Nina Deng, Frédéric Parent, Tony Manfred, Joe Aspler, Jean Hamel
In the first report of this series, we characterized the draw variation of newsprint webs in a number of North American newspaper pressrooms using the technique of laser Doppler velocimetry. We showed that there is a good correlation between web break rates and pressroom draw variation. In this report, we have extended the draw variation study to commercial pressrooms, including heatset offset, coldset directory offset, and gravure printing. A wide range of draw variations was seen, likely related to the wide range of press operating and maintenance conditions. Also, as is the case with daily newspaper pressrooms, the contribution of paper is small. For a given draw variation, the web break rate in a heatset offset pressroom is significantly higher than that in newsprint pressrooms. This may be due to the fact that heatset offset presses are more complex. Case studies demonstrated that the draw variation can be reduced through improved press maintenance and operation.
Keywords: Runnability, Web Breaks, Tension, Offset printing, Gravure Printing