May 02/24
Extrusion vs Injection Molding: What’s the Difference?
The first synthetic plastic was first invented a little over 100 years ago, and things have changed significantly since then.
We now have a huge number of plastics available along with various manufacturing processes. This makes it possible to design and produce a huge range of parts with all kinds of properties. Extrusion and injection molding are two of the most popular choices in today’s world, but how do they compare?
In this guide, we’ll look at extrusion vs injection molding so you can see some of the differences between the two. Keep reading for more.
Process
The injection molding and extrusion process have one key similarity. Both involve heating plastic to deform it and shape it using a dye.
Beyond this, they are quite different. For extrusion, the plastic is pushed through a specific shape to create the extruded product. It cools down and solidifies in the shape of the dye.
In injection molding, the liquified plastic goes into the injection mold and cools down while still inside. After it solidifies, the part is ejected for the next cycle.
Compatible Plastics
Extrusion is somewhat limited here as it only supports thermoplastics like PVC. Injection molding supports almost all thermoplastics and most thermoset plastics.
Melt Strength
The melt strength of extrusion is higher than that of injection molding. This is because it typically has higher melt strength requirements and some subsequent processing like thermoforming may be needed.
Mold Tooling
Injection molding uses a machine that has a clamping and injection unit. It requires a precise design cavity to work effectively. Extrusion simply requires a non-rubber extruder.
Precision
Injection molding is typically more precise than extrusion. This makes it a more suitable joice for complex parts. Note that this level of preparation means more mold preparation time, so extrusion can deliver quicker results.
Product Manufacturing
Due to the level of precision, injection molding is a more common choice when complex, accurate parts are needed. Extrusion is generally better for 2D parts and simple designs, especially when consistency is essential.
Costs
Injection molding is one of the more expensive types of molding. This is primarily due to the costs of producing molds which must be machined or 3D printed.
Extrusion is simpler, and it therefore tends to be less expensive. Bear in mind that this mainly applies to the production of parts. The overall setup costs for extrusion can still be quite high.
End-Use Application
Both of these processes work well with plastics. As injection molding can produce more complex parts, it’s often used for things like vehicle interior room components.
Extrusion is better suited for continuous components or repeatable parts. Things like pipes and PVC frames are common examples.
Extrusion vs Injection Molding: Which Should You Use?
Ultimately, it comes down to your specific needs. When looking at extrusion vs injection molding, think about the parts you need to produce.
If complexity is a major factor, injection molding may be ideal. For simple parts in large quantities, extrusion may be better.
Mayco International is a leading automotive supplier that uses the latest technologies to produce a huge range of parts. We’ve been in business since 2006 and currently operate out of 38 global locations. Take a look at our manufacturing services page to find out more about how we produce parts.