When a label printer retrofits an existing press or purchases a new press with UV LED, the company’s stakeholders and overall business operations experience an immediate and positive impact as soon as the equipment is up and running. To understand why this is the case, it is helpful to identify production challenges that UV LED curing addresses. Doing so provides insight into drivers of UV LED adoption in narrow web label and reveals why this revolutionary technology is so appealing to graphic designers, press operators, maintenance staff, quality managers, sales, purchasing, management, owners, and investors.
Similar to conventional UV curing, LEDs produce incredibly bold and vibrant print colours that are highly desired by brand owners and graphic designers. Where LED has the edge is in process efficiencies. This is because LED is innately better at curing pigmented formulations, especially white inks and densely pigmented inks. LED is also better at curing laminating adhesives, cold foil adhesives, cast and cure coatings, and thicker formulation laydowns. This is due to LED’s longer UVA wavelengths penetrating deeper into formulations; passing more easily through films and foils; and being less absorbed, scattered, and reflected by colour additives. Longer wavelengths allow a greater portion of energy to reach the formulation’s photoinitiators and initiate the chemical reaction. This facilitates greater opacity, better cure, and faster line speeds. For the stated applications, UV LED curing is a more efficient process.
A challenge with conventional arc lamps is that quartz tubes and electrodes gradually degrade from first strike. This can lead to reductions in UV output of 30 to 40% over 1500 hours of operation. By contrast, LED curing is a reliability improvement since UVA LEDs degrade at most 2% annually and provide stable UV energy for 10 or more years. In addition, reflectors and lamps in conventional systems are susceptible to contamination by the production environment. This can inhibit UV output by 50% or more whenever these critical components are not kept clean. Arc lamps that are over or under-cooled emit less UV output, and improperly or insufficiently cooled arc lamps are difficult to re-strike. All of this contributes to a black box troubleshooting scenario whenever curing issues arise. Alternatively, presses equipped with LED technology deliver consistent and reliable UV output over time; thereby, eliminating the UV source as a variable. This drives more reliable production processes, improves quality, reduces scrap, and prevents downtime.
In terms of maintenance, LED systems require a clean emitting window and properly maintained cooling system. In terms of spare parts, there are no lamps, reflectors, shutters, or actuator mechanisms. This reduces maintenance, eliminates consumables, improves up-time, and drives production yields. As long as LEDs are cooled properly with forced air or conditioned water-circulation, the technology is capable of providing many years of reliable service. A poorly engineered or improperly maintained thermal management system is the leading cause of any LED system that does not provide useful life in excess of 20K, 30K, and even 40K hours.
LEDs turn ON and OFF instantly and are unaffected by the frequency and total number of starts and stops. This eliminates warm-up, standby, and cool-down cycles associated with conventional UV. Instead of press operators waiting for UV systems to be ready, UV LED systems wait for press operators to be ready. This saves valuable production time.
UV LEDs do not emit heat generating infrared wavelengths and do not produce ozone. This allows printers and converters to run more thermally sensitive substrates and reduce wear and tear on machine components. Because there is no ozone, there is no need for extraction systems, roof penetration, or conditioned make-up air, all of which decreases installation and operating costs.
While LEDs eliminate heat generating infrared wavelengths, ultraviolet wavelengths are still a form of energy. Any portion of UV energy that does not go into the chemical reaction is immediately converted to thermal energy when it contacts the substrate, construction, or machine surface. Fortunately, this converted thermal energy is a fraction of the thermal energy radiated by conventional UV and is generally negligible when UV LED systems are integrated with a chilled roller or integrated air or water-cooled heat sink. This overall reduction in heat transfer makes LED curing ideally suited for shrink film and other thermally sensitive materials. In addition, reduced heat transfer improves process control especially when used in collaboration with chilled rollers that enable web temperature and reaction temperatures to be independently and precisely held within the optimal process window.
For many years, the cost of UV LED curing systems exceeded the cost of arc lamp systems. This is no longer the case for many GEW LED configurations which have a capital investment that is equivalent to and frequently less than conventional UV.
Finally, UV LED curing systems reduce total installed electrical power, decrease a facility’s peak power demand, and lower energy consumption during operation by as much as 75%. This translates into lower electricity bills which immediately impacts a business’s bottom line. Reducing installed power, peak demand, and consumption also has a direct impact on an organisation’s sustainability efforts. This is because UV LED decreases carbon footprint and the amount of reserve generating capacity power plants must maintain to meet a facility’s peak power demands. Lowering demand frees electrical energy for use elsewhere on the grid and drives better regional supply efficiencies. This is critical in the face of rising consumer, commercial, and industrial energy needs coupled with increasing energy costs and an over-burdened and aging electrical grid.
As printers and converters gain first-hand experience with LED systems, confidence in its viability as a curing technology grows as well as appreciation for how LED curing is a solution to various production and sustainability challenges. Following initial use, most are pleasantly surprised to the extent LED positively impacts the organisation’s operating economics and production environment. As a result, businesses that convert to LED on one press, quickly find themselves moving forward with additional lines. If your organisation has not yet started exploring LED for your own curing processes, it is something you should seriously consider.
Jennifer Heathcote is the Vice President, Business Development at GEW (EC) Limited’s US subsidiary GEW, Inc, where she is a leading authority on UV and UV LED across all applications in the printing, coating and converting industries.