Today, with advanced technology, cleaning the plastic extruder is not a big problem, but how to cleanthe plastic extrudercorrectly and cost-effectively without damage to the screw and barrel is a problem, and it will become a trouble if done improperly or cause big problem. Today, let’s talk about how to properly clean the plastic extruder (mainly the screw and barrel) for the sake of everyone.
01. How to properly clean the screw?
1) Choose the correct heating device
Using fire or fire to remove the plastic fixed on the screw is the most common and effective method for plastic processing units, but acetylene flame should never be used to clean the screw. The temperature of the acetylene flame can reach 3000°C. Cleaning the screw with acetylene flame will not only destroy the metal characteristics of the screw, but also significantly affect the mechanical tolerance of the screw.
If the acetylene flame turns into a persistent blue color when baking a certain part of the screw, it means that the metal structure of this part of the screw has changed, which will lead to a decrease in the wear resistance of this part, and even the occurrence of the wear resistance layer and the matrix. Metal stripping. In addition, the local heating of the acetylene flame will also cause overheating of one side of the screw, which will cause the screw to bend. Most screws are made of 4140.H.T. steel with very tight tolerances, generally within 0.03mm.
The straightness of the screw is mostly within 0.01mm. When the screw is baked and cooled by the acetylene flame, it is usually difficult to return to the original straightness. Correct and effective method: use a blowtorch to clean the screw immediately after use. Because the screw has heat during processing at this time, the heat distribution of the screw is still uniform.
2) Choose the correct cleaning agent
Today, with the highly developed commodity economy, there are many kinds of screw cleaners (screw cleaning materials) on the market, most of which are expensive and have different effects. Whether to use commercial cleaning agents depends on different manufacturers and production conditions; plastic processing enterprises can also use different resins as screw cleaning materials according to their own production conditions, which can save a lot of money for the unit.
3) Choose the correct cleaning method
The first step in cleaning the screw is to turn off the feeding insert, that is, 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 of the die stops flowing until. The temperature of all heated zones of the barrel should be set at 200°C. Cleaning begins as soon as the barrel reaches this temperature.
Depending on the extrusion process (the die may need to be removed to reduce the risk of excessive pressure at the front end of the extruder), cleaning must be done by one person: the operator observes the screw speed and torque from the control panel, while observing the extrusion to ensure that the system pressure does not become too high. During the whole process, the screw speed should be kept within 20r/min. In low pressure die applications, do not remove the die for cleaning first. Immediately stop the extrudate and remove the die head when the extrudate is completely converted from process resin to clean resin, and then restart the screw (within 10 r/min) to allow the residual clean resin to flow out.
02. How to properly clean the barrel?
Cleaning the barrel is much more convenient and easier than cleaning the screw, but it is also very important.
1) In preparation for cleaning the barrel, the barrel temperature was also set at 200°C.
2) Screw the round steel brush to the drill rod and the electric drill and install it as a cleaning tool, and then wrap the steel brush with a copper wire mesh.
3) Before inserting the cleaning tool into the barrel, sprinkle some stearic acid into the barrel, or sprinkle stearic acid on the copper wire mesh of the cleaning tool;
4) When the copper wire mesh enters the barrel, start the electric drill to make it rotate, and at the same time make it move back and forth artificially until the back and forth movement becomes free of resistance;
5) After the copper wire mesh is removed from the barrel, use a bunch of cotton cloth to wipe back and forth in the barrel to remove any cleaning resin or fatty acid residue; after several such back-and-forth wiping, the cleaning of the barrel is done. Thoroughly cleanedscrews and barrelsare ready to be assembled for the next production run!