The extrusion process of PVC door and window profile-1
1、 Production process
The production process of PVC door and window profile mainly includes single screw extrusion process and twin screw extrusion process. The raw materials used in the two processes are the mixed powder prepared in the previous process according to a certain formula. At present, the extrusion line of hard PVC door and window profile mostly uses conical screw.
（1） Single screw extrusion
The single screw extrusion process is especially suitable for the production of small batch and small size profile. The process flow is as follows:
Mixed powder → single screw extrusion granulation → single screw extrusion molding → setting → traction → cutting → turntable → finished product
（2） Twin screw extrusion
The twin-screw extrusion process can be directly molded with powder, with large production capacity, especially suitable for the production of large quantities of conventional profiles and large specifications of different profiles. The process flow is as follows:
Mixed powder → twin screw extrusion molding → setting → traction → cutting → turning table → finished product
2、 Key points of process control for extruding hard PVC door and window profile by twin screw extruder
The extrusion process of the profile of hard PVC doors and windows can be summarized as follows:
the modified PVC mixture is mixed by screw in the barrel, and under the action of internal friction and electric heating, the material gradually changes into the molten viscous flow state, and the material spirals towards the head direction under the flow of the rotating screw. After entering the die, the die cavity of the die is divided and compressed under high temperature and high pressure to extrude the blank which is similar to the section of the product, and then the blank is vacuum cooled and shaped by the die to meet the product design requirements.
Forming temperature, setting cooling, screw speed, traction speed and feeding speed are all important factors affecting the quality of profile products, which are described as follows:
(To be continued...)