Epoxy granite or mineral casting

[Swarfing]

I've been catching up on things with the forum and found this thread to be very interesting. Many years ago i worked in the flooring industry. The type of flooring our company did a lot of was expoxy resin coatings and floors. We used to do a lot of sculptured floors which had to handle high loads.

Granite was used as a high density filler for the hi loads. Silica sand was used for general use and mixing both together gave a happy medium for general use. Do'nt ask me for quantities as i can not remember but a company we did use was Flowcrete. We could order the stuff with fixed curing times.

Looking at the other thread in that link with the French build, i would have considered concreate with the thicknesses he was pouring. The advantage of epoxy resin is that you can get away with thinner sections (reinforce with mesh).

Things to think of are:

All fillers must be dry
Pea shingle makes an excelent cheap filler (wash and dry it before use)
Silica sand (paving gap filler from wickes)
This stuff shrinks
Always use mechanical mixing
Pouring too thick in one go is bad (add mesh to key pieces together), do it in a couple of pours before removing from the mould.
This stuff gets very hot so pour into moulds outside to avoid the nastys
Clean all items with thinners that are being sed within moulds
we worked to a max of 60mm for screeds in one go

if you use a release agent in the mould then you could use a gel coat to give you nice surface to paint afterwards.

Hope this helps

[mike mcdermid]

Strangley the chap Xavier mentioned this relies more closely on the principles of precasting concrete than my field of expertise which is composites and as such its just a different binder which is low enough not to exotherm with slow ARADUR hardner

Will drop the details to you guys wanting to have a play on wednesday when i'm back at work even for us in industry its a damn sit cheaper than having a machine bed fabbed they are sending me some bags 5 of quartz for trials and the Resin we already have ,and its easily obtainable

the only thing that need to be scaled down is the vibrating table

[Washout]

I've done some composite work and make the odd flight case for people using sheets of a carbon/kevlar/glass mix - the easiest way I have found of getting a glassy smooth finish is to use vacuum infusion onto a rigid sheet of perspex "mould" on a flat surface - you get glassy smooth finish with no bubbles.

Not sure, but you might be able to pull a thin infusion type resin through large sized grains of "rock" of some kind mixed with chopped fibres (I keep all my carbon/kevlar/glass off cuts for this purpose). If you can't vacuum through the aggregate, then pouring into a box mould with a perspex bottom should achieve good results. All the bubbles and crappy surface will be on the top and the shiny flat surface on the bottom, which you can then demould and flip over.

Heat would be my only concern, as large volumes which don't have a matrix of some kind tend to go off with cracks in them, but a few sheets of glass or carbon layered in the mixture should help solve that.

(Eyes up the gallon container of resin on the other side of the cave ;-) ).

Edit - nearly forgot - this link might hel with ratios http://www.talkcomposites.com/11/Res...ge-calculation

[mike mcdermid]

I've done some composite work and make the odd flight case for people using sheets of a carbon/kevlar/glass mix - the easiest way I have found of getting a glassy smooth finish is to use vacuum infusion onto a rigid sheet of perspex "mould" on a flat surface - you get glassy smooth finish with no bubbles.

Not sure, but you might be able to pull a thin infusion type resin through large sized grains of "rock" of some kind mixed with chopped fibres (I keep all my carbon/kevlar/glass off cuts for this purpose). If you can't vacuum through the aggregate, then pouring into a box mould with a perspex bottom should achieve good results. All the bubbles and crappy surface will be on the top and the shiny flat surface on the bottom, which you can then demould and flip over.

Heat would be my only concern, as large volumes which don't have a matrix of some kind tend to go off with cracks in them, but a few sheets of glass or carbon layered in the mixture should help solve that.

(Eyes up the gallon container of resin on the other side of the cave ;-) ).

Edit - nearly forgot - this link might hel with ratios Resin infusion; resin usage calculation

My interest in the bases was piqued because of previous works with carbon gantry mills,there have been discussions for stiffer machines and carbon does the job nicely

My original question was to ascertain if anyone had done this granite thing in the UK
It seems getting on to a company that can answer the questions as they manufacture the machine bases cleared all this up nicely

[Swarfing]

To answer your question ..Yes!

This was for platorms at low level height in clean rooms for machinery to sit on. One thing we added was loose fibreglass to the granite resin mix. As far as a workable idea? the answer is yes and a good one.

[D.C.]

You may want to have a chat with these guys they make an entire lathe out of concrete, not just the footings or the base and they do attach the linear rails straight to the concrete. Aparrently they were used all the time in WWII (along with concrete ships) because all the metal was going into things that kill people.

MAKE | The Concrete Lathe Project

http://concretelathe.wikispaces.com/...esign+Drawings

[WandrinAndy]

Many years ago, long before the internet, and when I lived in warmer climes, I had the whacky idea of building an outdoors pool table out of concrete instead of slate but it ended up on the round tuit list.

Now this thread's got me thinking about the idea again....

[irving2008]

INterestingly I was musing on the idea of a reinforced concrete z-axis support to replace the round column on my mill... one day in the distant future

By way of experiement I did the FEA on a 100x 100mm 5mm wall steel tube and a 100mm x 100mm concrete post, both 750mm high.

Ignoring any difficulties fixing the concrete post, the torsional stiffness wasnt so different. With an applied 200Nm twisting load 500mm out from the centre of the post :

Steel 0.34mm movement. Weight of column 34kg
Concrete 0.45mm movement, Weight 19kg. (thats with no reinforcement inside)

So with some refinement it certainly looks doable...

[m.marino]

If you want to talk to folks who work in some of the truly interesting end of Cement and ferrocement then you might want to look here Ferrocement Educational Network As they have been doing work with mesh re-enforced cement and other strangeness that makes some very interesting reading.

Michael

[steven.ji]

I do mineral casting