Calender

Calender ( from French calandre "role" ) is a system of several successive arranged heated and polished rolls of chilled cast iron or steel, through the columns of a melt or other materials be passed. It is used for the production of films of plastics ( PVC, PE, PS, etc.), rubber, metals (aluminum, tin) and paper.

Distinguishing features

A distinction Schmelzkalander for film production ( film semi ) and coating calenders for coating eg tissues, eg Conveyor belts. We distinguish between the types of a calender. These depend on the arrangement of the individual calender rolls in the side view. Are the usual types L, F, I and Z-form.

Kalanderarten

Depending on the arrangement of the rolls and the material supply a distinction between I-, L-, M -, and Z - calender. For rigid PVC processing mainly the L-form is used. PVC soft - processing can be implemented in the F- form, fabric sheets in the Z- calender.

Applications

Calender also be used for embossing, smoothing, compacting and calendering of paper and textiles. Further, webs can be solidified from the thermoplastic polymer to non-woven fabrics. It also be calendered elastomer mixture for the production of plates transport conveyor belts.

Textile industry

In the textile industry calender or assemblies of several calenders are used in a variety of ways, including as a precursor in the Krumpfungsprozess, for smoothing surfaces to squeeze out fleet surplus to evaporate in the hot fix or fleet residues ( hot calender ).

Paper industry

In the paper industry, surface properties such as gloss and smoothness, while reduction in thickness can be improved. By changing the pressure, temperature and rolling speed, different effects can be achieved. Calender located outside of the paper machine ( offline ) or within the paper machine drying section and between reel (online).

The procedure is called calendering or satin finishing.

Plastics industry

For plastics comparatively thick films are produced with the calendering ( calendering ). These then are, for example in the pharmaceutical industry for blister ( blister pack ) for use. Thin films made of PE ( trash bags ) are made ​​for example of time and cost, using blown film extrusion. Rubber sheets are produced in the range of 0.03 to 1 mm. These films are also doubled in the calender.

Production

In the construction of calenders, engineers are faced with several difficulties. In general, the applications require an extremely fine adjustable distance between the rolls, the width of the fabric should be as large as possible, the rollers have as little mass, but can withstand high pressure. Through the last three requirements, it is often inevitable that low bending effects along a roller occur (deflection ), also often thermal deformations. This is taken by (mostly tiny ) deviations from the cylindrical roller profile statement. Are used tons of profiles ( convex ground roll barrels ), which are slightly thickened in the middle, two counter-rotating trapezoidal profiles and S profiles. In the thickening one also speaks of a so-called camber. The last two profiles have the advantage that fine adjustments are made possible by distance changes in position of the rolls. The rollers may be changed to each other in parallel in the roll gap, or be restricted. Cabinets in the roller axes are no longer parallel.

Particularly in high-speed paper machine calenders of the oscillating behavior is dampened by antivibration compound in order to avoid cracks in the webs, despite the high speed.