Twin screw extruder by the transmission device, feeding device, screw, barrel, heater, the nose and the control cabinet cooling system.
Transmission device consists of a motor, gear box.
Motor which has two kinds of ac and dc, in general, the ac motor starting current is big, relatively stable dc motor start.
is the ratio of length to diameter screw extruder is an important symbol of specifications.
Cooling system should include two parts, part of the transmission case of lubricating oil cooling system, the system has a condenser and circulating pump.
Extract transmission box lubricating oil circulation pump after the condenser cooling into the transmission case, to keep the transmission case temperature below 40 ℃, to ensure the normal operation of transmission gear with life.
Another cooling system is screw cooling system, its function is to adjust screw district temperature, ensure the actual temperature and set temperature deviation control in minimum range, in particular, can alleviate because of friction tropical to local overheating.
loading equipment including hopper, speed regulating motor and small screw feeder.
Hopper is divided into the single hopper and mixing hopper.
For conveying powder material mixing system, which has a uniform conveying hot spots.
Screw feeder with single screw and twin screw, the general material, both screw fit, for powder system, double screw pushing effect better.
In recent years, has developed several charging mode, namely the lateral loading, the main ingredient from positive feed, fertilizer from the lateral loading.
Lateral position of the feeder should be according to the heat resistance of auxiliaries, the respect such as dispersion, injection molding processing, product appearance requirements to determine, feeder in the molten zone is appropriate, the side feeder has forced conveying function generally USES screw propeller.
twin-screw heater USES far infrared plate, plate adopts aluminum, and the nose heating jacket some use bronze coat, its characteristic is the use of copper is easily hot, is conducive to the nose temperature adjustment.
From different materials, the setting of the district heating power is also different, such as nylon series of high melting point, the incoming district heating power should choose high power, especially when large particles recycled material injection molding processing, the heating power is more bigger.
In kneading zone, as a result of kneading friction heating, heating power should be small.
Heating power has a great influence on the control of screw temperature, the heating power is big, big deviation adjustment, so when choosing the heating power, want to choose according to product thermal performance.
found in practical use, in the operation of the screw, the friction heat production become a part of the material melting heat source, and even the main heat source, heating control system using a single power supply is not enough to accurately control, tend to be local overtemperature, will lead to partial overtemperature polymer thermal degradation, oxidation turn yellow.
In addition, in be used actually, there is phenomenon of directly using the water as cooling medium, the looks be like simple, but this method is easy to cause electromagnetic valve jam for failure, therefore, the tap water contains a lot of calcium, under heating condition, easy to scale, the electromagnetic valve life expectancy.
Therefore, the use of soft water circulation is good, and often change supply cooling water, ensure the normal operation of the solenoid valve.
to use silicon controlled dc motor speed control and VVVF ac frequency control of motor speed, screw temperature by programmable controller and the control of microcomputer, and circulating water cooling linkage control.
Overload protection, the early twin-screw extruder mainly adopts the metal pin protection, namely the transmission gear box with the screw connection place the use of metal pin for protection, when overload, metal pin is cut piece, screw stops running, motor and gear box in the normal state.
At present, most manufacturers using current overload protection and metal pin protection with double protection control method make the equipment more safety.
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