The printing industry has closely examined the combination of material and cutting-edge angle that offers the maximum sharpness and durability of the knives used in cutting paper. The use of high-speed steel for the cutting edge of the knife in flat cutting machines has decreased noticeably, and now cemented carbide alloy is primarily used due to its hardness.
The hardness of high-speed steel is lower than that of cemented carbide alloy, but because of high-speed steel's tenacity, it is easy to process work at an acute angle when it is used as the cutting edge. Depending on the characteristics of the paper, cutting is sometimes smoother with high-speed steel than with the alloy, although the sharpness of high-speed steel is not long lasting.
While cemented carbide alloy provides hardness, it is known to chip easily. The quality, however, has significantly improved in recent years.
A variety of papers come to the worksite every day for cutting. And because of the increase in short runs of many different items, more clients are particular about paper. Paper grades offering strength and surface processing are become even more diverse. Additionally, since some recycled paper poses difficulties when cutting, an increasing number of users feel the knife's sharpness is lost more quickly than in the past.
Although changing the knife each time to match the paper grade would be better if possible, it would adversely affect working efficiency. There is now a wide variety of knives compatible with a wide range of paper grades that do not require using different ones for different jobs.
Whether the cutting edge is sharp or not depends not just on the paper grade but also on many other conditions, such as the direction of the paper grain, the temperature and humidity around the cutting machine, clamp pressure and the number of sheets cut at one time. Talk with Komori about selecting the knife and setting peripheral conditions to ensure optimum cutting.