The ability of lasers to weld polymers has been known for many years, but the level of acceptance of the process by industry lags far behind the acceptance of laser welding of metals. As with laser welding of metals, optimum joint performance is obtained when the joint configuration is designed for laser welding. Weld joint performance characteristics may include bond strength, leakage rate, process cycle time, part fit-up tolerances, and interface cracks or flash.
We report results of a study on laser welding of polymers to optimize joint configuration and performance for a simple, but practical case of a cap on a tube. To compare the effects of material on weld performance, the experiments were performed using both acrylic and polyethylene components. Several cap geometries were designed and produced with a range of dimensional tolerances. Caps were then laser welded onto tubes with a range of process parameters: power, speed, spot size, focus location. The resulting parts were subject to a series of tests, including vacuum testing for leak rate, tensile pull testing for bond strength, and macro-sectioning.