PAPERWATCH: As Presses Go Wider, So Goes Paper

With drupa comes news of bigger presses. Webs are arriving with reel stands capable of feeding larger 60´´ diameter rolls, and webs in 96´´ widths are in the offing. Sheetfeds are running faster, wider and longer, too. For paper mills, delivery of the larger format stock is technically quite feasible: Fine paper is now made on 409´´ (yes, 34´) wide machines running at 4,000 fpm. Wide rolls at the mill, however, do not automatically translate to wide sheets being readily available for the new VLF (very large format) presses.

What are the issues associated with large rolls and mega sheet sizes? First and foremost is availability. Large-format sheets are not stock items: minimums apply, and delivery times vary.

• The major domestic paper mills do not currently sell commercial grades in VLF sheet sizes.

• UPM-Kymmene announced capacity to sheet up to 83´´ paper at one facility and up to 74´´ at another—the focus of its PrintCity exhibit at drupa.

• xpedx says it has stepped up to procure paper and convert it into large sheets for existing VLF presses. But it is a custom process.

The next issue is weight. Handling monster-sized sheets is a challenge, since 500 sheets of 80-lb. 47×64´´ text paper weigh 250 lbs. The same quantity of 80-lb. cover paper weighs 460 lbs. Pallet jacks with extensions are necessary.

While today's wider presses have overcome past limitations and now lay ink uniformly across the sheet, transfer sheets from unit to unit without distortion and apply uniform pressure across the printing nip, will the paper itself be dimensionally stable? Lighter basis-weight papers and those with excessive coating (and less fiber) will be harder to back up.

The quality requirements for paper must now include minimal variation across the sheet. Caliper as well as ink and fountain solution absorptivity must be uniform. Sheet flatness is particularly important.

Proper conditioning and atmospheric control in the pressroom are more critical. VLF sheets have a greater tendency to curl than smaller sizes.

Wide rolls are less troublesome. Gravure led the way with 120´´ presses several years ago. However, large-diameter wide rolls test mill capabilities. Most mills have limited capability to manufacture large- diameter wide rolls of good quality.

Shipping and unloading the massive weight of wide, large-diameter rolls typically requires a heavy- duty clamp truck. Not all truck beds can withstand the weight of both the roll and the clamp truck. The relationship of weight to volume is such that the loading patterns for these big rolls requires strong bracing—transit damage is a concern.

Paper issues to address as presses grow in size are not insurmountable, but careful planning can avoid surprises. Start the conversation with your paper supplier to ensure adequate supply and quality. And be prepared to search for stocks.

ONLINE www.graphicartsonline.com/paper

VLF Sheetfed Dimensions

Make               Model           HxW"
Heidelberg        XL162           47x64
Heidelberg        XL 142          40x56
KBA                Rapida 205    60x81
KBA                Rapida 162    47x64
MAN Roland   900XXL        51x73
MAN Roland   900                47x64
Mitsubishi         6000LS/LX    41x56