Automatic closed-loop inking using Diamond Eye

The benefits of closed-loop inking system are simple: consistency of print across the run; elimination of operator variability meaning lesser dependence on skilled labour; uniformity across different presses; reduction of start-up waste. All this together in a way will contribute towards industrialised production.

The digital boom has imposed a severe competition  for print media. Balaji says, "The newspaper industry is trending towards stricter conformance to standards, and achieving greater consistency in quality by using materials and tehnical enhancements." Closed-loop inking system is one of such enhancement which Kasturi & Sons are implementing to improve their productivity.

The company uses Mitsubishi Diamond Spirit presses at their facility. The Diamond Eye is a trademark system of Mitsubishi used for controlling the ink supply on the press. According to Balaji, there are three facets to this system. Firstly, fingerprint of the press needs to be established which will remain as a reference standard followed by feeding the pre-press data of the job to be printed to the system. The Diamond Eye system is equipped with  four LED sensors: red, green, blue and infrared.

The sensors which spans the full width of the web measures column-wise densities being printed on the web. "The system then compares these values with the pre-press data and sends a feedback to the inking system depending up on the difference in what is being printed and what needs to be printed," adds Balaji. Based on this feedback, the difference is bridged by automatic adjustment of ink keys.

In the entire process, fingerprinting is the most significant part which includes creating look up tables for each substrates being used. This can be done by printing standard test chart to find out the gamut of the press. Particularly for newsprint, shade, ink absorption, surface uniformity and surface strength are the properties which determine the press fingerprint. These look up tables help the system to decide in adjusting the ink keys.

The system also provides an option for the operator to adjust the ink keys manually and then the system adjusts  accordingly.

"With the help of Diamond Eye, the company was able to achieve the Delta E values below 3.0 throughout the print run of up to 1,60,000 copies," concludes Balaji.  


Technical expert Kiran Prayagi reviews twelve print firms in India that have set the in-house standards, The Hindu being one of them.

Stay tuned for the annual issue of PrintWeek India ( 29 December 2012) for more details.