Lost-wax process copying method for the metal casting. Usually one-piece forms are manufactured. The models are usually made from wax, for some years increasingly also of plastics. In the process of the procedure both the model, and the form are destroyed. Therefore it also called procedures with lost model, occasionally also as procedures with lost form. Since however still different, completely different copying methods with lost form exist, latter designation should be avoided.
Another name for the procedure is cire perdu (frz. lost wax).
According to way of the structure of form one can differentiate in:
For this all plastic materials, whose bonding agent is gypsum, count e.g. refractory clay or brick-split. The wax models are provided with an ingate and either poured over dipped into the liquid plastic material or the models with the plastic material. After the gypsum tied, the forms must be burned depending upon size some days in the drying oven at temperatures to for instance 800"°C.
These forms coat the wax model with a bowl from fireproof plastic material. The difference lies in the structure of the form. While with the above-mentioned forms the plastic material is present in liquid way, with this method the plastic material is laid on to one or more processing steps in on the wax. The most frequently used plastic materials for this are clay/tone, and loam prepared special. Since some decades also quartz sand with water glass as bonding agents, and/or other fireproof materials such as zircon and olive in and with synthetic bonding agents. The latters often find in the decoration industry, the precision investment casting or the investment casting use.
Requirements of MaterialienDas model material must be mechanically loadable, so that it does not break with a forms or one distorts. The model material must leave itself completely, this to fuses applies particularly with the precision investment casting. Even if the model should be manufactured by means of a form, it should exhibit only a small or no shrinking.
The plastic materials are multiform, but all plastic materials should exhibit a combination of the following characteristics:
For the precision investment casting are additionally necessary:
Gypsum-bound embedding masses disintegrate easily and deliver thereby sulfur, which contaminates the casting metal.
From the requirements it can be seen easily that a set of materials are applicable. Here a selection of the different materials follows:
The principle of this procedure is for thousands of years is admitting and finds at least since that 4. pre-Christian millenium application in the metal handicraft. Important centers of metalworking were starting from that 5. Millenium Bulgaria with its early Kupferminen, as well as Anatolien with Kestrel and with one of the earliest tin mines and tin production of the old world (4.Jt v.Chr.). The procedure was also the indigenen peoples of Colombia and Central America, e.g. the Muisca (Eldorado), well-known. It e.g. uses for it. Tumbaga and formed cult articles.
See also: Pour (procedures)
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