Slitting and Rewinding
Slitting-Rewinding in narrow web label converting: an Indian perspective
Harveer Sahni, Chairman Weldon Celloplast Limited S
litting and rewinding are pre-printing and post printing processes in the narrow web label printing industry. Prior to printing, larger width labelstock rolls or jumbo rolls, as they are referred to, must be slit to the size as per the printing format of the label job in hand. The operation involves unwinding, slitting with circular knives or razor blades and rewinding. Paper stocks are slit with circular knives while fi lmic substrates are slit with razor blades. Additionally, the equipment would have web aligners and tension controls. Narrow web label printing in roll form made its entry in India in the early 1970s when narrow fl atbed label presses imported from Japan, started being used to print labels. 4 or 5-inch-wide label presses were in use on which single labels were printed, meaning that post printing slitting was not required. These presses would print at 5 to 10 meters per minute. By the 1990s, rotary narrow web CI label presses were launched and started going wider to 7inches and on to 10 inches, enabling printing of multiple labels across the web with need to slit them after printing and die cutting. Narrow web slitting and rewinding started being done online with an extra die cutting station and dual rewinders on the presses. These presses would run at anything between 30 to 50 meters per minute. It was an innovation to do unwinding, printing, die cutting and slitting online in a single pass.
Towards the latter half of the 1990s, when the modular presses like the Mark Andy 2200 were launched with speeds going up to 100 meters per minute and the demand for self-adhesive labels started to rise, converting companies started feeling the need to increase production. It was felt that online slitting rewinding was slowing down their speed, especially when there was need for frequent changeovers that took a lot of time. Instead of investing in another label press, it would be better to invest in a slitter rewinder. At this time, an offl ine narrow web slitting rewinding machine complementing the width of their label presses became a necessity. With the start of a
new millennium, FMCG and Pharma companies in particular, started insisting on inspection and defect detection of labels supplied to them. Online inspection would further slowdown the label conversion, so offl ine slitter rewinders were upgraded to perform unwinding, inspection, slitting and rewinding. These would have web aligners, sensors to detect labels, tension control, slitting and rewinding. A few years later, with the adoption of UV Flexo, printing speeds went up further. With the growth of retail consumerism, marketing teams in brand owners demanded embellishments, barcodes, and varnishing on labels. Each process slowed down the machine speed when fi nishing online. In such a situation, the simple slitting and rewinding machine became a fi nishing machine. It now has all that was mentioned before, plus registration control, die-cutting, waste matrix removal inspection, slitting and rewinding. Label printing technologies continue to diversify into diff erent tangents, what started from just fl atbed block printing, transformed to be employing technologies like intermittent letterpress, rotary fl exo, screen, gravure and a combination of all mentioned here, with a host of embellishments. The decorative processes included hot foiling, cold foiling, varnishing, embossing, debossing and many other such techniques. The diversity has culminated in the growth of digital printing, whereby the short runs and personalisation has received a shot in the arm. With the futuristic digital label printing and growing need for short runs made offl ine fi nishing an absolute necessity. The transformed slitter rewinders in the narrow web label industry to complement digital label printing became further evolved to become fi nishing equipment with a lot of automation and capabilities. For example, they can have one or two fl exo stations to do cold foiling or multiple types of varnishes, print barcodes with monochrome digital barcode printers, inspection system, intermittent or full rotary die cutting, waste matrix removal, slitting and rewinding fi nished label rolls.
38
June 2024
www.convertermag.com
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