Packaging printers are turning in increasing numbers to UV sheetfed, manufacturers’ alliance PrintCity outlines the options and the costs involved
Continuing high growth for UV printed products is driven by demand in different markets for the attributes that the process can deliver. Sheetfed UV is a premium process with many advantages compared to conventional sheetfed wet offset.Entry into UV is primarily a strategic decision because the process permits access to new market segments and buyer groups, with packaging pre-eminent among these, who are usually prepared to pay more for the premium effect of UV.
The role of Value Added Printing is to increase product differentiation, by enhancing the graphic design with the substrate selection, the choice of inks, special effect or metallic pigments, foiling, coatings, and finishing. Sheetfed UV provides the widest range of value added printing techniques on the widest range of substrates including foils and plastics.
UV’s production process advantages include minimised printed waste – no smearing or set-off; short turnaround time with almost immediate back-up and finishing from instant ink curing; no spray powder; and reduced pile changing. UV inks are considered to be environmentally friendly because they do not generate VOC solvent emissions.
However, the process requires specially equipped presses using specific consumables that have higher costs than oil-based ink systems. Best operating practices ensure high productivity and these have been clearly identified in PrintCity’s best practice guide Optimised Sheetfed UV printing.
Which UV ink system?
Two types of UV ink systems are available. Both can be used in either dedicated or alternating production with conventional oil-based inks. Both require the same health, safety and environmental procedures. However, each has different advantages and disadvantages.
Classic UV: The mature and predictable system that has been in constant use since the 1970s. These inks can be printed with or without coating, and are available for a wide range of applications, including food packaging, non-absorbent substrates and printing on all paper types. Presses are specifically adapted for UV operation using a proven set of consumables to provide optimum and stable performance with low risk of damage over a long life.
Non-classic UV (hybrid): A complex array of other UV ink systems that always need an inline UV flood coating to allow curing. This is ideal for occasional commercial printing to print low to medium area ink coverage but normally unsuited to matt and uncoated papers, non-absorbent substrates, and food packaging. These inks can be used for limited periods with conventional rollers but some ink types may require special Combi rollers and blankets.
UV/IR/hot-air dryers are required after the last print unit and the coater — additional interdeck dryers may be needed depending on ink coverage and speed. It is essential to ensure chemical compatibility of the rollers, blankets and washing agents.
Dedicated or alternating UV?
Dedicated: The press is set up and equipped to exclusively print UV. Optimised consumables eliminate risk of degradation from contamination, there is no cleaning downtime from changeover of ink types, and single process allows optimisation for maximum productivity. The disadvantages are some higher costs for ink and consumables.
Alternating: Mixed production of conventional oil-based ink and any type of UV ink system on the same press. This requires more frequent roller adjustment; thorough cleaning when changing ink types; careful selection of inks, coatings, washes, rollers and blankets that function together. These presses are ideal for unrestricted commercial and packaging printing on all substrates.
However, production time is lost when changing between inks and it is more difficult to fully optimise two processes on the same press.
UV economics?
UV printing is a value added process addressing wider markets that should generate higher sales revenues to compensate for any additional process costs. Selecting the right process depends on the substrates, the products to be printed, and the proportions of UV and conventional printing on the press. The economic impact of each option needs to be calculated as a total operating cost – investment, running costs, energy, consumables over a range of jobs. The PrintCity UV project team made an economic evaluation of different process options to give potential UV users a clearer and realistic comparison of the alternatives.
Key findings:
• The elimination of waiting time between process steps is an economic and competitive advantage. For example, conventional inks often require a neutral coating to allow immediate reverse side printing or finishing. An alternative at the same cost is to use Classic UV inks without coating to allow immediate handling and preserve the paper’s surface qualities. In addition, the total UV energy consumption is about 50 per cent less.
• Total energy consumption of UV printing and coating is almost identical to conventional offset and coating.
• There is a negligible cost difference between Classic UV and for Non-classic UV (hybrid) alternating with conventional inks on the same press.
• Flexible multi-purpose combination presses for alternating UV and conventional ink production are three to four per cent more expensive than a press dedicated to Classic UV.
Economic modeling
Nine process variations of ink and coating types were modelled for seven different press configurations. Optimally equipped presses were defined to ascertain comparative investment costs. Best practice target values were identified for day-to-day operation (including makeready and speed) assuming the optimisation of all parameters.
The annual production mix of the sample jobs is an average of 3 000 sheets per run for 35 per cent of the year, 5 000 sheets for 45 per cent of the year and 15 000 for 20 per cent of the year.
Two production shifts (3 750 hours/year) yield an annual job volume of 1,600- 1,800 jobs, totalling 17-19 million sheets — depending on press and process excluded all activities. Costs include printing plates but not finishing.
Results and comparisons
Conventional oil-based offset is the 100 per cent reference value and the results are presented as a percentage comparison to this.
1: The additional cost of using water-based coating in conventional offset is about 6 per cent. The coating provides surface protection, faster finishing or converting, an improvement in gloss, and allows some special effects.
2: UV offset without coating costs about 6 per cent more than conventional offset printing without coating. In both cases the surface properties of the paper are unchanged. For conventional offset there is a risk of set-off and smearing and a delay for postpress operations. The UV offset process does not have these limitations.
3: Classic UV offset without coating and conventional offset with coating have the same cost. Conventional inks plus coating protect the paper surface but modify its visual appearance and feel. UV printed images have high resistance to marking, faster reverse side printing and converting, and no detrimental impact on the paper surface. The dedicated UV press is less flexible than a conventional multi-purpose press with coating.
4: Classic UV with inline coating costs about 10 per cent more than UV without coating.
5: UV printing and coating costs 10 per cent more than conventional wet offset with coating. The UV advantages are higher gloss, high rub protection, fast production, and a wider range of special effects.
6-7-8: The direct comparison between conventional inks alternating with Classic UV (5+6); and for Non-classic (hybrid) UV (7+8) shows a negligible cost difference. Multi-purpose combination presses (5/6 and 7/8) are 3 to 4 per cent more expensive than single-purpose processes because their ink system changeover takes more time.
9: Primer UV process (9) is 19 per cent above the reference press costs. However, the double coater press offers a vast range of process combinations.
