Static Eliminators: Solutions for Winders, Unwinders and Slitters

Published: August 05, 2024

Choosing Eliminators for Best Performance and Price

By Dr. Kelly Robinson, Founder, Electrostatic Answers

For winders, unwinders and slitters, static control is focused on the wound rolls because static charges on wound rolls can severely shock operators, ignite fires in solvent handling operations, and cause stick and jamming of cut sheets in customer applications. Even small amounts of static charges on webs entering winding rolls can cause problems because rolls store all the charges on the long length of web being wound.

Choosing the right static eliminator for winding rolls, unwinding rolls and slitters is all about controlling static on rolls. First, let's look at winders.

Controlling static on winders is challenging because we need to neutralize static charges from at least two different sources: 1. static charges on the web entering the winding roll and 2. Static charges deposited on the winding roll from a lay-on roller.

Static Charges on the Entering Web

The web entering the winding roll in Figure 1 should be as charge-free as possible by practicing good static control upstream of the winder. For this winder, a nip controls the winding tension. Powered static bar S_nip neutralizes the static charges deposited on the web from the nip. This neutralizer should face the web surface that touched the polymer nip roller.

A powered static bar will fully neutralize the static charge, so use powered static neutralizers near the winding roll. Use a high-performance, short-range static bar because the distance to the web from the static bar remains constant on this web span.

Verify that the web entering the winding roll is nearly charge-free by making two static measurements: 1. Electric field E_in, and 2. Voltage V_in.

Measure electric field E_in in Figure 1 with a handheld electrostatic fieldmeter. Many are commercially available that are about the size of a card deck. The electric field E_in should not exceed 2 KV/ cm (5 KV/in). If electric field E_in is too big, clean or replace SB_nip.

Measure voltage V_in in Figure 1 using an electrostatic volt-meter. There are few commercially available electrostatic voltmeters.

I recommend using an Advanced Energy Trek 520-2¹ or equivalent. The voltage of the web when it is wrapped on a grounded, metal idler roller should not exceed 0.5 V/mm of web thickness. For example, when running a 2 mil (50 mm) thick web, voltage V_in on the web entering the winding roll should not exceed 25 V. If voltage V_in is too big, take additional voltage measurements upstream of the winder to find the source of the high voltage.

Static Charges from the Lay-on Roller

Lay-on rollers are often used on winding rolls to prevent telescoping by squeezing out air between the wound laps. An unwanted by-product from the lay-on roller in Figure 2 is charge on the outside surface of the winding roll.

Use powered static neutralizer SB_lay-on in Figure 2 to neutralize static charges on the winding roll. If you can mount this static bar to the frame of the lay-on roller, use a short-range static bar because the distance to the winding roll remains constant. The lay-on roller vibrates, which shortens the service life of the static bar. Use a mechanically strong static bar to extend the service life.

An alternative is to use powered static neutralizer SB-_winder in Figure 1 to neutralize static charges on the winding roll. Mount this static bar on a machine frame outside of the maximum diameter of the winding roll. Roll handling is easier with S_winder below the winding roll. Protect S_winder from damage by mounting it inside an electrically insulating, fiber-glass U-channel.

Controlling static charges on unwinding rolls protects the operation from static charges stored on the roll from previous processes. Static control for unwinding rolls is challenging because we need to neutralize charges on both surfaces of the web exiting the unwinding roll. The best practice is to use two powered static bars (see: K.S. Robinson, "Static Control for Roll-to-Roll Manufacturing, "IEEE Transactions on Industry Applications, vol. 59, no. 1, pp. 93-103, Jan.-Feb. 2023).2

Install a powered static neutralizer for each spindle on the unwind turret in Figure 2.

SB_A is for spindle A and SB_e is for spindle B. Static bars powered with 24 VDC are available so that additional sliprings for electrical power on the turret are not need-ed. Use long-range static bars for SB_a and S_B because distances to the unwinding rolls grows as the rolls expire.

After the web exits the unwinding turret, install two powered static bars SB_over and SB_under in Figure 2 to neutralize static charges on the web exiting the unwinding roll. These two static bars should be installed symmetrically, which means two things. First, a line drawn from one static bar to the other must intersect the web at a right angle. Second, the distance from each static bar to the web must be the same. Use high-performance, short-range static bars because the distance to the web remains constant.

