Injection molding and die-casting are age-old techniques used for manufacturing plastic and metal goods. From the sink in your kitchen to the plastic toy your little one likes playing with, pretty much every product around you goes through one of these processes to get its unique shape.
As a manufacturer, you may already have some questions regarding both processes. Which of the two processes is better?
What are the unique applications for both injection molding and die-casting? And how do you differentiate between the two of them?
The Key Differences
Injection molding and die-casting are two manufacturing processes used to create parts with high precision and accuracy. While they share some similarities, there are key differences between the two processes.
One major difference is the materials used. Injection molding is commonly used with plastics, rubber, and some metals, while die-casting is primarily used for metals with a low melting point, such as zinc, aluminum, and magnesium.
Another difference is in mold design. Injection molds are typically simpler in design and less expensive to produce than die-casting molds, as they don’t require as much durability to withstand lower pressure.
The process for each method is also slightly different. Injection molding involves injecting molten material into a mold under high pressure and then allowing it to cool and solidify before removing the part.
Die-casting, on the other hand, involves injecting molten material under high pressure into a mold coated with a release agent. The mold is then cooled and the part is removed. Surface finish is another factor to consider.
Injection-molded parts tend to have a smooth surface finish, while die-cast parts may have a slightly rougher surface due to the release agent used.
Tolerances are a significant difference between the two processes with Injection molding parts having very tight tolerances, making it ideal for precision parts. Die-casting, while still precise, may not achieve the same level of accuracy as injection molding.
Finally, cost is a factor to consider. Injection molding is typically less expensive than die-casting for small to medium-sized production runs, as the cost of the mold is lower.
Process for Injection Molding
Injection molding can help produce a wide range of plastic products. It is one of the most extensively used processes for manufacturing plastic parts because it is highly efficient and can produce large quantities of identical components.
The process involves the following steps:
- Material Selection: Common materials used are thermoplastics, such as polypropylene, polyethylene, and polycarbonate. It is essential to select the correct material for your application.
- Melting: The selected material is melted in a heated barrel and then forced into a cavity by the machine.
- Injection: Once the molten material is inside, it is allowed to cool and solidify to the shape of the mold cavity. The mold cavity is typically made of two halves held together by a clamping unit.
- Cooling: After the molten material has been injected, it can cool and solidify. The cooling time varies based on unique product specifications.
- Ejection: Once the part has solidified and cooled, the mold halves are opened, and the finished part is ejected from the mold cavity by an ejector system.
- Finishing: The finished part may undergo additional finishing processes, such as trimming excess material or applying a surface texture.
Injection Molding Applications
Injection molding is the preferred manufacturing process for businesses in many industries. Some of the applications of injection molding include:
Injection molding is the go-to manufacturing process in the automotive industry. The high durability of the plastic parts and the flexibility/longevity of the design make injection molding perfect for auto parts.
All the separate car parts in your vehicle, including mirror housings, bumpers, dashboard equipment, and cup holders, are much easier to manufacture through injection molding.
Medical parts require extensive attention to detail and strict policies. The United States requires all medical component manufacturers to use and carry resins with a seal of approval from the FDA.
The cost-efficient and high-volume processing of medical and pharmaceutical parts under injection molding can open new doors to success and increase revenue generation. The process can significantly reduce reworks caused by humans.
Aerospace and Defense
As is the case with most industries discussed in this article, aerospace components also need to meet defined standards. The parts need to be durable and lightweight.
Additionally, they should also withstand temperature changes. Thus, injection molded parts are very popular in aerospace industry.
Food and Beverage
All parts produced in the food and beverage industry go through extensive health and safety tests. FDA certifications alongside GMA-safe programs ensure the well-being of individuals using these products.
Injection molding is extremely feasible in construction goods and finished products. The high stability of the materials used and the mold’s exceptional durability when exposed to external elements, make for an impressive lifespan.
Injection molding also helps provide energy efficiency and cost efficiency compared to other goods such as wood and metal. All in all, the flexibility of the process ensures that a wide selection of finished goods can be produced through it.
