A twin screw extruder is considered the most efficient mixing and dispersing equipment for plastics processing. And it is widely used in different plastic processing industries, us as plastic compounding, modification, enforcement, decolonization & reaction, direction extrusion(sheet, film, board, profile), and recycling.
Since the twin screw extruder is everywhere in the plastic processing industry, it is very important for us to know the components of the twin screw extruder and how the twin screw extruder is built before getting into operation.
The base frame is obviously to support the machine. There are normally two kinds of base frames for the extruder. One is welded by slot steel, the other is casting. The welded base frame is mostly used by the suppliers. After the welding, the base frame should be stay for some days before application to release the inner force which could reach the best physical property.
The main motor is to drive the machine to a rated speed. It is very important to choose a good quality motor. Firstly we have to confirm the motor power based on the formula and the output requirements to get the best suitable power consumption, that is based on the experiment and extensive experiences. Our motor supplier includes Siemens, ABB, WEG, WN with different parameters as required by a specific application.
The gearbox is the heart of the extruder. The gearbox has speed reduction and distribution functions, it can reduce the rotational speed of the motor to the desired rotational speed of the shaft, and can also distribute the output torque to the two output shafts.
The gearbox lubrication cooling system mainly consists of three parts: An oil pump, Heat exchanger and filter. The forced oil lube system has two purposes:
- to lubricate the bearing and gears with oil
- to pump oil of a controlled temperature into the gearbox
The oil is pumped into the gearbox through the oil cooler and an oil filter by a pump.
A safety clutch is used for connecting the motor and extruder gearbox. The purpose is to prevent the gearbox, screw and barrel damage when the fault happens. When the extruder load is over the preset value, the safety clutch will disconnect immediately after getting the signal from the machine. Thus the whole machine will be stopped to avoid further damage to the gearbox, screw and barrel. COWELL use the European made safety clutch which is more stable and sensitive during operation, moreover, with smart design, it is very easy to reset the safety clutch after we trouble shooting.
Screw & Barrel
The screw & barrel are essential parts of a twin screw extruder, the flexible combination makes the twin screw extruder suitable for almost all different kinds of plastic applications.
The barrel and screw L/D depend on what specific application you are going to process. COWELL twin screw extruder barrel L/D is up to 68. which could meet almost all kinds of different formulas and plastic processing needs.
Suitable materials of barrel and screw choice is also a key point for the extruder application, there are different materials available for different applications. Choosing the best material will help you to make a good and competitive product on the market, considering the function/cost ratio.
A perfect screw configuration/profile makes your final product better and more competitive. COWELL team has extensive and extraordinary experience in screw configuration design.
The heater is used to heat up the screw and barrel, materials will go into the barrel at a rated speed. The heater will be preset at a certain temperature which can melt the materials before going to the die head or downstream.
There are different kinds of heaters available for the extruder, such as cast-AL heater, cast copper heater, cast -iron heater, ceramic heater, cartridge heater, infrared heater, electro-magnetic heater, oil heating, etc.
The popularly used heaters are cast heaters and cartridge heaters, while in recent years, the infrared heaters is frequently used due to the energy saving.
An efficient cooling system for the extruder is very crucial, especially for the heat sensitive materials. There are three ways to cool the barrel: water cooling, air cooling and oil cooling.
The most frequently used for twin screw extruder cooling is water cooling. The cooling water will goes into the barrel cooling channel by pump. It is a complete circulated system, cooled water goes in while hot water goes out back to the water tank.
The vacuum system is used for taking the low molecular and moisture out of the barrel which enables you to get better quality products. The vacuum port is usually located one or two barrels before the outlet of the twin screw extruder.
There different kinds of feeding systems available for twin screw extruders depends on customers’ preferences.
Volumetric feeder: The customer normally premixes the ingredients in the mixer and then loads the mixture into the volumetric feeder. It is an economical way to choose this type of solution.
Gravimetric feeder: This is an automatic feeding solution for customers without premixing or loading. Different ingredients will be fed into the extruder by separate gravimetric feeders. The feeding rate is more accurate compared to the volumetric feeder. And the final products are closer to the formula preset.
Electric Controlling System
The electric controlling system controls and monitors the extruder operation.
Control panel and HMI control are available for options.