Now that technology is developed, cleaning plastic extruders is not a big problem in the first place, but how to clean the plastic extruder correctly and economically, and quickly so that the screw and barrel are not damaged is a problem. If you do it improperly, it will become a big problem of trouble.
I. How to properly clean the screw
1. Select the correct heating device
Using fire or roasting to remove the plastic stuck to the screw is a common method for plastic processing units, but acetylene flame cannot be used to clean the screw.
The acetylene flame temperature 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 blue continuously when baking a part of the screw, it means that the metal structure of that part of the screw has changed, which will reduce the wear damage of the part, and even peel off the anti-wear layer from the base metal.
In addition, local heating with acetylene flame can also cause one side of the screw to overheat, which causes the screw to bend.
Most screws are made of 4140. H.T. Steel and the tolerances are very tight, 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 often difficult to return to the original flatness.
The right and quick way:
Use a blowtorch to clean the screw immediately after use. Because the screw carries heat from the processing process at this time, the heat distribution of the screw is still uniform.
2. Choose the right cleaner
Now that the commodity economy is highly developed, there is no shortage of screw cleaners (screw cleaners) on the market. Most of them are expensive and have different use effects.
Whether to use commercialized cleaners depends on different manufacturers and production conditions; plastic processing enterprises can also use different resins to make screw cleaners according to their own production conditions, which can save a lot of money per unit.
3. Choose the right cleaning method
To clean the screw, first, turn off the feeding plate, that is, close the discharge 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 zones of the barrel should be set at 200°C. As soon as the barrel reaches this temperature, start cleaning.
Depending on the extrusion process (the die may need to be removed to reduce the risk of excessive pressure at the front of the extruder), cleaning is done by one person: the operator observes the screw speed and torque from the control panel while observing the extrusion pressure to ensure that the system pressure is not too high.
The screw speed should be kept within 20r/min during the whole process. In the application of low pressure die, do not remove the die for cleaning first.
Immediately stop the machine and remove the die when the extrusion is converted from processing resin to cleaning resin, and restart the screw (speed within 10r/min) so that the residual cleaning resin can flow out.
4. Choose the right cleaning tool
Correct tools and cleaning materials should include:
- Heat-resistant gloves; 2, goggles; 3, copper scraper; 4, copper brush; 5, copper wire mesh; 6, stearic acid; 7, electric drill; 8, barrel ruler; 9, cotton cloth.
Once the cleaning resin stops extruding, the screw can be removed from the equipment.
For screws with a cooling system, remove the hose line and swivel connection before starting the screw extraction device (which may be attached to the gearbox).
Use a screw extractor to push the screw forward to expose 4-5 screws for cleaning.
The cleaning resin on the screw can be cleaned with a copper scraper brush. After the cleaning resin on the exposed screw is cleaned, 4-5 nuts will be pushed forward using the screw extraction device and continue cleaning. Again and again, most of the screws were pushed out of the barrel.
Once most of the cleaning resin is removed, sprinkle some stearic acid on the screw; then use a copper wire mesh to remove the remaining residue, and after the entire screw is wiped clean by the copper wire mesh, use a cotton cloth to wipe the next step. This is to ensure that the screw does not carry any contaminants the next time it is produced.
After the screw has been cleaned, you can set it aside until other tools are cleaned. If the screw needs to be preserved, a layer of grease should be applied to the surface to prevent rust.
Clean screws Do not use steel tools such as steel screwdrivers, scrapers, or pry bars to remove the plastic that sticks to the screw, as steel can damage the surface of the screw and barrel.
II. How to properly clean the barrel
Cleaning the barrel is much easier than cleaning the screws, but it is also very important.
1) When preparing to wash the barrel, the barrel temperature is also set at 200°C;
2) Screw the round steel brush to the drill rod and electric drill into a cleaning tool, and then wrap the steel brush with 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 rotate it, and at the same time artificially move it back and forth until this back and forth movement becomes unresistive;
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 residues; after several such wipes back and forth, the cleaning of the barrel is completed. The cleaned screw and barrel are ready to be assembled for the next production!