Lost-wax casting

The lost wax process is a molding process for metal and glass casting. It one-piece molds are usually made. The models are usually made of wax, for several years, increasingly, from plastics. In the course of the process, both the model and the mold is destroyed. Therefore, it is also referred to as a method of lost pattern, sometimes referred to as method with lost form. However, since other, completely different molding methods exist with lost form, the latter term should be avoided.

Another name for the procedure is cire perdue French ( "lost wax ").

Steps

Variants of the lost wax process

There are two types of forms that are built differently:

Block-like forms

This includes any form of substances whose binder is gypsum, such as grog or crushed brick. The wax models are provided with a gate and immersed either in liquid form or substance, the models are poured over the mold material. After the plaster has set, the forms must be burned depending on the size some days in a drying oven at temperatures up to about 800 ° C.

Forms with shell-like structure

These forms surround the wax model with a shell made ​​of a refractory mold material. When present in the above-mentioned shapes of the molding material in a liquid manner, is applied in this method, the molding material in one or more passes on the wax. The molded materials most commonly used for this purpose are clays and loams specially prepared. For several decades, quartz sand with water glass as a binder or other refractory materials such as zircon and olivine with synthetic binders. The latter often find in the jewelry industry, the precision casting or investment casting using.

Demands on the materials

The model material must be mechanically strong, so it does not break when molding or deformed. The model material must be completely melt out, this is especially true in the investment casting. If the model can be produced by means of a form, it should exhibit little or no shrinkage.

The molded materials are varied, but all mold materials should have a combination of the following properties:

  • Plasticity
  • Refractoriness
  • Gas permeability
  • Good decay after casting

For additional precision casting are required:

  • Dimension of behavior
  • Chemical stability

Gypsum -bonded investments readily decompose, indicating sulfur from which contaminated the cast metal.

From the requirements it follows that a number of materials are suitable, for example:

  • Clay mineral
  • Clay
  • Fire clay
  • Quartz sand
  • Crushed brick
  • Gypsum

History

The principle of this method has been known for thousands of years and found at least since the 4th millennium BC application in metal crafts. Major centers of metalworking were from the 5th millennium Bulgaria with his early copper mines as well as Kestrel and Göltepe in Anatolia with one of the earliest tin mines and tin production in the Old World ( 4th century BC).

The procedure was also the indigenous peoples of Colombia and Central America known, such as the Muisca ( Eldorado). They used it for example tumbaga and formed cult objects.

All major cast bronze art works of the early Middle Ages are incurred.

Today, for example, is the mascot for the Rolls -Royce (see Spirit of Ecstasy ) produced by the lost wax. Even in contemporary art finds this process his application because the impression is very accurately the fine Modellierstrukturen maps, as you can see from the example, bronze sculptures by the artist Norbert Marten. The dental technology uses this method also.

Middle America (region)
90177
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