Die Casting for Industrial Component

Die casting is a manufacturing method used to make a range of metal products, from complex automobile components to simple paper clips. The basic process involves injecting the molten metal into mold cavities where they harden to produce the desired shape.

This method minimizes the requirement for post-production machining and is used to produce metallic parts in bulk. Die casting is the preferred way of producing bulk metal parts in power tools, aerospace, and auto industries.

Die casting for industrial component

Increasing demand from various industries, including the automotive industry and manufacturing sector in the Asia-Pacific region, has led to the creation of die casting hubs, particularly in China.

The push for die casting is also due to the “Made in China” strategy adopted by China that is focused on boosting manufacturing in various sectors.

The prime advantage of choosing China for die casting is the low manufacturing costs and cheaper labor. In recent times, private manufacturers in China have continued to become more and more professional and competitive in making die-cast components. Regional manufacturers in some countries, including China, account for 55% of the global die casting market.

China has been a leader in metal die-casting and accounts for 45% of the world’s casting production. The volume of die castings made in China foundries reached 3.7 million tons in 2015. The die casting industry in China has registered a 13% annual growth rate in the last two decades.

A majority of die castings made in China are used for motorcycles and automobiles.

Advantages of die casting

• High-quality products can be produced in this method that has a long service life.
• Die casting produces bulk metal parts that retain their uniformity.
• The production process is quick and seamless as minimal maintenance is required for die casting tools.
• Any surface texture, geometry, size, and luster can be created using die casting.
• Wide-ranging assembly features, including drill holes, bosses, and studs, can be integrated into the design of the mold, which minimizes post-production assembly.
• High accuracy.
• Designs of varying complexities or details are repeatable.
• Reduced cost as there is only one process of production.
• Minimal scrap and waste material.

Die casting metals

There are many types of metals and alloys used in die casting, and the choice of a particular material depends on the weight, budget, and properties of the material. The most commonly used metals in die casting are non-ferrous metals, which are metals that do not contain a large amount of iron and are known for their malleability. Some examples of non-ferrous metals are copper, zinc, tin, aluminum, nickel, and titanium.

Out of these, the most commonly used non-ferrous metal is aluminum that has a share of as much as 80 percent of die casting. The other preferred non-ferrous metals are magnesium, zinc, copper, tin, and lead. These metals have specific properties that make each of them the ideal choice for a specific application. For instance, metals such as magnesium and aluminum have high melting points, while lead and zinc have low melting points. Other than melting points, each metal offers distinct advantages:

• Zinc is a preferred metal for die casting, given its high impact strength and ductility. Besides, zinc is easy to plate and economical when die casting small parts and prolongs die life.
• Magnesium is one of the easiest metals to machine while being the lightest alloy and has an excellent ratio of strength-to-weight ratio.
• Aluminum is a popular die casting metal as it has good corrosion resistance and is lightweight apart from having high dimensional stability to hold complex shapes. The other advantages of aluminum as a die casting metal are its strong mechanical properties, high electrical and thermal conductivity, and ability to retain strength even at high temperatures.
• Copper has the highest mechanical properties and is preferred for its high corrosion resistance, hardness, and excellent wear resistance. Like aluminum, copper also has excellent dimensional stability while its strength is very close to steel parts.
• Tin and lead have high density and are preferred for their special corrosion resistance properties. These metals offer optimal dimensional accuracy. However, lead is a heavy metal that is linked to health concerns. This is the reason why it is not used to make components for food-service applications. Another alloy of tin, lead, and antimony finds application in letterpress printing as well as hot foil blocking.
• Silicon tombac is an alloy made of zinc, silicon, and copper that gives it high strength and is typically used as an alternative for cast steel parts.

Types of die casting

Hot casting or hot-chamber die casting

Also called gooseneck casting, hot-chamber die casting is more commonly used as compared to the other main process of die casting. In hot casting, the injection mechanism’s cylinder chamber is immersed completely in a molten metal bath. A gooseneck feed system pulls the molten metal into the cavity of the die. The advantage of the hot casting process of die casting is that it has a high rate of production as compared to the cold chamber process.

While the chamber is directly in contact with the molten bath that enables convenient and quick mold injection, the risk for corrosion is high. Hot casting is therefore suited for metals with high fluidity and low melting points such as zinc, copper, and magnesium.

Cold-Chamber die casting

While the cold-chamber process of die casting resembles the hot-chamber process, the focus here is on minimizing corrosion of the machine rather than achieving production efficiency. In the cold chamber method, the molten metal is hand ladled or automatically fed into the injection system, eliminating the requirement of immersing the injection mechanism in a molten metal bath.

The cold-chamber die casting process is an excellent alternative for metals not suited to hot castings, such as aluminum and its alloys that have a high melting temperature.

