OPTICAL CORRECTION FOR HEAT BUILDUP IN THE CENTER OF TTIr PLASTICS WELDS

摘要

Through Transmission Infrared (TTIr) laser welding of plastics often results in voids forming in the center of the weld. These voids can lead to weak and unattractive welds. Their formation is due to non-uniform temperature distributions within the weld zone and out gassing of volatiles (such as moisture). This non-uniform temperature distribution has been demonstrated not only by a Gaussian laser light distribution but also by an even light distribution depending on the joint/part design. This paper reviews the development of tailored optics that re-shape the distribution of typical light/laser sources in order to promote uniform temperature distributions. It was seen in FEA models that by using uniform heat distributions, uniform temperature fields were produced in butt joint configurations. In addition it was seen that a distribution with high heat input on the outer edges produced uniform heating in lap shear joint configurations. Laboratory experiments verified these FEA predictions, and strong and attractive welds were generated.