Rolls bending

The calendering configuration of rolls may consist of two to at least seven rolls. The number of rolls and their arrangement characterizes them. Examples of the layout of the rolls are the true L , conventional inverted L , reverse fed inverted L , I , Z , and so on. The most popular are the four-roll inverted L and Z rolls. The Z calenders have the advantage of lower heat loss in the film or sheet because of the melts shorter travel and the machines simpler construction. They are simpler to construct because they need less compensation for roll bending. This compensation occurs because there are no more than two rolls in any vertical direction as opposed to three rolls in a four roll inverted L calender and so on. 

Residual stress generally from the effects of metal rolling, bending, or welding operations... 

It seems that the right setting of the cross axes setting practically can compensate the deflection of the rolls due to the nip forces. A compensation of roll deflection can also be achieved by means of outer roll bending devices, which is depicted in Figure 35.42. An additional counterdirected bending force is applied on the outer ends of the rolls. 

FIGURE 35.42 Illustration of the outer roll bending working principle. 

Calender to be equipped with crowned rolls, external roll bending, and adjustable cross axes setting (controlled)... 

Figure 35.43 shows a general layout of a dual-purpose calender line for coating steel cord and textile cord. The heart of the production line is the four-roll calender in an S-configuration. Two mbber sheets are formed in the upper and lower nip. The thin sheets are guided to the middle nip and the cords are coated in the middle nip between the two rubber sheets. Generally outer roll bending is applied on rolls 2 and 3 to compensate the roll deflection caused by the nip force in nip 2. Rolls 1 and 4 can be set crossed respectively to rolls 2 and 3. 

The distortion suffered by calender rolls resulting from the pressure of the rubber running between them. If uncorrected the deflection produces a rubber sheet thicker in the middle than at the edges. See Camber, Crossed Axes and Roll Bending, all techniques to compensate for calender bowl deflection. 

An apparatus for measuring the dynamic modulus and hysteresis of elastomers. The stress-strain oscillogram is shown on a ground-glass screen by means of an optical system. Now superseded by modem computer controlled servo hydraulic and dynamic mechanical thermal analysis machines. Roll Bending... 

Three common methods, which are commonly referred to as roll-crown, roll-crossing, and roll-bending, are employed to compensate for this deformation. Roll-crown indicates that the roll diameter at the center is slightly greater than at the edges. In principle, by applying an appropriate roll diameter and profile, roll deflection can be exactly... 

The second group of kinematic definition of the bending contour can also be subdivided into procedures with rotary and linear tool motion. The roll-bending procedures (three-, four-, and multiple-roll bending), incremental tube forming, sweeping, and other process combinations and... 

The elastic properties of materials exert pressure on calender rolls which causes their deformation. This is controlled by honing the surface of rolls, roll bending, or cross-axes. Modem calender automatically adjusts the gaps based on the data from the gauges scanning the entire width of the material. 

Bending and straight flanging Brake bending Roll bending... 

Roll bending n. In calendering of sheet, the practice of applying a bending moment to the ends of the calender rolls that opposes the bending caused by the pressure forces as the plastic is squeezed between the rolls. The object is to produce sheet whose thickness varies minimally across its width,... 

Once fluxed, all metals show as large aystals under the microscope. Using mechanical treatments such as rolling, bending, sheeting, and drawing, these crystals... 

The rolls are typically 4-10 ft. wide. The gap between rolls becomes progressively smaller as melt moves from 1-2, 2-3, and 3-4 rolls, and the final thickness is controlled by the last gap. The forces generated are immense rolls are crowned in the middle to compensate for the pressure and some systems employ roll bending to control the forces. Rolls turn at a differential rate to produce shear film exits the calender at 80-180 ft./min, and pounds per hour... 

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