Plastic Injection Molding

Finally, the rest of the company can secretly learn about plastic injection molding

Sometimes you just have to nod your head and pretend that you know what it is they are talking about. On the other hand, it sure would be nice to really understand how plastic injection molding works and what all those terms mean.

Often, terms like overmolding, two-shot molding, galling, hobbed-in, coined, toasted, NFG, shut-off, etc, etc, are just taken for granted. And usually, people don’t like to reveal that they just don’t know.
Really, it is in everyone’s best interest to truly have a fundamental grasp of the how and why of plastic injection molding. The explanations offered here are not technical, but rather a general idea of the concepts.


This page is for the “rest of the plastic mold company”

Some of the processes involved in plastics molding and moldmaking are easy to grasp, others are downright mysterious to an outsider. Click on any process below to learn more.


EDM, or electrical discharge machining

Of all the methods used to produce a plastic injection mold, EDM is the least understood. How can a non-technical person grasp it when you usually can’t even see what is going on? Since the workpiece is usually submerged in a tank of smelly, oily fluid, who could know what it’s all about?

The main reason to have a basic understanding of EDM is because it is the most essential process involved in plastic injection moldmaking. Before EDM, many operations were extremely difficult and time consuming.

Other names for EDM are: ram EDM, ED, spark erosion, and burner.


WEDM or wire electrical discharge machining

WEDM is sort of a cousin to EDM, in that it was developed quite a bit later. Wire EDM was originally thought to have a very limited application in plastic injection moldmaking, but it has proven to be indispensable.

Mold designers have become very creative in applying WEDM to build injection molds. In the not-so-distant-past, much of what is “wired ” was done on surface grinders. This was very tedious and difficult, requiring a high level of skill and expertise.

Much of what is done with WEDM was simply impossible otherwise. The shapes and contours attainable are sometimes only possible with this technology.

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