Extruder is a very common machine in the plastic indust […]
Extruder is a very common machine in the plastic industry. Keeping the extruder in the best working state can maintain the product stability and improve the production efficiency. In the process of daily use, it is inevitable that the production efficiency will decline. At this time, we need to clean and maintain the extruder. Let's take you to know some common cleaning methods of extruder.
1、 Non demolition cleaning method
1. Resin cleaning method
The method is to clean the machine with resin, such as polyester resin or epoxy resin. It is generally used in the cleaning machine or extruder of new equipment. This method can be used when some materials remain on the screw or screw barrel and the extrusion speed is slow, and the color difference of color change varieties is large.
Check whether the barrel material on the machine is clean, clean the working table of the plastic machine, set the required screw washing temperature (except for POM, PVC, TPE and TPU, the temperature must be 30 ℃ higher than the screw production temperature), and wait for the temperature and back pressure to reach the set value. Eject the residual screw into the air and add cleaning materials. The discharge is carried out by the process of fast slow fast injection. Pay attention to observe the color of the injected material. When the material changes color, manually press the screw to withdraw and then empty the injection; repeat the appeal operation process for 3 times. When the injection material does not show the color of the original product or there is no paste, the extruder can be considered clean.
2. Non resin cleaning method
In this method, the materials such as rice, corn, sawdust and toilet paper, which have certain friction force and are easy to crush, are heated to normal extrusion temperature in the extruder, and the friction force generated by these substances between the screw and the screw barrel is used to remove the resin gel attached to the surface of the screw and the screw barrel. Experience shows that the husk of rice has high hardness and high friction force, so the cleaning effect is ideal. After cleaning the machine with this method, it is necessary to open the screw cylinder again to check the cleaning condition. Under normal circumstances, it is necessary to use resin cleaning material to clean the machine again before the formal product production can be carried out.
Cleaning the extruder without dismantling the machine has the advantage of shortening the cleaning time of the machine, but there is also a risk of incomplete cleaning.
2、 Dismantling and cleaning method
1. Tools required
When dismantling the machine, some tools and cleaning materials should be used: heat resistant gloves, goggles, copper scraper, copper brush, copper wire mesh, stearic acid, electric drill, machine barrel ruler, cotton cloth, etc. In addition to these tools, you need to prepare:
4. 5 wooden sticks (diameter < screw diameter) × (length < injection stroke);
4. 5 wooden blocks (square, 100 mm × 100 mm × 300 mm); the removed screws should be placed on the wood blocks to prevent damage to the screws.
A pair of pliers;
Waste cotton cloth;
A long wooden or bamboo stick (diameter < screw diameter) × (length > heating cylinder length);
Nonflammable solvents such as trichloroethylene
2. Cleaning methods
The first step to clean the extruder is to close the discharge port at the bottom of the hopper. According to the different extrusion processes (it may be necessary to remove the die head to reduce the risk of excessive pressure at the front end of the extruder), the cleaning must be carried out by one person: the operator can observe the screw speed and torque from the control panel, and observe the extrusion pressure to ensure that the system pressure is not too high. First of all, do not remove the die head for cleaning. When the extrudate is completely converted from the processing resin to the cleaning resin, stop the machine immediately and remove the die head, and then let the residual clean resin flow out. Then reduce the screw speed to 15-25 R / min, and keep this speed until the melt flow at the front end of the die stops flowing.
2.1 screw cleaning
The mechanical method is to heat the extruder to the working temperature and push out the screw manually or automatically to remove the easily removed materials while it is hot.
Step 1: take the screw head apart and wipe the screw body with waste cotton cloth to remove most of the resin like precipitates; use a brass brush to remove the resin residue, or use a burner to heat the screw, and then use the waste cotton cloth or brass brush to remove the sediment on the screw.
Step 2: clean the screw head, check ring, thrust ring and mixing ring in the same way, and clean them with brass brush.
Step 3: after the screw is cooled, wipe off all oil stains with nonflammable solution.
Pay attention to do not abrade the surface of the parts during cleaning; before installing the screw head, evenly apply a layer of molybdenum disulfide lubricating ester or silicone oil on the thread to prevent the thread from seizing.
Fire roasting method:
It is the most common and effective way for plastic processing units to remove the plastic on the screw by burning or baking. (but never use acetylene flame to clean the screw. The temperature of acetylene flame can reach 3000 ℃. Cleaning the screw with acetylene flame will not only destroy the metal characteristics of the screw, but also significantly affect the mechanical tolerance of the screw. Because the screw has the heat in the process, the heat distribution of the screw is still uniform.
2.2 barrel cleaning
Step 1: first remove the nozzle head and barrel head, and remove the residue adhering to the inner surface of the barrel with a brass brush.
Step 2: wrap the waste cotton cloth on the end face of the wooden stick or long bamboo, and clean the inner surface of the cylinder. During the cleaning process, the cleaned waste cotton cloth should be replaced several times.
Step 3: clean the nozzle, especially the contact surface between the barrel and the nozzle. Be careful in this process to avoid resin leakage caused by rubbing the surface of the workpiece.
Step 4: when the temperature of the barrel drops to 30-50 ℃, wet the waste cotton cloth with solvent and clean the inner surface of the cylinder again in the way described in the second step.
Step 5: check and ensure that the inner surface of the cylinder is clean.
After cleaning the screw and barrel, we need to reassemble the machine correctly.
3.1 screw head installation
Step 1: place the screw on two equal height wood blocks, and set the operating handle on the keyway.
Step 2: evenly apply a layer of molybdenum disulfide grease or silicone oil on the screw head thread.
Step 3: insert the cleaned check ring, thrust ring and mixing ring into the screw head in turn.
Step 4: use the special spanner of screw head to hold the screw head and screw it in the opposite direction to complete the assembly of plasticizing components.
3.2 installation of barrel head and nozzle
Step 1: use the crane to lift the plasticizing components and clean them carefully.
Step 2: slowly push the plasticizing component into the barrel with the screw head outward.
Step 3: align the screw hole on the cylinder head with the screw hole on the barrel head, align the lip, and tap gently with the copper bar to make the fitting plane close.
Step 4: tighten the cylinder head bolt and install the cylinder head bolt.
Step 5: evenly apply a layer of molybdenum disulfide grease or silicone oil to the nozzle thread.
Step 6: screw the nozzle evenly into the screw hole of the barrel head to make the contact surface close.
Tighten the barrel head bolt to the appropriate torque value until the barrel, barrel head and its bolts reach the same value of temperature compensation.