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Shear knife cutting does help with higher web temperatures due to the amount of knife edge that is presented to the web in the cutting process.
Web temperature is an important parameter in razor knife slitting. While most slitting operations are at room temperature, there are processes in which the web must be slit at higher temperatures.
One such example is edge trim removal at the exit of film casting machines. Generally, webs are more difficult to slit at elevated web temperatures, because higher temperature reduces the film strength and permits the web to stretch over the blade cutting edge. The stretched edges will be wavy in appearance and can form bell ends on the mill roll.
Also, the stretched edges may produce stress risers that can promote tears in the web or trim, thus causing discontinuity to the process. In the case of casting film line trim removal, line downtime is very expensive. My experience has been that the web temperature should be less than 50 deg C for best results when razor slitting mill roll sheets...