Calenderen

Calenderen is the industrial process of passing a sheet or film between a stack of rotating rollers, called calendar rolls, to smooth the surface, adjust thickness (caliper), and modify finish and density. It is used in several industries, notably papermaking and plastics, where precise surface quality and thickness are important.

In papermaking, calendering follows formation and drying and serves to produce a uniform surface, improve printability, and control bulk. The process uses a sequence of hard and soft rolls under controlled temperature and pressure. Supercalendering—an arrangement of alternating hard and soft rolls—can yield very smooth, dense surfaces suitable for high-quality newsprint and coated papers.

In plastics and polymers, calendering forms films or sheets by passing molten or softened material through rollers. The technique allows control over thickness, surface finish, and mechanical properties. Roller temperature, line speed, nip pressure, moisture (where applicable), and the configuration of the roll stack determine the final product quality.

In rubber and other elastomers, calendering produces sheets and compounds for laminates and layered materials. The method is chosen for its ability to produce consistent thickness and surface texture across large areas.

Equipment and variables play a central role: nip pressure, roller temperature and hardness, the number of rolls, line speed, moisture content, and precise alignment. Proper control yields uniform caliper and smoothness, while poor control can cause marks, thickness variation, or surface defects.