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Casting 2
| Highly flexible and also suitable for development |
The investment casting combines flexibility in the production of components with precision and economic efficiency. In spite of the larger number of manufacturing steps it is suitable not only for small series because
the steps can be largely automated. Indeed, it can be applied during the development of a component, e.g., to try out different materials. 'investment casting' means, in this case, that preparations can be, to some
extent, avoided. For example, with cast screw-threading. Of course the development of undercut surfaces and cores pose no problem.
| Construction no different from other casting processes |
It starts, as usual, with the construction of a part in the CAD system of a computer. Then a suitable CNC lathe or milling machine produces a form in which a wax model is cast. This model corresponds precisely to the
part which is later made of metal, also in relation to the surface finish. If the model adheres to the specifications, several are produced and assembled to form a 'tree' (figure 1).
| The wax keeps the space free for the metal to be poured in. |
Lost-wax casting
After several passes through a ceramic liquid immersion bath, and after sanding down, the outcome can be seen in the above figure 2. 160°C hot steam causes the wax run off for re-usage. Hence, the alternative
name, 'lost wax technique'. Afterwards the empty shell must be made durable by heating it to approx. 1000°C to enable the casting of hot metal. You can see in the cross section of the connections to the single
castings, that the transport of the liquid metal to the respective form must be carried out as quickly as possible.
| Further treatment not necessary |
After having slowly cooled down, the component is separated from the tree and suitably polished, it is now, in effect, finished. Of course further treatment is possible. In addition, a thermal treatment can be applied to
improve the material characteristics. There are quality control checks on every component as well as random spot-checking. This also depends on the specifications of the construction. There are several possible
methods used to check for fissures, hardness and surface accuracy. Today even the melt can be checked using a spectral analysis. 08/08
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