to create and do jewelry castings. This device is for getting the air bubbles out of the investment (casting medium) before it sets up. G-Factor probably has something that does this same thing and probably resembles it for doing his bronze castings.

Anyway, you can tell it is quite old. I like antiques like this that can be put back into use and made to look interesting as well. The old guy was a bit sentimental about it I think, but when he sees the photos of it redone he should feel good in that it got a good home.

Here are the photos.

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The main use of this will be to get as many air bubbles out of the rubber molds as possible. This is important and lately has been more of a pain with the more complex items I have been making. I will also use it to try and get the little air bubbles out of the resin before it starts to set up. Basically it pulls a vacuum which makes the tiny air bubbles get huge where they rise and pop. Then release the vacuum and the returning ambient air pressure pushes the rubber for the mold or resin for a new part into all the little nooks and crannys that the bubbles were vacated from. Of course it will need a little experimentation at first.

But first things first, lets get it all put back into nice clean condition and get the defunct seals replaced on the vac pump Don't need any big oil leaks of that beast.

If there is something you would like me to cover in more detail, let me know. I am just taking a few photos of this in passing and creating the build as I go.

Thanks for looking in!
 
TOOL TIME - Restoring a Vacuum table for resin use

Nice restoration so far!

Regards,
 
TOOL TIME - Restoring a Vacuum table for resin use

I'm going to send my old gas station compressor up to you for restoration. (y)
 
TOOL TIME - Restoring a Vacuum table for resin use

Sweet.

The real beauty is when you design your mold to be vacuumed during the pour.

The vacuum removes all the air, not just bubbles in the material itself, which is where it really shines. Imagine a 1/35 'jazz hand'. The first air to go when vacuum creeps up will be the voids in the fingertips. By the time you get to 27-28 Inches of mercury the material is going to be wildly expanding with the surface looking like a bubble bath. At 29 inches, the bubbles with be bursting like it's furiously boiling soup. After a short while, that boiling, expanded mass will collapse on itself and the resin will shrink back into the mold. At that point you can leave it to setup or slowly release the vacuum, either way is fine, but if you leave it under vacuum, it has to remain under vacuum until fully set. If you release it, it has to be released before the end of the pot life.

I've poured 1/35 rifles (gate at the butt) that filled down to the sight that way. I've tried pouring them after vacuum, both under pressure and not and it's nearly impossible to completely fill a mold that thin and long without centrifical force and an exit.

The only downside is you have to design your mold with a healthy reservoir to contain the resin, about 10 times the mold capacity.
 
TOOL TIME - Restoring a Vacuum table for resin use

I'll have to send a picture of mine. Not as fancy as yours by far.

B)
 
TOOL TIME - Restoring a Vacuum table for resin use

Thanks for looking in everyone!

Terry, you should post a couple of photos, I would be interested in seeing what you use.

Sweet.

The real beauty is when you design your mold to be vacuumed during the pour.

The vacuum removes all the air, not just bubbles in the material itself, which is where it really shines. Imagine a 1/35 'jazz hand'. The first air to go when vacuum creeps up will be the voids in the fingertips. By the time you get to 27-28 Inches of mercury the material is going to be wildly expanding with the surface looking like a bubble bath. At 29 inches, the bubbles with be bursting like it's furiously boiling soup. After a short while, that boiling, expanded mass will collapse on itself and the resin will shrink back into the mold. At that point you can leave it to setup or slowly release the vacuum, either way is fine, but if you leave it under vacuum, it has to remain under vacuum until fully set. If you release it, it has to be released before the end of the pot life.

I've poured 1/35 rifles (gate at the butt) that filled down to the sight that way. I've tried pouring them after vacuum, both under pressure and not and it's nearly impossible to completely fill a mold that thin and long without centrifical force and an exit.

The only downside is you have to design your mold with a healthy reservoir to contain the resin, about 10 times the mold capacity.

Thanks for that info Jeff. I am sure that if I do anything complex that I will have to get some slower setting resin. The stuff I have been using sets up way too fast. That is fine for the small itty bitty stuff, with a one sided shallow mold.

Experimentation will be the byword for a bit I am sure. Good to know that there are some folks around here that have some experience! :woohoo: Better to ask a stupid question than to make a bunch of stupid mistakes. :bang head

I am sure there will be questions for you when I get closer to using this. Of course I am also hoping that the pump rebuilds nicely and doesn't crash and burn.
 
TOOL TIME - Restoring a Vacuum table for resin use

Keep in mind, if the pump is toast, you can get a new HVAC vacuum pump for about the same price as an AB compressor.

I've found a 7 minute pot life is a happy medium. Gives me a solid minute to mix, another to pour, then good 2-3 to achieve/release vacuum before there's any sign of reaction.

Longer works too, but then demolding time stretches out too long. At 7 minutes, I run the molds every hour on the hour for production.
 
TOOL TIME - Restoring a Vacuum table for resin use

Very cool and different project Paul!

It's looking great! Nice to see an old piece being used again!

