Introduction
Die casting involves heating metals into molten form before reshaping them into desired shapes and structures in a mold. This manufacturing technique has been in use as far back as the early 1800s, which, upon several advancements, ensured its yield of parts with dimensional accuracy.
This article is a comprehensive overview of die casting, including the type, steps in manufacturing parts, material options, surface finishing, and other intricate aspects.
What is Die Casting?
Die casting is a part fabrication process that involves melting metals and alloys before injecting them into a pre-made mold. In die cast molds, usually made of aluminum or steel, the liquefied metal cools and solidifies into the intended shape of the part.
These molds are usually manufactured using another process like CNC machining and are often for single use. This feature makes die casting a high-precision manufacturing process, ensuring repeatability and parts meet tight-tolerance requirements.
Classification of Die Casting Process
While there are several die casting processes, two common ones are used in manufacturing industries. They are the hit chamber and cold chamber die casting processes. Indeed, they are basically the same process, with specific distinctions.
Without much ado, let’s examine the two die casting processes.
Hot Chamber Die Casting
Hot chamber die casting is the quicker and more common process. However, it is better suited for low melting point metals and alloys like zinc, lead, and tin. The process involves injecting the already heated and molten metal directly into the die under high pressure, regulated with a hydraulic system. As the metal cools and solidifies into the desired shape in the die, making it a faster casting cycle.
Cold Chamber Die Casting
Since the hot chamber is more common and faster, the reverse is the case of the cold chamber die casting. Also, it is the more favorable choice for high melting point metals, like aluminum alloys. The process involves first channeling the molten metal into the cold chamber before injecting it into the die at extreme pressure.
The hydraulic system used in maintaining high pressure is similar for both methods. However, cold chamber die casting requires significantly higher pressure than hot chamber casing. The cold chamber die casting is the better method, considering it’s compatible with more metal options. Moreover, it reduces machine corrosion and the risk of damaging the pumping system.
The Steps in Die Casting
Regardless of the kind of die casting chamber you are working with, the operation follows similar steps. Below is a quick overview of the entire steps in the die casting process.
Mold Preparation and Clamping
The first step is to ready the mold for die casting. This step is actually critical, as it plays a crucial role in the result of the process. Mold reparation involves cleaning the die to remove every impurity and lubricating it for better injection and ejection of the eventual die cast. After mold preparation, clamp and secure the die to maintain high pressure.
Melting and Injection
While this step means you melt the metal and pour it into the shot chamber, there is a minute distinction. After melting the metal at high temperature and pressure, it is passed into a hot or cold chamber, depending on you are using. Afterward, the metal is injected into the hydraulic system, still at high pressure.
Cooling and Solidification
After injection, the die cast mold generally undergoes a cooling phase and an eventual solidification of its content. This phase is crucial for the durability of the die cast, hence the need for optimum cooling and solidification into the shape of the designed mold before ejection.
Ejection
Once solidified, the manufacturer unclamps the die mold, followed by the ejection mechanism, which pushes the solid casting out of the die.
Trimming and Other Post-Processing
At this stage, you already have your die cast part. Therefore, the manufacturer removes excesses in the spruce and runners, including those in the finished product. Use a trim saw or die to ensure optimal trimming. Afterward, you can engage in further post-processing operations such as anodizing or electroplating to further improve the general features of the product.
Common Materials for Die Casting Technique
While die casting is suitable for various metal options, it is preferred for low melting point metals. This feature makes it more commonly used for non-ferrous metals. Below is an overview of standard metal alloys compatible with die casting manufacturing techniques.
Aluminum Alloy
Examples of aluminum alloy for die casting include ADC12, ADC1, A360, A380, A413, B390, EN AC 43500, and A356. Like standard aluminum, these alloys are known for their excellent strength-to-weight ratio, making them a good choice for manufacturing lightweight parts that require considerable strength.
In addition, they are corrosion-resistant and have top-notch thermal conductivity, which makes aluminum alloys excellent for die casting. Moreover, aluminum die castings can maintain dimensional stability even after experiencing harsh conditions.
Zinc Alloy
Typical zinc alloys for die casting parts include ZDC3 and ZDC5. These zinc alloys are known for their melting point, which is less than 800 degrees Fahrenheit. This property makes them an excellent choice for die casting. Also, zinc die castings are highly ductile, having good thermal conductivity and dimensional stability, making them suitable for fabricating intricate designs.
