In the industrial sector, injection molding and extrusion are used for making different things with different shapes and sizes.
Extrusion is a method by which molten plastic or any other material is pushed through a two-dimensional die opening. It then passes through a series of shapes or sizes where the molten form gets the desired shape once it cools here. In the extrusion method, the finished products have a two-dimensional form which are continuous in length. The extrusion method produces linear shapes.
Both extrusion and injection molding have their own advantages. An advantage in the extrusion method over other methods is that it helps in creating complex cross-sections. Another advantage is that brittle and hard materials can be formed into any shape using the extrusion method. Moreover, the finished materials have a smooth surface finish when compared to other processes including the injection method. In the injection method, there is only minimal waste as the scrap can be recycled again.
The injection molding process is basically based on the molten die-casting method. The injection-molding unit consists of two elements: the injection unit, and the clamping unit. Unlike extrusion, injection molding forms three-dimensional shapes.
The injection molding process was first established in the 1930s. It was Joseph Brahman who patented the first extrusion process in 1797. However, the process was fully developed in 1820 after Thomas Burr developed the first hydraulic powered press. In 1894, the process was expanded to include brass and copper alloys.
Read more: Difference Between Injection Molding and Extrusion