Plastic machinery medium calenders are usually used with material conveying, sieve analysis, metering, kneading and mastication, etc., follow-up devices such as separation, traction, embossing, cooling, thickness measurement, coiling, and cutting, as well as transmission, monitoring and heating. The device consists of a complete calendering line calender, which produces soft and hard films, sheets, artificial leather, wallpaper and paving coils.
There are many types of calenders in plastic machinery. The number of pressing rolls is divided into two types: two rolls, three rolls, four rolls and five rolls. The pressing roller arrangement can be divided into F, Z, S, and L types.
Unlike other plastic machines, the calender consists of a frame, a press roll and its adjustments, a drive system and a heating system (Fig. 10 Plastic calender). The frames are usually made of cast iron and mounted directly on either side of the cast iron or cast steel frame to support the press roll bearings, shaft cross or press roll pre-bending devices, press roll adjustments, lubrication and other auxiliary devices. The press roll is made of chilled cast iron and cast steel, and its aspect ratio is selected according to the bending strength of the press roll material, which is about 2.6 to 3.5. In order to compensate for the defects of uneven thickness of the product caused by the bending deformation caused by the force of the pressing roller, the pressing roller is mostly formed into a waist drum shape, and the thickness unevenness of the product can be eliminated by the roller crossing device and the roller pre-bending device. Each press roller is driven by a separate motor. The pressure roller heating generally uses water vapor or superheated water, and the temperature difference between the two ends is required to be less than 1 °C. Each press roller has an independent automatic heating system. Modern calenders use roller bearings instead of conventional plain bearings to save energy, improve bearing life and product thickness accuracy.
Depending on the specifications of the calender, the thickness of the soft polyvinyl chloride film produced varies from 50 to 1000 m, and the minimum thickness of the hard polyvinyl chloride film is 60 m.
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