Once installed, energize only one of these two bars. When over-unwinding, energize only SB_over. SB_under should be turned-off. Similarly, when under-unwinding, energize only S_under SB_over should be turned-off.

Verify that the web in Figure 2 is nearly charge-free by making three static measurements: 1. Electric field E_roll, 2. Electric field E_span, and 3. Voltage V_unw.

Electric field E_roll in Figure 2 should not exceed 6 KV/cm (15 KV/in). If electric field E_roll is too big, clean or replace both static bars SB_A and SB_B.

Electric field E_span in Figure 2 should not exceed 2 KV/cm (5 KV/in). If electric field E_span is too big, clean or replace static bar SB_over or SB_under, whichever is energized.

The voltage V_unw in Figure 2 should not exceed 0.5 V/mm of web thickness. If voltage V_unw is too big, verify the function of SBA, SBB, and either SB_over or SB_under whichever is energized.

Static control for the slitter in Figure 3 uses powered static bars on the lay-on rollers from Figure 1 and two static neutralizers for the unwinding roll from Figure 2. When unwinding in only one orientation, passive static dissipater SD_in may be used instead of a powered dissipater to save money. The passive static dissipater may be a static brush, a tinsel strand, an ionizing cord, an ionizing rod or another equivalent device. Bristles that break from a static brush or tinsel may contaminate your product. lonizing cords or rods minimize contamination.

Slitters are compact and congested. It is difficult to find places to take verification measurements. Usually, I take measurements near the splice table.

Verify the operation of the unwind dissipaters in Figure 3 by making three static measurements: 1. Electric field E_roll, 2. Electric field E_span and 3. Voltage V_unw.

Electric field E_roll in Figure 3 should not exceed 6 KV/cm (15 KV/in). If electric field E_roll is too big, clean or replace SB_unw, which may be protected by mounting it inside an electrically insulating, fiberglass U-Channel.

Electric field E_span should not exceed 4 KV/cm (10 KV/in). If electric field E_span is too big, clean or replace static bar SB_unw and passive static dissipater SD_in.

Voltage V_unw in Figure 3 should not exceed 0.5 V/mm of web thickness. If voltage V_unw is too big, verify the function of SB_unw and SD_in. Electric field E_span should not exceed 4 KV/cm (10 KV/in). If electric field E_span is too big, clean or replace static bar SB_unw and passive static dissipater SD_in.

Voltage V_unw in Figure 3 should not exceed +0.5 V/mm of web thickness. If voltage V_unw is too big, verify the function of SB_unw and SD_in.

Verify that the winding slits in Figure 3 store little charge making two static measurements: 1. Electric field E_up and 2. Electric field E_low.

Electric field E_up in Figure 3 should not exceed 2 KV/cm (5 KV/in). If E_up is too big, clean or replace SB_up.

Electric field E_low in Figure 3 should not exceed 2 KV/cm (5 KV/in). If E_low is too big, clean or replace SB_low.

Finally, control the static charges on the web entering the slitter knives to minimize contamination from slitter debris. The slitter in Figure 3 has two sources of static charge just upstream of the knives: 1. The drive roller and 2. A bowed roller.

Dissipate static charges from touching the drive roller in Figure 3 using passive static dissipater SD_drv on the web exiting the drive roller facing the web surface that touched the polymer drive roller.

Dissipate static charges from touching the bowed roller in Figure 3 using passive static dissipater SD_bow on the web exiting the bowed roller facing the web surface that touched the roller.

Focus on winding and unwinding rolls to find the best static eliminators for winders, unwinders and slitters. Use high performance, short-range static bars when the distance to the web remains constant. Use long-range static bars on winding and unwinding rolls when the distance from the static bars to the roll surfaces varies. Save money by use passive static dissipaters far upstream of the winding rolls. Near the winding rolls, use powered static dissipaters.

1 https://www.advancedenergy.com/en-us/products/sense-and-measurement/esd-instrumentation/portable-fieldmeters-and-voltmeters/trek-520-series/#specifications

2 https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=9915453

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..