FEP pipe extrusion production uses the conical single-screw extruder . The entire process can be roughly divided into three areas: heating, constant temperature, and heat preservation. Heating and constant temperature are mainly located inside the extruder , and are divided into two relatively independent and interrelated parts with the exhaust hole as the boundary. The insulation area process consists of flow core, extrusion die and extrusion die.
There are two heat sources in the FEP pipe extrusion process. One is the external heat provided by the electric heater , and the other is the shearing, calendering and friction functions of the FEP material by the single screw, as well as the composition of the FEP itself. Internal heat caused by friction in the middle. The two heat sources play different roles in different stages of extrusion. Temperature control equipment controls only external heat. There is internal heat, and the shear force has a strong effect, but does not exceed the compression section required for material plasticization and the melting section, which mainly serves exhaust gas, is relatively stable and easier to control. Shear is relatively weak, mainly relying on external heat for heating, but the external heat cannot meet the feeding section of the plasticizing requirements of the raw material (especially the extruder with low external heat configuration); the measuring section where the shear force has exceeded the plasticizing requirements of the raw materials is also They are also generally not subject to manipulation by temperature control equipment. Therefore, in the temperature control of the entire extrusion process, the feeding section and measurement are the key and difficult points of temperature control.
FEP tube extruder
1. Temperature of the feeding part: The feeding part transfers heat to the screw cylinder through the electric heater. The temperature displayed is the temperature of the screw cylinder, not the temperature of the material. The temperature of the material is usually much lower than the temperature shown. When the material first enters the extruder through the feeding screw, the temperature is only about 30°C-40°C, and there is a big gap between the temperature rise of the material caused by the shear heat generated by the screw and the plasticization (vitrification) temperature. . At the same time, the material will pass through the exhaust hole when passing through the compression section, and the material needs to complete the conversion process of glass-like viscous flow state in the heating zone. It is required to be basically orange peel-like, without powdery substances, and tightly cover the surface of the spiral groove to avoid being sucked out of the exhaust hole by vacuum or blocked. Therefore, the function of the feeding part focuses on external heating, and the set temperature should be as high as possible so that the electric heating coil can provide sufficient external heating for the material. At this time, the electric heater often starts and shuts down, or even stops working.
Since the material enters the feeding section, there is still some time before the die is extruded. In addition, in order to prevent the material from bridging at the feed port or sticking to the wall in the machine, the set temperature should not be too high. Temperatures exceeding 270°C should be displayed. Although the setting temperature of the feeding section is low, for example, the setting temperature is about 250°C or even lower, it is still possible to produce products that meet internal quality standards. However, due to the relatively small supply of external heat, excessive reliance on shear heat to increase the temperature of the melt, and increased wear of the screw barrel, which will affect the service life of the extruder screw barrel, the gain outweighs the gain. Through our long-term observation of extruder equipment maintenance, we found that after only one or two years of use (some even less than a year), screw will suffer from serious wear and tear. Shenzhen Junsheng has proven through a lot of practice that in Under the premise that the feeding, extrusion speed and the set temperature of the measuring section remain unchanged, appropriately increasing the set temperature of the feeding section can effectively reduce the temperature difference between the display temperature of the measuring section and the set temperature, which fully explains the feeding section. The temperature plays a role in regulating shear heat to a certain extent.
FEP tube extruder
2. Compression part temperature: The material enters the compression part, has a large shearing effect, and rapidly heats up under the action of the screw shearing force. Setting a higher temperature helps reduce the viscosity of the material and accelerate fluidity, just like the feeding part, which can reduce the harm of shear heat.
3. Temperature of the melted part: The material in the melted part is basically melted. Due to the change in the volume of the thread groove (generally the compression ratio is less than 1), the melting pressure suddenly decreases, which can give full play to the functions of constant temperature and exhaust. Keeping the set temperature consistent or slightly higher than the compression section helps prevent the melt from cooling. As the melt pressure decreases, the temperature of the melt also decreases.
There are many sources of temperature for the extrusion of FEP pipes. When Shenzhen Junsheng produces FEP pipe extruders, it fully introduces its many years of FEP pipe production experience, reasonably sets the screw length-to-diameter ratio, and reasonably partitions the screws. After customers purchase the extruder, the products produced are thick and uniform, and can quickly occupy the market.
If you want to know more about FEP tube extruder, please continue to pay attention to Shenzhen Junsheng Technology Co., Ltd.
