In plastic extrusion molding equipment, the plastic extruder is usually called the main machine, and the subsequent equipment that is matched with the plastic extrusion molding machine is called the auxiliary machine. After more than 100 years of development, plastic extruders have derived from the original single-screw, multiple-screw, multi-screw, and even non-screw models.
The plastic extruder (host) can be used with various plastic forming auxiliary machines such as pipe, film, holding material, monofilament, flat wire, strapping, extruding net, board (sheet) material, profiled material, pelletizing, cable coating, etc. Matching to form various plastic extrusion molding production lines to produce various plastic products.
Therefore, plastic extrusion molding machinery is one of the widely used models in the plastics processing industry no matter now or in the future. It should be noted that after we use the plastic extrusion molding machine, we need to pay attention to maintenance and cleaning. Here, the editor of Xianji.com will briefly introduce you to the cleaning method of the plastic extrusion molding machine.
1. Choose the correct heating device
Burning or roasting to remove the plastic solid on the screw is the most common and effective method for plastic processing units. However, acetylene flame must not be used to clean the screw. The temperature of the acetylene flame can reach 3000°C. Cleaning the screw with the 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 to long-lasting blue when baking a certain part of the screw, it means that the metal structure of this part of the screw has changed, which will cause the wear resistance of this part to decrease, and even the anti-wear layer and matrix will occur. Metal peeling. In addition, the local heating of the acetylene flame will also cause overheating on one side of the screw, which will cause the screw to bend. Most screws are made of 4140.H.T. steel, with very close tolerances, generally within 0.03mm.
The straightness of the screw is mostly within 0.01mm. After the screw is baked and cooled by the acetylene flame, it is usually difficult to return to the original straightness. Correct and effective method: use a blowtorch to clean the screw immediately after use. Because the screw has heat during processing at this time, the heat distribution of the screw is still uniform.
2. Choose the right cleaning agent
Today, when the commodity economy is highly developed, there is no shortage of various screw cleaners (screw cleaning materials) on the market, most of which are expensive and have different effects. Whether to use commercial cleaning agents depends on 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. Choose the correct cleaning method
The first step in cleaning the screw is to close the feeding insert, that is, to close the discharge port 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 of the die stops flowing until. The temperature of all heating zones of the barrel should be set at 200°C. Once the barrel reaches this temperature, immediately begin cleaning.
Depending on the extrusion process (it may be necessary to remove the die head to reduce the risk of excessive pressure at the front end of the extruder), cleaning must be done by one person: the operator observes the screw speed and torque from the control panel, and observes the extrusion at the same time. To ensure that the system pressure will not be too high. During the whole process, the screw speed should be kept within 20r/min. In the application of low pressure die, first do not remove the die for cleaning. When the extrudate is completely converted from the processing resin to the clean resin, immediately stop the machine and remove the die head, and then restart the screw (rotational speed between 10r/min) to allow the remaining clean resin to flow out.
4. Choose the right cleaning tools
The correct and appropriate tools and cleaning materials should include:
Heat-resistant gloves; goggles; copper scraper; copper brush; copper wire mesh; stearic acid; electric drill; machine barrel ruler; cotton cloth.
Once the clean resin stops extruding, the screw can be withdrawn from the equipment. For the screw with cooling system, before starting the screw extraction device (the device may be attached to the gear box), first remove the hose line and the rotating connection. Use the screw extraction device to push the screw forward to expose the position of 4-5 screw blocks for cleaning.
The cleaning resin on the screw can be cleaned with a copper scraper and a copper brush. After the cleaning resin on the exposed screw is cleaned, the screw extraction device will advance 4-5 screw blocks forward and continue cleaning. After repeating this process, most of the screws are pushed out of the barrel.
Once most of the cleaning resin is removed, sprinkle some stearic acid on the screw; then use a copper wire mesh to remove the remaining residue. After the entire screw is polished by the copper wire mesh, use a cotton cloth for the final step of wiping. This is to ensure that the screw will not contain any contaminants in the next production. After the screw is completely cleaned, you can put it aside until the other tools are also completely cleaned. If the screw needs to be stored, a layer of grease should be applied to the surface to prevent rust.
Never use steel tools such as steel screwdrivers, scrapers or pry bars to clean the screw rod to remove the plastic stuck to the screw rod, because steel will damage the surface of the screw rod and barrel.
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