[lgalla]

Calvin good find,Gast pumps are easy to find surplus and 26Hg is probably the max vacuum you would want to subject a resin to before vaporizing some of the chemicals.When you subject a mix to negative pressure the entrapped air expands or boils out the air.Suitable vessels are vacuum bell jars[very expensive]or what I came up with,I use a 10gal Binks pressure pot as the vacuum chamber.I mix 1 gallon of material in a plastic pail and put it in the "vacuum chamber"The mix will foam or expand 3X the volume as the air is released.It is only safe to de gass 1or 1&1/2 gallons at atime or it will overflow.Negative pressure is very powerful that is the reason for a pressure pot.Vacuum can be stored like an air compressor tank four reserve.An aircompressor tank will collapse under vacuum.This is to illistrate why you must have a vacuum bell jar or paint pot as a degassing vessel.I did not really want to post about this as I figgured it was beyond the hobyist.If you get a Gast pump cheap it would also be useful as a vacuum clamp or hold down on a small router.My pump is a busch capable of 28.8Hg.This gives a pressure[for clamping]of nearly 15PSI this translates to something like 2000lbs on a square foot. Very heavy clamping.On a larger note a 4'X8' vacuum table needs at least a 15Hp pump because of CFM required.A small gast pump would be a handy item in a small shop.
Walter"Is it possible to mix "polymer-concrete with epoxy"?I don't know.Polymer concrete seems to be a generic name for regular concrete with additives,polyester based concrete,or even E/G.I have also had thoughts as other posters of "stealing the padio stones "and encapuslating them in E/G.Concrete takes years to stabilizeThe Hoover Dam is not fully cured yet.
Why take the chance.After a week epoxy is fully cured and extremley stable.
I always say"don't beleive everything you read"If you guys are interested in these subjects,don't beleive me totally,Do some of your own research on the subjects I am refering to.
Larry

[Geof]

Regarding vacuum degassing.

Go to the Princess Auto website or get their catalogue. They have a vacuum oil extractor that is powered by compressed air. It is a 5 gallon tank with a venturi vacuum generator on the top and an inlet hose with long thin tubes that fit down a small hole to extract the oil.

On 100 psi air the vacuum generator can evacuate the tank to a vacuum of about 15 to 20 inches which is plenty for vacuum degassing. It is possible to use the tank as avacuum reservoir, evacuate it as far as possible and then turn on the inlet valve to apply this vacuum as quickly or slowly as you like to something.

The regular price is $CAD199 but it comes on sale sometimes at $CAD150

[lgalla]

Walter
sorry I was composing a post before seeing your post.I am sorry I dont have time right now to full read the good link,but I beleive I know the jist of the subject.Other members have asked about pulling a vacuum and "injecting the resin"Great idea I must say as I tryed it years ago.It dosen't work.
Rather than directly refering to our E/G,I will refer to RIM and you can figure it out yourself and why it has no use to our process.
Resin injection molding a process whereby a two sided mold or 2 part mold is injected with resin.Fibre reinforcments are laid into the mold and it is closed.A tube is fitted to the injection port from the resin pumps.To ensure void free parts it is recommended to pull a vacuum to remove the air first before injection.A thought occurs "why bother injecting,let the vacuum suck in the resin.Another one of my great ideas bites the dust.It would take like 5 weeks for the resin to"suck in"The resin pumps inject at 1000psi or better.I hope you get the relationship.We are not going to suck epoxy through sand for wetting.
I am sorry to say my experience is from bright ideas and blowing it.Example:
puffed wheat as a light weight filler?naw performes much better as breakfest.
Beer cans as a light filler.Yes good idea.Picture a cavity say 5"X5"X7"we have to fill with Epoxy/sand.One pour will save time but the exotherm will be too high.Solution put a beer can in the middle.This will allow less material and a path for the exotherm heat to escape.I must specify the can must be empty.:cheers:
Larry

[walter]

I must specify the can must be empty.:cheers:
Larry

Again, good info.
I was about to put the whole can in there...

[ger21]

You can make a cheap venturi vacuum system. I spent about $60 to make the one I use for veneering. Check out www.joewoodworker.com for info.

Larry, I'm assuming you mean that vacuum infusion won't work for this application. There'a a ton of good info on the subject, but you're probably right, sucking resin through sand is a diffferent story.

[lgalla]

Geof I cannot find the oil extractor in the Princess Auto website.If it is a tank without a lid it is of little use.You need a removable lid so you can put in the mix container and not have to clean the tank.
Ger,after looking at Calvins link,I am glad to see this works.It is the same as RTM without the double mold and lower pressure and slower injection or sucking.The vacuum venturi is really cool,but I assume it requires a fair CFM or large air compressor.For continious use an E-bay Gast pump may be cheaper in the long run.Sucking through sand could work,but requires lots of expencive experiements.Anyhow every shop should have a vacuum,venturi or pump as they are useful as clamps or hold downs.
Larry

[Geof]

igalla here is a picture. You will find it in the automotive section on the Princess Auto site. I was not thinking about using this as the vacuum chamber, just the vacuum generator and a vacuum reserve tank.

[walter]

Here are few more machine frames- what do you guys think?
.

[myinisjap]

i have personally done some epoxy casting on a small scale and as mentioned some where in this thread i used blasting sand and the part i made was insanely and dense and extremely difficult to drill (it destroyed a couple titanium bits) i would show pics but the part was thrown out due to a mould mess up on my part and i have never tried again although i think i may

[vger]

i have personally done some epoxy casting on a small scale and as mentioned some where in this thread i used blasting sand and the part i made was insanely and dense and extremely difficult to drill (it destroyed a couple titanium bits) i would show pics but the part was thrown out due to a mould mess up on my part and i have never tried again although i think i may

Not sure which sand you used, black beauty ? Most naturally occuring sand is fairly hard stuff. SiO2 in the form of quartz makes up a lot of it. Some comes from weathered granite sources. If you use tooling that is used in the granite industry you should be able to machine, drill, polish, etc.... Diamonds are forever... sortof

[atenman1]

Hi Walter
Are those granite or epoxy granite? Seem like they was able to place a lot of insert.

[walter]

Hi Walter
Are those granite or epoxy granite? Seem like they was able to place a lot of insert.

Seems like a granite to me. These are just examples- we don't have to match their material, rigidity or anything- we could pour them out of soap and get better results than our current DIY frames...

[Geof]

..we could pour them out of soap and get better results than our current DIY frames...

I think you exagerrate a little but it brings to mind a thought I had about using a very high melting point wax; something around 300 F. If you had a wax with a very distinct melting point not a wide range it might be possible to cast aggregate reinforced wax.

[lgalla]

I had sujested previously sandblast sand as it is readily available and graded.BLACK BEAUTY is not quartz orSiO2.It is a coal slag product.
Larry

[RotarySMP]

Doesn't sandblasting sand have an additive to stop it bindng?

[myinisjap]

Doesn't sandblasting sand have an additive to stop it bindng?

not that i know of the reason for using blasting sand is because it is strong what else can you smash against steel and keep reusing it? and the only way to machine it is with diamond tools even those get worn

[brunog]

Hello all,
I've discovered this thread yesterday and personally believe this is the way to go to build.
However, to go this way I really think that somekind of skeleton must be placed inside the E/G to give it strength and also threaded inserts and/or threaded bars to prevent from having to drill in E/G after it has come out of the mold.

Also I would make several molds to simplify the casting process and there too insert pieces of metal pipe or conduit as sleeves for bolt hole locations and cork or rubber plugs for countesinks where bolts would slide in for assembly with the other sections of E/G.

This way it becomes even simpler for a DIY project, however planning is critical so that no special tooling is necessary.

Best regards

Bruno

[walter]

As you guys saw, there is plenty of things you can do with E/G or polymer-concrete- table, gantry, frames.

Now here's my personal favourite: self-leveling-floating-table. I would use that as a table "underlayment", for accurate mounting of linear rails.
.

[JerryFlyGuy]

Walter, I've had some experiance w/ all of this,and have to say that what you've posted is what I'd do next time. Larry mentioned it to me when I was going through the process of leveling my mill and I discarded the idea as to expensive and not what I wanted. Well, now that I've gone through the process of leveling some long rails and getting everthing straight, I think I'll give this route a try next time. I ended up potting my rail mounting plates w/ Epoxy anyway, it just wasn't as simple as what you've got here..

Jerry.. [whats that saying.. about hind sight.. hrrm.. I forget..]

[walter]

Walter, I've had some experiance w/ all of this,and have to say that what you've posted is what I'd do next time. Larry mentioned it to me when I was going through the process of leveling my mill....

Jerry,
you're the Originator. Reading your threads inspired me to think differently, you've put so much work into that frame!... There had to be another way. Hence the "self leveling floating table".


Larry,
The E/G idea is gaining steam. Congratulations!
Your steel framed 6x12x4 E/G will be a hit here.
I hope to see some cool pictures!
:cheers: