With the launch of GEW’s hybrid ArcLED UV curing system, barriers to adoption have now been further lowered. Within an ArcLED system, users are able to operate full hybrid UV curing, working with both mercury arc and LED lamp technology on the same press.
Answer: UV LED curing is a “photochemical” reaction that harnesses energy stored in longer ultraviolet wavelengths of light (365, 385, 385, 405 nm) to instantly set and adhere inks, coatings, adhesives and extrusions in manufacturing processes by reacting the molecular bonds of the applied materials. UV LED curing is not drying. This is because UV LED formulations are 100% solids and do not contain water or solvents that must be “evaporated” after application.
By contrast, drying involves the “evaporation” of liquid carrier mechanisms. Liquid carriers such as water and solvent are used in conventional formulations to adjust viscosity so that solid resins can be transferred and applied to surfaces. Drying refers to the removal of these liquid carriers after application. Drying can be time consuming, require long tunnels that consume valuable factory space, and incorporate the use of energy intensive thermal sources.
Question: Which applications get the best results with UV LED curing?
Answer: Printing inks, laminating and pressure-sensitive adhesives, wood fillers, and nitrogen inerted fibreoptic coatings are all ideally suited to being cured with UV LED. Viable UV LED printing methods include digital inkjet, screen, pad, flexo, letterpress, offset, and gravure.
White and highly pigmented inks are most suitable for LED curing. Longer UVA wavelengths and greater intensities penetrate through films and densely pigmented formulations better than mercury vapour lamps. In the special case of white inks, titanium dioxide (TiO2) additives absorb all wavelengths below 380 nm. UV LEDs emitting at 395 nm evade TiO2 particles in white inks which enables more UV light to be absorbed by photoinitiators.
Question: Is there a difference between UV LED and mercury arc UV formulations?
Answer: UV LED and conventional UV formulations do contain many similar ingredients. However, a decisive category of the formula, the photoinitiator blend, is often significantly different. This is the chemical component that responds to light. Different photoinitiators react to different wavelengths. For LED technology to deliver speed and full cure, formulations must include photoinitiators that react to longer UVA wavelengths. As a result, conventionally formulated UV chemistry should not be cured with UV LED and must be reformulated.
While some LED formulated inks & coatings can only be used with LED, many are being designed as dual cure. Dual cure versions are specifically formulated for LED but will also work with mercury lamps. Using dual cure inks, coatings, and adhesives helps reduce SKUs and eases the transition to LED.
Question: What is the energy saving with UV LED?
Answer: UV LED energy savings vary by system, integration, and means of operation, but typically energy savings are over 70% when compared to a mercury arc UV system running the same job.
A recent ROI analysis performed on a 45cm, 8 lamp system running two 8-hour shifts per day, 5-days a week, with a 60% duty cycle resulted in a savings of 16,000 GBP per annum.
This is 160,000 GBP over 10 years in both energy and operation costs.
This delivers approximately 7 tonnes of CO2 elimination and 46% total energy savings when compared to the most energy-efficient mercury arc systems (E2C) in the market.
GEW encourages companies to contact us for a proper assessment and analysis based on individual circumstances.
Question: Do I need a different power supply for UV LED?
Answer: UV LED lamps are powered by direct current (DC) whereas UV arc lamps use alternating current (AC). Therefore typically a different power supply is required.
However, RHINO ArcLED hybrid power supplies from GEW can supply both; automatically recognising the type of cassette and switching to the correct power output. This means both LED UV lampheads and conventional mercury arc lamps can be used with one single power supply and operated from the same touch control panel.
Question: Does LED UV work with everything?
Answer: While the entire portfolio of UV chemistry has not yet been reformulated for LED, the list of offerings continues to expand. Printing inks and laminating adhesives work well with LED. Unsupported films, shrink sleeves, and many delicate, heat-sensitive materials are also more easily processed with LED due to reduced thermal transfer. Varnishes, spot colours, and low migration formulations, however, still generally achieve better cure with arc lamps. Protective coatings also benefit from arc lamps as short UVC wavelengths deliver the best surface hardness.
The situation is constantly improving and the latest information should be sought from GEW before a decision is made.
Question: Do frequent starts and stops reduce the durability of LEDs?
Answer: No. Frequent on/off switching does not reduce the life of UV LEDs nor impact their durability. To the contrary, turning LEDs off when not needed extends the life of the system. During stand-by and line stops, UV LEDs should always be switched completely off. When LEDs are not emitting, they are not degrading.
Question: What happens after 40,000 hours?
Answer: Over the first 40,000 hours of emission, a typical LED system gradually loses 10-15% of its output capability. After 40,000 hours, the LEDs will continue to emit UV energy, but output will increasingly degrade making the probability of LED failure greater. When a single LED fails, the user will not notice, as surrounding LEDs automatically increase in power to accommodate any losses. When enough LEDs in a single area fail, curing suffers. At this point, users can either replace the failed LED module or replace the entire assembly to ensure uniformity of output across the curing width.
Question: Is LED UV more expensive than conventional UV?
Answer: CapEx and operating costs vary depending on the UV system, the integration, the formulation, and the needs of the application. In some instances, UV LED is more expensive. In others, it is comparable or even less expensive. GEW encourages companies to contact us for a proper assessment and ROI analysis based on individual circumstances.
Currently, for cure widths greater than 620mm (24″), the cost of a GEW LeoLED system is comparable to, and often less than, that of an arc UV system. LeoLED also eliminates the need for air extraction, ozone removal, and conditioned make-up air while achieving production speed targets, producing quality product, and capitalising on energy benefits inherent in LED technology.
Similarly, AeroLED, which is GEW’s air-cooled UV LED product, appropriate for web widths up to 60cm, has many of the benefits of LeoLED, but offers an even more economically viable option for printers. In fact, AeroLED can often have ROIs of less than one year, particularly when energy savings of up to 70% compared to conventional UV are factored in.
Answer: LED UV should be chosen based on three criteria: suitability for the process, availability of formulations, and the ability to achieve productivity gains. For additional guidance and information, please speak with your local GEW representative about the specifics of your application.
