BLOW MOLDING

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Plastic Blow Molding is a manufacturing process used to create hollow plastic parts, such as bottles, containers, tanks, and other hollow shapes, by inflating heated plastic within a mold. Blow molding efficiently produces lightweight, durable, hollow plastic products at high volumes, making it a staple in consumer packaging, automotive, healthcare, and other industries.

Benefits of Blow Molding

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  • High production speed: Fast cycles allow for large-volume output.
  • Cost-effective tooling: Mold costs are typically lower than injection molding.
  • Lightweight parts: Ideal for packaging applications needing minimal material use.
  • Good dimensional control: Especially in stretch blow molding, leading to consistent wall thickness.
  • Design flexibility: Can produce various shapes with handles, threads, or custom contours.
  • Recyclable materials: Supports sustainability with common use of PET and HDPE.

The Process:

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  1. Extrusion or Injection of Preform/Parison
    • Plastic resin is melted and shaped into a tube-like piece called a “parison” (in extrusion blow molding) or formed into a preform shape (in injection blow molding).
  2. Mold Closing
    • The mold closes around the hot plastic parison or preform, sealing the ends.
  3. Blowing and Inflation
    • Compressed air is injected into the heated plastic piece, inflating it to conform exactly to the internal shape of the mold.
  4. Cooling
    • The plastic cools quickly, taking the shape of the mold and solidifying into the final hollow product.
  5. Ejection
    • The mold opens, and the finished hollow plastic component is released or ejected.

Considerations

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Volume & Production Scale: Blow molding is very efficient at scale, especially for simple hollow parts.

Part Design: Ideal if part must be hollow (like a bottle or tank) and should be avoided if parts have internal complexity.

Surface Detail and Finish: Limited in complexity – not ideal for fine surface details or tight tolerances.

Part Size: Small to medium sizes are best; consider rotational molding for very large hollow parts.

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