Calendering Machine

A calendering machine, or calender, passes a sheet material, originally and still commonly cloth, but also paper, rubber, and plastic, between a series of hard pressure rollers to smooth its surface, add luster, and even out its thickness. The word comes from the Greek kylindros, meaning cylinder, and the technique reached Europe when Flemish refugees introduced calender mills to the Netherlands in the sixteenth and seventeenth centuries to press woolen serge cloth, while Chinese textile workers used heavy rollers to finish silk and cotton over roughly the same period. Calendering later expanded well beyond cloth: the American inventor Edwin M. Chaffee patented a four-roll rubber calender in 1836 and went on to collaborate with Charles Goodyear, and Germany achieved the first successful calendering of PVC plastic sheet in 1935. Modern calenders use hard heated rollers, often chilled cast iron or steel, paired with softer polymer-coated rollers, and the adjustable pressure between rollers, called nip pressure, is used today to finish textiles and paper as well as to manufacture tires and coat lithium-ion battery electrodes.