1. Choosing the right heating equipment

It is a common and useful 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 C. Cleaning the screw with acetylene flame will not only damage the metal characteristics of the screw, but also significantly affect the mechanical tolerance of the screw.

Assuming that the flame of acetylene flame turns durable blue when roasting a part of screw, it means that the metal structure of this part of screw has changed, which will lead to the decrease of wear resistance of this part, and even the abrasion resistance layer and matrix metal peeling. Other parts of acetylene flame heating will also constitute the screw side overheating, and then lead 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 useful method: use the blowtorch immediately after the screw is used for cleaning. Because the screw has heat in the process of processing, the heat distribution of the screw is still uniform.

2. Choose the right detergent

At present, the commodity economy is highly developed. There are many kinds of screw cleaners (screw cleaners) on the market. Most of them are expensive and have different application effects. Whether to use commercial detergents 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, that is, to close the lower outlet at the bottom of the hopper, and then to reduce the screw speed to 15-25r/min, and maintain this speed until the melt flow at the front of the die stops. The temperature of the whole heating zone of the barrel should be set at 200 degree C. Once the barrel reaches this temperature, start cleaning immediately.

Depending on the extrusion process (or the need to remove the die to reduce the risk of excessive pressure at the front end of the extruder), the cleaning is done by one person: the operator queries the screw speed and torque from the control panel and the extrusion pressure together 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, the first thing is to remove the die for cleaning. When the extrudate is converted from the processed resin to the clean resin, the machine stops immediately and the die head is removed. Then the screw (rotating speed is within 10r/min) is used to make the residual clean resin flow out.

4. Choose the right cleaning items

Correct and appropriate things 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 is extruded in succession, the screw can be removed from the equipment. For screw with cooling system, remove hose line and rotating connector before asserting screw extraction equipment (which may be attached to gear box). Use the screw extraction equipment to push the screw forward to reveal the orientation of 4-5 screw blocks for cleaning.

Clean resin on screw can be cleaned up with copper scraper brush. After the cleaning resin on the exposed screw is cleaned up, the screw extraction equipment will push forward 4-5 screw blocks and keep cleaning. So repeated, most of the screw was pushed out of the barrel.

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

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