The Die-Casting Process
Die-casting uses molten metal to create the perfect fit.
The process followed here is:
- Preparation: The first step in the process is to prepare the die or mold. This involves cleaning the die and applying necessary release agents.
- Melting: The metal to be used in the die-casting process is melted in a furnace. The temperature depends on the type of metal being used.
- Injection: Once the metal is melted, it is then properly injected, and pressure is applied through the machine.
- Solidification: The molten metal solidifies quickly as it cools inside the die. The cooling rate is controlled to ensure that the metal solidifies uniformly and without defects.
- Ejection: After the metal has solidified, the die is opened, and the part is ejected. Any excess metal is trimmed off.
- Finishing: The part is then cleaned and finished as required. This may involve removing any burrs or rough edges and polishing the surface.
- Inspection: Finally, the part is inspected to ensure that it meets the required specifications. This may involve checking for defects, measuring the dimensions, and performing other tests as needed.
For high precision, large quantities of intricate parts, such as, engine blocks and transmission boxes, die casting is the inevitable choice for manufacturers.
Similar to automotive applications, a wide variety of aerospace parts are also manufactured using die-casting processes.
This includes parts that require complex geometry and high precision, including structural, engine and landing gear mechanisms.
Die-casting is a popular choice for intricate electrical parts in computing equipments.
When to Use Die-casting and Injection Molding
We now look at when you should use die-casting and when to use injection molding:
Die-casting is best suited for producing high-volume, complex metal parts with consistent and tight tolerances.
It is particularly suitable for parts that require high strength and durability and those with intricate shapes and features that cannot be easily achieved through other manufacturing processes.
Die-casting is commonly used in the automotive, aerospace, and electronics industries, as well as for household appliances and many other applications.
On the other hand, injection molding is best suited for producing large quantities of identical plastic parts. It is a highly efficient process that can produce parts with excellent dimensional accuracy and consistency.
Injection molding can help produce various automotive parts, including interior and exterior components, such as dashboards, door panels, and bumpers.
The process is also used for a wide range of consumer goods, including toys, kitchenware, and electronics housings. Additionally, injection molding is used for medical equipment, packaging goods, and aerospace components.
Die-casting vs. Injection Molding: Comparing Their Molds
Die-casting is used to manufacture flexible metal shapes. The molten metal is typically a zinc alloy, aluminum, magnesium, or copper, and the molds used in the process are made from high-quality tool steel.
The resulting parts are typically strong and durable and can be produced with tight tolerances and excellent surface finishes.
The molds used in injection molding are typically made from aluminum or steel and can create a wide range of plastic parts, from small components to large enclosures.
The resulting parts are lightweight and can be produced with high levels of precision but may not be as strong or durable as die-cast metal parts.
Die-casting vs. Injection Molding: Pros & Cons
We now study the pros and cons of die-casting and injection molding:
Injection Molding Pros
- Injection molding can be flexible and works on multiple polymers, plastics, and resins.
- Injection molding can be quick
- Injection molding can be cost-effective and wastes no additional resources.
- The additional fillers strengthen the integrity of the mold.
Injection Molding Cons
- Setting up the equipment for injection molding can be a lengthy process.
- Precautions can be lengthy and cumbersome.
- Total operational costs can run high.
- Die-casting ensures a smooth and easy production process.
- The process allows for exact duplicates and ensures originality.
- Die-casting can be highly efficient.
- Die-casting can make it easy to manufacture complex parts.
- Products molded with die-casting are durable.
- Not effective for working on alloys like steel that have high melting points.
- It can be too expensive for small-scale manufacturers.
- Not ideal for larger parts.
- Metals may get porous if not managed with the required precautions.
Die-casting vs. Injection Molding Cost
The cost of die-casting and injection molding can vary significantly depending on the project’s specifics. Die-casting molds are typically more expensive than injection molding molds, as they are made from high-quality tool steel.
