1. Choosing the Right Heating Device

It is a common and effective method for plastic processing units to remove the plastic fixed on the screw by burning or roasting, but acetylene flame can not be used to clean the screw. The temperature of acetylene flame can reach 3000 degrees 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 when baking a part of the screw, it means that the metal structure of the part of the screw has changed, which will reduce the wear resistance of the part, and even lead to the abrasion resistance layer and matrix metal peeling. In addition, local heating with acetylene flame can also cause overheating on one side of the screw, leading to screw bending. Most of the screw rods are made of 4140.H.T. steel. The tolerance is very close, generally within 0.03mm.

The flatness of the screw is mostly within 0.01 mm. 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 the screw has heat in the process of processing, the heat distribution of the screw is still uniform.

2. Choose the right detergent

Today, with the highly developed commodity economy, there are many kinds of screw cleaners (screw cleaners) in the market. Most of them are expensive and have different effects. Whether or not to use commercial cleaners depends on different manufacturers and production conditions; plastic processing enterprises can also use different resins to make screw cleaning materials according to their own production conditions, which can save a lot of expenses for the unit.

3. Choosing the Right Cleaning Method

The first step to clean the screw is to turn off the feeding plug, i.e. to close the lower outlet 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 degrees C. Once the barrel reaches this temperature, start cleaning immediately.

Depending on the extrusion process (which may require removing the die head to reduce the risk of excessive pressure at the front end of the extruder), cleaning needs to be 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. Throughout the process, the screw speed should be kept within 20 r/min. In the application of low pressure die, first do not remove the die for cleaning. When the extrudate is converted from the processed resin to the cleaner resin, stop the machine immediately and remove the die head, then restart the screw (within 10 r/min) in order to make the residual cleaner resin flow out.

4. Choose the right cleaning tools

Correct and appropriate tools and cleaning materials should include:

Heat-resistant gloves; goggles; copper scraper; copper brush; copper wire mesh; stearic acid; electric drill; barrel ruler; cotton cloth.

Once the cleaning resin stops extruding, the screw can be pulled out of the equipment. For screw with cooling system, remove hose line and rotary connector before starting screw extraction equipment (which may be attached to gear box). Use screw extraction equipment to push the screw forward to expose 4-5 screw blocks for cleaning.

Cleaning resin on screw can be cleaned by copper scraper brush. After the cleaning resin on the exposed screw has been cleaned up, 4-5 screw blocks will be pushed forward in the use of screw extraction equipment and continue to clean. So repeatedly, most of the screw is pushed out of the barrel.

Once most of the cleaning resin is removed, some stearic acid is sprayed on the screw; then the remaining residue is removed by using copper wire mesh, and after the screw is polished by copper wire mesh, cotton cloth is used to wipe the last step. This is to ensure that the next production of screw will not carry any pollutants. After the screw is cleaned up, it can be put aside until other machines are cleaned up. If the screw needs to be preserved, it should be coated with grease to prevent rust.

Cleaning screw can not use steel tools, such as steel screwdriver, scraper or pry to remove plastic sticking to screw, because steel can damage the surface of screw and barrel.