Supersize me

Just a short while ago, when I was asked to write an article about large-format finishing, I instantaneously regretted not having spent more time investigating it last drupa, despite Heidelberg making a remarkable impression with their new XXL sized products! However, as I’m not affiliated with any of the machinery manufacturers and earn my money teaching at a university, I will apply industrial engineering to the print industry. Perhaps, some of my thoughts will help you lay out your future factory or give some new perspectives.

Let’s take a look at some of the small issues in stretching sheets to XXL, seemingly not of a big interest to those making the business plans. While some ideas are applicable to bindery only, a lot is of interest for printers, too.

Let’s start with gathering the constraints of XXL format offset litho. We can find the follwing standard press and/or sheet sizes around the globe above and including the popular 40”.

Common large-format press sheet sizes

As there are many different press manufacturers, some even offering to build customized size presses, this list can by no means be exhaustive. It’s very complicated to draw the line because of the additional blur induced by “standard” paper formats differing in the world.

Now, a look into a common misconception: the larger sheet size of the press does not automatically imply a decision about increased page counts for bindery signatures. There are a lot more factors to be considered when choosing the page count per signature. A larger print area might come in handy when a large-format, large page count and short-run book is to be produced; a lot of companies around the world gain that little advantage over their competitors folding and binding large page counts.

Others, meanwhile, positioned for more complex, versatile products, will emphasize that the placement of inlays, stickers or other added value products may command some completely different signature schemes. Printers might still be able to reap the benefits of printing these smaller signatures on one sheet, but the processing must differ. Also, quality will inevitably be an issue as pages on signatures over 32 will have to be turned and nudged in prepress to accommodate for the twist and shove going on when folding.

On the other hand, binderies looking into this field will need to draw the line only at this point: the folded signatures – delivered in whatever fashion is preferred in the bindery – is the input component to the binder or stitcher. Not a plain sheet. So, if concerns should arise regarding the volume of paper to be processed, binderies already dealing with Web offset output will not be challenged in this area. It’s the way to get to these signatures that differs.

‚Ä¢Printing XXL, folding XXL. Sheetfed folders are currently offered up to 56” infeed width. So, sheets up to the 51” x 73” class and even a bit more wide can be folded in one piece without cutting before. Different folder configurations allow to fold either large page-count signatures or 2-signature sheets in double-stream fashion by cutting inline on the folder’s knife shafts. The caveat on these workflows: folding schemes might be very non-standard, and press sheet layouts need to accommodate for a series of small details. Planning will be complicated, especially if trade binders deal with print-only companies on projects possibly controlled by publishers. Many of these details are possible points of failure with a clear potential of turning profit to loss. The challenge will be to communicate efficiently, stringently covering all theses areas, while not dousing the creativity in planning for new formats and production workflows, which might just give the little advantage.

•Printing XXL, folding smaller size. The printed sheets will have to be cut before folding. This might be the easiest way for trade binderies to accommodate for the larger presses. Two options here: some presses can be fitted with slitters, so sheets will be cut inline when printing; this will keep the binder happy, as there will be small to no investment needed. Secondly, sheets might as well be cut on larger guillotines.

It’s all about logistics. There are a plethora of issues arising when sheetfed goes XXL, and the way a company adresses these issues will make the difference regarding an efficient production.

While the basic pallet size for these operations is obvious, you might also look into their weight. Stock measuring 46” x 64” has an M-weight between 250 – 1250 pounds. Standard pallet trucks will take up a load of roughly 5,500 pounds. Maximum pile heights on machines are also limited by approximately 40”.

So, depending on the stock used, a pallet can take up from 21,000 sheets down to just 2,000 sheets. Given an average press speed of 8000 sheets per hour, one shift’s work output and input each will be the equivalent of two to 32 pallets, respectively. The latter being an equivalent of four pallets out and four pallets in per hour – weighing in at roughly 5,500 pounds each. Adequate storage near each machine should take care of at least an hour’s worth of material (feeder and delivery) – the more the better, possibly limiting out at 3/4 of a shift’s amount of material. Take into account the time needed for bringing the material to and from this area. Stacking pallets in this area is out of the question, as this is the material immediately needed for the running of the machine or coming off the line.

