KBA TR12B for web width of 14ft: Exploring a New Dimension
Press release from the issuing company
October 20, 2003 -- When our design team in Frankenthal set out to increase the maximum web width in rotogravure to 4.32m (14’) with the creation of the TR12B, they found it was a challenge that demanded all their skill and ingenuity.
The new press is a good bit wider than our previous maximum of 3.68m (12’1”) and represents a first in the global gravure marketplace. That being so, by the time the first press comes on stream at maul-belser Medienverbund in Nuremberg late next summer, each individual subassembly will have been completely redesigned. Several thousand engineering hours and countless computer simulations will have been invested in plotting a successful course in these uncharted waters.
It is pretty obvious that a reel measuring 4.32m wide, 1.27m (50”) in diameter and weighing 8 tonnes cannot be transported manually. The reels for the new press will be conveyed to the reelstands and loaded automatically by an in-floor conveyor system which will also dispose of the used reels automatically.
New reelstand geometry
The entire geometry of the reelstand has had to be redesigned to enable it to handle the broader web and correspondingly heavier reel. Here, the most important factors we had to consider, apart from the extra weight, were the forces acting on the web during acceleration, the critical running speed and safety aspects such as how to bring the web to a stop safely and in a minimum of time in the event of an emergency. When investigating the critical speed we worked closely with all the major suppliers of reel cores because we wanted, if possible, to keep to the standard core diameter of 150mm (59”).
On the new press we decided to position a preconditioning unit before the first printing unit. This prepares the web for printing by extracting moisture to create the optimum ambient humidity. The preconditioning unit is basically a glorified dryer with a bank of circular nozzles that blow a jet of warm air directly onto the web from above.
New advances in printing unit technology
But the brunt of our development work centred on the printing units because they are what determine print quality, and print quality is the be-all and end-all in rotogravure. We made all the idler rollers larger and changed the constituent material to carbon fibre so as to ensure a smoother acceleration and a uniform web tension. The use of carbon fibre idler rollers proved to be essential, particularly during non-stationary production sequences such as press run-up or reel changes. Dryer specifications, too, had to be made more rigorous. The blast of air from the nozzles must not be too strong because this could crease the web or cause it to drift out of position. On the other hand it must be strong enough to ensure that the ink dries on the web before it leaves the dryer. There are also limitations on the amount of heat that can be applied: if the temperature is set too high the web may shrink.
Another area of intensive research was the printing process itself and, more specifically, the interaction between the forme cylinder and ink application, the doctor blade and the impression roller. Every aspect of the printing sequence was clinically dissected and a series of CAD simulations made based on diverse calculations before we took the plunge and simulated test runs with 4.32m webs on existing rotogravure press lines. These experiments eventually gave rise to a new inking system and a new impression roller for the TR12B.
Optimised turner bars
The superstructure for the new super-wide press was re-engineered to enable it to handle 18 ribbons. The turner bars had to be reconfigured to allow all 18 ribbons to be diverted to one side of the double-width folder or the other, or combined in any sequence. On top of this we also had to ensure that ribbon tension remained uniform throughout, so that none of them could sag. The key to achieving this was to limit the extent to which the ribbon paths can be adjusted. This must be factored in at the imposition stage. Although the turner bar superstructure was constructed from existing components, it also had to undergo extensive modification. Here we concentrated on the main draw unit and ribbon guides. The draw rollers before and after the slitter must generate a uniform, slip-free pull. For the roller drive we used proven dedicated drives with Drivetronic controls. Determining the optimum size of the slitter turned out to be a much more challenging task. Our starting point here was the fact that the pairs of slitter knives must be positioned with absolute accuracy and the cross-bars for the guide rails must be extremely rigid. We used the finite element method to examine the rigidity and vibration-deadening reinforcement of the guide carriages, so as to prolong the service life of the slitter blades and ensure a clean cut.
All the rotogravure presses we have delivered to date with a web width of 3.5m (11’6”) or more are equipped with double folders to support the large number of ribbons involved. This enables them to run at a maximum rated speed of 60,000cyl.rph, with four pages around. The TR12B will also feature a double folder, and the type we have chosen is our proven 7:7 version with dedicated drives. Here the main emphasis of our activities was on the ribbon infeed into the cut-off cylinder assembly to safeguard a neat and accurate strike on all 18 ribbons.
Cutting-edge control technology
The console conceals cutting-edge technology for operating and controlling the entire press line. The preset system promotes a rapid press run-up to production speed following job changes, and cuts start-up waste to a minimum. The first-up error-reporting system, which flags the initial trigger message, makes it much easier for press and service personnel to track down the cause of malfunctions. This helps to minimise the down time that must be devoted to remedial action. All error messages are stored in an archive and can be traced back several days if necessary, making it easier to analyse malfunctions. On top of this the press is fitted with a modem to support the remote analysis of press status and error messages via telephone. This greatly reduces the risk of prolonged down times caused by difficulties in detecting errors in software or electronic modules.
The technical properties and production capabilities of the new TR12B were not the only aspects we put under the microscope in the course of our R&D activities: we also set about improving handling and serviceability, as a result of which maintenance personnel can now carry out service tasks faster and more easily. Many of the features we have developed for the new press will be incorporated in our other rotogravure presses for narrower webs.
WhatTheyThink is the global printing industry's leading independent media organization with both print and digital offerings, including WhatTheyThink.com, PrintingNews.com and WhatTheyThink magazine versioned with a Printing News and Wide-Format & Signage edition. Our mission is to provide cogent news and analysis about trends, technologies, operations, and events in all the markets that comprise today’s printing and sign industries including commercial, in-plant, mailing, finishing, sign, display, textile, industrial, finishing, labels, packaging, marketing technology, software and workflow.