Analysis of the cleaning method of plastic extrusion molding machine

1, choose the right heating device

The most common method is to use fire or fire to remove the plastic that is attached to the screw, but never use an 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, choose the right cleaner

There are many screw cleaners (screw cleaning materials) on the market, most of which are expensive and the results are mixed. Whether to use commercial detergents, depending on the manufacturer and production situation; plastic processing companies can also use different resins to make screw cleaning materials according to their own production conditions, which can save the company an expense.

3, choose the correct cleaning method

The first step in cleaning the screw is to close the feed insert, ie to close the lower opening of 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. until. 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 extrusion Pressure 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, choose the right cleaning tool

Proper and appropriate tools and cleaning materials should include:

Heat-resistant gloves; goggles; copper scrapers; copper brushes; copper mesh; stearic acid; electric drill; barrel ruler; 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 was finally 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 for the final step of wiping. 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.

Cleaning the screw is absolutely not possible with steel tools such as steel screwdrivers, scrapers or masts to remove the plastic stuck to the screw, as steel can damage the surface of the screw and barrel.