Epoxy granite vertical mill build log

[Nick]

Right so I’ve casted the base. I started by preparing the surface plate, I cleaned the underside with a wire wheel and then drilled and tapped several holes for M6 and M10 bolts, so the epoxy would anchor.

The surface plate had a hole drilled in the top when I got it, I thought this might be helpful to run wiring/pipes through, so I routed some PVC pipe to the back of the surface plate. Before I decided to cast the surface plate in epoxy, I did briefly try and cut it, I sealed this cut with silicone. I also drilled two pairs of holes in each side and passed pvc pipe through, this will let me pass some chains through to lift it.

The mould was made of melamine "furniture" board I got from wickes, sealed with silicone and then three applications of wax were applied (three was necessary in testing, it's a huge pain when it sticks). The surface plate was lowered with an engine crane face down into the mould.



Mixing the epoxy granite was the hardest part, it took ages. We did it in 25kg batches, with one person packing the mould while the other used a hand held mixer. We also had a bench grinder attached to the mould, with an eccentric weight, but it quickly ripped itself free of its base. It took just under two hours in total and I managed to add some steel plate to act as mounting points later on and a small section of steel as a future motor mount.



I let it cure for about 48 hours before removing the melamine mould.



There are some areas that haven't fully combined and some air inclusion, this is worse on the side away from the bench grinder and I think related to poor vibration. But overall i'm fairly happy with how it turned out. As a very crude test, I've put a tenth indicator on a 30cm extension and jumped up and down over the base, I can't really get it to deflect. It weighs about 220kg now.

I was also concerned that the curing epoxy would warp the surface, so I tried to map out the base with a indicator, there is very little movement (apart from the end I cut which shows about 2 thou of deviation). I also used a 2 foot straight edge, I can't pass a 0.02 mm feeler gauge under it. I don't think its warped significantly.

Next step is to scrape all of the cast iron inserts for the column, I've started to do this, its slow work, but I think will be possible. I'm going to have to think of a way to level the end of the base, my surface plate isn't big enough so i'm not entirely sure how to do this?

Nick