[Stepper Monkey]

For vibrating a large mass during vacuum de-bubbling, very sharp high-amplitude low-frequency shocks and varying harmonics perform better than anything else.
This is a high-falutin' way of saying we whack the form with a metal bar a lot while it is under vacuum on a spring-loaded table.

[walter]

Martin, I think you're pretty close. The E/G countertops are 'pressed' into their final shape and not 'sucked'. I'm sure there is vacuuming and vibrating but the presses are definitely there.

Article in post #634:

"At the time of production, the quartz and a very small amount of resin and color pigment are mixed until thoroughly combined and then poured into a large tray with a paper liner.
Once the mold is filled, it is moved to the vibrocompaction area, where massive presses squeeze the material to roughly half its original thickness. At the same time, a vacuum is applied and the mold vibrated to evacuate the air."

[martinw]

Martin, I think you're pretty close. The E/G countertops are 'pressed' into their final shape and not 'sucked'. I'm sure there is vacuuming and vibrating but the presses are definitely there.

Article in post #634:

"At the time of production, the quartz and a very small amount of resin and color pigment are mixed until thoroughly combined and then poured into a large tray with a paper liner.
Once the mold is filled, it is moved to the vibrocompaction area, where massive presses squeeze the material to roughly half its original thickness. At the same time, a vacuum is applied and the mold vibrated to evacuate the air."

Dear Walter,

I should have spotted that earlier.Sorry.

Anyway, what have we got here?

Crystals, vibrators industrial, vibrators personal, loud music to be played at the formwork, stuff that looks like cigarette smoke. Even "sporty stuff"

Looks like a hell of a party.

Best wishes,

Martin

[ger21]

When air is compressed, it heats up. That is why bicycle tyre pumps get hot when you pump (is this right????).

I think it gets hot from friction, Martin.

[walter]

Thanks Martin, I enjoyed that post.

I think we're pretty close here.. We may need to rework the formula a bit and raise the epoxy to 20% but we're close. Zumba's results were pretty good and he used like 25%..

We still have to use reinforcements so what's the difference..

Larry, could you comment on that?

[Geof]

I think it gets hot from friction, Martin.

No it is the compression. Google 'Ideal Gas Laws' or look it up on Wikipedia.

[martinw]

I think it gets hot from friction, Martin.

Dear Gerry,

Oh dear, I think you could be right.

I'll be back.

Best wishes,

Martin

[ger21]

No it is the compression. Google 'Ideal Gas Laws' or look it up on Wikipedia.

Not doubting that the pressure increases the temerature, but I think in this instance it is the friction. 30psi wouldn't cause a noticeable increase in temperature, would it? Too late to think about the math for the ideal Gas Law.

[lgalla]

Sandi your Quartz Cookies look good to me.I see you are talking about surface roughfness.If you want that .0005 surface you need to pour raw epoxy or micron filled with ground silica or quartz.It must overflow the sides.I will not elaborate as epoxy surface plates were covered in detail near the thread beginning.
Pressing only reduces the air bubble size.
In countertop production our mixes are 60%fill and 40%resin.Even at these high ratios de-gassing proves difficult.I have stated from the beginning 10% epoxy is going to be difficult to remove air.Check the PDF in post 718 of higher epoxy ratios and glass re-inforcement.
Just did a quick browse of many new posts and will return shortly after takin it all in
Larry

[Geof]

Not doubting that the pressure increases the temerature, but I think in this instance it is the friction. 30psi wouldn't cause a noticeable increase in temperature, would it? Too late to think about the math for the ideal Gas Law.

Do mental math. 30 psi is two atmospheres, a compression ratio of 2 to 1. A diesel engine will have a compression ratio of around 25 to 1, 12-1/2 times the bicycle pump, and will heat the compressed air to a temperature high enough to autoignite the fuel. The autoignition temperature for diesel is 210 degrees C so it has to be at least this hot or have undergone a temperature increase of around 190 degrees from an ambient temperature of 20; probably much more becasue you want to be well above autoignition.

So the bicycle pump can be expected to have a temperature increase of at least 190/12.5 or 15.2 degrees above ambient for a final temperature certainly higher than 35 degrees C.

P.S I cheated and used a calculator for 190/12.5 = 15.2

[lgalla]

(flame2)
Heat.Flame is for surface plates.Heating your E/G mix will lower the viscosity dramadically.E/G or that should read eg.1000cps epoxy at 70 F is 250cps at 95 degrees.This makes de-gassing and vibration easier.Precaution,Gel time is reduced.Only for slow epoxy.If someone comes up with the correct frequency to fluidize the dry mix,it is the way to go.
Lately we got back to concrete.The specs again are, concrete compressive stregenth 3,000 to 5000 psi.E/Q 18000 to 24000 psi.
Walter what is the Zumba post # on 20%?
Larry

[walter]

Larry, post #631

[walter]

I think the concrete info is a nice addition here- some people will definitely use "concrete" in their weldments or heavy machine bases (via rubber bags or otherwise).

