Injection molding and extrusion are similar manufacturing processes that can rapidly create high volumes of low-cost and identical plastic parts with the desired shape. However, the two processes also have some differences. The following article gives insights about the differences between injection molding and extrusion.
What Is Injection Molding?
Injection molding is a manufacturing process used to create parts by injecting molten material into a mold tool, then ejecting the solidified part with consistent quality. This process can amortize costs as one orders higher quantities of parts. High production volumes of complex parts can be achieved with injection molding. Therefore,the process is well suited to high-volume production of products with complicated shapes.
Advantages of Injection Molding
The followings are some advantages of injection molding in comparison with extrusion:
Quality
Injection molding can produce high-quality parts, which perform better than similar parts produced by other processes.
Precision
Injection molding can offer high precision and tolerances. The average tolerance of injection molds is around +/- 0.005 inches, facilitating the mass production of identical parts with tiny, intricate details.
Compatibility With Various Plastics
Injection molding is well suited to a variety of plastics, allowing greater versatility from a product development perspective.
Speed
Since most injection molded parts don’t need any post-processing, thousands of the same parts can be produced at a competitive speed with production cycles of 30 seconds or less. This brings down mold-to-consumer time for each piece.
Surface Texture Options
Injection molded parts have a wider range of surface texture options in comparison with other manufacturing processes. It helps enhance the functionality or aesthetic outlook of the final parts.
Disadvantages of Injection Molding
Some disadvantages exist in injection molding when compared with extrusion :
High Up-front Costs
Up-front costs are high due to the design, testing, and tooling required. In addition, both the machine and the mold have an impact on the cost.
Not Suitable for Low-Volume Production
Injection molding is a cost-effective process to produce high volumes of the identical parts. It is not suitable for low-volume production due to the high tooling cost and higher per-item costs.
Limited Metal Production
While injection molding can be performed with metals for the mass production of metal parts, injection molding is generally used to produce plastic parts.
Processing Time
IM can restock quickly but upfront tooling time drives lead time for first articles up.
Environmental Impact
Injection molding may have a negative impact on the environment because of the materials used in the process, some of which are difficult to degrade. And quite a bit of power is used to produce plastic products. 
Applications of Injection Molding
Injection molding is a popular process to manufacture parts at scale due to its high quality and effectiveness. It is widely used in different industries such as the automotive industry, the medical industry, consumer products and logistics industry. For example, the process can be used to create many things like bottle caps, toys, storage containers, mechanical parts (including gears), and most other plastic products available today. 
What Is Extrusion?
Extrusion is a manufacturing process where the material is forced through a die of the desired cross-section to create objects of a fixed cross-sectional profile. The process allows efficient and continuous production, and amortizes costs as one orders higher quantities of parts. It is an ideal process when multiple lengths of the same profile shape are required.
Advantages of Extrusion
Multiple Methods
There are 5 primary types of extrusion, including hot extrusion, cold extrusion, warm extrusion, friction extrusion and micro-extrusion. Each has its own unique characteristics and applications.
Material
Extrusion can be done with hot or cold material, including metals, polymers, ceramics, concrete, modelling clay, and foodstuffs.
An Affordable Metal Option
Metal extrusion is more affordable when compared with other metal processes, because it delivers consistent, quick, and quality results in the shorter time.
Disadvantages of Extrusion
Part-size Deviations
Extrusion fails to handle deviations in the cross-section or size. It is difficult to produce oversized products and products with special shapes.The final shapes lack of complexity.
Material Constraints
Extrusion has less material options in comparison with other processes like injection molding. Those materials that may degrade or lose properties under heat are not suitable for extrusion.
Rougher Surface
The surface of the product is rougher than that of injection molding and requires subsequent processing.
Poor dimensional accuracy
The process is complex and difficult to control, and the dimensional accuracy of the product is poor.
Environmental Costs
Extrusion can cause some severe environmental problems for dealing with heated plastic.
Applications of Extrusion
The extrusion process is used to create a wide range of products, including pipes, tubing, cables, sheets, ladders, scaffolds, conveyors, etc.
Differences Between Injection Molding and Extrusion
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