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What are the precautions for using a plastic sheet machine?


(1) The temperature of each section on the plastic sheet production equipment barrel gradually increases from the feeding section to the connection between the barrel and the forming mold.

(2) The temperature of the forming mold is slightly higher than the temperature of the barrel. Control the temperature above 5-10 ℃. The temperature at both ends of the mold is slightly higher than the temperature in the mold, and the temperature above is controlled at 5-10 ℃.

(3) In the form of feeding, the upper surface of the middle roller of the three rollers should be on a horizontal plane with the lower surface of the mold lip; The lip end face is parallel to the centerline of the middle roller, with a distance of 50-100mm.

(4) The gap between the mold lips should be slightly less than or equal to the thickness of the plate product, and the gap between the middle of the mold lips should be slightly less than the gap between the two end mold lips.

(5) Note that the roughness R of the three roll working surface should not exceed 0 2pm. When cleaning the roller surface, it is not allowed to scratch it with a hard steel knife. Copper knives should be used to clean the remaining material on the roller surface.

(6) The roller surface should have some middle height; The gap between the three rollers should be equal to or slightly greater than the thickness of the plate.

(7) The temperature control of the forming mold should be stable. When the temperature is high, the flow rate of molten material in the mold increases; When the temperature is low, the flow rate of molten material in the mold slows down. Unstable molten material flow rate can cause significant longitudinal thickness errors in plate (sheet) products.

(8) Pay attention to controlling the working surface temperature of the three rollers, which should be slightly higher for the inlet roller and slightly lower for the outlet roller. The temperature of the roller surface is too high, making it difficult for the slab to roll off, and the surface of the product is prone to horizontal lines; The temperature is too low, and the surface of the product is not glossy. According to this phenomenon, the temperature control of the roller surface should be adjusted in a timely manner.

(9) The operating speed of the three rollers is slightly higher than the extrusion speed of the slab from the mold mouth, with a general speed difference of no more than 10%. The working speed of the three rollers should be controlled smoothly, and running speeds that are too fast or too slow have a significant impact on the thickness error of the plate.

(10) When extruding polyolefin plastic sheets, the screw adopts a mutation type structure, with a compression ratio of (3-4): 1 and a melt flow rate of HDPE 0 3-2.0g/10min, LDPE 0.1-0.3g/10min, PP 0.5-1 5g/10min. ABS and other amorphous high polymer resin extruded plates (sheets) should use gradient screws with a compression ratio of (1.6-2) 5) : 1.

(11) The extrusion molding of plastic sheets, except for PVC, polyethylene, and polypropylene resins, which generally do not undergo dehumidification treatment before extrusion, other plastics (such as ABS, polyamide, etc.) should be required to undergo dehumidification and drying treatment before extrusion. Otherwise, an exhaust type extruder should be used for extrusion molding.

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