Understanding Die Casting Machines: How They Work and Their Benefits

A die casting machine is widely used for applying high pressure to force molten metal into the molds, forming the desired profile of metal components. Die casting machine is also known as a casting die. It is equipped with molds that consist of hardened, designed steel dies. The hardened dies play similar roles as the molds in injection molding machines which are used for shaping thermoplastics. Injection molding from the plastic products through feeding the molten plastic into the molds, the method is suitable for high volume production. Similarly, die casting is also ideal for forming a large volume of complex shaped metal parts by utilizing the customized molds. Depending on the application and a variety of casting materials, the operator can choose to utilize a hot chamber style of die casting machine or a cool chamber type. 

In general, the materials die casting machine is made of are non-ferrous metals, which include but not limited to tin-based alloys, copper alloys, lead alloys, zinc, magnesium, aluminum, and so on. Different from ferrous metals which have iron content and therefore vulnerable to rust while exposed to moisture, die casting machines made from non-ferrous metals share the strengths of non-ferrous metals.  They have ideal rust resistance and corrosion resistance, also, the metals have better malleability, the features help to lengthen the equipment life and ensure smooth casting operation.
 

Construction of Different Types of Metal Die Casting

Die casting machines can be subdivided into 2 styles, which include hot chamber die casting machine and cold chamber dies casting machine. It is important for the metalworking operator to identify the cast materials’ characteristics and the suitable casting methods when selecting the best die casting machine.
 

Hot Chamber Die Casting Machine

Hot chamber-type casting machines are also referred to as gooseneck machines. These machines rely on a pool of molten metals where the injection unit is immersed. The casting cycle in hot chamber type begins with the feeding of molten metal from the piston of the machine as the port is retracted to allow the materials to fill the gooseneck/cylinder. Then, the pneumatic powered or hydraulic-powered piston can force the metal out through the nozzles, making them entered into the molds/dies. Once the formed workpieces are solidified, the plunger will withdraw, and the dies will release the parts. The products will eventually be ejected from the casting dies and complete the cycle in a hot chamber-type die casting machine. 

Now let's take a look at the advantages and drawbacks of the hot chamber style of casting. The advantages here include the very short cycle times, which are typically about 15 cycles a minute. The cycle can even take less than one second when the tiny casting parts weigh less than 30 grams. Another benefit these die casting machines provide is the convenience operation where the metals are directly melted in the machines. As for the disadvantage of this casting system, the metal materials processed in hot chamber type are limited to those that have a low melting point, for example, zin alloys, tin alloys, lead alloys. Also, aluminum cannot be processed in hot chamber die casting since it tends to pick up iron in the molten metal pool.
 

Cold Chamber Die Casting Machine

When the casting materials are not recommended to be processed in a hot chamber type of die casting machine, the cold chamber type is the alternative choice. For example, aluminum-based alloys and other metals include copper, magnesium, and so on. Both zinc and magnesium are the most suitable and easiest metals for cold chamber casting. Aluminum is light in weight, having great stability for creating complicated shapes or thin walls in the die casting process. Aluminum also has great heat and electrical conductivity, permitting machining in high-temperature environments. 
The casting cycle in a cold chamber-style machine starts with the melting process that takes place in a separate heating furnace. Subsequently, a set amount of molten metal is conveyed into the “cool shot chamber” or injection cylinder by an automatic ladle or simply by hand. With high pressure, the cold shot will drive the materials into the mold by a mechanical or hydraulic piston. Since there are more than enough molten materials that are transferred into the cold chamber, sufficient pressure can be kept and fill the cavity firmly. 

Different from hot chamber types, the cold chamber dies casting machine’s big advantage is the ability to cast alloys with a high melting point because the cylinder is not immersed in the molten pool. The disadvantage of this type of casting lies in the longer cycle time because of the need to transport the molten materials from the heating furnace to the cold chamber.
 

Features of Die Casting Machine

Most die casting machines are manufactured and designed for mass production of unique metal projects because the equipment and the customized harden-treated dies (molds) are relatively expensive. They are more suitable for shaping small or medium-sized products with high precision dimensions. Die casting machines can be used to manufacture sharply defined shapes and produce high-quality smooth surface finishes. A big advantage of the die casting machines is that they remove the need for a secondary machining process, allowing a faster machining cycle, saving time effectively especially in large volume production. Depending on the use, the die casting machine can also apply with high strength bearings, extra heating units, and thread to enhance the functionality.