Offset Printing
Higher output and less effort with short grain
Friday 15. March 2013 - KBA C56 SG: enormous productivity with 56 pages in short grain
Currently, there are several new trends in commercial web offset. On the one hand reaching the highest possible page output per cylinder revolution with so called high-volume presses with up to 96 long-grain pages and on the other hand there is a focus on achieving the highest possible quality, production flexibility and economic efficiency supported by shorter makeready for smaller job runs up to 10,000 copies.
The cutting-edge 16-page KBA C16 is tailored to the second trend. It works with long grain pages, with the pages arranged on the plates in the direction of the web travel. Short-grain double-circumference presses, with the pages arranged at right angles to the web travel, are less common and not as well-known. These presses have enormous potential in terms of format flexibility, productivity and saving time when finishing. The concept of the new 56-page short-grain KBA C56 SG is based on exploiting this potential. One of these presses together with a C48 SG (48 pages in short grain) have been in operation at a long-standing Dutch KBA user, Em de Jong in Baarle-Nassau, for some time now.
Short grain boosts productivity
Maximum output is limited by the maximum possible web speed. Individual drives commonly found in parts, such as the reelstand or folder, in modern presses like the C16 and C56 SG could achieve higher web speeds than the physical characteristics of the substrate used allow, in terms of stability, stretching and shrinking. Short-grain presses can produce about 30% more printed sections per hour compared to long-grain presses running at the same production speed because of their smaller cylinder circumferences. For example, when comparing a 96-page long-grain press and a 56-page short-grain press, the 96-page press has 40% more page capacity on the cylinder. However, given the C56 SG’s higher cylinder speed, the hourly output of a 96-page press is only just 10% higher. The format size therefore does not determine the productivity of a commercial web press, a fact which is often forgotten.
No quarterfold necessary
A further advantage of short grain production can be seen in the folder. When printing A4 (8.27 x 11.7in) or similar sized products long-grain presses must have a quarterfold, but this is not the case in short grain. For physical reasons the quarterfold is, vendor-independent, the bottleneck. Before the product reaches the folder delivery, the printed section is first folded lengthways (former fold), is then cross folded (first cross fold) and is finally folded lengthways for a second time, the so called quarterfold. Every time the substrate is mechanically tampered with it is put under more physical strain, which when printing products with a high page count can limit the maximum possible running speed.
This differs to short grain: the web is slit and the ribbons are processed individually. Only the first length fold and the first cross fold are needed to produce products similar to long-grain products. The way in which the web is processed is similar to publication gravure printing. Many years ago KBA’s TRB presses reached a web speed of 17m/s and more. We have transferred the know-how we gathered back then to today’s commercial press superstructures and folders with success.
Enormous product range and fewer finishing tasks
The unique ergonomic-handling and accessibility of KBA superstructures is valued by printers the world over. Anyone who has ever moved ribbons or removed old webs from a press knows how valuable a generous amount of space is. This has traditionally been taken into account in KBA web presses and allows press operators to carry out their work comfortably and without any large obstacles. This is especially supported by the cantilevered turner bars. The C48 SG’s superstructure configuration allows for production with up to six ribbons. Up to eight ribbons can be processed by a former in the C56 SG. Optional extras, such as a skip slitter, a ribbon and section stitcher, can lead to a raft of new product options.
In this way sewn A4 products (8.27 x 11.7in) can be processed in folded A3 envelopes (11.7 x 16.54in) inline at top speed, which is suitable for large supermarkets and mail-order companies whose typical advertising products contain stitched inserts. This renders the time-consuming inserting of supplements into the ‘main product’ in a separate step superfluous. Inserting lines in finishing as well as the costly pre-production and the temporary storage of half-finished products before finishing are no longer necessary when producing in this way.
Having a raft of production options only makes sense if the print quality is good. Over 15 years ago KBA developed and launched metal blanket technology which supports a more precise circumferential register than sleeve technology. In contrast to sleeves, metal blankets cannot form so called ‘waves’, as the end of the metal blanket fits exactly into the rubber blanket channel.
Automation also with large print runs
Today it is hard to imagine printing small- to medium-run jobs without automatic plate changers. When printing large print jobs of more than 250,000 copies the shorter makeready times are economically less important, but a higher level of process stability is essential.
This also reduces the possibility of damaging the printing plates when mounting them manually, for example. It should not be forgotten that the plates for the C48 SG are 890 x 2,060mm (35 x 81in) and 890 x 2,280mm (35 x 90in) for the C56 SG, are larger than a normal house door. Therefore KBA offers a plate transport system from the plate processor to the upper or lower printing units.
All KBA commercial web presses have an automated start-up phase and optimised control technology to cut waste and to allow the printer to have a standardised press start-up and stop. KBA’s 16pp commercial web offset presses set new benchmarks with only a seven minute job change including paper and/or adjusting the web width (without changes to the ribbon lead). This can be done simply by pressing a button or automatically at the end of the run planned. The so called EasyPaperChange is made possible by the full integration of the KBA reelstands in the console and control technology and therefore ensures that the system is completely integrated. Something which not all of our competitors offer.
So far the C56 SG at Em. de Jong in Baarle-Nassau is the only 56-page short-grain press with a web width of 2,280mm (89.76in) in action worldwide. Interest in high-volume short-grain presses is great and we are confident that soon further printing houses will invest in this economically attractive technology from KBA.