Die Casting: The Process And The Techniques, Part 2
There are several secondary steps which may need to be taken once the casting is removed, such as removing excess metal and smoothing rough surfaces. However, die casting can create pieces of metal as thin as 1mm wide in these four simple steps, which makes it a more economic process than using stamping presses or machine tools that require the operation of multiple pieces of large machinery for metalwork.
The Life of a Die
A die casting die is built to do several things, each of equal importance, and quite often the die itself cannot produce a completed final product. While a die holds the liquid metal inside itself to create a cast, there also must be a place for the metal to enter the die and reach the inside. This means that when the metal cools, there will be small pieces of unwanted metal attached to the final cast called flash, which will need to be removed by hand or secondary machine.
Hydraulic presses can be used to remove the flash or scrap, while an older technique is to just saw off the flash by hand. A casting may need to be sanded or ground down to remove mold lines, and if any extra holes for screws or undercutting is necessary, this must be done outside of the die as well.
Die casting machines can apply a clamping force that ranges from 100 to 4,000 psi, and are typically divided into categories according to the type of metals they can cast. Hot chamber dies can cast metals with lower melting points, such as zinc, while cold chamber dies cast metals with higher melting points like aluminum.
Die casting dies typically have a lengthy lifespan, however over the course of several hundred thousand heatings and coolings, the dies' properties may begin to shift and weaken. Dies which make castings from aluminum and its alloys tend to have a shorter lifespan, simply due to the temperature required to make aluminum casts, while cold chamber dies tend to last almost indefinitely. Die sets for casting brass objects are extremely short-lived, and need to be replaced frequently, regardless of the strength of the cast.