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Understanding Die Casting: The Process, Materials, and Types
Metal die casting is a precise and efficient process of creating various metal parts. This method produces strong, accurate, lightweight components at a lower cost. The parts created through die casting are utilized in manufacturing both consumer and industrial products. While die casting is a versatile production process, it is essential to understand the technique before using it independently or hiring companies that offer related services. Therefore, it is necessary to learn what die casting is, how it works, its different types, and its advantages.
What Is Die Casting?
Die casting is a manufacturing process that creates high-precision metal parts by injecting molten metal into a mold, which then cools and hardens to form the desired shape. It is valued for its ability to create smooth, precise parts quickly and cost-effectively.
History of Die Casting
Die casting originated in the early to mid-19th century when printer parts such as gears and bell cranks were first cast. Initially, the process involved simple tools made of iron and coarse materials, with the molten metal hand-poured from a ladle. Over the 20th century, die casting evolved into a crucial method for manufacturing high-volume metal components. Today, fully automated and sophisticated production lines are the norm. However, some aspects of the original process, such as hand ladle filling, are still utilized in commercial applications for creating simple cavity tools.
Metal Materials Used On Die Casting
The manufacturing process suits non-ferrous materials such as aluminum, zinc, and magnesium alloys. Below are the best materials for the process and reasons why you should consider them:
Magnesium Alloys
Magnesium alloys have high fluidity and good castability, which helps reduce porosity during die mold filling. Die-casting experts prefer magnesium alloys over aluminum alloys because they are better suited for making parts with complex designs and have high corrosion resistance.
One popular magnesium alloy for casting is AZ91D, which is as strong as aluminum and steel but 33% and 75% lighter than both, respectively.
Die-casting magnesium alloys are easier to cast than metals like aluminum due to their compatibility with the hot-chamber die-casting process. Below are examples of commonly used magnesium alloys in die casting:
AS41B and AE42: These rare earth alloys have high-temperature resistance and excellent resistance to creep, corrosion, and ductility, but they are expensive.
AM60: AM60 is the go-to choice for automotive parts like panels and seat frames due to its mix of strength, ductility, vibration damping, and good castability.
AZ91D: This alloy is popular for powertrain components and mechanical parts due to its high strength-to-weight ratio, serious corrosion resistance, and castability.
Aluminum
Aluminum alloys are the most important materials used in high-volume die-cast production. They are best suited for hot chamber, high-pressure, or, more recently, vacuum die casting. These alloys can produce moderate to high-strength and high-precision parts. Additionally, aluminum alloys are still highly useful in lower-tech processes.
Aluminum-based die-casting alloys are an excellent choice for complicated, finely detailed pieces, as they are lightweight and provide exceptional dimensional stability. They strongly resist temperature fluctuations, corrosion, and electrical and thermal conductivity. Below are some commonly used aluminum alloys for die casting:
Aluminum Alloy 380: This is an all-purpose aluminum alloy that balances castability and mechanical characteristics. It is widely used to make furniture, frames, gearboxes, and more.
Aluminum Alloy B390: This alloy is exceptionally vibration—and wear-resistant. It is commonly used for pump housings, valve bodies, and impellers.
Aluminum Alloy 413: Thanks to its high-pressure compressibility, aluminum alloy 413 possesses outstanding casting properties. It is commonly used to make architectural parts, hydraulic cylinders, and food machinery.
Aluminum Alloy 443: Due to its superior ductility, Alloy 443 is the best aluminum alloy for die casting consumer goods that require plastic deformation after casting.
Copper
Copper alloys are important in die casting because they can withstand rapid cooling without cracking and create fine-grain structures. Additionally, they possess high strength, durability, and thermal conductivity, making them suitable for various industries.
Tin-Based Alloys
Tin-based alloys are soft and ductile metals with a low melting point of 232°C. They also have good corrosion resistance and flowability, making them suitable for metal die casting. Tin is often combined with other metals, such as copper and antimony, to improve their mechanical properties.
Zinc Alloys
Zinc alloys are highly sought-after for casting due to their high castability, low melting point, and high solidification rate. Below are some typical zinc die-casting alloys:
Zamak 2: This alloy contains extra copper, which gives it greater strength despite being slightly more expensive.
Zamak 3: This all-purpose zinc alloy is known for its ease of casting and dimensional stability. It is commonly used to produce plumbing parts and ceiling fans.
Zamak 5: Similar to Zamak 3, this zinc-based alloy offers less ductility but higher tensile strength. It is the preferred alloy for products such as wheel balancing weights.
Steps of The Die Casting Operation
The standard manufacturing process involves injecting molten metal into the die mold at a controlled pressure, as highlighted below:
Mold Preparation
First, computer-aided design (CAD) software is used to design the die mold. This software forms a 3D model of the die mold, which is then machined from a metal block using a CNC machine. After machining, the mold undergoes a heat-treating process to harden it.
