Offset Printing
Melter Druck: Instrument Flight with grey balance key to success
Wednesday 27. February 2013 - KBA QualiTronic combined with System Brunner Instrument Flight
Since 2006 a System Brunner Instrument Flight inline colour measure-ment and closed-loop control has been in action at Melter Druck in Mühlacker near Pforzheim Germany- in web offset printing. The colour security and reliability this solution has ensured each day led to the company deciding to work with Instrument Flight in sheetfed offset print-ing. This system is an extension of a KBA QualiTronic Color Control sys-tem in a KBA Rapida 106.
The Melter group has about 300 employees on its payroll. The company, founded in 1912, specialises in the complete production of direct mailings plus customisable text and image advertising print products with various finishing options. The realisation of drafts and data predominantly from advertising agencies takes place in web offset, sheetfed offset and digital print, as well as many possibilities for inline and offline finishing, post-press and inserting in envelopes. Once again Melter was awarded with the seal of approval from the German Dialogue Marketing Association for the areas of data processing, lettershop and fulfilment. Melter Druck is proof that money can be made by investing in energy-saving kit, such as heatset printing with a thermal air-purification system from KBA MetalPrint. In addition the company has an photovoltaic system with a collector area of over 1,000m² which is equally environmentally friendly.
Since 2006 colour control with grey balance priority
Both Heidelberg-Harris M-600 presses, installed in 1996 and 2001, were equipped with a Color Control System (CCS) from QuadTech combined with the System Brunner Instrument Flight software at the end of 2006. Since then the printing process on the 16-page presses featuring In-strument Flight have been controlled by grey balance priority. Technical manager Klaus-Dieter Marquart says: “We haven’t received any com-plaints regarding the M-600’s colour printing since then.” System Brun-ner, located in Locarno, Switzerland, launched Instrument Flight in 1991 as an online solution for sheetfed offset presses. After two years of de-veloping with QuadTech, in 2000 Instrument Flight was made available for web offset.
What does “grey balance priority” mean?
Both touchscreen monitors are active. Right is the Instrument Flight Bal-ance Navigator with its hexagonal colour space diagrams and left the position of the colour rule including a reminder to wash the blankets (4)Colour balance defines the relationships of the process colours with each other in all tonal areas, whereas grey balance defines the colour balance in the grey-scale area. Instrument Flight ensures a transfer from solid ink density regulation to a more precise “grey balance priority”. “Uniform solid priority” evaluates the four individual 100 per cent tone densities CMYK, but disregards important information regarding tonal values as part of the process standards.
In contrast, “grey balance priority” controls individual solid ink densities by taking into account more than 30 image-crucial parameters which are measured in the colour control strip including tonal values in CYMK and the three-colour grey balance fields in mid tone and full tone. This is more effective as 90 per cent of all colour differences arise through tonal fluctuations in the dots when overprinting transparent inks.
System Brunner’s expertise extends beyond numerous parameters. Its evaluation and ranking are crucial. Even the priorities are rated. At Melter the optimum “grey balance priority” does not mean 100 per cent grey balance control in heatset printing, but 60 per cent grey balance com-pared to 40 per cent single colour dot gain influence. In sheetfed offset, however, “grey balance priority” is rated differently.
Rapida 106 with sensible automation modules
In November 2011 a five-colour KBA Rapida 106 with coater replaced a competitor’s press. The VariDry high-performance dryer in the extended delivery can be equipped with UV radiators on occasions when using UV inks. A DriveTronic Feeder with maximum preset capabilities and a DriveTronic SIS sidelay-free sheet infeed support substrate flexibility. Given the high circulation of mailings, Melter Druck opted for an auto-matic plate changer, instead of the DriveTronic SPC simultaneous plate changer with individual drives.
Quality assurance is of utmost importance to the PSO-accredited print shop, which made Klaus-Dieter Marquart opt for KBA QualiTronic Color Control with Instrument Flight software by System Brunner. “Following our positive experience with web offset, there was no doubt that we wanted to have Instrument Flight in our Rapida”, says Marquart. “Instru-ment Flight can handle the range of substrates we use and their print properties. The substrates’ sensitive dot gain only stabilises one grey balance control, which optimally reacts to the changes in the use of fount solution and inks, so that even a trained eye hardly notices the deviations in the process.”
System Brunner recently created a “substrate library”, in which the print-ers can store the substrate – ink combinations as self-defined calibration data. If the substrate is used in a follow-up order again, the corresponding calibration data can be retrieved and the inline colour-measurement camera immediately obtains the extensively calibrated measurement readings.
Identical philosophy -differently implemented
Instrument Flight’s philosophy of inline colour measurement and control is the same in sheetfed offset as in web offset, however the Rapida’s technology demands a different solution. The most obvious difference is in the type of measuring system: in web offset the inline densitometer or spectrophotometer obtains complete colorimetric data, whereas in sheetfed offset QualiTronic Color Control’s colour-measuring camera has to be externally spectrophotometrically calibrated in order to achieve maximum measuring and control quality. The Rapida’s colour-measuring camera demands somewhat larger measuring patches for the colour control strips compared to heatset.
A further difference is that in web offset measuring takes place after the flotation dryer, but in sheetfed offset it takes place before the end dryer on a wet copy. Therefore the so-called drying drift in the density and CIELAB values must be taken into account by Instrument Flight in the Rapida.
Seeing as powder in used in sheetfed printing, in straight-on presses the powder from the front page can build up when perfecting. The press appears to then print somewhat “sharper” which is why both the printer and the colour control system would be inclined to increase the density more than is necessary. To combat this System Brunner has therefore developed an additional algorithm which prevents over inking and never-theless keeps the overall result in balance.
Printers who, like Klaus-Dieter Marquart, are aware of and value these important details will share his opinion that “With the optional extra In-strument Flight for the Rapida, KBA offers superior technology.”