Thanks for a great video! Very informative. Your formula/recipe is pretty close to a German machine tool company's (forget which) formula: 30% granite gravel (aka "Decomposed Granite"), 30% joint sand, 30% fine quartz sand, and 10% Epoxy. Home Depot or Lowe's has everything, possibly the Epoxy as well. Joint sand has a polymer sand in it. I like the idea of adding the glass media that you are using. The granite gravel should be washed and dried, but probably unnecessary. I was trying to find crushed Feldspar as it is an extremely hard stone, but probably unnecessary. I am planning a CNC mill capable of 500X-500Y-100Z, primarily for aluminum. I see also that you have minimal structural elements in the cast. From what I've learned this is a much better approach than welding up or bolting an underlying framework for the machine. Apparently, that actually weakens the cast.
I'm glad it was helpful. I have a big tub sink that I used to wash the gravel on. Put screen wire over the drain, dumped gravel in, and washed it well. Then, spread it out in a sheet metal table and warm it with a propane blower. I did the same with the sand, but it was much longer dry times. I found that 'filter' sand actually comes clean in the bag and started using that. It was also a slightly finer grain sand. I think it's mostly used for swimming pools.
Thanks for sharing your experiences Can you also show how you vibrate your cast? That's a thing I still haven't got a good solution for. I'm just beginning with that stuff and my tests turned out pretty crappy with lots of voids, even though I used 10% epoxy
I actually didnt vibrate it, but i did compact it using several tools. Its hard to compact at first because it only wants to spread out but as the casting fills it will begin compacting more. If you increase the epoxy to 8% or more by weight it will vibrate out better but it still seems to need compaction, so i only do compaction. If your mix is pourable, try tamping it with a wooden block. It should compact to a solid mass that gets very hard. When it cures after compacting and still has voids try increasing you finer aggregate amount.
