Extruder moulding control in brief

I. Heating and cooling system

The heating and cooling system of the extruder mainly refers to the heating and cooling of the barrel (also including the moulding die and screw) in the extrusion plasticizing system. The purpose of barrel (moulding die and screw) heating or cooling is to control the process temperature of raw materials in extrusion plasticisation, so that it is limited to a certain range, in order to ensure the normal production of plastic products made by the extruder.

1. Barrel heating

Extruder barrel (moulding die) heating method of resistance heating, electric induction heating method and heat carrier heating method. At present, the more widely used heating method is resistance heating method.

1) resistance heating.

Resistance heating method structure is relatively simple, it is mainly to let the current through the resistance of the relatively large wire (resistance wire) to produce heat, conduction to the barrel to be heated. Cast aluminium jacket resistance heater is the resistance wire in the metal tube, the tube is then filled with magnesium oxide powder and other insulating materials, and then cast the metal tube in the aluminium alloy. This resistance wire heating cast aluminium sleeve resistance heater, resistance wire in the tube due to magnesium oxide insulation powder insulation, sealing, preventing premature oxidation of the resistance wire, long life; aluminium alloy sleeve and barrel outer circle contact area is large, heat transfer performance is good.

2) Electric induction heating.

Electric induction heating device, the barrel using electric induction heating, the outer circumference of the barrel is equipped with a coil, the coil periphery and then loaded with magnetically conductive silicon steel sheet. When the coil has a current through, silicon steel sheet and the barrel to form a closed magnetic circuit, alternating magnetic flux induction makes the barrel to generate current, the barrel due to a certain resistance value and generate heat. The barrel is heated quickly by the induction heating method, and the working life of the materials used for induction is long, but the devices used for induction are more complicated.

3) Heat carrier heating.

With water vapour or oil as a heat carrier heating machine simple, need to have pipeline transport and heat carrier heating source (boiler or resistance heat source), equipment complexity, cost of business, temperature control is difficult, so it is very do with. However, this kind of heating method has soft and even temperature, which is very suitable for the heating of heat-sensitive plastics.

2. Barrel cooling

The cooling of the barrel of the extruder includes the cooling of the extruding and plasticising part of the machine, the cooling of the hopper seat part and the cooling of the screw. Cooling of the extrusion plasticising part of the extruder. The cooling of the plasticising part is mainly a cooling measure to prevent the working temperature of the machine from being too high. Cooling cooling methods include water cooling and air cooling. At present, the more widely used method is air cooling. It is with the fan directly blowing the parts of the barrel to be cooled down by the cold air to take away the heat of the barrel, so as to achieve the purpose of the barrel cooling. Fan cooling barrel method is simple, simple structure of the equipment, the barrel thermal shock is small, the cost is not high, maintenance and production operations are more convenient.

3. Cooling of hopper seat part.

Cooling of the hopper seat part of the cooling water is mostly used to cool down the cooling. The purpose of cooling is to prevent the hopper due to forced charging and generate excessive heat. In addition, also to prevent the screw charging section temperature is too high. These two parts of the temperature is too high, mainly affecting the hopper feed and into the screw feeding section of the material forward running conveyor.

4. Screw cooling.

Screw cooling commonly used heat-conducting medium oil, with a rotary joint structure, the rotation of the screw centre hole and the oil pipeline connection, so that the heat-carrying body oil through the rotary joint into the screw body, take away the heat of the screw, to achieve the purpose of the screw cooling.

Control system

Extruder control system, mainly refers to the working speed of the screw, barrel sections of the heating temperature, the temperature of the forming mould and products with molten material forming pressure control and so on. The role of these parts of the control device is to ensure that the extruder in the set process conditions, in order to make the extruder production of moulded plastic products work steadily and smoothly.

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