Contact person
Hans Christiansson
Application engineer
Contact Hans
Missing dots measurement
The problem of missing dots occurs especially in gravure printing.
Quantifying the amount of missing dots using the right tools allows you to monitor the problem to see if the if the print quality is acceptable.
Purpose
The print quality demands on gravure printed samples are often very high and missing dots will lower the print quality. The measured amount of missing dots correlates well to visual impression of the areas.
Besides to get a quantification of the amount of missing dots on the samples, it’s also possible to buy the software STFI-Mottling Expert and the missing dots toolbox from us to make the measurements in your own lab. The STFI-Mottling Expert method is described on the web page.
It is also possible to predict the missing dots by studying the unprinted surface of paper or paperboard. This helps you to understand how the product surface should be improved to get a better print quality. For this, we use the OptiTopo method.
Method
A flatbed scanner is used to collect the images in high resolution (1200 dpi) and the data is calibrated to reflectance using a calibration set. Image analysis including a distance transform is used to find the missing dots. The printed areas should be at least 15 x 15 mm.
Normally, several areas are evaluated for better accuracy.
Deliveries
Measurements of the amount of missing dots saved to an Excel file
