Best Practice: Static Control for Unwinding Rolls
- Published: January 26, 2026
By Kelly Robinson, Professional Engineer and Founder of Electrostatic Answers
Production processes have several operations, often beginning with web casting and finishing with slitting. Slitting, usually the last operation before shipping finished products to customers, is our last opportunity to neutralize static charges. The web often has “balanced charges,” with positive charges on one surface and an equal amount of negative charge on the other surface. Neutralizing balanced charges is particularly important for preventing high static on wound rolls.
Figure 1: Static Bar SB1 forms balanced charge. Diagram courtesy of Electrostatic Answers
Balanced charges on web cause static problems on winding rolls including shocking operators. First, let’s see how balanced charges are formed. Then we’ll look at neutralizing them.
Balanced Charge Formation
The web entering the nip in Figure 1 is charge free because we’ve done a good job with static control upstream. The rubber nip roller deposits static charges on the web surface that touches the roller. Measure these charges using fieldmeter reading ENip Out that responds to the charges in control volume CV1. While I rarely use my electrostatic voltmeter, it is sometimes helpful. If necessary, verify that the static charges are on the web surface that touched the roller using voltmeter reading VNip Face. VNip Back shows that the web surface that touched the metal nip roller has very little charge.
Powered static bar SB1 is intended to neutralize static charges from the Nip Roller. However, it is installed facing the back, uncharged web surface. SB1, responding to the static charges inside CV2, deposits neutralizing charges on the uncharged web surface that it faces.
A static dissipater installed facing the wrong side of the web forms balanced charge. The balanced charges formed by SB1 in Figure 1 are difficult to detect. Fieldmeter reading ESB1 Out is zero because there are equal numbers of positive and negative charges in CV3. If needed, measure VSB1 Back to verify that the previously charge-free, back web surface is now charged.
Similarly, balanced charges are difficult to neutralize. Powered static bar SB2 in Figure 3 provides no neutralizing ions because there are equal numbers of positive and negative charges in CV4. If necessary, measure VSB2 Face to verify that the web carries static charges after exiting SB2.
High static charges on winding rolls with low static charges on the entering web are symptoms of balanced charges. The balanced charges in Figure 1 cause high ERewind Roll readings even though ESB1 Out is zero.
Figure 2: Unwinding and rewinding with balanced charges. Diagram courtesy of Electrostatic Answers
Quickly assess the static performance of an operation by taking 4 fieldmeter readings in Figure 2; EUnwind Roll, EUnwind Span, ERewind Span, and ERewind Roll
Balanced charges persist in wound rolls. Balanced charges on the web when the Unwind Roll in Figure 2 was wound will be there when it is unwound. A high EUnwind Roll reading with a low EUnwind Span reading are symptoms of balance charges. If necessary, verify balanced charges by measuring VUnwind Out on the outside web surface and VUnwind In on the inside web surface.
If the operation has good static control, the web entering the Rewind Roll in Figure 2 will have low charge as indicated by ERewind Span. However, balanced charges persist. ERewind Roll will be similar to EUnwind Roll when the roll diameters are the same.
Figure 3: Best practice static control for an Unwinding Roll. Diagram courtesy of Electrostatic Answers
Neutralizing Balanced Charges
To improve static performance, neutralize balanced charges on the Unwind Roll in Figure 3. Powered static bar SBUnwind Roll neutralizes the static charges on the Unwind Roll. Measure EUnwind Roll to verify the performance of SBUnwind Roll. If necessary, measure VUnwind Out to verify that the outside surface of the web is charge-free.
The web exiting the Unwind Roll has static charge on its inside surface. Static bar SBUnwind Span neutralizes the static charges on the inside surface. Measure EUnwind Span to verify the performance of SBUnwind Span. Measure VUnwind In on the inside surface of the web to verify that the inside surface of the web is charge-free. VUnwind In verifies the performance of both SBUnwind Roll and SBUnwind Span.
Balanced charges are effectively dissipated when EUnwind is less than ±15 KV/in. When EUnwind exceeds ±15 KV/in, static control must be improved in the operation where the Unwind Roll was wound to achieve good static control.
With SBUnwind Roll and SBUnwind Span in Figure 3, a charge-free web enters the web path with good static control. With good static control, measure ERewind Span to verify that the web entering the Rewind Roll has no net charge. Measure ERewind Roll to verify that the Rewind Roll stores little charge. If necessary, measure VRewind In and VRewind Out to verify that there is no balanced charge on the web entering the Rewind Roll.
Even with good charge control on the web path in Figure 3, the web entering the Rewind Roll will likely have some residual static charges. SBRewind Roll neutralizes these residual charges that accumulate on the Rewind Roll.
Best Practice
Slitting is usually our last chance to neutralize static charges and especially balanced charges. Using this best practice static control on the slitter Unwind Roll ensures that product delivered to your customers has acceptably low static charges. For further information, please download the complimentary article by K. Robinson, “Static Control for Roll-to-Roll Manufacturing,” IEEE Transactions on Industry Applications, Vol. 59, No. 1, Jan/Feb 2023 (https://ieeexplore.ieee.org/document/9915453).
About the Author
Kelly Robinson, PE, PhD is a regular Paper, Film & Foil Converter contributor, specializing in static issues occurring in converting processes. Robinson is the founder of Electrostatic Answers, has 40+ years of experience in industrial problem-solving, is an IEEE Life Fellow, and was named Top Manufacturing Consulting Services Provider in 2023. Visit: https://www.linkedin.com/in/electrostaticanswers/
