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1)Use the right heating device
Using fire to remove plastic stuck to the screw is the most common and effective method for plastic processing, but acetylene flame should never be used to clean the screw. Acetylene flame temperature up to 3000℃, using it to clean the screw will not only destroy the metal properties of the screw, but also significantly affect the mechanical tolerance of the screw.
If acetylene flame in the baking screw a part of the flame into a lasting blue, it means that the screw part of the metal structure has changed, which will lead to the part of the wear resistance is reduced, and even wear resistance layer and matrix metal stripping. In addition, the use of acetylene flame local heating will also cause the screw side overheating, resulting in screw bending. Most screws are made of 4140.H.T. steel with very tight tolerances, generally within 0.03mm.
The flatness of the screw is mostly within 0.01mm. When the screw is baked and cooled by acetylene flame, it is usually difficult to return to the original flatness. Correct and effective method: use blowtorch to clean the screw immediately after use. Because then the screw with the processing process of heat, so the heat distribution of the screw is still uniform.
2) Use the right cleaning agent
Commodity economy is highly developed today, there is no lack of all kinds of screw cleaners (screw cleaning materials) on the market, most of them are expensive, the use effect is difficult to say. Whether to use commercial cleaners is depends on different situation and production of manufacturers. Plastic production enterprises can also according to their own production situation, using different resins to do screw cleaning material, which can save a large cost for the manufacturer.
3) Use the right cleaning method
The first step of cleaning the screw is to close the feeding insert plate, that is, to close the feeding port at the bottom of the hopper; Then reduce the screw speed to 15-25r/min, and keep this speed until the melt flow at the front end of the die stops flowing. The temperature of all heating areas of the barrel should be set at 200℃. Once the barrel reaches this temperature, start cleaning immediately.
According to different extrusion process (may need to remove the die head to reduce the risk of extruder front high pressure), the cleaning must be done by one person: the operator from the control panel to observe the screw rotation speed and torque, at the same time observe the extrusion pressure to ensure that the system pressure is not too high. In the whole process, the screw rotation speed should keep within 20 r/min. In the application of low-pressure die head, first do not remove the die head for cleaning. When the extrudates are completely converted from processing resin to clean resin, stop immediately and remove the die head, and then restart the screw (within 10r/min rotation speed) to allow the residual clean resin to flow out.