Ningbo Fangli Technology Co., Ltd. is a mechanical equipment manufacturer with nearly 30 years’ experiences of plastic pipe extrusion equipment, new environmental protection and new materials equipment. Since its establishment Fangli has been developed based on user’s demands. Through continuous improvement, independent R&D on the core technology and digestion & absorption of advanced technology and other means, we have developed PVC pipe extrusion line, PP-R pipe extrusion line, PE water supply / gas pipe extrusion line, which was recommended by the Chinese Ministry of Construction to replace imported products. We have gained the title of “First-class Brand in Zhejiang Province”.
Plastic extruder is a kind of mechanical equipment that can be used for a long time to continuously produce plastic products. Ningbo Fangli technology, as an extruder equipment manufacturer, found that a large part of the reasons for the scrapping of the extruder after long-term use are the damage of the extruder screw and barrel. Screw and barrel are the core components of extruder equipment. Once damaged, it will cause great losses to plastic manufacturers. Here we have sorted out some contents, hoping to help you avoid some situations or reduce the damage of these parts.
The screw and barrel of plastic extruder can directly affect the plasticization of plastic resin, the quality and production efficiency of plastic products. These indexes are very key for plastic products factory. In order to ensure product output and product quality, the mutual combination and matching accuracy of screw and barrel (such as assembly clearance) and the processing and manufacturing accuracy, material selection and processing technology of parts are very important.
Before talking about the causes of screw and barrel damage, we have to talk about how these two parts work for easy understanding. During the production and operation of extruder equipment, the screw rotates in the barrel, and the material is rubbed and sheared with them. Melting occurs with the increase of material temperature. In order to ensure the quality of plastic products, the pressure of materials in the barrel is generally high. With the rotation of the screw, the materials constantly rub with the screw and barrel and move forward under the forward force, Finally, it is extruded through die and other parts.
The damage causes of screw and barrel are as follows:
1、Normal friction loss. As mentioned above, when the extruder is running, the material will rub with the barrel screw. When any material is rubbed under excessive pressure, it will wear slowly over time. Therefore, we generally carry out corresponding metal treatment on the surface of the barrel and screw in contact with the material to improve the wear resistance of the metal surface. This friction loss is unavoidable. We can only take various ways to slow down the wear rate.
2、Corrosion loss. The materials used in extruder production cannot be non corrosive. Generally, we can only improve the corrosion resistance of parts to slow down the corrosion rate. For example, when we use plastic products related to polyethylene resin, the materials will move continuously in the barrel, and the residence time of materials in the barrel is not certain. There will always be a small amount of materials that stay in the barrel longer than the average residence time of materials. Under high temperature and high pressure, a small amount of polyethylene resin will decompose. The decomposition of polyethylene resin will produce hydrogen chloride gas, which will strengthen the corrosion of screw and barrel.
3、The filler is hard (calcium carbonate, wood flour, glass fiber, etc.). This situation is quite common. In order to meet the process requirements, it is inevitable to add these fillers in the production of plastic products, which can accelerate the friction loss and the wear of screw and barrel. This is also a normal phenomenon. We can't avoid it and can only try to slow down the loss rate of parts.
4、The material is not pure. Many plastics can be recycled. In order to save resource consumption, we will recycle, clean and crush some discarded plastics, and then put them back into the extruder for production. Because recycling and cleaning can not completely remove some harmful impurities, it can only be controlled within a certain purity range. These harmful impurities will not only affect the final quality of plastic products, but also accelerate the wear of screws and barrels. Even some materials will remain some metal foreign matters. During the operation of the extruder, the rotating torque of the screw will suddenly increase, and even exceed the strength limit of the extruder screw, which will break the screw and finally be scrapped.
5、Improper workmanship. If the process is improper, the most common thing is that the materials enter the next working section of the screw without complete plasticization and melting. Processing materials in the wrong shape in the inappropriate working section is a very serious error, which will not only accelerate the wear of the screw and barrel, but also ensure the final product quality.
6、Improper operation. Extruder equipment still needs operators to operate. Many equipment do not have the ability of full automation, such as improper temperature control and host speed control. Especially in the operation after the extruder is shut down, if the equipment manual is not correctly installed for operation, and the residual materials in the extruder are not fully melted, it will have a great impact on the screw, barrel, host reducer and main motor, which may cause damage to the parts.
The above is some information about the reasons for the damage of the screw and barrel of the plastic extruder after long-term use. If you need more information, you are welcome to contact Ningbo Fangli Technology Co., Ltd. or come to the factory for on-site investigation. We will provide you with professional technical guidance and equipment purchase suggestions.