More Metal Casting with Foam

More Lost-Foam Metal Casting

I wanted to do this small plaque as an Xmas present to be given at a party @ work. When I had the idea to make this item, I thought, perfect... I'll slip this in between real castings, and be done with weeks to spare.

I grossly underestimated the time required to cut the foam (approximately 1 to 1.5hs) if you really hussle and have everything set-up. The nice contoured edge are from a router bit. The lettering is traced onto the foam, and dremelled out with an assortment of 1/16th to 1/4" bits.

The voids and imperfect pours were not necessarily from too little metal, or the speed at which it was poured.

I have mellowed considerably in the last 20 years,. there was a time when I'd have been hurling all related instruments related to this project in all possible directions. Now I quietly look either for the reason or remedy to getting it right on the next try.

After a week of mulling over the problem, I thought a higher volume of metal through the sprue and a larger head of metal could only improve things.

By using a pop can with both top and bottom cut-out a better pool of metal can be poured before it starts to work through the foam. Without the can a quantity of metal actually pours right off the top of the foam for a split second before it drops into the mold.

This requires much more sand and deeper forming boxes, but if it actually works I can live with the extra effort.

My basic idea was to increase the "Hydrostatic Pressure" of the metal or head, to completely fill-out the mold.

This is a shot of the X-Ray plaque buried in a 5 gallon bucket with the new "Can Sprue".

Anybody with similar experience, that can see an obvious flaw or an even better way (keeping in mind how cheap I am)... Please feel free to Email me with suggestions.

Finally... Success!!!

Now that's one Mother of a Sprue! Solid Aluminum.

This is straight out of the sand and hasn't had a wire brush over it yet. The black is sand that is still bonded on the surface. The sand that I used for this casting is virgin Sand-Blasting Sand... 50 lbs for $4.00 Canadian.

It's considerably coarser than I'd like, now I really have to get some fine screening.

Unrelated to the Pop-Can-Sprue, this is a neat trick I got from Roy (Chipmaker). I quickly made my initials on the drive plate with a "Hot-Glue" gun, right onto the foam.

As Roy put it, you get what looks like a smooth weld bead.

...check the "Links" page for Roy's site.

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