Die-casting also requires a metal furnace to melt the metal, which can be costly.
Injection molding molds are typically less expensive than die-casting molds, as they are often made from aluminum or less expensive steel.
Injection molding also requires less energy than die-casting, as the plastic material used in the process melts at a lower temperature than metal.
Die-casting vs. Injection Molding Applications and Uses
Die-casting processing is commonly used in producing components for the automotive, aerospace, and electronics industries, as well as for household appliances and many other applications.
Injection molding can produce various plastic parts, from small components to large, complex parts such as automotive parts, toys, medical equipment, and household appliances.
Die-casting vs. Injection Molding: Manufacturing Use Cases
Die-casting allows for the production of complex shapes with tight tolerances, and it is highly efficient and cost-effective for high-volume production runs. Die-casting can be performed with various metals.
Injection molding is able to produce parts with high accuracy and consistency, making it ideal for high-volume manufacturing applications.
Comparison Table Between Injection Molding and Die-casting
|Lead Time||Generally faster||Longer lead time|
|Cost||Lower cost for smaller volumes||Higher cost for smaller volumes|
|Volume||Better suited for smaller volumes||Better suited for larger volumes|
|Materials||Plastic, Rubber, Elastomers, Composites||Metal, typically aluminum, zinc, and magnesium|
|Surface Finish||Can achieve a wide range of finishes||Typically, smoother finishes|
|Complexity||Can produce complex shapes with great accuracy||Better suited for simpler shapes|
Injection molding is generally faster and more cost-effective for smaller volumes and can work with a wider range of materials. It can produce complex shapes with great accuracy, but the surface finish may not be as smooth as die-casting.
On the other hand, die-casting is better suited for larger volumes and can produce parts with smoother surface finishes. However, it is generally more expensive for smaller volumes and has long lead times.
It is best suited for simpler shapes and can work with a limited range of metals, typically aluminum, zinc, and magnesium.
What Are the Mutual Alternatives to Metal Injection Molding and Die-casting?
There are several alternative manufacturing processes to metal injection molding and die-casting, depending on your project’s specific needs and requirements:
1. Sand Casting: Sand casting is a cost-effective method for producing large, heavy metal parts with a rough surface finish.
2. Investment Casting: Investment casting creates a low-wax cast to generate positive results for the product.
3. CNC Machining: CNC machining involves cutting away material from a solid metal block using a computer-controlled machine. This process is highly accurate and can produce complex parts with tight tolerances, but it is generally slower and more expensive than other methods.
4. 3D Printing: 3D printing involves creating a digital model of the part and then printing it layer by layer using various materials, including plastics, metals, and composites. This process is ideal for producing small, intricate parts but is generally slower and more expensive than traditional manufacturing methods.
Choosing Between Injection Molding and Die-casting
Here is how you can simplify your choice:
- Material: Determine whether your project requires a metal or plastic part. If you need a metal part, die-casting is the better option. If you need a plastic part, injection molding is the better option.
- Volume: Consider the volume of parts you need to produce. For smaller volumes, injection molding may be more cost-effective. For larger volumes, die-casting may be a better option.
- Cost: Consider the tooling, production, and post-processing cost for each process. Die-casting generally has higher tooling costs but lower production costs.
- Complexity: Evaluate the complexity of the part. Pick a choice based on what option works best for the said complexity.
- Surface Finish: Consider the required surface finish of the part. Die-casting generally produces a smoother finish than injection molding, which may be important for certain applications.
- Lead Time: Determine how quickly you need the parts. Injection molding generally has a faster lead time than die-casting.
Kemal: The Leading Provider for Injection Molding and Die-Casting
We at Kemal Precision Manufacturing LTD have the potential to meet your injection molding and die-casting requirements.
With almost 3 decades of experience in die-casting and injection molding, we understand the processes and their intricacies. We have catered to almost 2,000 plus businesses from multiple industries during our time in the industry.
Contact us at 770-365-0810 today to learn more about our injection molding and die-casting processes and which of the two may be better for you.