Transitioning From Offset to Digital Workflow
We are smack in the middle of a massive shift from offset to digital print. And in making that transition, both printers and vendors have had to put on their thinking caps when it comes to finishing. In the offset world, what comes off the sheetfed or web press is signaturized output. The sheet or web is converted into signatures for binding or saddle-stitching by folding into signatures. Signatures are then gathered on binder, saddle-stitching, or hard-cover gathering sections, then bound, stitched, or cased-in.
But on the web-fed digital side, the printed roll is your starting point. And unlike offset, the most common web width in continuous digital print is twenty inches, although 30- and 40-inch inkjet presses are out there. This is more challenging than it seems. Your finishing system must be able to cut, slit, fold and cut again to produce the proper sheet size set or book block that’s needed to pass on to the stitcher or binder. Not only that, but in today’s short-run environment, it must be able to quickly switch formats and sizes. Many digital print operations now run several different formats in a shift.
This combination has turned the traditional craftpersons bindery approach on its head. The new web-to-finish machines are the most automated systems we’ve ever seen — they are able to change finished formats with simple taps on a touchscreen. The process unwinds the web which is then plow-folded, slit, or slit-and-cut to produce a two-across or three across book block, mailer, ballot, other product. For book blocks, edge-gluing systems are also used to tack the block together before entry into the perfect binder (where the glue tack will be milled off). The demand for these new systems has inspired something of an arms race among vendors. Tecnau, Horizon — Hunkeler, MBO Digital, Muller Martini, Ehret, IBIS and others have all designed web-to-finish machines of varying levels of finishing ability and with various compelling features.
For book printers, there are complete end-to-end “book factories” available. These integrate several standalone modules so that there is a continuous process flow from web to finished book. The current throughput standard for digital web finishing is that the finishing end must run at between 500 to 700 linear fpm. No doubt we will see that figure creep upward in coming years.
My vendor contacts have introduced many new systems at drupa, and the word is that there is lots more to come. For those printers contemplating a digital web print addition, study the finishing end as thoroughly as you do the press. You must understand and determine the optimum Web-to-finish workflow for the products you produce. There are lots of choices available to you. Choose carefully.