Plastic Injection Molding: How It Works

From raw pellet to finished part, injection molding is a process designed for scalability, precision, and reliability. injection molding has evolved since it's conecption but the principle remains: Mass Manufacturing made easy.

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What Is Injection Molding?

Plastic injection molding is one of the most widely used methods of producing plastic parts at scale. The process transforms raw thermoplastic pellets into precise, repeatable components through four key stages:

Plasticization

The heated barrel of a molding machine prepares the raw material to be plasticized or turned into a liquid form by heating it up and the rotating screw finsihed the job by utilizing a process konwn as screw shear.

Injection

The molten plastic is injected under pressure into a steel mold cavity that defines the part’s shape.

Cooling

After injection the cavity pressure drops drastically as the part begins to cool, once it reaches the desired temperature the part is then ready for ejection.

Ejection

The finsihed part is released from the mold a process known as demolding and then it is ready for finishing, assembly or direct use. Finishing process can include but are not limited to machining, hot stamping, heat staking, pad printing, decorating and sonic welding.

Materials & Applications

The choice of material determines how a part will perform in real-world conditions. PharoPLAST works with a wide range of engineering and commodity thermoplastics to meet the needs of industries from consumer products to automotive, medical, and beyond.

  • Acrylonitrile Butadiene Styrene (ABS) – Durable, lightweight plastic used in toys, consumer electronics, and everyday goods (think LEGO® bricks).
  • Polycarbonate (PC) – Strong, impact-resistant plastic ideal for non-shattering lenses, safety shields, and structural parts.
  • Polystyrene (PS) – Economical and versatile, often used in packaging, disposable items, and lightweight housings.
  • Nylon (Polyamide, PA) – Engineered for strength and chemical resistance, common in automotive parts, gears, and waterproof components.
  • Acrylic (PMMA) – Crystal-clear plastic used in display panels, signage, aquariums, and light diffusers.

ABS (Acrylonitrile Butadiene Styrene)

PC Polycarbonate (Lexan)

PP Polypropylene

PA Polyamide (Nylon)

POM Polyoxylmethylene (Acetal or Delrin)

PEEK (poly ether ethylene ketone)

Why Choose Injection Molding

Injection molding remains the manufacturing method of choice for countless industries because of its unique advantages:

Scalability

Ideal for producing millions of identical parts quickly.

Consistency

Every cycle delivers the same precision and tolerances.

Cost Efficiency

Higher cavitation molds (multiple cavities per cycle) reduce cost per part by dividing machine time across more output.

Precision & Quality

Fine details, complex geometries, and tight tolerances are achievable.

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