Plastic injection micro-molding, as its name would imply, is an extremely specialized manufacturing process for producing astonishingly small, high-precision thermoplastic components and parts with micron tolerances. It’s become something of a buzzword in plastic injection molding because it pushes the boundries of that manufacturing process to an extreme — a very tiny extreme. 
The micro-molding process begins, as all plastic injection molding processes do, in a tooling area where a mold is created that has a cavity in the shape of the desired part. Thermoplastic resin is injected into this cavity, producing the component or part at blindingly high speed.
Size Matters
Obviously, the term “micro” suggests that micro-molding has something to do with size, but how small is small when talking about this process?
While size is indeed relative, most experts would agree micro-molding involves parts that weigh less than a gram. But size is only one criteria: the other two are precision and efficiency. It’s one thing to mold something tiny, it’s another thing entirely to mold it precisely and efficiently at rates of hundreds or even thousands-an-hour.
Machines Matter
Today anyone can buy a micro-molding injection press from a wide range of manufacturers. However, hardware alone does not a micro-molder make. It also takes:
- innovation
- processing
- expert tool building
Bring all of these elements together and you have the beginnings of a repeatable micro-molding process. The trick is experience — lots of trial and error then, finally, manufacturing perfection, on a massive scale.
Is Micro-Molding Scalable?
Yes. Not every application requires tiny parts; in many cases a customer has small (but not micro) molding needs that require challenging geometry and tight tolerances, but on a somewhat larger scale. For instance, a plastic part measuring about an inch long (which is larger than most micro-molded components) may have many micro-sized features — perhaps a .004” thin wall section, a .008” diameter hole, etc. — which fall squarely into the micro-molding category.
So there you have it — in a micro-molded nutshell. This is one “small” topic which has huge ramifications in the plastic injection molding world.