Experimental investigations in winding and unwinding operations

Abstract

The trend in winding in the paper industry can be simply characterized by : wider and faster with more dense webs with a lower level of accepted defects. This is valid for paper production and printing, especially in rotogravure.

Europe's rotogravure industry is investing in wider printing machines : 3.08 m -3.18 m - 3.48 m - 3.52 m - 3.60 m. These machines are already ordered and the widest will start up end of 1997. In the unwinding process the techniques of fiber cores is running to the edge of physical limits : vibrations. Experimental natural frequency analyses and trials on a core rotational test stand demonstrate limits and potentials of cores and unwind stands.

Jumbo reels in roto are exceeding masses of 5 tons. In the unwinding situation bursts near the core occur - the more often, the wider and heavier the reels are. A systematic winding test on a production winder with a modified unwind stand demonstrate the creation of bursts and leads to a method to avoid center bursts in jumbo reels for rotogravure.

In paper production there is an idea to produce machine wide reels with high diameters for a high efficiency an a minimum of paper losses. Limits in winding of LWC base paper are observed because of center bursts. Investigations of thermal phenomena in the center of big reels show characteristic temperature structures during winding. Bursts can be detected because they produce a local temperature "hot" spot. From this ideas can be created to develop a new winding test or inspection system to detect winding structures and winding failures.