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Twin Screw Compounding Extruder

For a modified polymer granulation line, there are three major machines: compounding extruder, pelletizer, feeders. An effective production line means a proper combination of these three equipment.
The twin screw extruder is a key component in this process as it plays a crucial role in determining the final product quality and efficiency. This article aims to provide an insight into the science behind twin screw extrusion and to show some projects in various application.

1.Configuration of a twin-screw compounding system

1.1 Drive train
In the extrusion process, the shear and energy for transferring, melting, mixing, are imparted via rotating screws.
Gearbox powered by motor provide equal speed and torque to the two screws at a suitable screw speed. 
The relation between Power, Rpm and Torque could be describe in formula:
In general, the greater torque means greater loading capacity of the screws,then the greater output.
JieYa manufactures  two series  :
HT-series  with specific torque higher than 11
SHJ-series  with specific torque around 5.
1.2  Feeding system
The “system” concept is critical, since processors need both good individual feeders and a good overall feeding system, from the refill mechanism to the extruder, if the compounding line is to operate efficiently.
When choosing feeders for a compounding line,you shoulud know:
  • materials’ particle sizes and shapes
  • Bulk densities
  • Flow characteristics (free-flowing or not)
  • Throughput and accuracy requirements for each feeder
Volumetric VS Gravimetric

 based on volume in speed.
Displacement principle: require uniform and consistent material supply for feed accuracies


based on weight in speed.
loss-in-weight technology, measures the reduced weight while dosing

Rifill machanism
1.manual pre-mix before fed
2.manual recalibrating when material changes density, bridges above the feed trough or changes its flow behaviors

1.automatic refilling, separate multiple feed streams at the same time
2.Self-calibrating when material fluctuations happen
Suitable for
1.Refilling a loss-in-weight feeder
2.most effective with relatively free-flowing uniform-density materials, such as pellet

1.high feeding accuracy required. (Pharmaceutical and food production)
2 high automation required

1.3 Compounding extruder
Compounding extruder is core part of twin screw extrusion to achieve a high-quality,homogeneous melt by modular designed screws and barrels.
Reconfiguration of the segmented barrels and screws provides the extruder flexibility not seen in other technology, such as single screw extrusion. It saves cost for customers who want to use one equipment to accomplish several production tasks.
Usually, we divided the barrel /screws into individual zones according to process tasks, such like intake zone, melting zone, vacuum zone and meter zone. Each barrel section is independently heated and cooled for precise barrel-temperature control. Each zone may be 4-5 L/D long.
Benefit Of Jieya Twin Screw Co-rotating Extruder
Our products are the result of nearly20 years of activity in manufacturing co rotating twin-screw extruders within a range of Ø 20 to 135 mm.
Excellent Dispersion at High Throughput Rate
Optimum Do/Di means more free volume for dispersing and distributing as well as high material loading
 Easy Operation
Self-cleaning effect of the two intermeshing co-rotating screws result in fast cleaning and therefore fast change of color.
 Reliable performance
Modular designed screw element and barrel realize accurate control of temperature, residence time which are crucial to the process.
Low Cost, Long Lifetime of Spare Parts
Equipped with CNC machining centers, our factory produces screws and barrels are manufactured by ourselves, enabling a tight control of quality and cost.
1.4 Pelletizing system
Granulation is an important part  in the total production process.In order to cut material efficiently, you’ll need a granulator configured specifically for your application.There are two categories of pelletizing system: Strand pelletizing VS Die-face Pelletizing. The main difference is the timing of cut,after cooling or before.
Cool cut
Strands come out from the die of twin screw extruder and then cooled by water bath. The guide rollers make the strands separate until they solidify. Then they are air dried and fed into nip rolls to a multi knife-blade rotor operating against fixed blades.

Hot cut
Die-face pelletizers produce pellets by the use of knives rotating rapidly across a multiple-hole die plate. The pellets are cooled in air alone with a water mist or by subsequent immersion into a water chamber.
Underwater pelletizing is currently the most used hot face pelletizing system in the plastics compounding field.
Before sizing the granulator appropriately,you should need information:
•Application : blow molding, injection molding, extrusion, recycling—imposes different demands on a granulator.
•Material: Different materials can react very differently in a granulator.
•Part dimensions: Try to capture the range of potential part sizes include largest and smallest, thickest and thinnest.
•Capacity: What lb/hr or kg/hr is expected?

Through careful analysis of the above information,We will recommend an appropriate solution for what the processor is trying to achieve. This should include options on rotor and cutting-chamber design and the number of fixed knives required...
2.How to evaluate extrusion system

For twin-screw extrusion processes, an effective production line means effective combination of each machine and extrusion conditions(temperature, residence time ,pressure).However, challenges can exist anywhere: from the feed system through the process section to  granulating machine.For example:
In the feed section, Low-bulk density polymer powder, difficult-to-handle materials may stick or flow poorly through feeding equipment, limiting the feeding rate, ultimately limiting the output.
In the process section, an improperly designed melting section may not be able to fully melt the polymer above a certain throughput rate. Improper residence time will result in polymer melting too early, that may reduce the mixing 
In granulation process,lack of maintenance alone can lead to poor quality granulate with excessive fines and high dust content in the material and in the plant environment.
An effective compounding system should be meet several requirements:

output, energy consumption
heat homogenization ,degree of mixing, quality of dispersion,  stability of extruder throughput, structural changes – degradation, quality of the extrudate – appearance,   physical properties
3.customer experience
length of service life, production versatility, automation of extrusion process
For us designer and manufacturer, we have great responsibility to ensure that the product will conform to customer requirements, comply with specification, meet cost targets, and ensure quality in every aspect of the product, including its manufacture and assembly. 
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