Laser plastics welding

Process principles of plastics welding

Laser welding of polymers is predominantly carried out as the through-transmission welding process. As most thermoplastic polymers provide a high optical transmittance of radiation in the visual and near infra-red wavelengths, the laser radiation can be applied through a transmitting top layer into the welding plane. The lower joining partner, containing a radiation-absorbing colorant, absorbs the incident radiation, thus generating the required heat for melting and fusing the joining partners. As both joining partners are kept in a tight thermal contact, heat conduction into the transmissive top layer causes it to melt, leading to the desired cohesive junction of both parts.

The principle of laser transmission welding is currently being implemented with different welding methods. The most commonly used ones are the contour- and the scanner-based welding methods which are distinguished by the way that the required energy is deposited in the joining partners. As each of the procedures has its own specific advantages or characteristics, a decision must be made as to which type of welding method should be employed for each application.