15 June 2020 Digital Printing Technologies

Screen adds drying to improve inkjet performance

Screen is upgrading its inkjet web presses for commercial print with more powerful dryers to meet demanding applications and boosting the speed of its inkjet label press.

Screen is adding two new models to the TruepressJet 520HD reelfed inkjet press portfolio.

Screen now has four models in the range, from a high speed mono only press for books to high quality printing capable of matching litho quality and the output per hour of a B2 sheetfed press. All are using the advanced SC inks which were introduced at Drupa in 2018 and can print on standard offset papers without pretreatment or coating. This technology has ended the problem of adherence of the water based ink on coated papers. Now the innovations are to be found in drying. This is a key difference between the machines in the range.

The TPJ 520HD mono is a black only press which requires no thermal drying system. Instead it uses a compact Near Infra Red unit which uses radiated energy to drive off water in the ink and which has no impact on the temperature of the paper. It is a highly energy efficient approach and a space saving solution. There is also no lengthy heat up period before the press can be used in the morning or after a break.

The press addresses the need to print on litho papers, say GPrint or Arctic Silk, that have been difficult to print digitally. Now a publisher can run the same paper during the initial order phase of a new title printing digitally, though the bulk offset phase and again on the same paper when running a print on demand model.

The flagship press is now the TPJ520HD-AD (Advanced Dryer) model which uses a new drying unit, using a combination of small heated rollers surrounding a larger heat drum along a paper path that winds between the different rollers. This delivers more drying power than is currently possible with NIR and so means that the press can run at 150m/min and with higher ink coverage than the standard TPJ520HD.

This model is limited to 50m/min using a combination of a heated drum and hot air drying. The TPJ520HD+ includes a NIR drying unit and supports speed to 100m/min at 1200x600dpi on coated papers. This was introduced at Hunkeler Innovation Days in 2019.

The TPJ520HD-AD takes throughput to 150m/min on coated papers with an imaging resolution of 600x600dpi. All three models will operate at this speed on inkjet approved papers.

As well as the SC ink, which has a gamut that is almost a perfect match for offset litho inks, Screen’s long prepress experience is called on for colour management and the scanning inspection systems that feedback into dynamic nozzle alignment, pinpoint registration and ease of operation.

The press uses piezo printheads with four levels of grayscale which are under the control for ink optimisation that calculates the minimal amount of ink used in each colour. For spot colours, the choice is made about the closest match from samples printed on a chart. The values for that colour and substrate are locked in and can be recalled instantly when printing the same spot colour in future. Since the TP520 was introduced in 2006, some 1,500 print engines have been installed, either as Screen presses or badged by an OEM.

Drupa was planned as the launch for a second significant upgrade for Screen. This are new versions of the L350UV label press, with the SAI model printing with low migration inks and the Z model printing at 80m/min maximum. As with the commercial presses, the label machines cover the requirements of any printer from the E level offering a 50m/min throughput when running CMYK and slowing to 30m/minute running with white; the S model as the standard machine in four or six colours (Screen has added a gamut extending blue to the ink choice) running at 60m/min and 50m/min when printing white.

The company has notched 170 installations of the label press and is now pushing further into packaging, with announcements of a press for flexible packaging print using water based inks, a press for single pass corrugated production and an offer for carton printers.

The PacJet FL830 is expected to be available from March next year. It will print on an 830mm wide web at 75m/minute with food safe CMYK and white inks. The initial availability will be printing on PET and OPP media with runs at 4,000 metres or less. Further substrates will be added.

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The Screen L350UV label press has more than 170 installations, and is being offered in high speed Z versions and with low migration inks for food packaging.

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