Nonwoven does not shear like film

A film slits cleanly because the material fails along a line and stays there. Nonwoven is a mat of filaments held together by bonding, and the cut depends on severing those filaments rather than parting a continuous sheet. That changes the requirements: the edge has to be keen enough to sever fibre, the clearance has to be tight enough that the filaments cannot slip between the knives, and the blade has to stay that way for a long run because a nonwoven line rarely stops to change knives.

The visible failure is different too. Film gives you burr; nonwoven gives you a fuzzy edge, loose fibre and dust. On a medical or hygiene line, that fuzz is not cosmetic — it is material that ends up in the machine, on the product, or in the air.

What we make

• Top slitting knives — dish and flat form, for air or spring loaded holders
• Bottom slitting knives — counter rings, plain or grooved
• Matched top-and-bottom pairs, ground and checked together
• Longitudinal slitting blades for machines that use a straight blade against a roller
• Pneumatic slitting knives for lines that engage the knife on the fly

Clearance matters more here than on film

With film, a slightly wide clearance gives you a burr. With nonwoven, a wide clearance lets filaments pass between the knives uncut, and you get a stringy edge that looks like a blunt blade. This is the single most common misdiagnosis on nonwoven lines: the operator changes the knife, the fuzz stays, and the actual problem was the clearance or a worn bottom ring.

Our preference is to make the pair together and set the clearance against the actual web weight and thickness, rather than supplying a knife to a nominal figure. If you are replacing only half a pair, send both and we will at least match the geometry.

Where a nonwoven slitter fails

• Fuzzy, fibrous cut edge. Filaments not severed — clearance too wide, or the edge has rounded.
• Edge stretched or pulled rather than cut. Web tension too high, or a dull edge dragging.
• Dust and loose fibre building up at the slitter. Edge finish too coarse, or the knife is crushing rather than shearing.
• Uneven wear around the circumference. Run-out in the holder or arbor, before the blade.
• Slit width drifting across the web. Bottom ring face run-out, or a loose bore fit.

Edge geometry and steel

Nonwoven generally wants a keener edge angle than paper and a finer surface finish than film, because the cutting action depends on severing filaments at a small scale. We work in tool steel, high-speed steel and, where wear demands it, carbide — the choice follows the web (fine meltblown is less abrasive than a heavily filled spunbond) and the line speed. Tell us the gsm and the composition if you know it; it changes the recommendation more than the machine brand does.

How we match an existing slitter pair

Send both knives. We measure outside diameter, bore, thickness, bevel angle and, for a grooved bottom ring, the groove dimensions. Then we ask what the cut looks like now: fuzzy, stringy, dusting, or wandering. Each of those points to a different cause, and matching dimensions alone will not fix a problem that lives in the clearance.

Nonwoven slitting questions

Can I run the same knives on spunbond and meltblown?

Often yes, but the clearance may need to change with the web. Meltblown is finer and lighter; a setting that works on a heavy spunbond can leave a meltblown edge stringy.

How often should a nonwoven slitter be changed?

There is no fixed interval — it depends on gsm, filler content, line speed and how tight your edge tolerance is. Watch the cut edge: when fuzz starts appearing consistently, the edge is telling you.

Do you make the grooved bottom rings too?

Yes. Send the top knife section and the groove dimensions, or the worn ring, and we will match both sides of the pair.