The conical twin screw barrel for extrusion
also known as the barrel, is an important part of the injection system. It completes the transportation, plasticization and injection of plastics together with the screw. It is also used by other equipment (heater, cooling equipment, feeding hopper, The equipment support of metering equipment, etc.), the barrel is generally made of an integral structure. There is a certain gap between the inner hole of the barrel and the screw. The external equipment is heating and cooling equipment. The barrel equipment is on the injection seat, that is, the feeding hopper seat, and the front end is connected to the nozzle. The form of the feeding port of the double alloy screw barrel.
Since most of the injection molding machines use gravity feeding and forced feeding, the cross-sectional shape of the feeding port must be transported during feeding.In order to increase the conveying capacity, the feeding port should try to increase the screw area and the contact area between the screw and the barrel. The cross-sectional shape of the feeding port can be symmetrical or offset. Symmetrical feeding port is too small, easy to make and low in conveying capacity. Offset feeding port is suitable for high-speed feeding of screw and has better conveying capacity, but is difficult to manufacture. When the spiral forced feeding equipment is used, the top view shape of the feeding port should be symmetrical and circular, and the gravity feeding should be biased, and the heating and cooling of the barrel should be used.
Barrels are widely used resistance heating strip heaters, cast aluminum heaters, ceramic heaters, etc. Because the resistance heater is small in size, easy to manufacture and maintain, in the compression section, a heater with a larger heating power should be equipped. During the plasticization process of the material, the shear heat is small.Generally, the barrel does not have a separate cooling device, but relies on natural cooling. In order to maintain a good feeding and conveying effect and prevent the heat of the barrel from being transferred to the transmission part, a cooling water jacket is set at the feeding port to cool and resist heat.
The screw is an important part of the plasticizing part of the raw material, and its processing accuracy and work quality will directly affect the molding quality of plastic products. The screw of the injection molding machine works under the environment of high temperature, high pressure, high mechanical torque and high friction for a long time. The first few factors are required by the process conditions, and the loss caused by friction is inevitable. However, if you ignore the causes of wear and do not try to reduce the wear as much as possible, the working life of the screw will be greatly reduced, and the wear and corrosion of the equipment should be prevented or reduced to prolong the service life of the equipment.