:popcorn
 
TOOL TIME - Restoring a Vacuum table for resin use

As I posted previously the Rustolium is crap! It doesn't even want to sand off correctly. I sand it and it comes off in little rollie bits like eraser stubble from a vinyl eraser. Looks like a trip to the auto parts store to get some paint stripper. Then I will just do like I should have done in the first place and put a little filler on the areas where I had to flatten up the dents. Then sand, then primer, then paint (with good paint).

Am also debating about using a bit thicker piece of plywood on the bottom than the stuff I have. The motor and vac pump are so heavy that the steel base part could just break the 3/8 thick plywood that I have. Will think on that more later.

With the weather turning a little cooler I really want to get all the stuff on this unit done. Cool and comfortable are great, but I am not a fan of cold.
 
TOOL TIME - Restoring a Vacuum table for resin use

This is so cool. Never saw anything like this before. The fact your restoring it to be a working tool is great stuff. (y)
 
TOOL TIME - Restoring a Vacuum table for resin use

I see a trend. Our most recently departed friend and expert miniature maker, Paul Steffenson, had a vacuum pot you could SEE into. Your vacuum table ROCKS! My converted PSI Cooker may prove to opaque to be practical. :notworthy

https://www.youtube.com/watch?v=lBEn3a4TIUw
 
TOOL TIME - Restoring a Vacuum table for resin use

Thanks for the comment guys! Much appreciated!

Right now I am fighting with the cabinet and the paint. I am going to have to get some paint stripper to remove the horrible Rustolium crap. It doesn't sand off, but comes off in little rollie stuff. I would have to sand until my arm falls off to get it down to where I could paint on some primer. Also since I didn't get a good finish with the HAMMERED paint, the "mostly removed" dents are showing back up. I have some experience with working with sheet metal, but will have to use a touch of bondo filler to fully smooth out the worst dent areas.

Since we are now packing and getting ready to move to our new building at work I have not been doing much at home. With the weather getting down to the low 80's and upper 70's though I better get with it.

The original photos of the bell jar really don't do it justice. IT WAS FILTHY! :sick: Carefully cleaned it and built some styrofoam packing for it in a good box to keep it safe. It is a hand made item. Has some rough spots but for it's size it really isn't all that heavy. It will be a neat piece of furniture stuff to have around.
 
TOOL TIME - Restoring a Vacuum table for resin use

OK. I admit ignorance. I've been using Smooth Cast 320 to pour my 1/700 model castings, and I'm getting a myriad of teeny bubbles. my most recent vac time was 15 inches, and slow bleed-down to atmospheric. All my vac-exposed castings are POOP!! My epoxy-plastic is 6 months old. I vac'ed the A & B containers separately to eliminate moisture. Still no improvement. I use 20-30cc ata a time, so I have a lot left. Is it too old? 320 says "limited shelf life" right on the plastic bottles. :bang head :bang head :bang head
Your thoughts?? :notworthy
 
TOOL TIME - Restoring a Vacuum table for resin use

OK. I admit ignorance. I've been using Smooth Cast 320 to pour my 1/700 model castings, and I'm getting a myriad of teeny bubbles. my most recent vac time was 15 inches, and slow bleed-down to atmospheric. All my vac-exposed castings are POOP!! My epoxy-plastic is 6 months old. I vac'ed the A & B containers separately to eliminate moisture. Still no improvement. I use 20-30cc ata a time, so I have a lot left. Is it too old? 320 says "limited shelf life" right on the plastic bottles. :bang head :bang head :bang head
Your thoughts?? :notworthy

I have dine recently a lot of very tiny castings for the micro detail on my bigger builds. Usually I mix 5 to 10 "drops" of part B and an equal amount of A. Makes it easy to get the mix even. I measure out the part B first since it is thinner and harder to control. Part A is a bit thicker so it just doesn't run out as fast.

The last time I was casting, I notice that the part B had started to separate. It has developed a clear layer on the top. I know it is old, but as I enjoy doing the tiny pours I went ahead and thoroughly mixed it before doing my drop count. Added the same amount of part A and did the casting. On the tiny stuff I usually mix quick, pour using a steel tool I have to fill the little cavities, chase out the odd bubbles and get them to rise then apply my acrylic top plate and squeeze the excess resin with bubbles away from the mold and let it set up. I have noticed with the resin aging that a lot of miniature bubbles will tend to form from nothing within it as it sets up. It is worse if I mess with the mixed resin in the mold beyond a certain point.

If I get it right quickly and have minimal bubble chasing the parts have been OK lately. But they have also had the bubble froth effect if I mess with the resin too much. Old resin I am sure, but have so much left at this point I can play with it for a few really tiny parts. I don't mind too much if I have to make 10 or 15 micro pours to get 3 or 4 good parts at this point. If I were doing production to sell it would be a different story. Cheap practice. I also have a small watchmaker heater that I set the mold and setting resin on to help with the process. I set it where the heat level is cool enough to touch and hold my fingers on it for 5 to 10 seconds but more than that can get uncomfortable.

