Recently, there has been quite a bit of discussion around injection screws and their role in the plastic extrusion operation and process. While conventional wisdom has dictated that injection screws are necessary in order to get the plastic into processing, new technology may be changing all of that. Here are just a few of the newest thoughts on whether or not injection screws are still needed for the plastic extrusion process:
- New technology has recently emerged. Some of the newest technology, created by Spiral Logic of Hong Kong, is a screw that doesn’t provide any compression at all. Instead of using friction to heat up the plastics, this company is now using heater bands to melt the plastic prior to it hitting the die.
- Heating the plastic without the screw is solving processing problems. There have always been technical challenges in injection screw technology. With the advent of using heater bands, some of these problems have been eliminated. Issues with temperature, the density of the material, uniform viscosity and achieving consistent pressure have all been solved.
- Fixed screws are also a possibility. Fixed screws – one that is only used to extrude the plastic into the mold – is another option instead of injection screws. Using a fixed screw in conjunction with conductive heating is another new technology that is seeing some traction instead of the injection screw option.
- Mixing screws offer versatility. The new mixing screw can be adapted to many different resins and temperatures for better consistency in processing.
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