Die casting is the manufacturing process of choice when producing high volumes of relatively complex metal parts and is widely used due to its versatility, reliability, and accuracy. Die casting eliminates all or most secondary operations needed to make a metal part; however, post-machining is common to meet tighter critical-to-function tolerances. Die cast parts can also be post-processed in any finish their respective CNC machined counterparts can.
What is Die Casting?
Die casting is a type of metal casting that uses high pressure to force molten metal into a mold cavity formed by two dies. It shares traits with the plastic manufacturing process of injection molding. Within the larger metal casting landscape, die casting is one of the most popular techniques due to its accuracy, high quality, and level of detail. The broader category of metal casting, which has existed for thousands of years, contains many different casting processes that use a mold to form liquid metal. Historically, such a process usually involved pouring the liquid metal into the mold with the aid of gravity and many metal casting processes still work this way.
How Die Casting Works?
In simple terms, metal die casting works by using high pressure to force molten metal into a mold cavity, which is formed by two hardened steel dies. Once the cavity is filled, the molten metal cools and solidifies, and the dies open up so the parts can be removed. In practice, however, there are many steps in the process, and skilled engineers are required to operate die casting equipment.
Here we will divide the die casting process into three stages:
How to Make a Die Casting Mold?
A die casting mold consist of at least two halves: the cover side (mounted on a fixed plate) and the ejector side (on a moveable plate). Some dies also have other sections like slides and cores, which are used to produce more complex parts, such as those with holes and threads. Depending on the size of the manufactured parts, a die casting mold may have multiple cavities to enable the production of multiple parts per cycle. Tooling for die casting must be incredibly strong and thermally resistant, in addition to having good wear resistance and ductility. They are therefore made from high-performance hardened tool steels - often heat-treated - allowing them to go through hundreds of casting cycles per hour and up to two million cycles over their entire lifespan. Die casting tooling must maintain performance under very high clamping forces. Making a die casting mold starts with computer-aided design (CAD) used in conjunction with casting-specific design and simulation tools. As with injection molds, tooling for die casting must have sprue holes, runners, and gates to allow the molten material to enter the cavity. Locking pins and ejector pins must also be incorporated to secure the mold and facilitate ejection. The digital design of the mold allows for the creation of complex shapes and tight tolerances. CNC machining is widely used to manufacture the die casting tooling. Typically, die casting moldmaking begins with rough machining of the mold shape, followed by heat treatment of the metal mold, then finally a round of finish machining. Prototype-grade dies can also be made using rapid tooling, using either CNC machining or other processes like selective laser sintering (SLS).