How to properly clean and change color and refueling plastic extruder

How to properly clean plastic extruder?

First, how to properly clean the screw
The use of fire or fire to remove the plastic fixed on the screw is a  common method for the plastic processing unit, but it is absolutely impossible to use the acetylene flame to clean the screw. The temperature of the acetylene flame can reach 3000 °C. Cleaning with an acetylene flame will not only destroy the metal characteristics of the screw but also significantly affect the mechanical tolerance of the screw. If the flame of the acetylene flame becomes a permanent blue color when baking a part of the screw, it means that the metal structure of the screw has changed, which will result in a decrease in wear resistance of the part, and even wear-resistant layers and substrates. Metal peeling. In addition, local heating with an acetylene flame can also cause overheating of one side of the screw, which causes the screw to bend. Most of the screws are made of 4140 HT steel with tight tolerances, typically within 0.03 mm. The straightness of the screw is mostly within 0.01 mm. When the screw is baked and cooled by the acetylene flame, it is usually difficult to return to the original flatness. Correct and effective method: Use the blower to clean the screw immediately after use. Since the screw has heat during processing, the heat distribution of the screw is still uniform.

(2) Choosing the right cleaning agent
Today,  the commodity economy is highly developed. There are many kinds of screw cleaners (screw cleaning materials) on the market, most of which are expensive and the effects are mixed. Whether to use commercial detergents, according to different manufacturers and production conditions; plastic processing companies can also use different resins to make screw cleaning materials according to their own production conditions, which can save a lot of money for the unit.

(3) Choosing the correct cleaning method
The cleaning step of the screw is to close the feeding insert, that is, to close the lower opening 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. Once the barrel reaches this temperature, it begins to clean immediately. Depending on the extrusion process (the die may need to be removed to reduce the risk of excessive pressure on the front of the extruder), it must be done by one person during cleaning: the operator observes the screw speed and torque from the control panel while observing the squeeze Pressure is applied to ensure that system pressure is not too high. The screw speed should be kept within 20 r/min throughout the process. In low-pressure die applications, do not remove the die for cleaning. Immediately when the extrudate is completely converted from the processing resin to the cleaning resin, the die is removed and the screw is restarted  (within a rotation speed of 10 r/min) to allow the residual cleaning resin to flow out.

(4) Choosing the right cleaning tool The correct and appropriate tools and cleaning materials should include:
1,  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 withdrawn from the device. For screws with a cooling system, remove the hose line and the swivel connection before starting the screw extraction device (which may be attached to the gearbox). Use a screw extraction device to push the screw forward to expose the position of 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, the screw extraction device will advance 4-5 screws and continue cleaning. Repeatedly, most of the screw of Zui was pushed out of the barrel.
Once most of the cleaning resin has been removed, sprinkle some stearic acid onto the screw; then use the copper wire mesh to remove the remaining residue. After the entire screw is polished by the copper wire, use a  cotton cloth to wipe it one step later. This is to ensure that the screw will not carry any contaminants in the next production. After the screw has been completely cleaned, it can be set aside until the other implements are completely cleaned. If the screw needs to be stored, apply a layer of grease to the surface to prevent rust.

The cleaning screw must never be used with steel tools such as steel screwdrivers, scrapers or masts to remove the plastic stuck to the screw, as the steel can damage the surface of the screw and barrel.

Second, how to properly clean the barrel
Cleaning the barrel is much easier and easier than cleaning the screw, but it is also very important.
1) When preparing to clean the barrel, the barrel temperature is also set at 200 °C.
2)  Screw the round steel brush to the drill pipe and the electric drill as a cleaning tool, then wrap the steel brush with a copper wire mesh.
3)  Before inserting the cleaning tool into the barrel, sprinkle some  stearic acid into the barrel or sprinkle stearic acid onto the copper  wire of the cleaning tool;
4)  When the copper mesh enters the barrel, the electric drill is started  to rotate, and the movement is artificially moved back and forth until  the forward and backward movement becomes no resistance;
5)  After the copper wire mesh is removed from the barrel, use a bundle of cotton cloth to wipe back and forth in the barrel to remove any cleaning resin or stearic acid residue; after several such round-trip cleaning,  the barrel cleaning is done. The thoroughly cleaned screw and barrel can be assembled at any time for the next production!!

Cleaning color change, refueling screw, and mold precautions
With the diversity of products, diversification, product color is richer and richer, the conversion between different materials, the conversion between different colors, resulting in long conversion time, more waste,  causing a lot of confusion on production management and operation, the following small series A few ideas for your reference, please correct me.
1.  First clean the outside of the equipment. After converting different materials and changing colors, it is necessary to clean the original raw materials without any dead ends. Especially, it is not easy to wipe the place. Do not leave a dead end. . For the screw and the residual material in the barrel, it must be squeezed out and emptied. For complicated equipment and molds, it should be removed and cleaned if necessary.
2.  If the cleaning agent is cleaned after cleaning, if there is no material to be heated and the material to be extruded is extruded, look at the appearance of the extruded product, and the color can be put into normal production. If not, proceed as above.
3, a few small experiences for reference
A.  If the production of different materials and colors is frequently changed, the same mold can be configured. The mold is a place that is difficult to clean, which saves time and materials.
B.  For different colors of the same material, it can be modified in the feeding port, and the color masterbatch is used for production. It is not suitable to use toner to add a production. Can reduce the impact of different links on color.
C.  It is possible to change the appearance color of the product by co-extrusion, which can also reduce the trouble of the conversion.
D.  For the conversion between materials, if the conditions are met, the products and equipment of the same series of materials should be used.  That is to say, PP pipe equipment should be used, and other products of  PP materials should be made as much as possible. Do not make PE  products. Otherwise, if it is not clean, it will affect the performance of the product.

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