Magnesium Alloy
The standard magnesium alloy for die casting parts is AZ91D. Its principal property is lightweight, making it a popular choice for creating components for the aerospace industry, where low density is a critical criterion. However, magnesium is generally used in manufacturing because of its flammability.
Copper alloy
Examples of copper alloys for die casting include H58, H59, H62, H65, and H68. Copper alloys are known for their excellent conductive properties. Also, they are relatively resistant to corrosion. These two features make them a good choice for fabricating die casts.
Surface Finishing and Post Processing Options for Die Casting Parts
Die casting parts are compatible with various surface finishing and post-processing options. Below is a brief overview of different finishes that suit die casting product.
Sand Blasting
Sand blasting sometimes called abrasive blasting involves propelling abrasive material on the parts’ surface under high pressure. Depending on its use, it could smoothen a rough surface, roughen a smooth surface, or just help mask die casting blemishes and flaws. It’s pretty similar to bead blasting.
However, sand blasting is more aggressive and creates more dense coatings. Therefore, it’s a better choice for riding die casting metal surfaces of contaminants. Still, both serve similar applications to improve the overall surface property of a part, including aesthetics and resistance to impact, scratch, and corrosion.
Powder Coating
Powder coating is a typical finishing operation for die casting parts. It involves the application of charged powder particles on the surface of a material. However, it ensures the masking of manufacturing flaws and blemishes while improving thickness, appearance, and mechanical properties.
Therefore, the finished product is more durable and resistant to scratch, impact, and corrosion. Moreover, powder coating is eco-friendly, as it does not use nor generate any toxic or harmful material.
Painting
Painting is arguably the most used surface finishing because of its simplicity. It involves spraying paints or sometimes enamel or lacquer on the surface of the finished part. The end result of this surface finish is a shinier and more aesthetically appealing part.
Anodizing
Anodizing is another process that improves the surface quality of a die casting metal surface. The process involves creating an anodic oxide film on the surface of the metal, providing an extra layer of thickness and improving aesthetics. Unlike the previous finishing discussed, it is relatively expensive.
Also, it is a more standard finish for aluminum parts, though other non-ferrous metals like zinc, too, are compatible with this finish. After this finish, the resulting die cast piece has improved appearance and mechanical and chemical resistance, increasing its durability.
Plating
Plating involves the standard electroplating or the electroless process. Either process involves coating the die-casting parts with another metal with improved mechanical and chemical properties, such as corrosion resistance. The main difference is that while electric current catalyzes the electroplating process, minerals catalyze the electroless plating of the die-cast parts.
Teflon Coating
Teflon coating is a chemical coating process that involves using Teflon – a plastic material chemically known as polytetrafluoroethylene (PTFE). The process consists of spraying the metal surface with this waterproof plastic, which improves the part. The resulting surface is non-corrosive and less reactive, as a mechanical barrier shielding the part, ensuring increased durability.
Impregnation
Impregnation is another coating process, called saturation coating or porosity sealing because it uses porous substrates with a structure containing pores that penetrate the entire substrate. The resulting process ensures the filling of pores with thermosets and resin polymers, further reinforcing the material. Therefore, the resulting die cast material is improved with better mechanical, chemical, and overall surface properties.
Machinists and OEMs must clean their casting parts before engaging in any finishing operation. While the surface finishing helps mask impurities, it is better to reduce or remove some of them, like oil and lubricant, before finishing to enhance the quality of the finish further.
Applications of Die Casting Parts
Die casting is highly versatile, suitable for creating different structures, including complex parts. This feature makes it a common manufacturing technique in various industries. Below is a brief overview of its use in some of the world’s popular industries.
Automotive Industry
Die casting is a typical process for fabricating parts for the automotive industry. It is used for creating simple to complex parts, such as gear, engine blocks and cylinder heads, gladhands, connectors, and transmission components, among other parts.
Aerospace Industry
Because of its relatively high precision, versatility, and cost-effectiveness, it is suitable for creating parts for the aerospace industry. It produces parts that meet specified quality and safety standards. These parts can withstand harsh conditions, ensuring durability and tight tolerance specifications.
Electronics and Consumer Goods Industry
The electrical industry is another important sector that uses die casting products for the fabrication of various appliances. The manufacturing process is used to create electrical and household components like switchgear, circuit breakers, connector rods, compressor pistons, panel boards, etc.
