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One of the all time favourites because of its ease of use and predictable results. Green sand will also retain moisture for weeks on end in a plastic garbage bin.
Green sand is the most efficient, low cost way for the hobby worker to start making moulds for metal casting. But the trouble with green sand is the need for a Muller to make your first batch. Green sand does require maintenance and looking after to get the best results, but it will last for many years for hobby use, and can be used over and over again.
Co2 Gas System & Dry Sand.
The Co2 system is also an easy system for the hobby worker to use, it is frequently used in trade schools or colleges for foundry practice instructions because of the basic equipment requirements, small batches of moulding sand can be readily made up.
Generally it is quite easy to use, and repeatable results are not difficult to achieve. However there is one thing that can be detrimental to the Co2 performance and that is if any excess moisture is contained in the sand, moisture levels above 0.5% will impair the performance of the sand and give poor moulding results.
One drawback with co2 is the rental cost of the gas bottles, and the expense of gas cylinder regulators required for correct gas line pressure. Sand consumed in the moulding process is usually discarded after each use, which could present a problem if you are constantly casting.
The Self-Set moulding Process.
The self-set system is also very easy to use, all you need is good clean foundry grade sand, a silicate resin to mix with the sand and a catalyst to create the reaction in the silicate, which normally takes around ten minutes on a warm day.
The equipment required consists of: A mixer, a small hand held power drill fitted with a simple paint mixer will suffice. And an accurate digital kitchen scale to measure precisely the chemicals you'll be using.
The silicate is quite expensive to buy, and is supplied in 20 litre and 200 litre drum sizes, the hobby foundry worker may need to cultivate a friendship with the commercial foundry operater in your area.
There are several different systems that can be used, they are too complex to explain here. Suppliers such as Foseco have free info product user guide sheets to explain exactly how to use their products. The chemicals are generally quite safe to use as long as you follow the manufactures safety instructions, as you always should.
The EPS or Full Mould System.
EPS = Expanded Poly-Styrene resembles investment casting in that a single-part flask is used, so that no parting lines-and hence no fins appear on the finished casting. It is essentially a 'one-off' process, since the consumable pattern is carved from expanded polystyrene.
This is a polymer derived from benzene and ethylene, and in its expanded form it contains only 2 % actual solid polystyrene. Readers will be familiar with the substance, which is used in the manufacture of ceiling tiles, and also as a packaging material for fragile audio & electronic equipment.
An expendable pattern, complete with runners and risers, is cut from expanded polystyrene, and is completely surrounded with dry clean sand in a simple box or can. The molten metal is then poured on to the pattern, which melts and burns very quickly, (vaporises) leaving a cavity, which is immediately occupied by the molten metal. No solid residue is formed, and the carbon dioxide and water vapour evolved in the combustion of the polystyrene do not dissolve in the molten metal, but escapes through the permeable mould sand as a gas. The EPS process does produce a very strong odour.
Moulding can be achieved merely by pouring readily available clean dry Sea Sand around the pattern. As the polystyrene burns, it produces a tacky bond between the sand grains just long enough for a skin of metal to form.
This moulding system is used extensively in the engineering industries; the process is used in the manufacture of large press-tool die-holders, and smaller components in the 'one-off category. Casting tolerances come very close to that of the investment casting technique. This system does have a wide range of applications for the experienced hobby metal caster.
If you want to learn more about how to melt and cast metal in sand please visit our web site soon. You may use this article at your website, or in your newsletter. The only requirement is inclusion of the following sentence - Article by: Col Croucher of http://www.myhomefoundry.com - the definitive source for hobby foundry workers of all ages.
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