By Olivia Cahoon
Part 2 of 3
Traditional UV and UV LED curing devices create an energy source that dries ink, coatings, and adhesives. Curing devices are available with flood or spot curing capabilities in UV or UV LED light sources.
UV flood devices apply moderate- to high-intensity UV to an entire object while spot curing focuses on a designated area for adhesives and special effects. Application and compatible substrates dictate whether flood or spot is more ideal.
UV spot curing devices typically cure in speeds from one to ten seconds. They are available in a variety of light delivery options including diameter, length, and single or multiple lamp configurations. Although spot systems are offered as traditional UV devices, they are often used with high-intensity UV LED for cooler substrate temperatures and thermally sensitive materials.
Spot curing devices are designed for low- and high-volume production applications especially in automotive, electronics, industrial, medical, and optical industries. The device focuses on a specified area and cures the ink or coating to the substrate. In smaller-sized applications that require high curing, like plotting items to boards, Meredith Stines, president/CEO, American Ultraviolet, suggests a spot curing unit. He offers, “spot curing can offer more intensity because it’s focused on a targeted area.”
According to Sara Jennings, senior technical marketing engineer, Phoseon Technology, spot curing devices are used in research and development laboratories and for UV-curable adhesives in production applications where parts are less than 0.5 inches in diameter. For larger applications, curing systems are available with multiple LED heads focused in multiple combinations.
Spot UV systems cure special effects like glitter, texture, or gloss in defined print areas. “It can make one part of an image stand out over the rest of the printed piece,” explains Jack Karas, managing partner, Oxytech Systems, Inc.
Projects that include special inks and a spot varnish on the same sheet risk the ink changing hue under UV light. Spot curing targets the spot varnish without affecting the ink. “Narrow spot systems cure only where needed and don’t affect the rest of the printed surface while accepting a wide web and maintain high production speeds,” adds Karas.
UV flood devices cure substrates while providing additional protection and durability from scratches, scuffs, water, and chemicals. Flood coating is often applied to crafts, displays, packaging, signage, and manufactured products. “UV flood systems are used for batch curing or hitting various areas on a printed circuit board or other three-dimensional objects,” says Stines.
According to Jennings, UV LED systems include two categories—pinning and full cure. Full cure exposes ink to enough UV energy to completely harden the material. It uses a light source with more total energy to fully cure the ink with either single or multiple passes.
“Pinning is the process of exposing ink to low intensity UV to partially cure the ink drops, which reduces dot gain and provides improved image quality,” shares Jennings. Pinning light sources are typically small and thin enough to mount between inkjet printheads.
In industrial and assembly applications, flood devices use moderate- to high-intensity UV lamps to cure adhesives, coatings, and inks. The devices consist of a power supply, reflector housing, and metal halide bulb. Some devices include mounting stands, UV shields, and shutter assemblies.
Flood curing systems bond, seal, and encapsulate materials up to eight inches in size in industrial applications. They are also used for applications with large cured areas like flat panel displays and other electronic devices, says Jennings. “Flood curing devices are more ideal for larger areas or assembly of multiple small parts at one time.”
UV flood coatings are also commonly applied to magazines and newsletter covers that require an ultra-high gloss finish or protection from outside elements, explains Karas. Applications that require further finishing processes may also benefit from UV flood coatings.
Manufacturers use curing technology for high quality, durability, and speed. UV flood and spot systems offer the ability to coat an entire object or add special effects to a designated area. Before selecting a curing technology, manufacturers should consider if the application benefits more from flood or spot curing.
Apr2018, Industrial Print Magazine