THE CHALLENGE

Germany-based printing company Ellerhold Aktiengesellschaft wanted to enhance the printing quality of its large-format posters from its MLM_2600_NG digital printing machine, developed and built by its manufacturing subsidiary, Ellerhold Maschinenfabrik GmbH. Specifically, the printheads showed variation in printed density both between the heads and across each head, which produced clearly visible bands within some types of printed output.

Global Graphics Software’s Technical Services team worked with Ellerhold’s process engineer, Patrick Prezewowsky, to enhance the quality of the printed output using its award-winning technology, ScreenPro. A very fast and efficient multi-level screening engine that mitigates artifacts such as streaking and mottling from the inkjet print process, ScreenPro can be used in any print workflow, including Adobe®, Caldera, Esko, EFI and Sofha, with any combination of inks, substrates, printheads and electronics.

The team used ScreenPro’s PrintFlat technology to smooth out the banding present on Ellerhold’s large-format posters. PrintFlat corrects for density non-uniformity, which results in banding commonly caused by variation within a printhead or between printheads and is very time consuming to correct in hardware.

In ScreenPro every nozzle can be addressed separately on any head/electronics to achieve very fine granularity. PrintFlat adjusts the density within ScreenPro to produce uniform density across a print bar. The process can be automated for closed-loop correction and, unlike correction by adjustment of voltages, there is no effect on jetting stability or head lifetime, nor ink pressure and timing/drop speed variation.

The Technical Services team carried out tests, analysed the scanned prints and created a PrintFlat calibration workflow for the MLM_2600_NG designed to compensate for the non-uniformity in output across the print bar (poster width).

The team also used a variant of Global Graphics Software’s Advanced Inkjet Screens™ (AIS), available with ScreenPro and the Harlequin RIP®, which they adapted specially for scanning-head systems. These proved very effective.

Before

With PrintFlat

THE RESULT

Now Ellerhold’s process engineer uses Global Graphics Software’s online inkjet press calibration service, printflat.com, to upload the scans and automatically receive the correct calibrations so he can go ahead and print. The PrintFlat.com service is available to registered users who upload their PrintFlat scans and receive the calibrations they need to run their inkjet press at optimum quality.