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110-PP air ducts

Working principle of PP air duct injection molding machine

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PP air duct injection molding machine (Polypropylene Duct Injection Molding Machine) is equipment used to manufacture polypropylene (Polypropylene, PP) air ducts or pipes. It works similarly to a regular injection molding machine, but is specifically designed to produce pipes and ducts.

The following is the basic working principle of PP air duct injection molding machine:

  • Loading: First, load polypropylene or other plastic pellets into the hopper of the injection molding machine. These granules often require pre-treatment, such as drying, to ensure their quality and performance.
  • Heating and melting: The injection molding machine contains a heating element inside, usually a heater or electric heater. These heating elements heat the plastic pellets to their melting temperature, turning them into an injectable melt.
  • Injection: Once the plastic pellets are completely melted, the machine uses a screw to inject the melt into the mold. Molds are specially designed to produce the desired shape and size of ducts or ducts.
  • Cooling: Once the melt is injected into the mold, the cooling system begins to work, rapidly cooling and solidifying the plastic. This ensures that the finished duct or pipe retains its desired shape.
  • Mold opening and discharge: Once the plastic has cooled and solidified, the mold separates, allowing the finished duct or pipe to be removed from it. This process is usually automated but requires supervision by an equipment operator.
  • Inspection and Packaging: Finally, the produced duct or pipe undergoes quality inspection to ensure it meets specifications. They are then typically packaged and labeled, ready for shipment or further processing.

The working principle of the PP air duct injection molding machine is based on the injection molding process and can automatically and continuously produce high-quality polypropylene air duct and pipe products. This type of equipment is widely used in heating, ventilation and air conditioning systems.

The difference between PP injection molded air duct and manually processed PP air duct

PP duct elbow welding

There are some key differences between PP injection molded air duct and hand-processed PP air duct. These differences mainly involve production process, cost, quality and some specific characteristics. Here are some of the main differences between them:

Production Process:

  • PP injection molded air ducts are produced automatically via injection molding machines, which means they are manufactured continuously, consistently, and in large quantities with a high degree of precision and consistency.
  • Artificially processed PP air ducts are handmade and are usually suitable for small batches or special customized products. This can lead to lower production efficiency and some size and shape inconsistencies.


  • PP injection molded air duct usually requires high investment to purchase and maintain injection molding equipment, but lower unit costs can be achieved in mass production.
  • Hand-finished PP ducts typically have a higher unit cost because they require more labor and time to manufacture.

Quality and precision:

  • PP injection molded air ducts generally have greater precision and consistency because they are produced by machines that meet higher quality standards.
  • Manually machined PP ducting can cause inconsistencies in quality and accuracy due to operator skill, process technology, and material variations.


  • The production of PP injection molded air ducts is generally faster and more efficient, and is particularly suitable for high-volume production.
  • Manually processed PP air ducts are produced slowly and are suitable for small batch production or situations that require special design.


  • The PP injection molded air duct production process is highly automated and requires less human intervention.
  • Manually processed PP air ducts require more manual operation and supervision.

Consistency and Specifications:

  • PP injection molded ducts are often better able to meet precise specifications and requirements because they are manufactured from pre-designed molds.
  • Manually machined PP ducts may have size and shape variations because they typically do not use strict molds.

When choosing a production method for PP air ducts, factors such as project size, budget, quality requirements, and production speed need to be considered. Injection molded air duct is suitable for mass production and projects with high quality and precision requirements, while manually processed PP air duct is suitable for small batch production and projects with special needs.

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