Calendering of LWC Web Offset Paper, 1998 Finishing and Converting Conference Proceedings
Two new generation 12-nip off-line calenders started up at UPM-Kymmene Rauma Mill in January 1998 together with the new PM 4 producing light weight coated paper for mainly offset printing applications. The paper is coated on-machine with an annual production capacity of 400,000 metric tons, being the largest LWC producing line in the world.
With paper machine speeds around 1800 m/min plus demanding levels of paper surface properties, special emphasis was given to calendering from the early stages of the project.
This paper follows the analysis, specification, design engineering and installation phases of the project with respect to the calendering technology used. The vendor decision required testing and analysis of all available multinip calendering concepts. Rauma chose to invest in totally new calendering technology capable of high speeds in a multinip configuration.
The relevant operating principles of these multinip calenders will be presented as they relate to production results of gloss, smoothness, speed and capacity. For Rauma PM4 the implementation of the new calendering technology means first and foremost a first class printing surface. The LWC produced by the new machine has typical gloss values over 60% Hunter Gloss and smoothness values around 1.0 PPSS10. For future grade development, Rauma’s calenders have substantial unused calendering potential.