What is Die Casting? Definition, Types, Process, Materials

Introduzione

Die-casting is a widely used manufacturing process for high-precision, intricate parts from die-casting alloys. In this metal-casting process, molten metal is pressurized into a precision die cavity. The resulting parts stand out for their high dimensional accuracy and consistency, producing large batch volumes. It is often described as the metal equivalent of plastic injection molding.

Let’s discuss the fundamentals of die-casting in detail. We’ll break down this article into the die-casting process flow, its types, compatible materials, advantages, limitations, and applications.

Die Casting Process Flow

The following step-by-step defines the detailed process flow of die-casting. It usually involves 6 key steps. Depending on the material used, the application, and the process, the mechanics may change. However, the key process flow remains the same.

1- Mold creation

The die-casting process starts by preparing a mold, which is the “metal die”. It is an internal cavity with the shape of the product made from hardened steel. Metal dies are durable and made to withstand extreme temperatures and pressure.

For precise mold design, advanced CAM/CAD and CFD software are used. With th software, engineers can design molds exactly according to the product-specific requirements while simulating the intricate details. These details include heat dissipation rate, internal friction, flow rates, temperature distribution, and more.

After the 3D CAD file is made, a mold is created using advanced CNC machining. Engineers ensure the mold’s precision, as it is crucial for the accuracy of the resulting product. A high-quality mold prevents molding defects and saves you extra costs. Several trial runs before final mold preparation.

2- Mold Preparation

Mold is prepared by setting up in such a way as to produce quality results. To prepare the mold, its two halves are heated and thoroughly cleaned for injection. Additionally, they are lubricated or prepared using a releasing agent.

The primary role of a lubricant or releasing agent is to prevent the casted product from sticking in the mold. Also, besides easing the die-cast product ejection process, it serves other functions, which are as follows:

• Helps maintain the temperature of the die
• Lower the internal friction
• Prevent premature solidification

After the mold is prepared, it is closed and clamped under high pressure and set for molten metal injection.

3- Molten Metal Injection

This step involves molten injection into the mold. Manufacturers can inject molten metal in two ways, depending on the die-casting method: gravity die-casting and high-pressure die-casting.

• Gravity die casting involves injecting molten metal under the force of gravity. Once the molten metal is poured into the ladle, it flows down the sprue into the main cavity.
• High-pressure die-casting uses highly pressurized molten metal to fill the mold. It is one of the preferred methods compared to the former. This is because of its range of benefits. These include dimensional stability, the potential to produce intricate thin-walled structures, improved filling, and a smooth surface finish.

4- Cooling and Solidification

After complete filling, the mold is allowed to cool. cooling must be done at a controlled rate and given enough time to get a fine microstructure of the final product. Mold contains cooling channels that run throughout the structure and carry liquid or oil. This helps dissipate heat from the mold and prevents internal and surface defects in the product.

5- Mold Opening and Ejection of Casting

Now it’s time to open the clamped mold and eject the solidified cast. As you lubricate the surface, ejection can be a straightforward, manual process. While ejection can be automated utilizing ejector pins, safely remove the casted part from the die.

6- Finishing

After ejection, the cast product may need extra finishing. So, it must undergo a finishing process, such as grinding and CNC machining. This step removes all excess material, such as spurs and runners. This waste material can be reused by melting it again.

Main Types of Die Casting

Hot Chamber Die Casting

Hot chamber die casting involves melting the metal in the internal furnace located inside the casting machine. This furnace is connected to the internal cavity via a gooseneck. As the metal melts, it is forced into the internal cavity through the gooseneck at high speed and pressure by a plunger. When the molten metal solidifies, the plunger retracts. Then the solidified part is ejected as the mold opens.

The system works quickly, taking 20 minutes per cycle. But the temperature range is limited because the pump could be damaged by high temperatures. Therefore, hot chamber die casting is designed for metal alloys with low melting points, such as zinc alloy, lead alloy, and magnesium alloys. At the same time, it’s best for creating complex-shaped products in bulk with accuracy and consistency. Other benefits include a longer lifespan and greater corrosion resistance in the produced parts.

Cold Chamber Die Casting

In cold-chamber die casting, the metal is melted outside the furnace. Here, the process involves melting at high temperatures. This is one of the major differences between hot and cold chamber die casting.

The molten metal is then transferred to the shot chamber at room temperature using a ladle. The hydraulically operated ram in the shot chamber forces the molten metal into the metal die at high pressure. It maintains high pressure, up to 2000-20,000 PSI, during the process until the part solidifies. As the process completes, the mold is clamped, and the part is ejected.

Cold chamber die casting is best suited for metals with high melting points. These include copper, aluminum, and their alloys. The parts made by this process offer high strength and hardness.

Common Materials

Vantaggi della pressofusione

• Mass Production: The short cycle time makes operations efficient and enables high-volume orders to be completed in minimal time. If you use automated machines, production efficiency can increase significantly.
• Complexity: The high speed and pressure involved lead the molten metal to push through thin channels. Therefore, highly intricate metal parts can be produced with high reliability, offering strength and durability.
• Dimensional accuracy: Die-cast parts offer tight tolerances and consistency across large batches.
• First-rate low-cost operation: When you produce high-volume batches, the per-part cost is significantly lower. That’s where it stands out among other casting processes.
• Smooth surface finish: High-quality materials yield smooth finishes. Most products may not require finishing, as their aesthetic appeal may improve after casting due to the fine microstructure formed.
• Design flexibility: Clients can choose intricate designs featuring thin-walled or complex shapes, as they are easy to produce.
• Strength and durability: Cold-chamber die-castings offer high strength and durability. Due to their exceptional strength, these products are preferred for demanding applications.

Limitations of Die Casting

• High initial investment: the cost of dies and other casting equipment may increase the initial investment. This can affect companies producing low-volume parts. At the same time, it may benefit large companies that manufacture in bulk.
• Size and weight limitations: Larger parts require larger dies and equipment. So the size restriction may be a limitation of the die-casting process, allowing you to produce small to medium-sized parts.
• Turbulence can be a problem: As the injection of the molten metal involves high speed and pressure, it can possibly generate turbulence. Although it is a problem, it can be addressed through smart design choices during die creation.
• Limited material choice: Die-casting uses non-ferrous materials, and these are limited.
• Surface defects: Turbulence and other factors during the process may affect the products. It can lead to surface defects, including porosity, wrapping, and cracks.

Applications of Die Casting

• Aerospaziale: A wide variety of die-cast products are produced, which include structural components, valve bodies, brackets, engine parts, etc. Intricate internal components, such as interior fittings, are also created.
• Automobile: This sector accounts for the largest share of the die-cast market. Products include Large engine blocks, cylinder heads, transmission cases, steering knuckles, and suspension arms.
• Medico: Die-cast medical products range from handheld devices to sturdy internal frames and enclosures for heavy machinery.
• Consumer electronics: It includes housings and frames of laptops, mobile phones, and other devices. Aluminum castings are used in processors and LED lighting systems.

Conclusione

Die casting is an advanced process used to manufacture a wide range of products, from basic components to complex parts, across multiple industries. It offers numerous benefits that surpass those of other casting processes. The dimensional accuracy, surface finish, strength, and cost-effectiveness of bulk production are the process’s major strengths. If you are looking to enhance your production needs, choose a reliable die-casting manufacturer!