If a workflow with inline slitter on the press is chosen, buying a pallet truck with long forks might be considered, so the delivery paper can be stacked on two pallets. Both can be picked up at the same time going in sideways with the pallet truck.

Each pallet stored along an aisle beneath a machine can be accessed at all times; best to make sure the alleys will be wide enough for the pallets to be turned in the aisle (the diagonal size of paper being a rough first guess), ensuring you can use your pallet storage space optimally. Should powered trucks be used, the alleys might even need to be wider.

Given the arm’s reach of an average person, starting from a sheet size of 28√ó40, handling layers of sheets will get difficult. People won’t be able to reach both corners of the longer edge at the same time – not even speaking of controlled handling of heavier packs of sheets. Very large formats will be almost impossible to handle appropriately.

Even single sheets weigh in heavy (e.g. 46” x 64”); a sheet of 56-pound offset stock will weigh approximately a quarter of a pound, while a-230 pound offset will weigh just around a pound per sheet!

Given trained operators might be able to work five tonnes per shift, if worse hits bad, they’ll not even cope with one hour’s worth of presswork in one shift. So, manually re-stacking and turning piles will no loger be an option. When dealing in large-format, it isn’t a question of the economical trade-off: “cost of the press helper versus cost of pile-turners.” The sheer size and time neded to create an accurate press-ready stack of paper by hand simply makes this manual endeavour impossible. There are plenty of different pile-turners out there – the decision will be a fairly easy one. The pile-turner should be near the press to avoid wasting money on carting the pallets around too much.

Now, if the sheets need to be cut before folding, the choice of the correct sheet lay is essential, as some jogging tables might not be able to operate both sides.

The size of the guillotine has to rise above the popular 115cm range; there will be an inevitable demand for pile-lifting equipment as well as a large-format jogging table. If handling XXL will be demanded more often, it might be worthwile to start talks with your equipment suppliers. There will be two general directions to go for:

‚Ä¢Gradually build up a large-format cutting line. Paper will be handled by an operator. Considering the weight of the single sheets and piles, workplace ergonomic aspects will make a large impact on operators’ performance and health, ultimately bringing up the lines’ productivity and profitability. The very minimum wishlist should include a pile-lifter, large air-cushioned transfer tables, an adequately-sized jogging table, at least one pile-lifter with stack guide rails to form folder stacks from cut sheets and a guillotine at the best coping with the diagonal measure of the maximum sheet size accepted. If possible, upgrade to automatic stackers for the output.
‚Ä¢Invest in a full-fledged automatic cutting line. This line will feature the same basic workstations as mentioned above, but the destacking and handling will be done by robotic arms and machines. These lines might cut a large hole in the budget, but above 40” they should bring an obvious advantage in productivity compared to the setup mentioned above. The downside: design might impose restrictions in the number of sheet parts buffered, restricting even smaller format sheets and signatures. There will always be a tradeoff between high productivity at a given point of operation and high flexibility at lower overall output.

If the decision is made to invest in new, large-format folders, there won’t be a large number of manufacturers offering equipment. However, despite XXL presses existing for a time before, some finishing machinery manufacturers have gone out of their way to improve and evolve their high-tech. They’ve put a lot of effort into addressing the issues of ergonomics (e.g. access to knife shafts) and sheet handling (foul sheet detectors, automatic ejection of said misprint), decreasing makeready times and improving productivity.

Depending on the final destination of folded signatures, investments in stackers or log stackers might be considered; XL sheetfed might be competing with Web offset, so you want to make sure not to slow down certain binders/stitchers by not being able to fulfill the feeder logistics needs of downstream equipment.

When deciding to go large, there are a lot of small differences that make a big impact on the investments’ outcome. While I addressed a couple of them, there might be other completely different issues lurking around your shop.

When entering large-format, the sheer size and weight of entities handled will easily overwhelm the average worker’s powers. Companies should be concered with protecting their most valuable asset: skilled, flexible personnel operating the machines at an optimum speed throughout the year while sustaining high producivity. It’s in addressing these issues that companies will show their proficiency in industrial thinking and operations, thus creating a sustainable profit.