Since there is such a variety of nonwoven fabrics, we use different types of knives to slit different types fabric. One type of knife used primarily in light weight and thermoplastic nonwovens is the crush cut knife. An older name for this type of knife is score cutter. The knife uses a semi sharp circular blade that is pneumatically loaded against a hardened anvil roll. The blade crushes the fibers and causes the fabric to split. Since it crushes the fibers and does not shear them, it does tend to leave some fuzz on the edge of the material. It works the same way a pizza cutter works. The anvil roll is actually covered with hardened sleeves that can be replaced. The sleeves are harder than the knife blade steel. The knife holders usually mount on a dovetail steel bar and are easily removed and repositioned.
As you can see in the picture, there are various types of blades that can be mounted in the knife holder. An advantage to this type of knife is that they are very thin and the knife holders can be mounted close together for cutting narrow strips of material. Another advantage is that the blades can quickly be changed when they get dull.
It is important to not that the blades have to be sharpened properly. Score cut knives are not sharpened to a razor sharp point. Rather, they have a rounded point usually of A (.002” to .004” radius), B (.006” to .008” radius) or C (.010” to .012” radius).