calender, machine that has wide application in the finishing of textile fabrics, the production of vinyl plastic sheeting, rubber sheeting, coated fabrics, and the manufacture of paper.
The mechanized plain calender was in common use in the mid-18th century after having been introduced into England from Flanders in the 17th century. A special type called the friction calender was patented in 1805 by William Smith, and the schreiner calender was developed about 1895. Calenders for embossing and moiréing are other types in use.
Calenders are made in many different forms and employ from 2 to 12 heavy rollers, usually mounted vertically in a series on a strong frame. The essentials of the machine are the pressure and temperature applied when the material being processed passes under or between the rollers. The number, arrangement, and type of rollers are the chief factors that determine how the calender functions. In the finishing of broad-woven fabrics, calendering produces results similar to ironing clothes. The pressure applied closes the threads, removes creases from the cloth, flattens it to the required thickness, and imparts a smoothness and lustre, or tither special effects, to the cloth.
In the plastics industry calendering is a method for producing vinyl film or sheeting. Resin and other ingredients are blended and formed into a hot plastic mass and passed through the hot rollers of the calender. The plastic emerges as a flat film or sheet whose thickness is determined and made uniform by the gap set on the gauging rollers of the calender. Similar applications are employed in the production of coated fabrics or rubber sheeting.