Control Static on a Winding Roll

Posted 10th October 2016 by Kelly Robinson

Static sparks on a winding rolls can shock operators and damage thin coatings such as release layers. To suppress sparks on the winding roll and to have low static when the roll is unwound in the next operation, use an active static bar to dissipate static on the outside surface of the winding roll and make certain that the web entering the winding roll is as charge-free as possible. Even with good charge control upstream of the winder, the web entering the winding roll will carry some static. This small amount of static accumulates in the winding roll causing sparks. The static bar on the winding roll will suppress these sparks.
Good static control upstream of the winder is the key to having low static when the roll is unwound. Make sure that the web entering the winding roll is as charge-free as possible.

Fig. 1: This winder has a tension control nip, a dancer (float roller) to control
the winder motor, and a lay-on roller to improve wound roll quality.
Let’s suppress sparks on the winding roll in Figure 1 and make sure that it has low static when we unwind it in the next operation. This winder has 3 important elements; (1) a nip to control with winding tension, (2) a dancer (float roller) to control with winder motor, and (3) a lay-on roller to improve wound roll quality. Initially, to keep things simple, we’ll assume that we’ve done a good job controlling static upstream of the winder and that the web entering the tension control nip in Figure 1 is charge-free.
Nip rollers can deposit a large amount of static on the web. And, we know that the static will be on the web surface that touched the polymer nip roller. The best practice is to locate active static bar SBNIP in Figure 1 on the web span exiting the tension control nip facing the web surface that touched the polymer nip roller. With SBNIP, the web entering the dancer is nearly charge-free.
A dancer (float roller) can deposit a significant amount of static on the web because roller alignment is difficult to maintain. When roller alignment is imperfect, sliding contact with the roller charges the web. The static charges deposited on the web by the dancer in Figure 1 will be on the bottom surface of the web. While the static deposited on the web by dancers is usually modest, even this low level of static will cause sparking on the winding roll because all of the charge on the entering web accumulates on the winding roll.
Normally, the best practice is to install a static dissipator on the web span exiting the dancer facing the web surface that touched the roller. However, in this case, the charged, bottom web surface becomes the outside surface of the winding roll. So, we can dissipate static from the dancer with static bar SBROLL in Figure 1.
A lay-on roller is often used on a winding roll to improve winding. The lay-on roller also deposits static charges on the web surface that touches the roller. And, this web surface becomes the outside surface of the winding roll. The best practice is to locate active static bar SBROLL to dissipate static on the outside surface of the winding roll. The bracket holding SBROLL may be attached to the lay-on roller frame so that the static bar moves with the lay-on roller.
With static bar SBROLLER in Figure 1, we achieved our first static control goal of suppressing sparks on the winding roll. And, with static bar SBNIP, we achieve our second goal of having low static when the roll in unwound in the next operation.
Please feel free to contact me if you have any questions or if you would like additional information. My email address is: Kelly.Robinson@ElectrostaticAnswers.com.

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