An Overview of Plastic Injection Molding


A wide range of plastic applications has become part of daily life. Many industries rely on plastic because of its cheapness and long durability. There are a variety of plastics used for different purposes. Raw plastic is the most common material used in injection molding to produce every day’s items or parts.

How Did Plastic Injection Molding Introduced? (History Overview)

Plastic Injection Molding is the popular method of the manufacturing process to produce a large volume of complex and high-quality parts from thermoplastic or thermoset plastic granules.   

John Wesley Hyatt was the father of injection molding and the inverter of plastic. In the 1872s, the history of injection molding began when Hyaat invented the first injection molding machine. It was a simple plunger used to push celluloid into a mold by a heating cylinder. The development of the plastics manufacturing industry started to grow when the comb, button, and other tiny items took place.

In the 1940s, it marked the rapid growth of the plastic injection molding industry for mass production after World War II. The thermoplastic including PVC, polystyrene and other plastic materials introduced to create molded plastic parts. This process continued with the innovation of new technology to increase more efficient production. 

In the 1946s, James Watson Hendry invented the extrusion screw (rotating screw) in the injection machine to mix the materials before injecting and improve the quality of plastic injection molded parts. Since then, it revolutionized modern plastic injection molding to expand on a large scale and controlled the entire production process by the operating machining system.

In today’s plastic manufacturing company, extrusion screw types of machines are more popular than traditional plunger types.

Thermoplastic Used to Manufacture Plastic Products:

There are many thermoplastics are available used to produce complex, flexible, and high-quality parts on the specification of the product. Some industries include medical, industrial, aerospace, electronics, food, sports equipment, and automotive use thermoplastic to make plastic injection molded parts:

  1. Acrylonitrile Butadiene Styrene (ABS): This material is light-weighted and flexible, used to make everyday items.
  • Drainage system
  • Kitchenette
  • Polyvinyl Chloride (PVC): PVC products involve rigid and soft plastic that is suitable for construction.
  • Flooring.
  • Building Siding.
  • Rigid Pipes
  • Wire insulation
  • Polyethylene Terephthalate (PETE): PETE is the most usable, cheapest, light-weighted, and recyclable material. This type of part finds empty in rubbish to reuse and recycle.
  • Plastic Bottles
  • Plastic Cans
  • Polystyrene (PS): Polystyrene is suitable for making rigid and transparent parts.
  • Home appliances
  • CD and DVD cases
  • Automotive parts
  • Medical instruments 
  • TV and Computers
  • Polypropylene (PP): Polypropylene is a tough and heat-resistant material to bend products. It requires lots of bending to mold.
  • Plastic furniture
  • Luggage
  • Auto components
  • Toys
  • Medical equipment
  • Polyethylene: Polyethylene is the most popular thermoplastic used to produce crystalline plastic bags. Two kinds of polyethylene plastic, selected on the basis of the product’s needs, involve:

High-Density Polyethylene (HDPE)

  • Food containers
  • Recycled water bottles
  • Toys

Low-Density Polyethylene (LDPE)

  • Shopping Bags
  • Plastic Bags
  • Beverages Box
  • Wire insulation

How Thermoplastic Pellets Turn into Final Products: (Modern Overview)

Plastic Injection Molding Machine plays a scientific role in molding the final finished parts or products. The process starts with injecting plastic pellets into a hollow mold. It fills the mold with molten plastic to the fullest. A mold starts to get cooled and hardened, turning into the desired shape. The final finished products come out from the mold and complete a production cycle. Thousands of identical parts or products can produce in one cycle in a short span of time. This process is repeatable, in that the production cycle continues from the start to perform the same steps.   

Thermoplastic chooses according to its physical and chemical properties to produce complex, tolerable, accurate, durable and high-quality plastic products in large volumes.

It enabled the manufacturing process to grow. The number of technology introduces year over year to expand the production and quality of plastic components. Plastic injection molding is a scientific manufacturing process where a wide range of plastic materials inject, producing a million different products.  

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About the Author: Peter Beaumont

Peter Beaumont is a senior reporter on Daily Mid Time Global Development desk. He has reported extensively from conflict zones including Africa, the Balkans and the Middle East and is the author of The Secret Life of War: Journeys Through Modern Conflict. Email: