1, choose the right heating device
Use of fire or roasted to remove the plastic screwed on the screw, plastic processing unit is the most common and most effective way, but absolutely can not use acetylene flame to clean the screw. Acetylene flame temperature up to 3000 ° C, acetylene flame to clean Please clean the screw will not only destroy the metal characteristics of the screw, but will also significantly affect the mechanical tolerance screw.
If the acetylene flame burns a certain part of the flame into a long-lasting blue, then that part of the screw structure of the metal has changed, which will result in reduced wear resistance of the site, or even wear layer and the substrate Metal stripping.Additional use of acetylene flame local heating can also cause one side of the screw overheating, resulting in screw bending.Most screw made of 4140.HT steel, the tolerance is very close, generally less than 0.03mm.
Most of the flatness of the screw is within 0.01mm, it is usually difficult to return to the original straightness when the screw is baked and cooled by the acetylene flame. Correct and effective method: Use the torch immediately after the screw is used to clean Screw with heat in the process, so the screw heat distribution is still uniform.
2, choose the right detergent
Today, a highly developed commodity economy, there are many different types of screw cleaners (screw cleaners) on the market, most of which are expensive and have mixed results. Whether commercial cleaners are used or not depends on different manufacturers and production conditions Set; plastic processing enterprises can also be based on their own production conditions, the use of different resins to do screw cleaning material, save a small unit for a small expenditure.
3, choose the correct method of cleaning
The first step to clean the screw is to turn off the feed flapper, which is to close the discharge opening at the bottom of the hopper; then reduce the screw speed to 15-25 r / min and stop this flow until the melt flow at the tip of the die stops The temperature of all heated zones of the barrel should be set at 200 ° C. Once the barrel reaches this temperature, cleaning is started immediately.
Depending on the extrusion process (which may require removal of the die to reduce the risk of overpressurizing the front end of the extruder), it must be done by one person during cleaning: the operator observes the screw speed and torque from the control panel and observes the squeeze Out of the pressure to ensure that the system pressure will not be too high throughout the process, the screw speed should be maintained at 20r / min in the low-pressure die applications, first do not remove the die for cleaning in the extrusion from the processing Immediately shut down and remove the die when the resin is fully converted to cleaning resin, and then restart the screw (speed between 10r / min) to allow residual cleaning resin to flow out.
4, use the correct cleaning tools
Properly appropriate tools and cleaning materials should include:
Heat-resistant gloves; Goggles; Copper scraper; Copper brush; Copper mesh; Stearic acid; Drill;
Once the cleaning resin has been stopped, the screw can be removed from the unit. For a screw with a cooling system, before starting the screw extraction unit (this unit may be attached to a gear unit), remove the hose line and rotary connector Use a screw extraction device 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 copper brush.After the cleaning resin on the exposed screw is cleaned, 4-5 screws will be propelled forward and continue to be cleaned using the screw extraction device. Part of the screw is pushed out of the barrel.
Once most of the cleaning resin has been removed, sprinkle some of the stearic acid onto the screw; then use a copper wire mesh to remove the remaining residue and use the cotton cloth for the final step after the entire screw is polished by the copper mesh Make sure that the screw will be free from any contaminants during the next production. After the screw is completely cleaned, it can be set aside until the other equipment is completely cleaned. If the screw needs to be stored, Layer grease to prevent rust.
Cleaning the screw Never use steel tools, such as steel screwdrivers, scrapers or pry bars, to remove the plastic adhering to the screws because the steel can damage the surfaces of the screws and the barrel.