Web Lines | How To Choose the Right Tabbing Tape
- Published: December 13, 2016, By Tim Walker
Tabbing tape needs to be strong enough to stick to the roll, but weak enough to break so the new roll’s bumped and bonded leading tail will break away from the unwinding roll.
In my previous column on Unwind Splice Reliability, I promised to provide more details on tabbing tape.
For bump-splices to succeed, the tabbing tape has two important functions.
- Function 1: Tabbing tape adhesive bond and strength >> Force of air drag
First, the tabbing tape adhesive must be strong enough to stay bonded even under high-speed conditions. The force of air drag is a function of speed, but also the neatness of the splice preparation.
If the new roll-splicing tape does not lie flat to the roll, any buckle or curl away from the roll’s surface can become a sail, grabbing the "wind" and exerting force on the tabbing tape adhesive bond and break strength. Poor, non-flat splice preparation may cause few problems at lower speed, but may be unreliable at high speeds (e.g., over 1000 fpm).
A significant and unique problem of bump-splicing to the release coated paper is that this tabbing tape must bond to the release-coated side of the paper. Using a low cost option, such as ¼ in. wide masking tape strips, may work great for film tabbing, but will prove a poor choice for release coated webs. Many splicing tape and specialty tabbing tapes are formulated to have high adhesion to release coated materials.
- Function 2: Splicing tape bond >> Tabbing tape strength
Once the bump roller presses the expiring web into the new roll’s splicing tape, the splicing tape must quickly form a tack or green strength bond to the running web great enough to tear the tabbing tape and to release the new roll to unwind. The green or tack bond strength is a function of adhesive, bump nip load (and ensured contact), real contact area, shape of splicing tape (straight across or chevron), and speed.
Splicing tapes are pressure-sensitive adhesives (PSA) that require pressure in the contact to form a good bond. Splicing can fail if the bump roller contacts too lightly or fails to contact due to bouncing, out-of-roundness, or mis-timing. High speed video is a great tool for evaluating bump roller contact. Amazingly, recent smart phones have 30 frame per second slow motion video capabilities that can be great for diagnosing unwind splicing.
Splicing tape may be applied in straight or angle geometry. Angled or chevron splicing tape geometries require more contact time of the bump roller over the complete machine direction length of the tape.
Butterfly or dog bone shaped tabbing tapes have a great combination of large contact area for strong bond during roll acceleration and narrow "break away" sections. One drawback to the dumbbell tabs is they need a little more care and time to apply. They usually come pre-cut on a release liner, but they need to be peeled off and applied with some positional accuracy without damaging the strips.
Web handling expert Tim Walker, president of TJWalker+Assoc., has 25 years of experience in web processes, education, development, and production problem solving. Contact him at 651-686-5400; This email address is being protected from spambots. You need JavaScript enabled to view it.; www.webhandling.com.
