4. Conclusion

Calendering is an essential sheet finishing operation, particularly for developing the printability properties of the substrate. Since paper machines are generally designed for the production of specific types of paper, this limits the choice of calendering process. Today, multinip technologies are becoming increasingly efficient. As far as the new extended nip processes are concerned, they are still in the process of being deployed industrially, and their preferred fields seem to be packaging papers and boards (such as coated boards for folding boxes). Technical developments (rollers, frames, automation) have enabled these calenders to reach the high output levels of paper machines. Nevertheless, they require particularly high levels of investment and maintenance downtime, which is still detrimental in terms of productivity.