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What are the Precautions for Plastic Sheet Extruder
The temperature of each section on the barrel of the plastic sheet extruder gradually increases from the feeding section to the junction of the barrel and the molding die. The molding die temperature is slightly higher than the barrel temperature. The higher temperature is controlled at 5-10℃. ...
The temperature of each section on the barrel of the plastic sheet extruder gradually increases from the feeding section to the junction of the barrel and the molding die.
The molding die temperature is slightly higher than the barrel temperature. The higher temperature is controlled at 5-10℃. The temperature at both ends of the mold is slightly higher than the middle temperature of the mold, and the higher temperature is controlled at 5-10°C.
In the form of sheet feeding, the upper surface of the middle roller of the three rollers should be on the same level as the lower surface of the mold lip. The end face of the lip is parallel to the center line of the middle roller, and the distance is 50-100mm.
The mold lip gap should be slightly less than or equal to the thickness of the sheet product. The gap between the die lips should be slightly smaller than the gap between the die lips on both sides.
Note that the roughness R of the three-roll working surface should not be greater than 0.2pm. When cleaning the roller surface, it is not allowed to scratch the roller surface with a hard knife, and a copper knife should be used to clean the residual material on the roller surface.
The roller surface should have some medium height, and the gap between the three rollers should be equal to or slightly larger than the thickness of the sheet.
The temperature control of the forming mold should be stable. When the temperature is high, the melt flow rate in the mold becomes faster, and when the temperature is low, the melt flow rate in the mold becomes slower. Unstable melt flow rate will cause large errors in the longitudinal thickness of the sheet product.
Pay attention to controlling the working surface temperature of the three rollers, the temperature of the feed roller should be slightly higher, and the temperature of the output roller should be slightly lower. The temperature of the roll surface is too high, and the slab is not easy to roll off. The surface of the product is easy to produce horizontal stripes; the temperature is low, and the surface of the product is not shiny. According to this phenomenon, the roller surface temperature control should be adjusted in time.
The operating speed of the three rolls is slightly higher than the extrusion speed of the slab from the die mouth, and the general speed difference is not more than 10%. The working speed of the three-roller should be controlled smoothly, and the running speed of too fast or too slow has a great influence on the thickness error of the sheet.
Extrusion molding of plastic sheet, except PVC, polyethylene and polypropylene resins are generally not processed before extrusion, other plastics (such as ABS, polyamide, etc.) should be dried before extrusion deal with. Otherwise, use a vented extruder for extrusion molding