Investigation of process colours variations of electrophotography colour production presses

In this investigation is approached method for assessing and evaluation of colour repeatability and variation for digital electrophotography printing presses. Two of most popular midlevel electrophotography colour production presses were chosen. These presses are widely used in printing houses for the printing of book covers, posters, etc. in small circulations. The similar perception of quality of digital production to the offset printing quality (ISO 12647-2:2013 ) is required from most of the clients of printing houses, publishers, etc. One of the problems of midlevel electrophotography colour production presses are variations of colours in the printing run and variations of colours during the time – weeks, months, years. The variation degree depends on many factors like – the precision of internal calibration method and types of sensors during the printing run, quality of used materials, calibration precision made by press operator, temperature and humidity variation, etc. (Kachin, Spiridonov, 2000) Specially designed for experiment test forms have been printed on two of most widely used materials for book covers, business cards, etc. – 300 g/m2 matt-coated board and 300 g/m2 offset uncoated board. The evaluation method is based on colorimetrical and densitometrical measurements (Kachin, Spiridonov, 2004) of 100 continuous printed sheets. The experiment was repeated in different time periods -between 6 hours and 4 months, to collect data for colour variation between reprinting the same test images in the time.