What is die casting? Essentially, die casting uses stee […]
What is die casting? Essentially, die casting uses steel molds called dies in which molten metal is forced into using extremely high pressure. From steel sinks to tiny toy cars, die casting is a versatile technique that allows for various levels of complexity in production, while still maintaining absolute precision to create a flawless end product.
There are generally four key steps in the process of die casting, and each must be fully completed before moving onto the next phase. However, before these steps can begin, the die worker must ensure that the die casting machine is at the required temperature. If the die is still cold when the molten metal is injected, it will solidify too quickly without conforming to the correct shape. According to the size of the intended cast, heating can take anywhere from several hours to several minutes. After the die has reached the right temperature for the job, casting can begin.
First of all, spray the mold with lubricant and close it. This helps to regulate the temperature inside of the die, while also allowing for an easier removal of the cast object later on. The lubricant functions much in the same way as household cooking spray is used on a baking pan.
Secondly, inject the molten metal into the die. The metal is inserted at an extremely high pressure, which allows the metal to conform to the precise shape of the die, without the dangers of lumps or air pockets inside the product.
Thirdly, cool the mold, and wait for the metal to solidify. In some cases, the mold may be immersed or sprayed with cold water to help the casting become solid faster than simply waiting for it. A high pressure is maintained inside the mold, which ensures the metal doesn't change properties while inside the die.
And finally, open the die and remove the solid cast.
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 economical process than using stamping presses or machine tools that require the operation of multiple pieces of large machinery for metalwork.
As a rule, 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.