MACHINERY | WINDERS
Troubleshooting roll-winding defects
US-based Maxcess has produced a guide to common roll-winding defects. It says that troubleshooting these – and alerting winders and operators to problems on the web – helps reduce scrap and improve throughput. It says there are four common defects to look out for.
Poor roll winding starts Problem: Seeing an obvious differ- ence between the web near the core and the rest of the winding roll can lead to a poor start. Solution: To prevent poor starts, tighten the web before fastening it to the core. Use good quality, properly stored cores. Begin with the correct torque, nip or web tension.
Collapsed, offset, loose cores Problem: Core problems can stem from collapsed, offset or loose rolls.
Collapsed rolls stem from stacking rolls on end too high, with the bottom rolls crushing in an axial direction. An offset core causes an abrupt position- ing shift along the edge of the roll. A loose core causes rotational displace- ment with the web. Solution: Core problems start when the web is wound too softly. It should be wound evenly, but harder at the start. Avoid stacking rolls too high to reduce offset. Make necessary tension adjustments gradually at the winder.
Low-quality roll edges Problem: Poor slitting causes a rough, fuzzy, or dented roll-edged appear- ance. Edges may be frayed, and the web edge may not be straight. Fibres may be visible within packaging or on the film. A black cloth may reveal the presence of slitter ‘dust’. Solutions: First, ensure slitters are
tor to bring the blank rolls into the Martin MBSF unit on the same side. Martin’s solution was to supply a reverse
Below: Goebel IMS has supplied primary slitter rewinders to a Chinese producer of BOPET film
direction unwind/splicer that allows rolls to be loaded from the opposite side. This created another problem for single-person operation: as the new roll was being loaded, the operator could not see what was happening on the press. This was also easily solved, by fitting a camera to the delivery end of the press – feeding a monitor on the opposite side at the Martin MBSF unit, according to the company.
sharpened. For shear slitting, slitters should be adjusted and set for the right cant angle and blade overlap. Slitter blades at the nip point should be moving slightly faster than the web. If it seems slower, the speed differential between web and slitters may need adjusting.
Telescoped or dished rolls Problem: The defect shows a progres- sive roll edge misalignment that can be concave or convex. Solution: Ensure caliper is consistent across the web width. Control tension throughout the wind. Ensure cores do not shift. This may indicate upstream problems that are creating thickness or moisture variations in the web. Proper torque transfer from winding shaft to core, along with precise control of web tension, are also essential.
Speed increase Rollomatic says it has improved its high-speed roll winder (HRW) to meet increasing demands from film and sheet manufacturers – so it now has a smaller footprint, is lower, and can be adapted into an in-line production environment. The HRW’s design makes it easy to tread the machine with an accumulator. Loading of cores is simplified with a floor-reachable magazine. Roll change is performed automatically without the need for taping or gluing of cores. A swing panel option allows the line to be operated from various positions.
Users can still benefit from the high number of roll changes per minute on lower-gauge film. For heavy-gauge film, the HRW can be equipped with a specially designed knife, allowing the cutting of eight layers of 6 mil film (more than 1200 microns in total). Film can be wound on different core sizes including the most standard 1.5in (38mm) and 3in (76mm). The winder can wind roll diameters up to 10.6in (270 mm). HRW can be adapted to out-of-line production
at speeds up to 820 ft/min (250 m/min). It comes with a safety shaft to avoid operator access to the area with moving parts. Prior to this, it supplied a roll winder to
36 FILM & SHEET EXTRUSION | April 2023
www.filmandsheet.com
IMAGE: GOEBEL-IMS
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