SJ Series Plastic Single Screw Extruder Machine
ISO Standard SJ Series Plastic Single Screw Extruder Machine is main part of the core operations in polymer processing and is also a key component in many other processing operations. The foremost goal of a single screw extrusion process is to build pressure in a polymer melt so that it can be extruded through a die or injected into a mold. Most machines are plasticating: they bring in solids in pellet or powder form and melt them as well as building pressure.
Single screw extrusion is one of the methods used for processing materials of synthetic plastics both in powder and molten form. It is mainly used to improve the quality of the melt as well as increase its production by creating pressure in the molten polymer. This forces the extrusion of the polymer. Single screw extrusion is mostly used for polymers that are pure. If they are made of different materials, twin screw extrusion is used. Single screw extruders can either be used as part of a large extrusion system or used as stand-alone machine for extrusion.
The extruder consists of the following: barrel, screw, controls, drive mechanism and arrangement of resin feed. As the screw turns, it moves the resin within the hot barrel. In this way, it reaches the required temperatures as well as mixes thoroughly to form a melt that is homogenous. The pressure which is built up by the single screw extruders then forces the melt from the extruder. It gets out shaped like a die. The whole system has barrier screw that makes sure that the whole resin does not melt in basic extrusion screw
The single-screw plasticating process starts with the mixing of the feedstock mate- rials. Typically, several different feedstocks are added to the hopper, such as fresh resin pellets, recycle material, additives, and a color concentrate. The recycle mate- rial typically comes from the grinding of edge trim, web material from thermo- forming processes, or off-specification film and sheet. Often these components need to be dried and blended prior to adding them to the hopper.
Next, the feed- stock flows via gravity from the hopper through the feed throat of the feed casing and into the solids-conveying section of the screw. Typically this feed casing is cooled using water. The feed section of the screw is typically designed with a con- stant depth and is about 4 to 8 barrel diameters in axial length. Directly after the solids-conveying section is a section where the channel depth tapers to a shallow depth-metering section. The tapered-depth section is commonly referred to as the transition or melting section.
In general, the metering section is also a constant depth, but many variations exist where the channels oscillate in depth. The meter- ing section pumps and pressurizes the material for the downstream unit opera- tions, including static mixers, screen filtering devices, gear pumps, secondary extruders, and dies. The total length of the extruder screw and barrel is typically measured in barrel diameters or as a length-to-diameter (L/D) ratio. Section lengths are often specified in barrel diameters or simply diameters.
Main Technolgy Parameter of L/D 38:1 SJ Single Screw Extruder
| Model | SJ60/38 | SJ75/38 | SJ90/38 | SJ120/38 |
| L/D | 38:1 | 38:1 | 38:1 | 38:1 |
| Power | 110KW | 160KW | 280KW | 355KW |
| Capacity | 400kg/h | 600kg/h | 950kg/h | 1200kg/h |
Advantages of Single Screw Extruders
- Compared to twin screw extruders, they are far much superior at extruding materials that are common.
- They are also far much cheaper than other screw extruders.
- They have less shear when compared to twin screw extruders.
- They can be used in operations for a very wide range of different types of materials.
- They have a very high throughput
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