Robotic UV Curing: A Cost-Effective Way to Cure Large 3-Dplastic Parts

摘要

Plastic part manufacturers are paying more attention to UV curing as a means to produce their parts. The interest is driven by several advantages of UV: 1. UV cure is fast. Coatings can be cured in a tiny fraction of the time needed for traditional cure systems. 2. Little heat is required. UV curing relies on light energy and not heat to driveolymerization. This mechanism is ideally suited to temperature sensitive substrates. 3. The UV process minimizes the emission of hazardous VOCs. Many popular plastic UV coatings are very high solids formulations with little or not solvent. 4. UV formulations may exhibit superior properties. Many UV formulations are noted for high gloss, superior scratch and mar resistance — properties often sought in plastic part manufacturing. While UV curing is new relatively new to the plastics market, it is the established way to cure coating materials. In graphic arts for example, many UV varnishes, inks and adhesives are cured with UV. DVDs are produced with UV bonding adhesives and often decorated with UV cured inks. Wooden flooring, optical fibers, and printed circuit board resists all use UV. But these parts are simple compared to most plastic parts. They are small, they are flat, or they are relatively simple shapes. The markets that have accepted UV have often been markets lending themselves to UV exposure by simple fixed lamps. Surely this has developed because without direct line of sight between the part surface and the UV lamp there can be no cure. For the last few years , as makers of large and complex 3D plastic and composite parts explored the UV option they found that the established techniques of placing fixed lamps end-to-end to be fraught with technical problems and high price tags. Many projects where the coating was developed and proven stalled when the price quotation for a system of 10, 15 or 20 or more UV lamps was presented. This paper describes recent developments using robotically actuated UV lamps to cure large and complex parts. Both the technical and economic benefits of this approach are described and compared to the traditional approach of using large fixed-lamp arrays. While many of the example used here are from automotive applications, the adoption of automotive-type methods in other industrial installations such demonstrate that these practices are applicable to a wide range of plastic part manufacturers as well.