There are some bigger items I will be making in the near future and my tiny part process won't work too well on those thus the Vac-table.

As to the resin I use, it is made by Alumilite and is available at my local Hobby Lobby stores. Yeah it can set up quite quick, but so far has done everything I have wanted.

As to your problem, it sounds like old resin. I am sure Jeff (Ausf) knows more about this than both us put together, but my guess is he would say the same thing. :hmmm

I store my resin at room temp (about 75 degrees) in my hobby room and it has held up now for almost a year.
 
TOOL TIME - Restoring a Vacuum table for resin use

OK. I admit ignorance. I've been using Smooth Cast 320 to pour my 1/700 model castings, and I'm getting a myriad of teeny bubbles. my most recent vac time was 15 inches, and slow bleed-down to atmospheric. All my vac-exposed castings are POOP!! My epoxy-plastic is 6 months old. I vac'ed the A & B containers separately to eliminate moisture. Still no improvement. I use 20-30cc ata a time, so I have a lot left. Is it too old? 320 says "limited shelf life" right on the plastic bottles. :bang head :bang head :bang head
Your thoughts?? :notworthy

Smooth Cast is one of the best resins on the market. From your description, you are mishandling the product.

Urethane resins are so moisture sensitive that once opened, the clock is ticking. There are ways to counter it, but you need to do it carefully. The yellowish liquid is the isocyanate. It reacts with the slightest atmospheric moisture and creates a crust. You'll find that on the bottle rim, but also in your nose, throat and lungs (that's what makes it dangerous). I have a friend who worked in a lab with aquariums and had an iso spill. The outgassing iso reacted with the water and formed a crust on the surface overnight and suffocated all the specimens.

I decant the gallon kits in smaller poly prop bottles to handle. I keep them in sealed plastic bags and only open them for the absolute shortest amount of time it takes to pour, then seal them before mixing. I've kept kits of 300, 310 and 320 fresh for years that way. You can't vacuum out the moisture, you can only add an inert gas to the container to push out the air.

In terms of vacuum, it's a extremely specific act, it's not like vacuum forming plastic. It needs to be 29 inches, anything less is actually worse since it doesn't pull the bubbles out, just makes more.

It's really a Catch-22. You must shake the containers to mix or you risk a bad run, but that creates bubbles. Mixing the two components creates bubbles. Pouring creates bubbles. The only way to beat it is by pulling 29 inches until it collapses on itself.
 
TOOL TIME - Restoring a Vacuum table for resin use

Thanks Jeff I knew you would know a lot more than I would.

Do you have any idea what is going on with my part B (it is the tan colored liquid) It has in the last month started to separate. The tan part is on the bottom and a clear layer now about an inch thick is on the top. They will mix fairly well as I swirl the bottle a fair amount rather than just shake it. Both my bottles have the tips with the little red caps which I can meter out a few drops at a time. Have very little crusting. I always wipe the tip off with a paper towel and recap it immediately. The part A is a clear liquid and is a bit thicker than the part B. It is the same as always.
 
TOOL TIME - Restoring a Vacuum table for resin use

Part A is the relatively stable, inert part. It doesn't absorb moisture and I always measure that part first and add any colorant or micro balloon to it since it isn't time critical.

I treat Part B like a time bomb. All of my containers are opaque, so I'm not sure of separation. I shake it vigorously for at least a minute for the first pour of the day and usually for 10 seconds or so before each successive pour that day. I measure, wipe the bottle and seal it. Then I mix, pour the mold and apply vacuum. While the vacuum is building, I seal Part B in two layers of giant ziplock bags, squeezing the air out. After that I take care of the Part A bottle and by then I'm reaching 29 inches. I watch it until it collapses, kill the pump, watching the timer. Depending on the remaining time, I'll either wait a bit or start the slow release of the vacuum. Once at zero, I close it all down and leave it to cure. On production days, I usually do that every hour on the hour. The whole process takes about 8-10 minutes, including de-mold, clean, pour and walk away.

After a few days the inner ziploc bag collects a sort of 'sand' of reacted Part B granules. That's what you would have in your lungs if you inhaled it direct.

I do all of this in the spray booth while wearing a respirator. Although there's no respirator (nor will there ever be) that filters isocyanates, the OV cartridge with a fine particulate filter does help get some of the other nasties out and since I'm out of the airstream, my exposure is almost nil. I was told I could wet the particle filter to trap iso, but I'm not concerned since I'm not hovering over the mold.

About 30 years ago I was working in my shop making full sized dummies. They were simple latex slushes that I'd fill with expandable foam (same iso as in resin) meant for long shots where you wouldn't see detail. One day the phone rang and it was a callback on a different question from the guy who did all that work on John Carpenters The Thing. When in conversation it came up that I was pouring these dummies in the basement with no vent he flipped out, explaining they use respirators while outside with a fan blowing away from them. It kind of made an impression on me.

Isocyanates are one of those things that creep up on you. You don't feel any ill effects until you become sensitized or have severe overexposure and develop chronic disease like asthma. Once sensitized, you can't be around them again.
 
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