Injection Molding Process 6 Steps and How Does It Work?

2024-02-26 16:18:52

Injection molding is a highly reliable and high-quality process commonly used to produce plastic components, from small precision parts to large automotive components. The global plastic injection molding market is projected to grow at a rate of 4.8% from 2021 to 2030. This article will provide an in-depth look at the injection molding process, how it works, the steps involved, and the products that can be made from this process.



What is Injection Molding Process?

The injection molding process is a method for manufacturing plastic products used in various industries. It works by injecting melted plastic granules into a mold, which then cools and solidifies into the desired shape and size of the required plastic products. 

Plastic injection molding is a widely used in industries like automotive, medical, and consumer goods for a variety of reasons, including:

  • Design Flexibility: Injection molding offers unmatched design flexibility, allowing for the production of highly intricate and complex shapes. This flexibility extends to the choice of materials, colors, and surface finishes, giving manufacturers a wide range of options to meet their specific requirements.
  • High Efficiency: Once the process is set up and tested, injection molding machines can efficiently produce high volumes of components. The use of servo injection molding machines further enhances energy efficiency during production.
  • Minimal Material Waste: Injection molding is a highly efficient process that generates minimal material waste. Any excess material, or "flash," can often be recycled and reused in the production process, reducing overall material costs and environmental impact.
  • Consistent Quality: Injection molding provides consistent part-to-part quality, ensuring that each component meets the required specifications. This consistency is crucial for industries where precision and uniformity are paramount.
  • Wide Range of Applications: Injection molding is suitable for a wide range of applications across various industries, including automotive, medical, electronics, and consumer goods. Its versatility and flexibility make it an ideal choice for manufacturing a diverse range of products.
  • Cost-Effectiveness: While the initial tooling costs for injection molding can be high, the per-unit cost of production decreases significantly for high-volume runs. This cost-effectiveness makes injection molding a cost-effective solution for large-scale production.
  • Fast Production Times: Injection molding can produce parts quickly, with cycle times ranging from a few seconds to a few minutes. This fast production speed makes it ideal for meeting tight deadlines and responding quickly to market demands.
  • Improved Strength and Durability: Injection-molded parts are known for their high strength and durability, making them suitable for applications where reliability and longevity are essential.
  • Automation Compatibility: Injection molding is well-suited for automation, allowing for the integration of robotic systems to handle part removal, inspection, and packaging. This automation helps further improve efficiency and reduce labor costs.

Further reading related to injection molding: What are Fundamentals of Injection Molding? 3 Keys to Injection Molding Plant



6 Injection Molding Process Steps

The plastic injection molding process involves 6 steps, each crucial to ensuring the final product meets quality standards. 

1. Clamping

This initial step involves closing the two halves of the injection mold, which are typically made of metal. The mold is held closed under high pressure by a clamping unit to ensure the proper formation of the plastic part.

2. Injection

Once the mold is closed, the plastic material, usually in the form of granules or pellets, is heated until it reaches a molten state. The molten plastic is then injected into the closed mold cavity under high pressure, filling the cavity and taking on the shape of the mold.

Further reading related to injection: Features > Injection Unit

3. Dwelling

During the dwelling phase, the molten plastic can dwell or remain in the mold cavity for a specific period. This ensures that the entire cavity is filled and that the plastic material is evenly distributed, resulting in a uniform and high-quality product.

4. Cooling

After the plastic has been injected and has filled the mold cavity, it is allowed to cool and solidify. Cooling is a critical step as it determines the final properties of the plastic part, including its strength and dimensional stability.

5. Mold Opening

Once the plastic part has cooled and solidified, the mold is opened using a clamping motor. The two halves of the mold are separated, and the newly formed plastic part is ejected from the mold cavity.

6. Ejection

In the final step of the process, an ejector bar is used to push the solidified plastic part out of the mold cavity. Any excess material, known as flash, is trimmed off using cutters to ensure the final product meets the required specifications.

6 steps in injection machine process



How does Injection Molding Process Work?

