What is the difference between injection molding and extrusion?

Differences in principle:

Extrusion: Extrusion is to heat and melt solid plastic raw materials, make it through the extrusion of the screw through the specific shape of the die, and then cool and finalize, and continuously produce plastic products with the same cross-section shape, such as pipes, plates, films, etc.

Injection molding: Injection molding is to inject the molten plastic into the closed mold through high pressure, and then open the mold to remove the plastic products after cooling and curing. The injection molding process is intermittent and suitable for the production of plastic parts with complex shapes.

Differences in applicable raw materials:

Extrusion: Suitable for most thermoplastics and some thermosetting plastics, such as PVC, PS, ABS, PC, PE, PP, PA, etc.

Injection molding: Suitable for almost all thermoplastics and some thermosetting plastics, such as phenolic plastics.

Differences in product characteristics:

Extrusion: Extrusion products are usually continuous long strips with the same cross-section shape and can be infinitely long in length. Such as pipes, characterized by continuous production, through the sink, extrusion while cooling. As long as the material continues, it can be extruded all the time, tens of thousands of meters can be, there is no material head.

Injection molding: Injection molding products can be a variety of complex shapes of plastic parts, usually single or group products, a variety of sizes and shapes. For example: plastic washbasins, plastic shells, tool handles, soft rubber toys and so on. Features: can not be continuous production, need to cool a mold and then play a mold. And it has a feed head.

Differences in application areas:

Extrusion: mainly used in the production of pipe, plate, film, wire and cable and other continuous profiles.

Injection molding: widely used in the production of daily necessities, toys, auto parts, electronic and electrical shells and other complex shape plastic products.

Differences in processing methods:

Extrusion: By heating and softening the plastic material, and then extrusion molding through the extruder head, you can make longer plastic products, such as plastic sheets, tubes, lines, etc.

Injection molding: By heating and softening the plastic material, and then extrusion molding through the extruder head, you can make longer plastic products, such as plastic plates, tubes, lines, etc.

Differences in mold use:

Extrusion: The mold is simple, for the mouth die set core die, similar to two rings set together, extrusion pipe shape, and then through the sink cooling hardening.

Injection molding: The mold has an upper and lower die, which is closed and processed inside the cavity, which is the same shape as the product.

In summary, extrusion and injection molding have their own characteristics and advantages, and the choice of processing method depends on the shape, size, type of raw materials and production needs of the desired product.