There are five possible zones in a thermoplastic screw. Since terminology is not standardized in the industry, different names may refer to these zones. Different types of polymer will have differing screw designs, some not incorporating all of the possible zones.

Feed zone. Also called solids conveying. This zone feeds the resin into the extruder.

Melt zone. Also called the transition zone. The resin is melted in this section.

 Pressurizing zone. Also called metering or melt conveying. This zone gives the plastic uniform pressure and flow characteristics.

Decompression zone. In this zone, the melt is unpressurized, allowing trapped gases (hydrochloride) to escape and be vented out.

 Mixing zone. There are two types of mixing zone. They either distribute small particles evenly, or break large particles into small ones which can then be mixed.

  Often screw length is referenced to its diameter in terms of an L:D ratio. For instance, a 6-inch (150 mm) diameter screw at 24:1 will be 144 inches (12 ft) long, and 192 inches (16 ft) at 32:1. In years past screw ratios of 24:1 were fairly common, but modern machines use 32:1, or higher ratios, which allow better mixing at higher throughput.
Each zone will be equipped with one or more thermocouples or RTDs for temperature control. 

About First-rate Mold Solution Co., Ltd.
First-rate Mold Solution Co., Ltd. in China, provide industry design,mold design,mold manufacturing,molding analysis,project management service.

 About www.firstratemold.com
our website has a lot of professional knowledges in mold industry in blog and news, also we are interested in CAD/CAM/CAE, such as AUTOCAD,UGNX, PRO/E,CATIA, CIMATRON, SOLIDWORKS, MOLDFLOW and so on,we welcome professional engineer,mold maker and someone who are interested in injection molding,plastic product,injection mold and mold industry to our section of blog and news,we would like to share with them