Machine Vision & Web Inspection From mirrors to cameras standards on all their suppliers.
2. The raw materials used in the packaging industry such as plastics or coated cardboard are signifi cantly more expensive than the paper used in publication printing. This means that packaging printers are more acutely sensitive to wastage rates.
3. Designs are often intricate and usually small. Packaging also frequently carries product information printed in small point sizes and bar codes. Manual inspection is clearly unsuited (more- or-less useless in the case of bar codes) to such material.
I
nspection systems have been used in the printing and converting industry for decades now. We see new generations come and go. As early as 1940s we saw the rotating mirrors optimised on roll-to-roll presses. That was soon followed using high frequency strobes, followed by the passive sampling-based viewing systems, then the active sampling-based viewing systems and fi nally within the past decade the full web width, 100 per cent inspection solutions.
If we look at the milestones to-date, the progress can be seen. • Rotating mirror viewers used from the 1930’s through to the 1990’s.
• Stroboscopic viewers used from the 1970’s through today.
• Camera based video viewers, introduced in the 1980’s.
• Aff ordable Camera based sampling systems in the 1990’s
• Line Scan camera based 100 per cent print inspection in colour introduced in the 2000’s
• Cloud based networks using commercial scanners So why do printers require camera-based print inspection and what is the return on investment? The print inspection industry has constantly targeted a single segment of the printing market - the packaging segment. Packaging is the ideal entry point because of three distinct characteristics. 1. Client quality standards are extremely high. The vast bulk of printed packaging is used in the FMCG industries, where consumers associate (indeed often confuse) packaging quality with product quality. The industry is also mainly in the hands of large, commercially aware companies, which can impose stringent quality
Printing is a material-intensive and relatively low-margin industry. Printers are under continuous and increasing pressure to increase productivity and improve output quality while at the same time reducing production costs. Even a small reduction in waste levels can have a signifi cant impact on the printer’s profi tability.
ADVANTAGES OF CAMERA-BASED INSPECTION IN PRINTING
The printing process is subject to a multitude of faults. The most common faults are: • Mis-registration, where one colour impression is misaligned against others
• Colour variations, where ink quality or operational conditions such as temperature or humidity changes the colours from those desired
• Defects, where physical incidents in the printing process such as ink shortage or excess at critical points, lead typically to streaks or blank patches. Intrusive dust particles are a common cause of defects.
Prior to camera based print inspection, printers had only very weak tools available to inspect print jobs while they were in process. Strobe, rotating mirrors and operator ‘eye’s’ can all provide some
inspection benefi t. Ultimately, however, they all depend on operator attention, slower machine speed and operator competence.
Operator attention is inconsistent even under ideal conditions. It is essentially reactive, declining once the print job has started and only rising once output quality has fallen below acceptable level and requires rectifi cation. Attention starts to decline again once the fault has been rectifi ed. Human inspection is subject to a range of further disadvantages: • Inconsistent attention span. A problem compounded by the print industry’s traditional bias towards male workers
• Subjectivity of judgment as to what is acceptable • Workplace distractions • Insuffi cient sensitivity for process control • Varying skill level from operator to operator • Imprecision. The human eye is inevitably relatively insensitive in gauging variations Viewed in terms of the impact on printers’
profi tability the case is also compelling. Most printers spend about half of revenue on material. Wastage rates of 8-20 per cent thus translate to 4-10 per cent of revenue. With operating margins running at no more than 10 per cent and down to 5 per cent often enough, it can thus be seen, as wastage can absorb the equivalent of the printer’s entire profi t on a job.
MAKING MORE MONEY WITH YOUR WEB PRESS
In a recent survey of existing TruColor print inspection system users the results proved that the introduction of a TruColor high resolution Digital print inspection system contributed directly to an increase in profi ts by reducing waste, reducing setup/make-ready or change over time, increasing press speeds, increasing print quality and increasing overall pressroom productivity.
26
September 2025
www.convertermag.com
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