Clamping
The initial step in die casting is clamping. To facilitate effective injection and removal of the solidified product, cleaning and lubricating the die is crucial to remove any impurities. Once the die is clean and lubricated, apply strong pressure to clamp and close it.
Casting
After the metal has cooled and hardened, the mold is opened, and the part is ejected. To avoid potential injuries, ensure the part has completely cooled before handling.
Cooling
Once the casting has been set, it must be cooled and removed from the mold. This is a crucial step for maintaining the casting’s structural integrity. Manufacturers typically use forced or natural cooling during this stage of die casting. However, the choice of cooling method often depends on the casting’s size and complexity.
Ejection
After completely solidifying the cast, unclamp the die mold to activate the machine’s ejector pins. It will push out the solidified part. To make ejecting the part easier, lubricate the mold before injecting the molten metal and incorporate a draft angle.
Trimming
In the final stage, excess metal in the finished product’s sprue and runner is removed using tools like saws, grinders, or trim dies. The removed parts can be recycled, but care must be taken to prevent damage to the casting.
Types Of Die Casting
There are various types of die casting, each with unique benefits. The two most common types are cold chamber and hot chamber.
Hot Chamber Die Casting
The hot chamber die casting process suits materials with low melting points, such as lead, zinc, magnesium alloys, and tin. Avoid contact with metals or alloys with a higher melting point to prevent pump damage. Inject melted metal into the die using hydraulic pressure.
Hot-chamber_die_casting_machine_schematic
Cold Chamber Die Casting
Cold chamber die casting is a crucial process for metals with high melting temperatures, such as aluminum, copper, and their alloys, that cannot be processed in a hot chamber die casting machine without damaging it. This method is essential for creating components that require the superior strength and thermal properties these metals provide, making it vital in the automotive, aerospace, and heavy machinery industries.
In contrast to the hot chamber process, the cold chamber process involves manually ladling molten metal into a cold chamber where a hydraulic or mechanical plunger forces the metal into a die cavity. This separation of the melting process from the press allows for handling metals that would otherwise degrade the machine components due to their high melting points.
The cold chamber casting system is especially valued for its ability to produce large, sturdy parts with exceptional mechanical properties and high durability. The process also accommodates higher melting temperatures and, thus, wider alloy choices, making it flexible and indispensable for producing critical parts that must withstand extreme conditions.
Different Variations of Die Casting
The variations were suitable for addressing defects and other issues during the casting process.
Vacuum Die Casting
Vacuum casting differs from traditional casting because it uses a vacuum to prevent air entrapment, resulting in improved surface finish and dimensional accuracy. This casting process is widely used in the automotive, medical, and aerospace industries to produce parts such as transmission cases, aluminum implants, and brackets.
Semisolid Die Casting
Semisolid die casting(SSDC), known as thixomolding or rheocasting, produces parts with tight tolerances and dimensional accuracy. It applies to making parts with complex geometries, such as transmissions, engine mounts, and electronic housings.
Low-pressure or Gravity Die Casting
This method simplifies tooling and equipment, enabling low-pressure casting of thicker parts using gravity-fed or hand-ladled fill. It is ideal for symmetrical, round aluminum die casting components.
Squeeze Die Casting
The process involves filling the tool and closing it tightly, forcing the filling material into small cavity sections that would not usually fill quickly. This casting method is well-suited for highly viscous metals such as copper, zinc, and nickel.
Benefits And Limitations Of Die Casting Process
Die casting is a rapid and cost-effective production method that produces hundreds of thousands of precise and dimensionally accurate pieces from a single mold. Here are some of its benefits and limitations.
Benefits of Die Casting Process
Please remember the following points about die casting:
Cost-effective
Die casting is an incredibly cost-effective manufacturing method for large production runs. As production volume increases, the cost per part decreases significantly, making it a highly efficient option for your manufacturing needs.
Good Mechanical Properties
Die casting produces components with excellent mechanical strength, superior to forged parts. It also results in parts with enhanced conductivity, hardness, and durability.
Excellent Finishing
Depending on your needs, die casting allows for rapidly producing complex parts with smooth or textured surfaces.
Fast Delivery
When the die casting mold is prepared, the average die casting process cycle is usually quite short, often taking only a few days, depending on the size and characteristics of the material.
Disadvantages of Die Casting Process
Labor Intensive
The process requires continuous monitoring and supervision, especially during the cooling phase.
Non-Alterable Dies
Die are made of hardened steel, so they cannot be altered or adjusted. Additionally, they are expensive to produce.
Restricted Material Use
Die casting is only compatible with metals with a high fluidity, limiting the variety and types of materials that can be used in the process.
Factors To Evaluate When Scheduling Die Casting Geometry
The design of die casting shapes influences how the parts are filled and cooled, affecting porosity, grain, and stress. Factors to consider when creating die-casting geometries include:
Corners and Filets
Filets, the curved sections of the casting where two surfaces meet at a sharp angle, are added to a die casting to eliminate disliked sharp edges and corners. Extensive inner and outer corner radii benefit the cast part.