Low-Pressure die casting

The low-pressure process is ideally suited for components with symmetry on their axis of rotation, such as vehicle wheels. In low pressure die casting, the mold is vertically situated on top of the molten metal bath while a riser tube connects the two sections. Application of pressure ranging from 20 to 100kPa leads to the metal being pulled into the mold.

Vacuum Pressure Casting or VPC

Vacuum pressure casting is one of the newer methods of casting that ensures minimal porosity and enhanced strength. The process is similar to the one used in the low-pressure method except that the molten metal bath and die casting locations are reversed. Molten metal is forced into the mold by the vacuum created in the cylinder chamber.

Squeeze die casting

Squeeze casting is an alternative for casting metals with low fluidity. The open die gets filled with molten metal in this process. The die then squeezes to force the metal to enter the molding.

Semi-Solid casting process

Also known as Thixoforming, semi-solid die casting also delivers maximum density and minimal porosity. The process involves cutting the workpiece using a machine into smaller slugs, which are then heated. When the metal attains a slushy texture between solid and liquid states, it is forced by a shot sleeve to the mold cavity. This method offers enhanced precision and is suitable for non-ferrous materials such as aluminum and magnesium alloys.

How to find high-quality die casting manufacturers in China

There are many manufacturers in China that are invested in die casting which enables mass production of bulk metal parts at low cost.

There are more than 26,000 metal die casting factories in China, many of which focus on non-ferrous castings. In the last couple of years, China has produced 49.3 million metric tons of die castings annually.

Clusters of die casting factories can be found in certain provinces, such as Hebei province.

Before you start your search for a die casting supplier in China, you need to ensure that you have clarity on the component you need, its application, and the kind of manufacturer that can best meet your requirements.

Step 1: As there are different levels of manufacturers in China, you need to think about what level of die casting supplier you need to work with. If there are stringent quality and precision requirements for your products, it is best to work with the middle level to bigger factors that have an established quality control process. If budget is the main criteria, you can partner with smaller die casting manufacturers who can offer economical manufacturer solutions.

At this stage, it is important for you to have an approximate budget that should include the various landed expenses, shipping, packaging, custom fee, and other handling fee.

Step 2: The typical places for searching for a die-cast manufacturer in China include B2B platforms and marketplaces such as Alibaba.com, Global Sources, Tradekey, DHGate, and Made in China. Attending trade fairs such as the Canton Fair is also a great way to find a reliable die casting manufacturer.

There is also an international die casting exhibition organized in China that connects overseas buyers and markets that showcases solutions in the die casting industry while promoting mutual learning opportunities.

Step 3: Check the manufacturer’s background and look for information on the factory location, its size, and capabilities, apart from ratings and reviews. Sites such as Alibaba.com provides a Gold membership status that can mean that the company has undergone a basic level of vetting while Global Sources conducts stringent checks to ensure the authenticity of suppliers. You can then narrow your list to about four to five die casting manufacturers who potentially meet your criteria.

Step 4: Visiting the factory in person is the best way to verify the manufacturer’s authenticity, capabilities, and to check the quality control measures. Once you choose a die casting manufacturer in China, the next step is to negotiate prices.

An OEM contract/business purchasing contract and NDA have to be then prepared in Chinese and signed. These documents have to clearly describe the product quality specification, lead time, order quantity, and other terms.

Step 5: A communication window has to be then set up with the die casting manufacturer so that it is easy for you to maintain ongoing contact with them. This will enable you to get regular project updates and monitor quality control on an ongoing basis. If possible, your staff member or you can personally visit the factory to ensure your quality specifications and timelines are being adhered to. For most buyers in the U.S. or E.U, this can be difficult and expensive.

Step 6: The next step is to choose a shipping method (air or ocean) and coordinate with freight forwarders to ensure your metal parts reach you on time and in a safe condition.

Step 7: While die casting has definite advantages, there can also be certain disadvantages that include

• Cost - Complex, large tools in die casting can involve a high cost of manufacturing

• Shrinkage and warping - Metals tend to shrink as they convert to solids from a liquid state that can give rise to tears and cracks. Reputed manufacturers in China use the latest technology and techniques to allow for shrinkage when die casting. Warping can happen after or during the solidification process that can alter the dimensions.

• Suitable only for high volume - Die casting is perfectly suited for making products in bulk. If your production requirements are smaller, you may have to choose other methods while the expenses of making lesser quantities are also high.

A reliable manufacturer who specializes in die casting in China will be able to provide effective solutions for most of your concerns. However, visiting the factory in person and handling ongoing quality inspections and communication are vital to getting high-quality products from China. This is where a reputable China sourcing agent who specializes in die casting comes in. By handling the end-to-end process of identifying the right die casting manufacturer in China, negotiating terms, drawing up contracts, conducting in-person quality checks, and handling shipment, the sourcing agent can ensure you get the best of die casting products.

Sourcing Allies is a team of expert China sourcing agents that has helped western customers manufacture and source products from low-cost regions since 2006.

For more on China sourcing visit our website or write to us at info@sourcingallies.com.