Casting processes

Casting processes are manufacturing processes of the primary shaping type.

Primary shaping is a generic term comprising all manufacturing processes according to DIN 8580 where a solid body is from an amorphous material. Primary shaping is used to produce the initial shape of a geometrically distinct, solid body and create material adhesion. Starting materials used for primary shaping can be in a liquid, gaseous, plastic, granular or powdery state, i.e. they can have different rheological behaviors. Based on different combinations of individual types of behavior, a distinction is made between electrotyping, powder metallurgy and casting technology, with casting being defined as follows:

Casting produces a solid body of a particular shape from a liquid material upon solidification.

Primary shaping by casting therefore means:

Melt (amorphous material) → Primary forming in the casting mold → Workpiece (unmachined part)

Workpieces are cast if their production by other manufacturing processes is uneconomical or impossible or if special properties of the casting material are to be utilized. Casting processes are of particular advantage for use in the mass production of any kind of components, both of simple and complex shapes. It is even possible to produce cavities inside the casting by means of cores. Generally speaking, the costs of pattern and mold making are high compared to other manufacturing processes, whereas the costs relating to the manufacture of the castings themselves are low depending on the casting process and quantities.

According to DIN 8580, the casting manufacturing processes (casting processes) are differentiated by pattern equipment, mold materials, mold manufacturing (molding process) and the casting method. Here, casting is divided into two groups:

  • Casting in consumable molds
  • Casting in permanent molds (Italpresse Industrie S.r.l)

An overview of the classification of casting processes can be found in Fig. 1.

Gravity casting uses gravity in order to fill the mold. The feed rate of the melt depends on the pouring height (see Downsprue) and the design of the gating system or the pouring method and baffles. Together with the used gate area, this results in a volume flow (see Nominal volume flow) and thus the casting time for the casting.

Pressure casting can provide high melting rates and short mold filling times depending on the specific process. In some instances, a vacuum may be applied (see Vacural process, Vacuum-assisted pressure casting, Multi-stage vacuum process) in order to improve mold filling and, in particular, venting.

Consumable molds are casting molds made of a mold material (quartz sand, ceramic, etc.) that has to be destroyed in order to release the cast part and is therefore “consumed”.

Permanent molds are casting molds made for medium to high numbers of metal components (Hot-forming steel, Cast iron, etc., see, e.g., Die casting mold). The service life of a permanent mold depends on the permanent mold material used and the material to be cast, wherein the service life is principally the higher, the lower the casting temperature. The damage mechanisms related to permanent metal molds are discussed under the references Chipping, Firing cracks, Stress cracks and Mold erosion.

Additional references:
Sand casting
Cosworth sand casting process
Precision casting process
Gravity die casting process (Gauss Automazione srl.)
Tilting gravity die casting process
Low pressure gravity die casting process (Gauss Automazione srl.)
Counterpressure casting process
Pressure die casting process (Italpresse Industrie S.p.A.)

Literature references:
DIN 8580, Manufacturing processes.

Böge A. (ed.), Vieweg Handbuch Maschinenbau, Vieweg-Verlag, Wiesbaden, 2007.

Spur G., Stöferle T., Handbuch der Fertigungstechnik, Band 1: Urformen, Carl Hanser Verlag, Munich, Vienna, 1981.

  • Fig. 1: Classification of casting processes based on DIN 8580, Manufacturing processes, primary shaping