TL;DR

Web breaks at the slit zone are caused by dull blades, excessive web tension, or nicks in the web guide rolls. Inspect blades, reduce web tension by 10%, and check all rolls in the web path.

What you might see

web breaks concentrated at or just downstream of the slit zone
torn web edge visible at the break point
tension spike in the machine log before break
increased frequency of breaks on narrow slit widths

Likely causes

Tap to mark as ruled out

Dull slitter blade creating a torn rather than a clean cut, initiating edge cracks
Web tension set above the maximum for the material tensile strength
Nick or burr on a web guide roll creating stress concentration at that point
Incoming reel with edge cracks carried into the slit zone

Required tools

Cut-resistant gloves (blade-rated)
Fine honing stone
Tension meter
LOTO kit

Safety first

Slitter blades are razor sharp. Use cut-resistant gloves at all times near the slit head.
Web breaks under tension create a whipping hazard. Stand to the side of the web path during break investigation.

Procedure

7 steps · ~45 min

1
Log the MD position of recent breaks relative to the reel to determine if breaks cluster at reel starts or at a consistent tension level.[1]
2
Reduce web tension by 10% of the current setpoint and observe break frequency for one full set before further adjustment.
3
Stop the machine and lock out. Inspect all slit blades for nicking, dullness, or contamination.
Warning: Use cut-resistant gloves rated for blade handling when inspecting slitter blades.
4
Replace any blade showing edge damage. Even a small nick creates a stress riser in the slit web edge.[1]
5
Run a gloved hand slowly along every guide roll, spreading roll, and idler roll surface to feel for nicks, burrs, or raised splices. Mark any defects found.
6
Remove any burrs on roll surfaces with a fine honing stone. Replace rolls with deep nicks.
7
Inspect the incoming reel for edge cracks before starting a new set. Reject reels with visible edge damage.

Sources

Atlas Converting Atlas CW1000 / 5000 Slitter Rewinder general technical documentation, Atlas Converting
Slitter rewinder web break analysis and blade management, general converting machinery practice (general)

More guides for Atlas Converting Atlas CW1000 / 5000

How to fix slit width variation on an Atlas CW1000 Slitter Rewinder

Slit width variation is most often caused by slitter blade lateral play or dull blades. Verify blade holder torque, replace worn blades, and check the web tension profile.

~45 min7 steps

How to fix telescoping rewind rolls on an Atlas CW5000 Slitter Rewinder

Telescoping rolls are caused by incorrect rewind tension taper or misaligned rewind cores. Check the tension taper profile, core alignment, and unwind brake for the current material.