In part one of this two-part blog series, we went over some of the primary vocabulary areas to have a handle on when working with custom injection molding professionals. This is a detailed industry, one that has several distinct terms and phrases you might be exposed to, and while no one expects you to be an instant expert, having a general idea of some of the most common can be very valuable.

At EnviroTech Custom Injection Molders, we offer a wide range of custom and bulk injection molding services to fill your every need. In today’s part two, we’ll go over a few more important terms and areas.

Various Processes

There are a few different potential processes that might be used for plastic injection molding:

  • Hydraulic process: The most common process here is hydraulic, which uses a hydraulic cylinder machine to clamp two halves of a mold together at a high pressure. Pellets are melted from here, then injected into the mold cavity. Once the plastic has hardened, the halves are separated, the part is removed and the process is
  • Electric process: Developed in the early 1980s, electric press technology is a quieter, faster and more accurate format that’s also sometimes used. It allows for digitally controlled motors rather than hydraulics, with repeatable characteristics that are highly valuable for many projects.
  • Hybrid process: Hybrid machines also exist, combining the high-level force of a hydraulic machine with the precision and energy savings of electric machines. These methods are becoming more and more popular.

Runner System

There needs to be a channel for melted material to flow into part cavities, and this is known as a runner system. There are both hot runner and cold runner systems, each best for certain applications. Here’s a more detailed explanation about hot vs. cold runner systems, if you’re interested.

Robotic Tooling

There are several areas of the injection molding processes where robots can play a role, the most prominent of which is end-of-arm tooling that helps automate several processes. Abbreviated EOAT, this tooling helps make the job even more precise.

Hopper and Barrel

You need somewhere to store the plastic to be used in the injection process, and this is known as a hopper. This may contain a dryer unit for pre-processing and/or some small magnets to stop any harmful particles from entering.

When pellets are used, they are fed from the hopper into a barrel. In this barrel, the material is melted in a controlled way and injected into the mold cavity.


Finally, the classification method for the force needed to keep the mold halves closed during the injection process is known as tonnage. Tonnage can range from under 5 tons up to above 4,000 tons. Our team will help you determine the proper press size and tonnage load needed for your project. Contact us today!

For more on important terms to understand within the custom injection molding world, or to learn about any of our other services, speak to the staff at EnviroTech Custom Injection Molders.