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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).

Work procedures

  1. A desired article is modelled from wax. This is the model or wax model.
  2. The plastic material is prepared.
  3. The model will provided with gate and vent holes (in foundries such models also as "the wax" designation)
  4. The model is encased with plastic material/embedding mass; the form of planting develops.
  5. The form of planting is out-melted; the form cavity develops.
  6. Depending upon embedding mass the form is possibly burned ("celebration bricked in the earth stands the form from loam burned"…")
  7. Melted metal is poured into the form.
  8. The metal solidifies in the form.
  9. The form is smashed, in order to infer the raw casting.

Variants of the lost-wax process

According to way of the structure of form one can differentiate in:

  1. Block shaped molds
  2. Forms with dish-shaped structure

Block shaped forms

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.

Forms with dish-shaped structure

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.

Materials

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:

  1. Flexibility
  2. Refractoriness
  3. Gas permeability
  4. Good decay after the casting

For the precision investment casting are additionally necessary:

  1. Dimension behavior
  2. Chemical stability

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:

  1. Clay mineral
  2. Loam
  3. Refractory clay
  4. Quartz sand
  5. Brick-split
  6. Gypsum

History

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.

Related links

http://www.archaeometallurgie.de/verfahren/lehmform.html

See also: Pour (procedures)


Articles in category "Lost-wax process"

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» Lost form
» Lost-wax process
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