The variety of shapes and sizes, angles and curves, edges and recesses present in a 3-dimensional object requires that the lamps deliver UV energy to all the surfaces.
Many applications in industrial three-dimensional coating, require curing of "optically thick" coatings; that is, coatings which have a high absorptivity of UV light. This has the effect of rapidly diminishing the energy density of the UV, as it travels through the coating. To ensure adequate curing, sufficient UV must reach the bottom of the coating. Coatings with high film weight, pigmentation, or filler levels present the greatest challenge for achieving good through cure. Delivering high peak irradiance UV to the coating maximizes through cure. On flat substrates, using elliptical reflectors and ensuring the coating runs through the area of highest peak irradiance at the focus of the UV energy ensures adequate cure. When curing coatings on 3-dimensional objects, this is much more difficult.
A compact, modular lamp system can be arranged to follow the contours of a part, or targeted at specific areas. By modifying the elliptical reflector cavity of the microwave-powered UV lamp, the focus can be altered, pushing it further from the lamp face and widening the focal area. This reduces the high peak irradiance, but allows a more consistent irradiance level to be achieved over a longer distance, while still maintaining the advantage of converging and diverging rays to minimize shadowing. See Table 1 for a comparison.
Table 1 - Comparison of peak irradiance values in W/cm2, 240 W/cm lamp (600 W/in)
