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Precautions For Sheet Metal Machine
- Sep 18, 2018 -

(1) Plastic sheet production equipment on the barrel of the temperature from the beginning of the feeding section to the cylinder and mold connection temperature gradually increased [1]. 

(2) Mold temperature is slightly higher than the barrel temperature. High out temperature control at 5---10 ℃.The temperature of the mold at both ends is slightly higher than the temperature in the mold, the temperature is controlled at 5-10 ℃.

(3) into the form, the three-roll upper roller surface should be with the mold lip under the surface of a horizontal plane; The lip end is parallel to the center line of the middle roller, and is 50~100mm apart.

(4) Mold lip clearance should be slightly less than or equal to the thickness of the plate products, the middle gap between the lip should be slightly smaller than the two sides of the lip gap. 

(5) Note that the roughness of the three-roll face R should not be greater than 0. 2pm.When cleaning the roll surface, do not use hard steel blade scraping roller surface, should use copper knife to clean the roller surface residue.

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

(7) Molding mold temperature control to be stable. When the temperature is high, the melt flows faster in the mold, and the molten material flows slowly in the mold when the temperature is low.

The instability of the melt flow rate will cause the plate (sheet) product longitudinal thickness error. 

(8) Pay attention to control the three-roll face temperature, should be a little higher temperature of the sheet roll, the roll temperature is slightly lower. Roller surface temperature is high, the slab is not easy to take off the roller, the product surface prone to cross-grain, low temperature, the product surface is not shiny.

According to this phenomenon, the roller surface temperature control should be adjusted in time. 

(9) The running speed of the three rollers is slightly higher than the extrusion speed of the slab from the mold mouth, the general speed difference does not exceed 10%.

The working speed of three rollers should be controlled smoothly, the running speed of too fast or too slow can influence the thickness error of the plate greatly. 

(10) Polyolefin Plastic Extrusion Molding Plate (sheet) material, screw selection of the mutant structure, compression ratio of (3-4): 1, melt flow rate: HDPE 0.3~2.0G/10MIN,LDPE 0.1~0.3g/1omin,pp 0.5~1. 5g/10min.

ABS and other non-crystalline polymer resin extrusion Molding plate (sheet), should choose a tapered screw, compression ratio of (1.6 12.5): 1. (11) Plastic Sheet (sheet) extrusion molding, in addition to polyvinyl chloride, polyethylene and polypropylene resin before extrusion generally do not dehumidification treatment, some other plastics (such as ABS, polyamide, etc.) should be in the extrusion before the need for dehumidification in the dry treatment. Otherwise, the exhaust type extruder should be used for extrusion.


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