I am again faced with the woes of winter…already! We are converting more & more recycled liner, however, we constantly battle with cracking. Of course my guys want to blame the paper. I want to experiment with different anvils & score heads. I hear some people say going to a softer durometer helps, & some say changing score profiles help. Do you have any insight regarding this matter? Are there any tests that I can conduct to eliminate the “paper being to dry” as an excuse? Do you hear this type of complaint often? Any feedback would be helpful.
This dryness that we often talk about is really a matter of paper chemistry and paper physics. As we see more and more non corrugated fibres enter our system this cracking phenomenon is likely to manifest itself to even a greater magnitude than we know today. Containerboards made from recovered fibre contain less lignin, the thermoplastic polymer that comes from the pulping process which gives linerboard and medium elastic properties. This property allows new containerboards to form and flow around scoring heads and die knives, scores, and perfs. Recycled containerboards are more challenging.
Recycled containerboards are comprised of shorter fibres with fewer fibrils so that there are fewer and generally weaker bonding sites for the fibres to “join hands.” These shorter fibres are more likely to “break” or crack in the converting process. Because there are fewer bonding sites in recycled containerboard the sheets have the propensity to give off more moisture during the combining operation, so dryer board is delivered to the converting equipment.
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