Casting & Diecasting

Benefits of Casting

Die casting presents a number of benefits over other manufacturing methods, including plastic injection molding and other casting methods:

• Broader range of materials. Die casting can process a wider range of materials, including low fluidity metals.
• More variable wall thicknesses. The die casting process can produce parts with thinner walls than are possible with sand or permanent mold casting methods.
• Higher tensile strength. Die cast parts demonstrate tensile strengths as high as 415 megapascals.
• Superior durability and structural integrity. Compared to plastic molded parts, die cast parts are stronger, more stable, and demonstrate greater resistance to heat, radiation, weathering, and chemicals.
• Tighter tolerances and exceptional dimensional accuracy. Depending on the material, typical accuracies for die cast parts range from 0.1 mm for the first 2.5 cm and 0.02 mm for each additional centimeter
• Finer surface finishes. The smoother surfaces produced by die casting reduces the need for and cost of secondary machining operations.
• Longer tool service life. Die casting molds exhibit greater durability and longevity, especially for zinc and magnesium tools.
• Reduced material waste. Compared to manufacturing methods such as stamping and machining, die casting uses a larger portion of the raw material. Additionally, in some cases, unused material can be reused in future die casting operations.
• Faster production times. By eliminating the need for finishing operations, die casting reduces the number of steps (and the amount of time) required to produce a finished part,
• Better cost-effectiveness. By optimizing the material usage, reducing lead times, and minimizing tool replacement, the die casting process decreases the total cost of production.

Types of Castings

Variants of the die casting process include low-pressure die casting, vacuum die casting, squeeze die casting, and semi-solid die casting. Depending on the material employed and the shape and size of the intended part, one die casting method may provide superior results over another.

Low-Pressure Die Casting
In low-pressure die casting, a riser tube connects the die directly to the molten metal bath located below. Once the machine operator pressurizes the chamber (between 20–100kPA), the molten metal moves upwards through the tube and into the mold. By eliminating the need for feeders, this die casting process yields a more sizable output compared to some other casting methods.

Low-pressure die casting is suitable for fabricating aluminum components and parts that are symmetric around an axis of rotation.

Vacuum Die Casting
Vacuum pressure casting (also referred to as VPC) is a newer die casting method that is ideal for projects requiring minimal porosity and enhanced strength. The casting process is similar to that of low-pressure die casting. However, while in low-pressure casting the die is positioned above the molten metal bath, in vacuum die casting the locations of the components are switched. This process alteration allows the tube to act as a vacuum and forces molten metal into the die cavity.

Squeeze Die Casting
Squeeze die casting allows manufacturers to cast alloys and metals with low fluidity. The casting process enables the fabrication of denser parts and products and is highly suitable for secondary heat treating stages.

During a squeeze casting operation, molten metal fills an open die. Once filled, the die squeezes shut around the molten metal and forces the material into the recessed areas of the molding, ensuring that every portion is adequately filled.

Semi-Solid Die Casting
Semi-solid die casting—also known as thixoforming— is similar to vacuum die casting in that the process tends to produce parts with maximum density and minimal porosity.
Semi-solid die casting relies on a machine to cut the workpiece into smaller slugs for melting. When the metal reaches a phase transition and begins to change from solid to liquid, a shot sleeve forces the metal into a mold cavity to harden into the desired shape.