Shattered tempered glass instead of gravel

Hi

I have hard time sourcing the necessary grades of sand and gravel for my very simple tabletop EG build (especially as I don´t drive and live in a city far from this sort of industry), and was thinking this morning if it would be possible to use glass instead? There is a car window repair shop right next to my client so I could probably get the glass from there.

My main consern is the smoothness of the stuff, maybe epoxy won´t stick sufficiently on it..? Then of course the size difference is not the optimum neither.

But otherwise, glass is very rigid material.

Would be cool to make a (semi)transparent machine base!

-PropellerHat

The material would probably be hard enough. But tempered glass shatters into fairly uniform bits. That would leave a lot of space to fill around each one. The ideal granite mixture contains a mixture of coarse to medium and fine particles so the smaller ones fill in the gaps between the larger ones and make a basically solid mass that just requires a little epoxy to stabilize it.

Hi

Was the site down globally or how come I couldn´t load it for many days...

Yeah , The pieces are very similar in size indeed. I found some pool filter "Glass sand" from local hardware store that could fit in the voids left by the old windshields, but there maybe should still be some other sized stuff on top of those 2.

Anyway, I have finally managed to get all the gravel and sand I needed for my build, and washed and dried it too, and today it looks like it is time for the pour!

I´ve been planning and postponing this day for 4 years :D

https://www.cnczone.com/forums/attac...d=468084&stc=1

Waitng for the result!

Oh I forgot completely to update the string!

Here it is, ready. I had horrible difficulties to remove the mold because of being lazy and stupid with trying out teflon spray instead of wax as a mold release. Had to brake the mold into chunks, then chisel down what still was attached to the cast, and finally with a heat gun and chisels I managed to peel the surface of the mold off of the cast. The surface pour went "fine" allthough one huge leak was discovered the next morning that requiered me to cast the rail surfaces again.

What really surprised me was the amount of pullup of tehe resin on the inserts that I cast in, I was hoping the resin to climb 1-2mm but it was something around 4 in the end. I then had to countersunk the inserts a lot to get rid of the hill around them, to get the bed flat.

Then of course there was ripple on the surface of the cast. I have hard time to understand this effect, since while pouring it was mirror flat. Anyway, the result is sort of smooth, you can barely feel the ripple by hand. If it looks like causing problems maybe I cast the surface again with some other resin.

This is a hobby machine so probably it is lready good enough, after the ridiculously highly resonating aluminum extrusion machine frame that I had before.

Oh yes, Normal gravels were used instead of glass :D

-PropellerHat
https://www.cnczone.com/forums/attac...d=471408&stc=1
https://www.cnczone.com/forums/attac...d=471410&stc=1
https://www.cnczone.com/forums/attac...d=471412&stc=1

Hi PH - The rippled surface is because epoxy sets in cells. A cell exotherms and gets hot which expands, this pushes the liquid epoxy next to it aside slightly and then this cell gets hot due to heat transfer and this wrinkle moves through the entire surface. Yoiu have to use a very low activity epoxy that cures very slowly to get mirror surfaces. Glas and sand is the same stuff so use glass if its free. By "pullup " do you mean the meniscus? Looks good keep us informed. Peter

Hi Peteeng

With "pullup" I mean the amount the epoxy is pulled up the inserts because of its´ surface tension. The resin I used is slow, 72hrs to get solid. And after that it still feels elastic.

I also made a test run back in the days with the same stuff in winter conditions, and it took something like 10 days to get not sticky. That time I got a bit more uneven surface, but thought it to be because of the temperature.

You can re-cast the surface layer with a high quality low viscosity bartop epoxy if you don't have flat surface to use as a mold.

Once poured, you can use a hair dryer on the resin to remove air bubbles and make it cure flat. With this method you'll only have to scrape the edges.

You can reduce the surface tension by spraying an isopropyl alcohol mist on the surface too.

Or, you could use the machine to make the bed flat using a regular spoil-board surfacing bit. That way it won't just be flat, it would be perfectly level with your rails.