Static Control for Slitting into Narrow Webs

Published: October 20, 2025

By Kelly Robinson, PE, PhD, Electrostatic Answers

Slitting is a complicated process. The fracture line in Figure 1 initiated a knife splits the incoming web into two ribbons. The mechanical fracture of the incoming web has two, unwanted by-products; airborne debris and static charges. Even well-controlled slitting generates airborne debris.

After slitting, the freshly exposed edges of the exiting ribbons in Figure 1 are charged because fracturing separates charge. One edge has positive charges and the other has negative charges. Webs are thin so that the charged area is usually very small. However, when a wide roll is slit into many, narrow ribbons, fracture charging is significant.

Tribocharging also separates charge when two chemically different materials touch and separate. For example, a polypropylene (PP) web exits a silicone rubber (polydimethylsiloxane or PDMS) nip roller with charges on the surface that touched the compliant nip roller. PP is chemically different from PDMS so tribocharging occurs at the exiting nip where the PP web peels from the PDMS nip roller. PP is also different from steel, aluminum, or hard coated aluminum (alumina). My experience is that tribocharging from touching a metal or alumina roller surface is very small compared with charging from a compliant nip roller.

Slitters have three static control zones:

• Unwinding Wide Roll to Drive Roller
• Drive Roller to Knives
• Knives to Winding Slits

1. Unwinding Roll to Driver Roller

Goal: A charge-free web enters the Drive Roller.

Charges on the Wide Roll are from the process where the roll was wound. Powered static bar SB_Roll neutralizes charges on the outside of the Unwinding Wide Roll. SB_Roll should be a long-range static bar with a neutralization range up to about 20 inches because the distance from the static bar to the wide roll increases as the roll expires. If the web speed exceeds about 100 fpm (30 mpm), mount two long-range bars side-by-side to achieve high neutralization efficiency.

Static bar SB_span dissipates charges on the inside surface of the web that exited the Unwinding Wide Roll. This static bar should be a short-range static bar with a neutralization range up to about 4 inches. Short-range static bars should provide good neutralization efficiency up to line speeds of about 1,000 fpm (300 mpm).

Reading E_Roll in Figure 2 verifies SB_Roll and should not exceed +5 KV/in. If the reading is too big, clean or replace SB_Roll. Reading E_splice verifies SB_span and should not exceed +2 KV/in. If the reading is too big, clean or replace SB_Roll. Use a handheld electrostatic voltmeter to take reading splice in Figure 2 to verify overall static performance.

The reading should not exceed £0.5 V per micron of web thickness. For example, when running 1 mil (25 um) thick PP web, splice should not exceed +13 V. If the reading is too big, check both SB_Roll and SB_Span.

2. Drive Roller to Knives

Goal: A charge-free web enters the Knives.

Static bar SB_Drive in Figure 3 neutralizes charges from touching the polymer covered Drive Roller. Use a powered static bar rather than a passive dissipater like a tinsel strand or a static brush. A passive dissipater leaves a small amount of charge on the web. A powered static bar fully neutralizes the charge. With more knives slitting a wide web into many ribbons, more debris is generated. Fully neutralize charge on the web entering the knives to minimize deposition of airborne contaminates.

The Spreader Roller in Figure 3 just before entering the knives can deposit a significant amount of charge on the web. SB_Spread neutralizes charges from touching the Spreader Roller.

The web entering the Knives in Figure 3 should be nearly charge-free with good, upstream static control. However, there is usually no room near the slitter knives to take static readings. Rely on visual inspection to spot charging sources and choose static dissipater locations.

3. Knives to Winding Slits

Goal: Wind a charge-tree web.

Static bar SB_RollUp, in Figure 4 neutralizes charges on the Upper Winding Slits. SB_{Roll Low} neutralizes charges on the Lower Winding Slits. Mount SB_RollUp and SB_{Roll Low} on the Lay-On Roller frame so that the distance from the static bar to the winding slits is constant. Use a mechanically strong short-range static bar because vibrations from the Lay-On Roller limit the service life of the static bar.

Take readings E_upper and E_Lower to verity the operation of SB_RollUp and SB_RollLow. Each reading should not exceed +5 KV/in. If reading E_upper is too big, verify the operation of SB_RollUp. If reading E_lower is too big, verify the operation of SB_RollLow.

When slitting a wide roll into many narrow ribbons, the side-walls of the winding slits are charged by fracture charging of the slit edges illustrated in Figure 1. This fracture charge must be dissipated after the Separation Roller where the edges of the slit ribbons are exposed. SB_upper neutralizes charges on the upper ribbons and SB_Lower neutralizes the lower ribbons.

Take readings E_upper and E_lower on the sidewalls of the winding slits to verify the operation of static bars Supper and SB_Lower. The readings should not exceed £5 KV/in. If sidewall reading E_upper is too big, verify the operation of Supper. If reading sidewall E_Lower is too big, verify the operation of SB_Lower.

Slitting is a complicated process where knives fracture the wide web into narrow ribbons. The over-arching static control goals are to deliver charge-free slits to the customer and to minimize contamination. Airborne debris can deposit causing contamination. Minimize static charges on the slit ribbons to minimize electrostatic attraction of contaminates.

About the Author

Dr. Kelly Robinson writes on static issues occurring in converting processes. Robinson founded Electrostatic Answers, has 40-plus years experience in industrial problem solving and was named Top Manufacturing Consulting Services Provider 2023 by Managing MFG. He can be reached at This email address is being protected from spambots. You need JavaScript enabled to view it..