About how to make large plastic molds

Injection molding is ubiquitous as a manufacturing process—in fact, the majority of plastic products in the world today are manufactured by injection molding. While it is an ideal technique for large-scale production needs, traditional CNC machined metal molds have prohibitive high costs and long lead times for low-volume production.

With thermoplastic materials, they can be recycled and are used again. Sometimes this happens right on the factory floor. They grind up the sprues/runners and any reject parts. Then they add that material back into the raw material that goes into the injection molding press.

Injection Molding Leverages Repetition & Consistency
Injection molding is very repeatable. That is, the second part you produce is going to be practically identical to the first one etc. This is a wonderful characteristic when trying to produce brand consistency and part reliability in high volume production.

How does injection molding work?
In principle, injection molding is simply the process of squeezing liquid plastic into a mold and waiting for it to harden. In practice, however, it’s a little more complicated than that.

There is a wide range of material possibilities with injection molding, so the first stage of the process involves selecting an appropriate thermosetting plastic — a material that can be melted, injected and then cooled to rapidly form a plastic part. Many materials can be used for this process, including rigid, flexible and rubber-like plastics.

Before the injection molding cycle starts, the material is usually acquired in granular form. But before it can be turned into a part, it must be heated and transformed into its molten form. This process is carried out by a heated barrel. The material, stored in a hopper, is forced by a ram into the heated barrel, where it liquifies. It is then pushed toward the mold by a reciprocating screw.