STUDY OF CONTROLLABILITY OF MELT DEPTH IN INFRARED LASER PENETRATION WELDING OF THERMOPLASTICS

摘要

Extended research has been carried out concerning our proposed penetration welding technique for overlapped thermoplastics using infrared lasers with transparent heat sinks. Numerical simulations for a heat transfer model in welding process were conducted to test the effect of various kinds of welding conditions on the melt depth of plastics. The temperature profile variations in plastics to be welded during heating process were obtained by manipulating different parameters, such as the heat sink, the plastic material, the thickness of (he plastic, the absorption coefficient, the incident radiation power density and the irradiation time. The results show that the melt depth and the starting time of melting greatly depend upon the radiation absorption and thermal diffusion in the plastics. For example, as the absorption coefficient of plastics increases, the starting position of melting in the plastics approaches the irradiated surface. It is therefore worthwhile for overlap welding to know the depth at which the maximum temperature appears inside of the plastics during radiation heating. This is dependent on the heat conductivity of heat sinks, the thickness of the plastic, the absorption coefficient, the radiation power density and the irradiation time.