Kimitoshi Sato

Laser welding of plastics transparent to near-infrared radiation

This paper deals with a development of laser welding of colored plastics. Welding of thermoplastics using near-IR lasers has been seen in wide industrial application. Most of thermoplastics are transparent to near-IR laser. Particular characteristic of near-IR laser radiation has the ability to heat the interface between the transparent part and absorbent one colored with pigments. However, it is difficult to weld a pair of transparent materials by a laser beam, since there is no absorption region within them. In this paper, the influence of near-IR transparent plastics on the yield strength of their weldments has been studied: various colored plastics transparent to diode laser radiation were tested as the welding material. The heat transfer within a welding system was also analyzed and assessed the appropriate absorptivity and transmittance of overlapping colored plastic.

A novel CO2 laser welding of plastics using a transparent solid heat sink without causing thermal damage

The paper introduces a novel concept of CO2 laser welding of thermoplastics which is applicable to manufacturing medical appliances, micro-scale devices and the products requiring the smooth surfaces of welded region. The procedure has a few features: (1) to place a solid heat sink transparent to a infrared radiation beam in contact with an irradiated plastic to cool the surface during welding process, (2) to use no pigmentation or dye for radiation absorption enhancement, (3) to sustain thermal damage on the surface, and (4) to avoid the emission of harmful gas due to decomposition of plastics. The feasibility of the welding procedure for natural transparent plastics such as polyolefin and perfluoroalkoxy resins without any surface damage was examined using a CO2 laser as a radiation source with a solid heat sink. The experiments for overlapped films welding as well as tubes welding were conducted by means of the CO2 laser. The heat transfer analyses in the welding process were also carried out to obtain the temperature profiles in the plastics during the welding process.The paper introduces a novel concept of CO2 laser welding of thermoplastics which is applicable to manufacturing medical appliances, micro-scale devices and the products requiring the smooth surfaces of welded region. The procedure has a few features: (1) to place a solid heat sink transparent to a infrared radiation beam in contact with an irradiated plastic to cool the surface during welding process, (2) to use no pigmentation or dye for radiation absorption enhancement, (3) to sustain thermal damage on the surface, and (4) to avoid the emission of harmful gas due to decomposition of plastics. The feasibility of the welding procedure for natural transparent plastics such as polyolefin and perfluoroalkoxy resins without any surface damage was examined using a CO2 laser as a radiation source with a solid heat sink. The experiments for overlapped films welding as well as tubes welding were conducted by means of the CO2 laser. The heat transfer analyses in the welding process were also carried out to obtain...