How to clean twin screw extruder screw correctly
The screw is the heart of the twin-screw extruder and the key component of the twin-screw extruder. It determines the production efficiency, plasticizing quality, dispersity of the additives, melt temperature and power consumption of the twin-screw extruder. Here is to introduce the steps of cleaning the screw of the twin screw extruder:
1. Choose the right heating device
It is the most common and effective way for plastic processing unit to remove the plastic fixed on the screw of twin-screw extruder by fire or fire roasting. But never use acetylene flame to clean the screw.
Acetylene flame temperature up to 3000°C, with acetylene flame to clean please clean the screw will not only destroy the metal characteristics of the screw, but also affect the mechanical tolerance of the screw. If the acetylene flame in a part of the baking screw flame into a durable blue, then it means that the metal structure of this part of the screw has changed, which will lead to the part of the wear resistance to reduce, and even wear resistance layer and matrix metal stripping. In addition, local heating of acetylene flame will also cause overheating on one side of the screw, resulting in bending of the screw.
Correct and effective method: use blowtorch to clean the screw immediately after use. Because of the heat in the processing process of the screw at this time, the heat distribution of the screw is still uniform.
2.Choose the right detergent
Today, the commodity economy is highly developed, there is no shortage of all kinds of screw cleaner (screw cleaning materials) on the market, most of them are expensive, the use effect is not good or bad. Whether to use commercial cleaners, according to different manufacturers and production conditions; Plastic modification processing enterprises can also use different resins to do screw cleaning materials according to their own production conditions, which can save a large amount of expenses for the unit.
3.Choose the right cleaning method
The first step of cleaning the screw is to turn off the feeding insert plate, that is, to close the feeding port at the bottom of the hopper; Then reduce the screw speed to 15-25r/min and maintain this speed until the melt flow stops at the front of the die head. All heating areas of the barrel shall be set at 200°C. Once the barrel reaches this temperature, begin cleaning immediately. Depending on the extrusion process (the die head may need to be removed to reduce the risk of excessive pressure at the front of the extruder).
The cleaning must be done by one person: the operator watches the screw speed and torque from the control panel and also watches the extrusion pressure to ensure that the system pressure is not too high. During the whole process, the screw speed should be kept within 20r/min. In the application of low pressure die head, first do not remove the die head for cleaning. Immediately stop the machine and remove the die head when the extruder is fully converted from the processed resin to the cleaning resin, and then restart the screw (between 10r/min) in order to drain the residual cleaning resin.
4.Choose the right cleaning tools
Proper tools and cleaning materials should include: heat resistant gloves, goggles, copper scraper, copper brush, copper wire mesh, stearic acid, drill, barrel ruler, cotton cloth.
The cleaning resin on the screw can be cleaned with copper scraper and copper brush. After the cleaning resin on the exposed screw has been cleaned, the use of screw extraction equipment will advance 4-5 screw blocks and continue cleaning. This is repeated and eventually most of the screw is pushed out of the barrel.
You should never clean a screw using a steel tool, such as a steel screwdriver, scraper, or pry bar to remove the plastic stuck to the screw, as steel can damage the surface of the screw.
