The laser welding technique is based upon the light transmission of a polymer and its absorbing characteristics. To weld two plastic parts it is necessary that one part can transmit laser light and that the other part can absorb laser light.

figure 1

figure 1:

A: The absorbent material takes the energy and a melt arises

C: The heat is conducted to the the transparant part, the melt is arising here too.

D: The complete melt is solidified under external pressure and a perfect fuse is born.

The absorbed laser beam energy is converted into heat, leading to local plasticization of the polymer. A regulated welding pool arises in the contact area of the two parts which, after cooling down, results in a high-graded and strong connection.

Most of the available plastics are absorbing light in the IR and UV range (see the beige curve in figure 2). Generally plastics are transparant or a little bit milky in the visible- and near IR range. To adjust the absorption characterictic, so that they are suitable for laser welding, pigment additives are embedded in the polymer matrix (black curve).

figure 2

More information:
Laserwelding of Plastics, Ir.Luc Janssen, Mareco, 2008.
Laser High Tech on River Maas, Susanne Lötzsch, Rofin/Baasel, 2007

Sources:
Carl Baasel Lasertech GMBH
Mareco Kunststoffen B.V., R&D

3D Lasewelding at Mareco Kunststoffen B.V. has been made possible thanks to the LIOF and the European Commnission.