Heating and cooling of the extruder barrel


There have been several successful heating methods in the past. The eddy current magnetic lines generated by the induction coil heat the metal, which is a rapid heating method with little maintenance and high efficiency. There are still a number of manufacturers available for delivery and still in production. A cooling jacket is provided to directly supply cooling water to the outside of the barrel to provide a very efficient cooling method. 'Coated composite extruders are generally designed to avoid the use of steam or liquid jackets because they may leak to adjacent web products. 'Casting aluminum or brass, mica strips and segmented ceramic strip resistor heaters are used where cooling is not required. . In most cases, the barrel heating zone should be equipped with a cooling facility to allow the metal to cool down during periods of excessive temperature or rapid cooling shutdown. Utilizing the surrounding atmosphere, forced ventilation above the planar heater, or forced air cooling above the fin heater, because the cooling response is slow and the efficiency of this convection cooling method is low, it is generally used only for special processes. process. Water cooling is an effective and common method because water is proportionally controlled per unit time flow through a tube located inside the heater. Water and glycol solutions up to a 50:50 ratio are commonly used to reduce corrosion and increase fluid boiling point. Extruders equipped with cast aluminum electric resistance heaters with internal water-cooled tubes in various areas are very common. Cast aluminum can also be used in extruder barrels with zone temperatures up to about 340 °C. Above this service temperature, a cast copper body can be used. But the price is higher.
The cooling water temperature to each zone must be controlled and should be recycled. It is best to use a small pool to store mineral-free water. The pump draws water from the pool and pumps it to the water supply branch containing the zone flow metering valve, and if necessary, an open and close solenoid valve that regulates the amount of water passing through the heater. After the water passes through the heater, it is collected in a drain branch and then cooled in a water-to-water heat exchanger before returning to the sink. The heater inlet and outlet joints are prone to leakage due to thermal shock, so the old-fashioned copper tubes have been replaced by spiral-fastened flexible hoses. The barrel area is temperature-sensitive (usually a "J" type thermocouple) to achieve the desired temperature. It is mounted in the middle of the section and 50% of the joint is buried in the wall. The sensor signal is detected by the controller
The controller can receive the desired set value set by the operation work. The controller must compare the setpoint to the actual valve condition to determine heating, cooling, or nothing. The controller maintains the accuracy and ability of the actual temperature in the zone as close as possible to a given value to achieve a stable zone temperature and to help avoid resin temperature fluctuations. This should be a primary consideration. Proportional timing hot/cold partition controllers or system microprocessors are the most commonly used in this regard.

  • 28/09/2018
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