Detecting Faulty Hairlines in Packaging Gravure - FAQ


What are Faulty Hairlines in image data files?
Faulty hairline is a very thin line (usually 1 pixel wide) which may rarely appear in Tiff files used for engraving.
An example of Faulty Hairline (please note the high-zoom level which is needed to view the line)
What is the source of Faulty Hairlines?
As far as we know, the main source might be rendering errors during the generation of the Tiff files for engraving. We suspect that faulty hardware (like PC memory, or some hard disk errors) may also cause this problem.
How often do such lines appear?
At this stage, we do not know exactly how rare this phenomenon is (yet). We assume that an engraving house may face this problem few times a year (maybe once per few hundred cylinders).
Strangely enough, when going over the existing samples we have at PSik, we have found at least one sample where the problem exists. Yet, it seems nobody was aware of it.
Does it only happen in gravure?
There are some hints that this phenomenon might sometimes appear in flexo files as well, due to the same reasons.

Dealing with Faulty Hairlines

Why is it so difficult to identify Faulty Hairlines before engraving?
It is very hard to distinguish this line in the data, as you need to zoom in to the pixel level and go all over the file. In many cases, it is more often identified on the cylinder after engraving and also as part of the press proof process.
The faulty hairline might not be a complete line but a partial one. It could also be positive or negative or consisting of various gray level values. It may be found only in a specific separation(s) and maybe less “jumping to the eye” due to the oversampling used in gravure.

The Faulty Hairlines Detection Process

What is PSik’s Faulty Hairlines Detection process?
The process is going over the Tiff files and tries to identify hairlines which are suspicious to be faulty. When found, an alert is given and a box is drawn around the hairline.
What are the key benefits of this process?
Several ones:
  • Faulty hairlines are detected at the earliest stage possible in the workflow. It also means that further operations that could go wrong, like engraving, chroming and press proof, will not take place.
  • The detection is done by a computer algorithm and not by human vision. Hence, operator time is saved there is no relying on human skills.

In which products is this process integrated into?
At this stage, the process is planned to be part of DeltaProof 3.0 and DeltaViewer 3.0.