Draft
In die casting, a draft is a taper that allows the alloy to fit snugly inside the casting as it cools and solidifies. The larger internal draft helps easily and accurately eject the completed part from the die.
Pockets
Die-cast designs can include pockets to make parts lightweight. These pockets, called metal savers, are essentially holes or open areas in the die’s design. Well-placed pockets make the finished part lighter without compromising its structural integrity.
Wall Thickness Uniformity
An ideal design should result in consistent wall thickness throughout the casting. This doesn’t mean the thickness should be the same everywhere, but substantial differences in wall thickness should be minimized. Uniform thickness makes controlling the metal flow into the die easier and ensures a complete fill.
Ribs and Bosses
Bosses are used as stand-offs and mounting pointswhile ribs provide support without thickening the wall. Integrate rethe quired bosses and ribs directly into the die-cast to increase strength and reduce sharp corners.
Guidance To Create High-Quality Metal Die Cast Parts
Die casting involves injecting molten material into a mold. However, to achieve optimal part quality, consider the following tips.
Use High-Quality Materials
Choose high-quality alloys for your die-cast products and ensure they are free from contaminants and impurities. Additionally, it is important to calibrate your die-casting machine correctly to achieve optimal performance and consistent material properties.
Quality Control
Remember to implement efficient quality control procedures when producing high-quality die-cast parts. This involves monitoring process parameters, inspecting parts for flaws, and taking corrective actions. Also, consider implementing statistical process control (SPC) techniques to identify trends and make data-driven decisions.
Optimize Die Design
Optimizing your die design is crucial for ensuring high-quality products. Factors such as wall thickness, draft angles, and fillets should be considered to facilitate easy ejection of the part from the mold. Additionally, the positioning of gates and runners should be carefully planned to ensure smooth entry of molten metal into the cavity, preventing gaps or flaws.
Surface Finish Options For Die Casting
Die-cast parts need a well-finished exterior to ensure longevity, protection, and an appealing appearance. Various finishing options are available for die-cast items.
Plating and Ceramic Coating
Plating and ceramic coating are methods used to give die-cast parts a desired surface finish. Both processes enhance the product’s aesthetics and, in some cases, its conductivity with a thin finish layer.
Powder Coating
When powder coating, charged particles are applied to the surface of the die-cast component. This method is preferred for its uniform application, better control over thickness, and ability to conceal minor imperfections on the die-cast surface.
Painting
For many materials, paint serves as additional protection or decoration. It is optimal to clean the metal surface before applying the paint to remove contaminants like oil and apply an undercoat (primer) to aid adherence.
Antiquing
For zinc casting, this surface finishing gives the cast an aged look. It involves coating the casting with a colored material, such as copper sulfide, after electroplating it with copper or other alloys.
Various Applications of Die Casting Products
Die casting is a process used to create a wide range of highly functional and unique parts. Here are some applications:
Consumer and Industrial Products: This method can make consumer parts like connecting rods, heat sinks, sink faucets, and compressor pistons.
Automotive: This technology is used to make miniature engines, transmission cases, gears, and other specialized components required in the automotive industry.
Aerospace: The aerospace industry requires superior quality, lightweight metal parts that meet strict quality standards. Die casting is an inexpensive way to meet these requirements.
Enze: Your Trustworthy Die Casting Service Supplier
Die casting is an essential method for producing metal parts and is known for cost-effectiveness and efficiency. While the process is simple, it does require expertise. Therefore, it is preferable to outsource to a reputable company like Enze. Enze is a trusted partner for high-quality die-casting services. Our professional team handles various machining projects, offering precision and efficiency in producing complex die-cast components. We cater to industry requirements, including automotive, electronics, medical, and aerospace. Whether you need prototyping or mass production, Enze’s reliable die casting solutions ensure superior performance and quality for your projects.
Conclusion
Many of our products are produced using the die casting method. Die casting is useful for different industries because it can manufacture highly precise metal parts and components.
FAQs
Is the Post-Machining Process Required After Die Casting?
Post-machining depends on the specific requirements of the part. Some parts may need additional machining operations, such as grinding, to improve surface finish or achieve tighter tolerances. Additionally, the castings can be left unfinished for the next manufacturing stage.
How many types of die-casting dies?
There are four types of die-casting dies: single cavity die, multiple cavity die, unit die, and combination die.
What is the difference between die casting and injection molding?
Die-casting is used for metals like zinc, aluminum, and magnesium, while injection molding is used for plastics, rubber, and some metals.
What is the cost of die casting?
Aluminum die-casting prices vary based on part complexity, size, and production volume.
Can die casting be used for prototyping?
Die casting can be used for prototyping, especially for metal parts with a low melting point.
