As digital web presses get faster and run lengths longer, the function of sheeters and rotary cutters is becoming ever more significant. Their role in converting printed stocks into finished products in a single inline process, without compromising the speed of the press, can greatly improve the efficiency of a print operation.
When buying a sheeter, a printer should, first and foremost, make sure it can run as fast as their digital press, explains Robin Brown, digital solutions division national sales manager at Friedheim International.The buyer also needs to check the sheeter’s paper weight and width ranges, says Brown. "The standard width of a digital press used to be 520mm, but I’d say it’s probably now 770mm," he adds. "Make sure the machine is flexible enough to handle both sizes."
Double-cut sheeters are very much the norm these days, as they are able to cut out segments of waste paper and jump back on to the register without losing speed. Some machines allow you to take out different slug sizes, too – Brown claims the Ehret machines are intelligent enough to cut to a different-sized repeat on every printed sheet.
Getting heavy
Rotary cutters work in a similar way in that the knives can be placed anywhere around the circumference of the sheet. According to Purdy Graphic Systems managing director Adrian Purdy, rotary cutters are ideal for heavier substrates like book covers. "With rotary cutters you can take pre-folded 130gsm stock and make cuts wherever you want," he explains. "The Global Web Finishing machines that we sell can cut up to five pieces out of every repeat."
Rather than cut across the direction of the web, a rotary trimmer will simply trim off the side of a partially finished stock – often folded, and in some cases glued and stitched as well.
In most cases, converting equipment is bought directly from a press vendor these days, who will sell the kit as part of an inline press and finishing package.
WHAT'S NEW IN... CONVERTING FOR WEB-FED PRESSES
• RR Donnelley’s proprietary hybrid inkjet and web offset press, the ProteusJet, became fully operational in August. Designed for on-demand book printing, transpromo and direct mail, the 762mm-wide four-colour machine can be run in three modes – offset only, offset plus digital and digital only
• Swiss digital and web finishing specialist Hunkeler will be running its ‘Innovation Days’ trade show in Lucerne again next February. The biennial show specialises in all things digital, including inline and offline digital finishing
• Domino unveiled the N600, a narrow-web colour label press, at Ipex earlier this year. With a standard speed of 50 linear metres per minute, Domino claims the machine is twice the speed of most inkjet rivals, and much faster than
the electrophotographic machines from the likes of HP and Xeikon
