The Die Casting Process is traditionally composed of four steps, with additional steps being taken after the process is complete to inspect, assess and finish the cast piece and prepare it for use. The die casting process is able to produce very high volumes of extremely precisely-cast products, but due to the specialist equipment required, it has a high initial capital cost.
Once this original cost is met – with the casting dies made, the casting equipment and the related components bought and installed – the simple four-step casting process can effectively produce large volumes of identical components, so there is a tradeoff, in that the high cost of setup can be counterbalanced by producing a large volume of castings. This means that die casting is most suitable for mass production, and may not be cost-effective at other industrial levels.
The Die Casting Process
The Die Casting Process is comprised of four easily-replicable steps: die preparation, filling, ejection and shakeout. These steps proceed as follows:
- Die Preparation
The dies must be raised to the correct temperature for casting and lubricated, usually with a mixture of oil in water. This makes sure that the aluminium being cast forms correctly, as a set of dies which is too cold can result in any number of problems, from folds in the material and misshapen castings to “cold fronts”, where the metal solidified partway through and additional metal was poured on top, forming a line of weakness which compromises the piece.
All of these issues may be mitigated or eliminated by correctly heating the dies, and the use of a lubricant of oil in water means that the castings can be easily separated from the mould. The water evaporates on contact with the dies, cooling them and depositing a perfect layer of oil lubricant which will help to free the casting later.
The next stage in the die casting process is to close the prepared dies and inject molten metal into them, either at pressure or by using gravity to draw the material through. The pressure applied to inject the metal is kept constant while it solidifies, ensuring as few bubbles and miscasts as possible.
Once the casting has cooled down enough to be ready for removal, the dies are opened, and special “ejector pins” knock the casting out of the mould.
The shakeout stage isn’t really a “casting” stage since all the casting has been done at this point – but it is essential to the completion of a satisfactory product. After the die casting is complete, any extraneous metal must be removed, including the sprue and runner (the metal from the channels through the dies which lead to the actual mould, and jut out of the finished piece).
Once that is all done, the newly-cast component can be inspected for defects like gas bubbles and cracks, before being put to use! If you have any questions about the die casting process, don’t hesitate to ask the experts – you can get in touch with Lupton & Place any time by calling 01282 422361 or visiting their website!