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Injection Molding

What is injection molding?

Injection molding is a manufacturing process in which molten polymer is injected under pressure into a precision-made mold, where it cools and solidifies into the required shape. It is ideal for producing complex, consistent components in medium-to-high volumes, offering fast production cycles, repeatable quality, and low per-part cost once the mold tooling is created.

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How the Process Works

  • 1. Design review

    We review your component specifications and CAD drawings, as well as your required volume to see if injection molding would be suitable.

  • 2. Material Selection

    We help you choose the right material for your performance and cost goals.

  • 3. Precision Injecting

    Polymer granules are heated until molten, then pressed into a precisely engineered mold. The polymer cools and solidifies into the required shape, after which the mold opens and the finished component is ejected.

  • 4. Inspection and Certification

    Your component(s) are then fully inspected and sent to you with a CoC.

  • When would you choose this method?

    Injection molding is usually chosen for medium-to-high production volumes where consistent quality, fast manufacturing cycles, and a low cost per part are important. It is particularly suitable for complex components that can be produced repeatedly from the same design, provided the volume justifies the initial mould-tooling investment.

    Common injection-moulded components include:

    • Screws
    • Housings and enclosures
    • Electrical connectors and insulators
    • Clips, fasteners and brackets
    • Gears, bushes and spacers
    • Seals and protective caps
    • Medical-device components
    • Automotive interior and under-bonnet parts
    • Appliance and electronic components
    • Handles, knobs and buttons
    • Fluid-handling fittings
    • Packaging closures and containers
    • Complex components with integrated ribs, bosses or snap-fit features

  • Why choose this method?

    Injection molding is preferred when large quantities of identical polymer components are required quickly and consistently. Although mold tooling involves a higher initial investment, the process delivers short production cycles and a very low cost per part at scale.

    Compared with CNC machining, injection moulding creates complex shapes with less material waste and can incorporate ribs, bosses, clips, threads and textured surfaces into a single component. Compared with compression moulding, it generally provides faster cycles, tighter dimensional control and greater flexibility for thin walls and intricate details.

  • The benefits of this method:

    • Fast, repeatable high-volume production
    • Low unit cost once tooling is established
    • Complex features formed in one operation
    • Consistent dimensions and surface finish
    • Minimal material waste
    • Reduced need for secondary machining
    • Wide selection of polymers, colours and additives
    • Potential to automate much of the production process

Various Sizes of Injection Molding Machines

Injection molding machines vary depending on their clamping force to keep their mold closed. The pressure produced is measured in tons and commonly split into these size categories:

Small Machines (5 to 200 tons)

  • This size is best for small, detailed, or simple plastic parts
  • Most screws are manufactured in this size

Medium Machines (200 to 500 tons)

  • This is used for general-purpose consumer goods and automotive interior pieces

Large Machines (500 to 2,000 tons)

  • Built for heavy industrial parts, large automotive panels, or large containers

Extra Large/ Giga-Molding Machines (2,000 to 12,000 tons)

  • Massive industrial giants use this-sized machine for large vehicle components and large pallets.

Limitations of Injection Molding

Injection molding is an ideal manufacturing method for high volumes of complex parts; however, it is not suitable for all customized pieces. Producing a mold for components is costly and must be justified by the volume of pieces being produced. Furthermore, if the product's design changes, then the mold will need to be altered or replaced. This leads to high minimum production volumes.

When a component is suited to injection molding, manufacturers must be wary of potential molding defects caused by gate marks, sink marks, and flash.

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