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
