Casting glossary of terms
Casting is a process where molten metal is poured into a cavity / mould. Once solidified, the molten metal makes a firm metal shape. There are several methods of casting including investment casting, sand casting and gravity die casting.
A casting is a metal shape / object that has been created by molten metal being poured into a mould. Castings can be produced from several different metals including steel, copper, iron and aluminium.
Gravity Die Casting
Gravity die casting is a die casting process in which molten metal is poured into moulds and the cast is created by the force of gravity. The technique requires no external pressure to create the casting. This is unlike high pressure casting techniques where molten metal is forced into the mould through high pressure injection systems.
Shapes up to 5kg in weight can be cast using gravity die casting and the process is used to create more intricate shapes.
Hammer forging is a process in which a metal is enclosed within a die set. A hammer is then used which applies the energy to forge the piece. In drop forging, the hammer is dropped from a height onto the die to create the pressure to cast the forging from the die.
Heat Treatments are the heating and cooling processes carried out on solidified metals and alloys in order to achieve required physical and mechanical properties such as softness, hardness, brittleness, stress relief and normalisation.
Investment Casting is a casting method in which wax or a thermo-softening plastic pattern is enclosed in refractory slurry (silica, water and binders) to create a mould. When the slurry has dried / hardened, the wax or plastic is melted and flows out of the mould to leave behind a cavity / void for the casting. The chosen metal can then be poured into the mould to fill the cavity and create a casting. This casting method has been used for thousands of years and was utilised in Ancient Egypt and China.
Injection Moulding is a process in which thermoplastics / thermosetting plastics are fed into a chamber, heated, softened and then forced into a mould. The material is pressurised within the mould until it hardens suitably to be removed. Any colour of plastic can be used to create the moulding.
Powder Coating is a type of paint finish which is applied as a powder. This powder is applied electrostatically and is usually a thermoplastic or thermoset polymer. In general, powder coating is more robust / tougher than a normal paint finish. The casting / metal forging is either placed in a bed of powder which is usually electrostatically charged or the charged powder is sprayed onto the item (the charge holds the particles in place). The item is then heated so that the powder melts on to the item and forms the smooth paint film. This film then dries and becomes very resistant to damage such as scratches.
Precision assemblies are complex or simple assembled units of precision machined components such as metal and plastic. Precison assemblies can be created using adhesives, welding and soldering.
Press Forging is a metal forging method in which the material (metal) is placed between dies and forged by a slow, continuous pressure via a hydraulic press. This process can be can be conducted in varying temperatures (hot or cold).
Sand Casting is a casting process in which compacted, damp sand is compressed around a pattern to create a mould. Once the pattern is removed, molten metal is poured into the cavity to form the casting. When the metal has solidified, the sand can be simply broken up, leaving the casting ready for cooling. The sand is often removed using a vibration machine.
Sand castings can be created using stainless steels, carbon steels and iron.
Shot Blasting / Abrasive Blasting
Shot Blasting is a process in which a surface is cleaned by attacking it with a high pressure stream of abrasive material. This method removes any undesirable characteristics on the surface such as contaminants (rust, paint) and rough sections. The procedure can also be used to shape the material or create a rough appearance on a smooth surface. The abrasive material used can be sand, silica or metal balls and these are propelled by compressed air or a mechanical impellor.