The injection molding process is a critical method for manufacturing plastic parts on a large scale. It involves several stages and parameters that must be carefully controlled to ensure the quality and consistency of the final product. Selecting the right equipment is crucial for this process, as it enhances production efficiency and ensures quality and consistency in injection molding products.


Select Suitable Thermoplastic and Mold

When choosing a thermoplastic for the injection molding process, before the actual process begins, it's crucial to select suitable thermoplastics and plastic injection molds to consider the specific needs of the final component, including mechanical properties, chemical resistance, and appearance, as well as the mold design and production process. 

The most common thermoplastics used in injection molding and their characteristics are:

  • Acrylonitrile-Butadiene-Styrene (ABS): Smooth, rigid, and tough finish, suitable for components requiring tensile strength and stability.
  • Nylons (PA): Available in various types, offering good temperature and chemical resistance and the ability to absorb moisture.
  • Polycarbonate (PC): Lightweight, with high impact strength, stability, and good electrical properties.
  • Polypropylene (PP): Semi-rigid, translucent, and tough, with good fatigue and heat resistance.

Manufacturers must consider how the thermoplastic and mold interact, as certain plastics may not be suitable for particular mold designs. For example, ABS is ideal for electronic housings and toys, while PA is great for mechanical parts, gear wheels, bearings, and automotive components due to its good temperature, chemical resistance, and ability to absorb moisture. PP is commonly used for packaging and containers, while PC is suitable for lightweight parts with electrical properties.

The design of injection molds consists of the mold cavity and the core. The mold cavity is a fixed part into which the plastic is injected, while the core is a moving part that helps form the component's final shape. Depending on requirements, mold tools can be designed to produce multiple or complex components. Due to the high pressures and temperatures, mold tools are typically made from steel or aluminum.


Choose Appropriate Injection Molding Machine

When the mold and plastic granules are prepared, the mold is placed on the injection machine. Plastic granules are then poured into the machine's hopper, where they are heated and melted by the machine's barrel and the reciprocating screw's friction. The melted plastic is then injected into the mold cavity, where it cools and solidifies into the desired shape and size.

injection molding machine



Injection Molding Products

The injection molding process can be used with a wide variety of thermoplastics and thermosetting polymers, making it suitable for a range of applications. Here are some commonly produced items:

  • Bottles and Containers: Plastic bottles for beverages, cleaning products, and personal care items are often made using injection molding. These containers are lightweight, durable, and cost-effective.
  • Automotive Parts: Injection molding is used to manufacture many components in vehicles, including dashboards, bumpers, and interior trim pieces. It allows for the production of complex shapes and precise dimensions, making it ideal for automotive applications.
  • Electronic Enclosures: Plastic cases for electronic devices such as smartphones, computers, and appliances are often produced using injection molding. This process allows for the integration of features such as snap-fit assembly and component mounting points.
  • Toys and Games: Plastic toys and game pieces are commonly made using injection molding due to their ability to produce large quantities of identical items quickly. The process also allows for the creation of intricate designs and details.
  • Medical Devices: Many medical devices, such as syringes, IV tubes, and pill bottles, are manufactured using injection molding. The process ensures that these products are sterile, lightweight, and cost-effective.
  • Packaging: Injection molding produces various packaging materials, including caps and closures, trays, and tubs. These products are lightweight, durable, and often recyclable.
  • Household Items: Injection molding is used to make many everyday items, such as kitchen utensils, storage containers, and hangers. The process allows for the production of these items in a wide range of colors and styles.



Dependable injection molding machine manufacturer

Injection molding is a highly versatile and efficient manufacturing process for producing a wide range of plastic products. From small precision parts to large automotive components, injection molding offers numerous benefits, including mass production capabilities, precision and consistency, and the ability to produce complex geometries. By understanding the injection molding process and selecting the right materials and equipment, manufacturers can produce high-quality plastic parts cost-effectively and efficiently. If you are searching for a dependable injection molding machine manufacturer, please contact us.



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