When factories make plastic products, one of the first big choices is deciding how to mold them. Deciding between squeezing plastic out (extrusion) and shooting it into a mold (injection molding) is super common. These two ways are responsible for much of the world's plastic waste. Both melt and form plastic, but they're good at different things, cost different amounts, and work best for different products.

In this guide, we'll explain how each way works, what they're best at, and how to figure out which one is right for what you need.

Injection molding is a way to mass-produce plastic parts. It's great for making detailed, 3D shapes.

First, tiny plastic pieces go into a container. Then, a screw melts the plastic inside a hot tube. The melted plastic is then pushed into a mold (usually made of steel or aluminum) with a lot of force—we're talking over 30,000 PSI!

Inside the mold, the plastic cools down fast against the sides. It takes the shape of the mold, including any small details like threads or logos. Once it's hard, the mold opens, and pins push the finished part out. This whole process can take anywhere from 15 seconds to 2 minutes, give or take, depending on the part.

People like injection molding because the end products are very accurate. You can make tons of parts that are all exactly the same. It also works with molds that make multiple parts at once.

All of these qualities make injection molding vital for things that must be precise and consistent.

Extrusion operates on an entirely different principle. It is a continuous process intended to manufacture products with a constant cross-section. Plastic pellets go into an extruder. Inside, a screw turns and pushes the pellets forward, squeezing them and heating them until they melt into liquid. Then, this melted plastic is pushed through a mold that gives it its shape.

Right after the plastic comes out of the mold, it's still soft. It then runs through coolers like water baths or is blasted with air to help it harden and keep its shape. After that, the final product is pulled along, cut to the right size, rolled up, or worked on some more, like getting printed or laminated.

Because this process can move between 10 and 500 feet every minute, extrusion is a great option if you need a lot of stuff made quickly and don't need super tricky shapes.

No single molding process is universally superior. Each excels under specific conditions and presents trade-offs elsewhere.

Here's a simple look at key metrics for better decisions. This table shows the variances, based on what works best in manufacturing.

If your need is for structurally complex, high-precision, detail-rich discrete parts, especially in high-volume production where you aim for the lowest unit cost, then injection molding is undoubtedly your ideal choice.Injection molding is great for:

If you require continuous-length profiles with an unchanging cross-section, and relatively looser tolerance is acceptable, then extrusion molding will save you substantial upfront tooling investment. Extrusion is perfect for:

Sometimes, you can mix methods. Like, you can take a basic extruded pipe and add a threaded or snap-fit connector to one end using injection molding. Or, imagine molding a mounting bracket right onto an extruded shape. That way, you get a single, better product that does more.

Do you need really accurate parts with complicated shapes? Don't let the wrong tools slow you down. We build high-quality, high-precision injection molding machines that'll help you make stuff faster and better. Get in touch with our tech team today for a free quote!

Extrusion molding and injection molding aren't about one being better than the other—it's about picking the right one for the job. Extrusion molding is great for long, continuous plastic pieces, while injection molding rocks at making lots of detailed, precise parts.

If you know what each can do, you can choose the best way to balance costs, quality, and how well your product will hold up. That way, the right process will back your product from start to finish.