Page 51 - FINAT Yearbook 2019
P. 51

So far, the group has tested the readings of in-line UV sensors correlated with ink coverage, color and ink temperature. Initial tests have shown that the sensors certainly provide a helpful relative measure for specific jobs.
Tests using solvent rubs, FTIR and other methods have been conducted to gauge the level of cure.
Among the group’s initial conclusions are:
• In-line UV print cure testing is critical to ensure consistent print production – especially in the absence of other process controls;
• UV-cured print will post-cure, but this will not compensate for poor initial curing;
• Coatings and dark colours on the last print units are critical;
• Ink curing is affected by film weight and temperature. There is inhibition of curing at low temperatures – for example
where chill rollers are used;
• Oxygen inhibition is an issue at low film weights; insufficient
through-curing is an issue at high ink film weights;
• Commercially available UV dose strips and in-line UV
irradiance monitors are effective in-line process controls
but need to be calibrated;
• Calibration of worst-case scenarios can be used as a
control method.
As a follow-up, samples from controlled press runs have already been submitted for migration testing to establish a possible correlation between the results, and further practical experimentation and development of best practice guidance are underway.
Final conclusions will be presented at the FINAT Technical Seminar in Barcelona, 4-6 March 2020.
ReTaesltinPgraitnBotbsJt ob UV Curing Technologies...
Testing at Sun Chemical
• 17-18 April 2019
• Bobst M6
– Flexographic 10 colour 670mm web fed
• Attendees: Bobst, Sun Chemical, Flint, GEW, IST, Etivoet
          UV Curing Technologies... Real Print Job
GEW (EC) Limited
                UV solutions for demanding printing applications
UV Curing Technologies...
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