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Do You Know What is Injection Molding?
Source:https://www.keyence.com/ss/products/measure-sys/machining/injection-molding/about.jsp | Author:advertising-1 | Published time: 2023-03-07 | 1066 Views | Share:

Nozzle for injecting melted material

After forming, the runners are trimmed from the molded part to complete the process.

After forming, the runners are trimmed from the molded part to complete the process.


How does it work?

Although on the face of it, the injection molding process may seem simple, there are many parameters which need to be tightly controlled to ensure the overall quality of the plastic components produced. Understanding the process and parameters in some depth will help manufacturers to identify plastic components producers who can provide the quality and consistency they need.


Step 1: selecting the right thermoplastic and mold

Before the actual process begins, it’s key that the right thermoplastics and molds are selected or created, as these are the essential elements that create and form the final components. Indeed, to make the right selection, manufacturers need to consider how the thermoplastic and mold interact together, as certain types of plastics might not be suitable for particular mold designs.

Each mold tool is made up of two parts: the cavity and the core. The cavity is a fixed part that the plastic is injected into, and the core is a moving part that fits into the cavity to help form the component’s final shape. Depending on requirements, mold tools can be designed to produce multiple or complex components. The repeated high pressures and temperatures that mold tools are put under mean they are typically made from steel or aluminum.

Due to the high level of design and quality of materials involved, developing mold tools is a long and expensive process. Hence, before creating a final bespoke mold, it’s recommended that tools are created, prototyped and tested using computer aided design (CAD) and 3D printing technology. These tools can be used to digitally develop or create a prototype mold that can then be tested in the machine with the chosen thermoplastic.

Testing the tool with the right thermoplastic is key to ensuring that the final component has the right properties. Each thermoplastic offers different characteristics, temperature and pressure resistances due to their molecular structure. Plastics with an ordered molecular structure are called semi-crystalline and those with a looser structure are known as amorphous plastics.

Each plastic’s properties will make them appropriate for use in certain molds and components. The most common thermoplastics used in injection molding and their characteristics include:

  • Acrylonitrile-Butadiene-Styrene (ABS) – with a smooth, rigid and tough finish, ABS is great for components that require tensile strength and stability.

  • Nylons (PA) – available in a range of types, different nylons offer various properties. Typically, nylons have good temperature and chemical resistance and can absorb moisture.

  • Polycarbonate (PC) – a high-performance plastic, PC is lightweight, has high impact strength and stability, alongside some good electrical properties.

  • Polypropylene (PP) – with good fatigue and heat resistance, PP is semi-rigid, translucent and tough.

The final thermoplastic selection will depend on the characteristics that manufacturers need from their final component and the design of the mold tool. For example, if a manufacturer needs a lightweight part with electrical properties, then PC will be appropriate, but only if the mold doesn’t need to operate above 135C or at very high pressures, which the plastic won’t be able to resist.