Medical Industry
Die casting is able to create parts that adhere to FDA standards and safety regulations, making it a suitable process for fabricating medical devices and toolings. The process is used to create durable medical instruments and equipment.
Other Applications
Besides all the applications discussed above, die casting still offers applications in various industries, such as manufacturing parts for furniture or other household components. For example, it is used in fabricating hardware such as sink faucets, drawer pulls and knobs, door handles, toys, power tool casings, heat sinks, etc.
Pros and Cons of Die Casting
This section will discuss the pros and cons of die casting in manufacturing parts and structures.
Pros of Die Casting
Die casting is a common manufacturing process because of its low production cost and manufacturing ease. Below are more specific die casting benefits.
- Allows the creation of simple to complex parts
- Less labor and tooling costs compared to other processes like machining
- Offers high precision manufacturing and maintains tight tolerance specifications
- Quick production rates at high efficiency
- It’s a highly versatile process suitable for various metal types, including aluminum, zinc, copper, and magnesium.
- Eco-friendly, as most of the materials for this process are recyclable
Cons of Die Casting
Below are some of the drawbacks of this process
- Unsuitable for large sheet metal structures
- Depending on part complexity, die casting might have extended production cycle times.
- Unsuitable for metals with high melting points
Factors That Impact Die Casting Costs
Die casting is relatively cost-effective compared to other manufacturing processes like machining and 3D printing. However, some specific criteria may increase the manufacturing costs of die casting. \
Below is an overview of some of these factors.
Tooling and Mold Costs
Regardless of the manufacturing process, the mold and entire tooling cost plays a crucial role in the resulting production cost. With regards to die casting, manufacturers often have first to fabricate the mold before proceeding to die cast the part. Therefore, the manufacturing process for creating the die cast mold will determine the cost.
Choice of Material
The selected material for die casting also imparts the manufacturing cost. Generally, some materials are more expensive; for example, aluminum is more expensive than carbon steel, and titanium is even more expensive than aluminum. Therefore, using a costly material, you expect an overall increase in the total production cost. Moreover, some materials may require more heat and pressure to die cast. In this case, they increase production costs through processing.
Surface Finishing Options
The post-processing operations that the die cast requires also influence the production cost. This includes the basic finishing, such as trimming, to more extensive ones, like painting and electroplating. Therefore, the actual cost of this operation will affect the price.
While trimming is mostly expected for all die casting products, manufacturers may improve appearance through further finishing, improving the part’s durability and total costs. For instance, you expect painting to cost less than plating or other sophisticated secondary finishing.
Tolerance and Quality Requirements
Strict tolerance and quality standards influence manufacturing costs. Manufacturers often require specialized tooling and surface finishing to ensure parts attain tight tolerance and high-quality requirements. Manufacturing these parts requires extra care, increased precision monitoring, and quality analysis, which attract more expenses.
Parts Size, Weight, and Volume
The required size, weight, and quantity of die cast parts also affect costs. For example, the size and weight determine the material usage, manufacturing time, and energy use. Therefore, more extensive and heavier components will cost more. However, bulk volume manufacturing may reduce costs per part, as it requires the same tooling and specifications yet spreads the production costs over the individual components.
Zintilon’s Expert Die Casting Services
While die casting is relatively simple, achieving desirable outcomes requires expertise. Therefore, you should partner with a reputable service to help ensure your fabrication attains all the necessary design specifications.
Zintilon is an expert die casting service provider. We boast highly knowledgeable professionals with the right skill to help ensure your die casting products suits your intended use. We even offer expert advice on the best way to create your piece if you need clarification.
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Conclusion
Die casting is a vital metal parts fabrication process. It is highly versatile, cost-effective, and efficient for creating parts of varying shapes, structures, and precision standards. These properties make it a valuable manufacturing technique for industrial manufacturing. This article provides a detailed review of everything you need to understand about the process before selecting it for your fabrication.
FAQs
What is a Die Cast?
A die cast refers to the outcome of the die casting manufacturing process. It’s a part metal component manufactured by die casting.
What is Die Casting Tool?
The die casting tool refers explicitly to the die or steel mold, which is integral to the casting process. The mold is usually pre-made using an appropriate manufacturing process, which defines the intended product’s shape, design, structure, and other specifications.
How Does Die Casting Differ From Injection Molding?
While both processes share some similarities, and some may even mistake them as the same method, die casting and injection molding are distinct. The main distinction is that die casting fabricates metal parts, and injection molding is preferred for creating plastic parts.
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