Over the years the basic business process has remained unchanged.
To begin you must make or commission an ‘original’ or ‘master pattern’. This is then used to make a production mould from which copies can be cast. The moulds are traditionally made from two discs of black rubber, one of which has a hole in its centre through which molten metal can be poured.
The ‘masters’ are placed between the two discs which are then put in a special metal casket. This is then placed under conditions of temperature and pressure.
The casket ensures the moulds retain the same external shape but inside the pressure forces the rubber to form around the contours of the ‘masters’.
The temperature causes chemicals present in the rubber discs to react and the rubber ‘vulcanizes’. Basically this means that its physical properties change and whilst it retains a certain amount of flexibility when it has cooled, it will retain its basic shape.
When the ‘masters’ are removed, the mould retains their shapes within it. Feeds are cut from the central hole in one disc to the cavities left by the ‘masters’ and the mould is then clamped, spun at speed and molten whitemetal is poured into it. This flows through the feeds and fills the cavities taking on the shape of the ‘masters’.
Once cool the castings are removed, checked for defects and then either packed for sale or cleaned prior to painting.