Laser welding polymers

Several industrial plastic welding methods are known and deployed across the manufacturing industries. They include hot gas welding, impulse welding, high frequency welding and ultrasonic welding. Each have their strengths and limitations, but it is known that the laser welding offer large possibilities, high throughput and many advantages compared to others methods.

Plastic welding of workpieces or films, implies to fuse together parts under the action of pressure and heat, causing the crosslinking of their molecular chains. There is mainly two technologies in polymer laser welding: Transmission welding and absorption welding.

Transmission welding uses a laser wavelength which is transparent to a first plastic so that the laser can reach the interface with another plastic which is absorptive. Some additive can be added at the interface between the two parts to be welded to enhance local absorption if both plastics are transparent to the laser wavelength. Absorptive laser welding is a process to weld two thin films of plastic that absorb partially the laser input energy. In this case, the laser energy is absorbed through the whole thickness of the films.

For both processes, a contact pressure is required between the two parts to achieve a strong bond. This pressure can be applied through vacuum or mechanical devices.