There are many plastic products factories that need to use the chiller to cool the machine. Many friends often don’t know what type of chiller to use when they buy industrial chillers, to achieve their required cooling effect, or not. Know what kind of machine is more suitable for your own production workshop. So now, DLLPLASTICS tell you about the cooling in plastic extrusion molding, and hopes to help some friends.
Generally divided into screw cooling, fuselage cooling, and product cooling.
1, screw cooling
The function of screw cooling is to eliminate frictional overheating, stabilize the plastic extrusion pressure, promote the plastic mixing evenly, and improve the plasticizing quality. However, its use must be appropriate, especially not too much, otherwise the plastic melt in the barrel suddenly cools, which can lead to serious accidents. Screw cooling is absolutely forbidden before extrusion, otherwise it will cause serious equipment accidents.
2, the fuselage cooling
The function of the fuselage cooling is to increase the heat dissipation of the barrel to overcome the temperature rise caused by frictional overheating, because this temperature rise cannot be stopped during the extrusion process of the plastic, even after the heating power supply is cut off, so that the reasonable temperature cannot be long-term. To maintain, heat must be added to cool the barrel to maintain heat balance during extrusion. The fuselage cooling is carried out in stages, mainly based on fan cooling. Considering the different functions of the fuselage sections, pay special attention to the use of homogenization section cooling.
3, product cooling
Product cooling is an important measure to ensure the geometry and internal structure of the product. After the plastic extrusion layer leaves the machine head, it should be cooled immediately, otherwise it will be deformed under the action of gravity. For non-crystalline materials such as polyvinyl chloride, the problem of crystallization can be ignored. The plastic product can be quenched by direct cooling with water, so that it is cold-permeable in the cooling water tank and is no longer deformed. The cooling of crystalline polymers such as polyethylene and polypropylene should take into account the crystallization problem. If the quenching method is adopted, it will adversely affect the microstructure of the plastic product and generate internal stress, which is the result of cracking of the product in the future. One of the reasons must be paid attention to in the extrusion process; the extrusion coating of crystalline plastics such as polyethylene and polypropylene should be carried out by a stepwise cooling method using warm water cooling. Generally, depending on the auxiliary equipment of the equipment, the cooling water tank should be divided. Sectional section, the water temperature can be started from the plastic extrusion layer into the first section of the water tank from 75 ° C to 85 ° C, the water temperature is reduced step by step, until room temperature, the smaller the temperature difference of each section of water temperature is more reasonable.