Digital Print Hits the Bindery - Head On
It’s beyond the shadow of a doubt that digital print has transformed the printing industry. The enormous number of innovations that have been introduced over the past 10 years—both print engine technology and software—mean we’re in a brave new world of workflow and output.
But, what about those folks in…you know, the BINDERY? That little-discussed place where all those weird machines—like cutters, folders, binders and the other—reside? Well, digital has created a fair amount of heartaches for bindroids. It goes with the technology.
The majority of digital printers installed so far have been toner-based, cut-sheet machines. Toner is pretty high-tech stuff. Essentially, its micro-beads of particles encapsulated in a coating, which is melted by a fusing apparatus.
The chemistry and physics of printing with toner dictate that these particles are laid on the substrate and pressed at high temperatures to ensure that they are “fused” with the paper. In many machines, special fusing oil is also deposited on the sheet to assist in this process. This creates some special problems when it comes to prodicing a finished product.
Among the challenges are:
• Toner Cracking
When folding full-bleed sheets with conventional buckle folders, the toner will separate from the substrate along the fold line. This has bedeviled finishers for some time. But it has also created opportunity, as several finishing suppliers have come up with fixes. The best known of these are creasing systems that apply a crease before the fold. Special creasing discs can be mounted on the folder, and there are several folding systems designed specifically for digital substrates.
• The Binding Problem
The fusing oils used by some digital print engines have caused many bindroids to pull their hair out when they discovered that these coatings on the page prevented the standard hot-melt adhesives used for perfect binding from adhering. As you can imagine, this was not a small problem.
One of the possible solutions to this was switching to PUR (polyurethane reactive) hot melt. PUR cures by chemical bond, rather than the thermal process of EVA. While a solution, PUR is far trickier to use than EVA hot-melt (and the adhesive systems themselves are more expensive). So it took both time and investment to find a “cure” for finishing these new digitally printed products.
Almost all digitally printed book covers must be laminated. As good as various UV and aqueous coatings are these days, nothing compares to the protection offered by a good laminate film. The problem emerges when the digital sheet meets the lamination film. I’ve seen recent posts on bindery group boards that reported the lamination easily separates from the toner-printed sheet (lifting the toner off with it!).
In other cases, a partial de-lamination occurs when the book (and cover) receive their final trim in a three-knife trimmer. This has become something of a multi-faceted problem requiring multiple solutions. The lamination film companies (and equipment vendors) have developed aggressive bonding “sticky” films in response, trimmer equipment vendors have manufactured higher-pressure machines, and other steps have been taken.
There are theories galore regarding the true culprits here. Is it the toner? The fusing chemicals? Or perhaps the digital paper itself?
I read a post today in which a firm swore by a process of sending the laminated covers through a separate heat press to achieve a better bond between film and substrate.
The finale to this story is that while digital technology has revolutionized the print process, it has also created multiple challenges for the bindery at the same time.
But bindroids are adaptable! And we’ll solve any problem thrown at us.