The Plastic Injection Molding Process

When an outsider first encounters the plastic injection molding process it is totally bewildering. There is so much equipment that is interconnected and everything is moving automatically that you wonder how it can all work so well.

Like most industrial processes, one thing builds on another and when you break it down into it's individual components, it all makes sense. Another amazing thing is that this manufacturers and suppliers come from anywhere on earth, and it is all integrated, usually.

The injection molding machine might be made in Austria, the sprue-picking robot in the USA, the plastic material in France, the hot runner system in Canada, and the mold maker could be in China.

Plastic injection molding process

1. An company or inventor gets an idea for a product, new or improved
2. An industrial designer comes up with a possible design
3. A prototype is possibly made out of plastic, wood, metal or SL (stereo lithography)
4. A final design is approved
5. An injection mold maker is given the job to produce a production mold out of tool steel. This could be pre-hardened, such as NAK-55 or 80, P-20, or PX-5.
6. Depending on the product, it might be made for a blow mold, transfer mold, compression mold, thermosetting mold, vacuum forming mold, stack mold, insert mold, silicone mold or even metal injection mold.
7. A custom molder is chosen, or the process could be done in-house.
8. The actual molding process is quite involved, from selecting the proper type and grade of plastic, the correct molding machine, the cycle time, and the machine settings for the process.
9. The parts are inspected for defects, perhaps have a secondary operation performed, such as a coating, then they are packaged and shipped. Very few companies keep much inventory on hand these days because of JIT and lean manufacturing.
10. Many other processes enter in, such as overmolding, metal stamping, release agents, custom resins for the plastic and a great deal of organization.

Another side of the process that is often ignored is the post-consumer aspect. What happens to all this plastic stuff is of great concern for everyone. With the entire global community becoming increasingly consumer driven any processor needs to consider what happens to their plastic products after they are discarded.

Many plastics can be recycled, such as plastic bottles, others simply cannot and must be buried in landfills or dumped somewhere else. Newer bioplastics, which are completely biodegradable, show a great deal of promise to help with this problem, but there is a long way to go.