After implementing Certified Engraving, 4Packaging has become the world’s first company to be HD-certified by Hell. This certification recognizes the outstanding results 4Packaging continuously achieves in the four categories of edge sharpness, detail reproduction, reproducibility and quality assurance.
Moving forward, cylinder engravers that achieve outstanding results in printing form production will be HD-certified by Hell Gravure Systems. This certification is based on the four categories – edge sharpness, detail reproductions, reproducibility and quality assurance. A total of seven HelioKlischograph K500 systems and three Cellaxy laser engravers are used at 4Packaging. All of these are equipped with the latest HD software features.
By awarding the HD certification to 4Packaging, Hell is rewarding the company’s expert handling of HD technology and stringent quality standards. In an article in Flexo+Tief-Druck 5-2021, Jan Breiholdt of Hell has explained the processes that are looked at in the Hell HD certification and how 4Packaging has implemented them over more than a dozen years. We excerpt Breiholdt’s comments below.
Edge sharpness using MultiTune
Traditional engraving produces a sawtooth effect. This is because screen ruling and write resolution cannot be set independently of each other. When using the usual screen rulings of 60 or 70 l/cm, gradations are visible to the naked eye – even at a normal viewing distance. Higher screen rulings such as 100 l/cm can be used, but this results in lower printing density and longer engraving times.
4Packaging uses MultiTune on all its electromechanical engraving systems for improved edge sharpness. MultiTune is an adjustment process that produces sharper contours and reduces dragging and ringing. It is particularly effective for horizontal contours and has no impact at all on the machine’s engraving speed or productivity.
Narrow engraving tolerances result in high color fidelity during proof printing and production, and also enable rapid color adjustment in the press. It is therefore vital in electromechanical engraving to calibrate the system before each engraving. This measure – called the ‘testcut’ – ensures the current condition of the engraving copper and engraving system has no impact on the engraving result. Using the SprintEasy measuring station, the current condition of the engraving stylus is also taken into account during the testcut.
4Packaging utilizes SprintEasy as a vital quality tool for cylinder engraving and uses the CellEye calibration procedure on the HelioKlischograph systems. CellEye combines measurement using an autofocus camera with an algorithm that automatically aligns the target engraving values and the actual engraving values. The procedure is based on a volume-oriented, three-dimensional measurement that compensates for geometrical distortions and the stylus wear of the engraving diamond.
The gold standard of high-resolution cylinder engraving is direct laser engraving. 4Packaging has been manufacturing laser-engraved gravure cylinders for 13 years and currently has three Cellaxy direct lasers. These are used for embossing and high-resolution linework and half-tone reproductions. A large share of the orders are for cigarette packaging, but other forms of high-quality packaging are also becoming increasingly popular. Recently, 4Packaging successfully matched the printing characteristics of conventionally engraved cylinders and laser-engraved cylinders. In this way, it standardized its laser engraving process. Now printers can run either individual cylinders from the color set or a complete color set with laser-engraved cylinders without any additional fingerprinting. Another advantage for printers, according to 4Packaging, is the significant ink saving that the laser-engraved cylinder offers compared to conventional engraving. The fully automated line installed at 4Packaging for the premium preparation of laser-engraved cylinders is unique and creates the basis for perfect reproducibility.
Fine lines and text are always a challenge in gravure printing. This is not just because of the above-mentioned problem with edge sharpness. Another issue in gravure printing is that fine elements are normally reproduced more thinly than in the original. This applies equally to positive and negative elements. Repro data normally has to be corrected manually in line with specific engraving requirements to correct this effect. Manual correction takes a lot of time and it is very easy to make mistakes. In addition, ma- king very fine text thicker can cause open elements to close up or individual letters to run into each other. In both cases, this can make text much more difficult to read.
High Quality Hinting Pro (HQH Pro) provides 4Packaging with a process that automatically optimizes engraving data. This process has no impact at all on the engraving machine’s speed or productivity.
The aim of quality assurance is to deliver consistently high quality to customers. This involves identifying tolerances that cannot be allowed in cylinder production as early as possible in order to prevent costly remakes. Certified Engraving processes measure and record critical cylinder production parameters directly on the output device. This means tolerances in cylinder production and cylinder engraving that cannot be allowed are spotted quickly. For example, Certified Engraving measures cylinder engraving at pre-defined locations and visualizes larger engraved areas with the help of a stitching function. This detects slipping on the cylinder and any height difference between the engraving styluses in multi-channel operation. All measured values and camera images are documented in a customer-specific engraving certificate. All in all, Certified Engraving makes the entire cylinder manufacturing process more-reliable and also reduces the need for proof printing. The software is installed on all 4Packaging engraving systems. The quality data obtained is stored centrally at first and is then incorporated into the cylinder certificate at 4Packaging’s in-house quality station.