6 Step of Plastic Injection Molding

Plastic injection molding is a fully customizable manufacturing process with various applications across industries.

Injection molding is a common plastics part manufacturing process with various applications across the automotive, medical, consumer goods, electronics, energy, and food and beverage ect industries. It’s so common that the global market size came in well over $200 billion in 2021, with significant growth predicted through 2030. Despite the ubiquity of injection-molded thermoplastics, most people are unaware of how much we depend on these products, nor do they consider the manufacturing method. We’d like to talk about plastic injection molding.

What is Injection Molding?

Injection molding is almost precisely what it sounds like: the manufacturing process of injecting molten material, in our case, thermoplastics, into a mold, then cooling and solidifying it to produce a part. Although it seems simple, it’s an exacting, complex process well suited to manufacturing unusual shapes and large volumes of components. It’s efficient, repeatable, and cost-effective without sacrificing quality. 

Chances are you’ve encountered an injection molded component today, whether you know it or not. Injection molding technology produces lifesaving medical devices, auto parts, electronic switches and housings countless other items. Parts produced with injection molding are light, durable, and resistant to extremetemperatures, depending on the type of resin used.

The Plastic Injection Molding Process
1) Designing and Prototyping
Before molten plastic becomes a component, there must be a design. The DFM (design for manufacturability) process starts with blueprints, specs, and CAD files that are revised, tested, and refined until they are ready for production. The appropriate type of thermoplastic is chosen at this stage to ensure that the final component has the right properties.
2) Tooling
Once the prototype is approved, the final plastic mold is created for mass production. Each mold consists of a cavity (the fixed part that the plastic is injected into) and a core (a moving part that fits into the cavity to help form the component’s final shape). Manufacturers custom build each mold in-house for maximum efficiency, quality, and cost savings.

3) Feeding and Melting
Raw material of the chosen engineering-grade thermoplastic is fed into the hopper of an injection molding machine. A long, cylindrical heated barrel with an injection screw sits next to the hopper. A gate sits at the end of the barrel, and the mold tool is connected to the gate. The turning of the screw and the heat from the barrel gradually warm and melt the thermoplastic until it is molten and ready to inject.

4) Injection part
When the molten plastic reaches the end of the barrel, the gate closes, and the injection screw moves back, drawing through a set amount of plastic. As the pressure in the screw builds up, the two parts of the mold tool close together. The clamp pressure from the mold and the injection pressure must be balanced to ensure that the part forms correctly. When the proper pressure is reached, the gate opens, the screw moves forward, and the molten plastic is injected into the mold.

5) Holding and Cooling
After injection, the plastic is held under pressure in the mold for a set period. The holding period allows the plastic to pack out the mold fully, ensuring the part is formed correctly. After holding, the injection screw draws back, the pressure is released, and the part is allowed to cool in the mold. Cooling can take anywhere from seconds to a few minutes.

6) Finishing
After cooling, the injection molding machine will eject the part. Any finishing needed, such as polishing, dying, or removing excess plastic, is completed.

Custom Plastic Injection Molding
Because plastic injection molding is so versatile, it lends itself to customization. Every part of the process can be tailored to fit your unique needs, from material selection to component color and custom mold design. There’s no reason to rely on off-the-shelf solutions regarding injection molding.

Yuanfang specializes in customized plastic injection molding solutions for many industries. Our tool making process, in-house fabrication and tool maintenance capabilities, and dedication to finding the best solution for your injection molding needs ensures that you’ll come out on top. Show us where your finish line is, as we’ll build a custom injection molding solution to get you there on time and within budget. Looking forward to receiving your inquiry.

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