Guide to UV Measurement
Categories of UV Curing
UV systems might be divided into three categories, distinguished by the mechanical arrangement of curing lamps:
Linear Curing includes all sheet and web printing and coating. Essentially, a flat, two-dimensional surface is passed through the field of UV lamps (or lamps are passed over the surface). Typically, tubular lamps with reflectors are used. Reflectors may be semi-elliptical, parabolic, or special shapes. The lamps extend across the process surface, and the lamps are ‘responsible' for the uniformity of exposure across the process, while the motion of the work surface is ‘responsible' for the uniformity of exposure along the direction of travel.
Flood, or Area Curing is distinguished by the UV “illumination” of larger surfaces that may be flat or 3-dimensional, and motions that may be complex, for example, chain-on-edge conveyors or paint lines. Exposure may be either static or dynamic. Lamps may be arranged to suit the part and/or its motion. This category can include robotically-controlled positioning or motion of the lamp(s) over complex surfaces. The mechanics of this category poses special problems for radiometric measurements, owing to complex surfaces, or to complex motion.
Spot Curing is characterized by small, carefully directed “spot” of UV for curing of small areas, such as adhesives or small areas of of marking. Radiometry for spot cure systems is different from that for Linear or Flood systems; measurement of output is done with a closed system