The Science Behind Prototype Injection Molding


Prototype injection molding mainly uses plastics as raw material. The plastic resins are heated and forced into cavity mold at high pressure to create the desired design. The molds can be used several times, mostly if they are made of aluminum or steel. Plastic injection molding is ideal for mass production of parts and prototypes, although you can use it for low volume production. Prototype injection molding may be expensive and time-consuming, especially when developing molds from steel. Aluminum molds re relatively cheaper since aluminum is quite affordable and readily available. The prototyping process is fast since the melted plastic is cooled rapidly, and sometimes prototypes do not require post-processing.

When is prototype injection molding appropriate

  • When materials used cannot be machined. Flexible plastics like Polycarbonate are sometimes hard to machine.
  • Mass production with a limited budget. Once you have a mold, the process is cost effective and relatively cheaper than other techniques. You can use a steel mold multiple times without losing your dimensions.
  • When high precision, tight tolerance, and complex geometries are required. Small parts with complex geometries are best made through injection molding.

Some materials used in 3D printing are also used in injection molding. Standard materials are; Acrylonitrile butadiene styrene (ABS), Polycarbonate, Nylon, Polypropylene, Polyethene.

Most of these plastics have a low melting point making them ideal for injection molding.

Advantages of plastic over metal

  • May have higher tensile strength than some metals
  • Low melting point
  • Lower product weight

The advantages of prototype injection molding

Prototype injection is used for consumer electronics and home appliances


Prototype injection is efficient, especially if you are using long-lasting molds. Steel and aluminum molds are made through machining- this implies that your design dimensions are accurate. Machined molds have excellent surface finishing eliminating some post-processing needs like sanding and polishing.

Accuracy and a better detailing

Melted plastic is injected into the molds at high pressure, ensuring that it reaches all corners and curves emerge entirely. Although some require support structures, you can easily remove them through machining.


Although making molds is regarded as expensive, the rest of the process is affordable. It would help if you also kept in mind the molds made of steel and aluminum can be used over 2500 times without altering dimensional accuracy

High tensile strength

To increase tensile strength, fillers are also added during the injection. If you require coloring, dyes are also injected during production.

Prototype injection molding is ideal for high volume production since it will offset the mold design expenses. Some prototypes are made ready-to-go finish, meaning that they do not need any add-ons. A recent trend we are noticing is integrating 3D printing in injection molding to reduce costs and save on time. One drawback with 3D printed molds is you cannot use them for high volume production. If you were to look at some of our toothbrushes, you would notice that the materials are arranged in layers. You may think the science behind it is 3D printing, but it is a technique called over-molding.


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