I need to build the entire structure so I'm sticking with steel reinforced E/Q.

[lgalla]

Thanks Walt.
A quick pass with the torch or paint stripping gun would fluidize Zumbas foam on the top surface.Heat expands the air allowing the bubbles to burst.I appears many members assume an accurate surface is obtainable from a pour of E/G.This is only true if the bottom of the mold is the accurate surface required.Otherwise the surface plate is necessary.
Larry

[lgalla]

Walter I like the concrete posts and info also as If we could accept the higher epoxy ratio and get the same viscosity as a concrete mix,concrete vibrators should work well and solve many problems.
Larry

[pupa]

Dear Walter,

Anyway, what have we got here?

Crystals, vibrators industrial, vibrators personal, loud music to be played at the formwork, stuff that looks like cigarette smoke. Even "sporty stuff"

Looks like a hell of a party.

Best wishes,

Martin

The life of a DIY hobbyist. Always intriguing. With experiments the solutions will come thats for sure.
Pity someone specific went quiet.:stickpoke he must be partying :cheers: thinking we are :drowning: ? But not Yet!

[pupa]

Not doubting that the pressure increases the temerature, but I think in this instance it is the friction. 30psi wouldn't cause a noticeable increase in temperature, would it? Too late to think about the math for the ideal Gas Law.

Easy to use hot air, if it would help is another issue. I think the solution would lie in adding a binder that would make it less viscous and easier to handle would be the trick. There is a lot of reference to additives in the articles on the net but no specifics (Yet) the closest I can find is the pre treatment with Silane in the article I posted below. It had a massive bearing in strength increase re document thus there should be better distribution. Also their quoted ratios as found best is quite different.

The two silane coupling agents were y-aminopropyl triethoxy silane (Silane-
I) and y-methacryloxy propyl trimethoxy silane (Silane-II). These coupling
agents were applied in two ways (i) addition of the coupling agent to the resin,
and (ii) pretreatment on aggregates in aqueous medium.

[greybeard]

Quote ......Once the mold is filled, it is moved to the vibrocompaction area, where massive presses squeeze the material to roughly half its original thickness. At the same time, a vacuum is applied and the mold vibrated to evacuate the air."......
unquote

There has been a number of posts about vac/pressure, possibly started from the original posting partially quote above.

On my reading of it, the press in merely a mechanical press not air pressure in the mould.
So you have pressure and vacuum.
Regards
John

[Stepper Monkey]

I am coming into this really late, so if I repeat something already covered let me know.

I am not sure if you have already determined that only specific epoxies are suitable for your matrix, but I have worked with structural slow epoxies before that have almost the same viscosity and surface tension as water. The downside is the 12+ hour cure times unless heat is applied to bring it down to an hour or two, which is the only reason they are not often commercially used. Too slow for most production.
How do you think that composite Turquoise made up of tiny Turquiose chips is so hard, indestructible, and uniform that it can made in blocks then get slabbed into slices and made into belt buckes and the like with not even microscopic occlusions visible on it's polished surfaces? (if it's made right)
There is epoxy designed to fill even micropores in porous rock. It is used to both stabilize porous, crumbly stones for jewelry, and to let them take a polish.

Also, I have used vulcan bar and cartridge heaters to keep fluid and forms hot, that works marvelously. If heat is necessary I can't think of any better, cheaper, or more reliable way to do it and regulate it. I could fill up two screens detailing the physics behind the compressed air thing and why not to go there, just take it from me you don't want to go there. Simply hit up Grainger.

[romihs]

Sandi your Quartz Cookies look good to me.I see you are talking about surface roughfness.If you want that .0005 surface you need to pour raw epoxy or micron filled with ground silica or quartz.It must overflow the sides.I will not elaborate as epoxy surface plates were covered in detail near the thread beginning.
Pressing only reduces the air bubble size.
In countertop production our mixes are 60%fill and 40%resin.Even at these high ratios de-gassing proves difficult.I have stated from the beginning 10% epoxy is going to be difficult to remove air.Check the PDF in post 718 of higher epoxy ratios and glass re-inforcement.
Just did a quick browse of many new posts and will return shortly after takin it all in
Larry

Larry,

Thanks for the complements..
I am not concerned so much about the roughness of the surface as with the overall strength of the E/Q. My goal is to reduce the air as much as possible so that I have the strongest structure possible.

I plan to use the E/Q with metal inserts for the machine construction.
I can't remember if I've mentioned this, but I am busy building a mini CNC machine from ALU. Since stumbling across this thread, I've been (chair) myself for having spent all that money on the ALU...
So I want to replace the AUL with E/Q and inserts for the rails and all parts that need to be bolted to the base.

Regards

Sandi