In the afternoon the group visited the Nagoya printing plant of the world’s largest-circulation newspaper, the Yomiuri Shimbun. The president, Mr. Katemasu, welcomed us and introduced his company, which prints mainly various Yomiuri titles including a sports paper and a number of tabloid subcontract papers as well.
Mr. Uchiu from Mitsubishi Heavy Industries introduced the image-based closed-loop on-press colour density control system, called CQC = Colour Quality Control, based on the Mitsubishi Diamond Eye technology. Mr. Wakamatsu from Yomiuri presented this system in detail.
Yomiuri prints at 29 plants on 95 presses and at several contract printers around Japan and abroad. The audited circulation of the main product is 10,020,688 in the morning and 3,690,346 in the evening. The Nagoya plant started operation in 2008 and uses Mitsubishi presses, all equipped with CQC. The Yomiuri newsprint demand per year is four times the demand of the entire Danish newspaper industry.
Ensuring a uniform high print quality throughout all markets was the driving factor for Yomiuri to require an automatic colour control system that would be used at all printing plants and that would be based on the same target colour data everywhere. Over the past ten years Yomiuri installed CTP systems in all of their plants and started to send the same page data to all of them. Nevertheless a certain colour difference in printing still existed, mainly due to different dot gain characteristics. The dot gain fluctuation could be up to 5% between presses.
An in-house quality evaluation system was introduced as well as the Yomiuri Colour Academy for training colour operation staff. A standard colour evaluation page (including a colour management characterisation IT8 chart) was specified and is used on a regular basis to check presses.
The concept of the CQC system included:
- No colour bars, image-based colour control instead (colour control elements would not be accepted in the Japanese market)
- Making use of the colour average colour data of the ink zones
- Control show-through
- Woking automatically
- Enabling the monitoring of the entire system
The system developed in co-operation with the press supplier Mitsubishi consists of the CTP data system, the image server, the main controller and the press-based web-wide colour scanner (or sensor). The functionality of the system includes density control, monitoring, dampening control and plate check. The benefits are faster colour adjustment, less requirements for skilled operators, uniform print quality across all plants, lower start-up waste (currently 400 copies at cold and 200 at hot starts), defect detection and the provision of data for system analysis.
