Although expensive and still a rarity, there is little doubt that laser welding of thermoplastics will grow in popularity. There are a number of reasons for this. For one thing, laser welding is extremely precise and does not generate flash or particulates, in contrast to other methods such as ultrasonic, spin, vibration and heat welding. This makes laser welding ideal for assembling medical devices and automotive taillights. It is also energy efficient and fast, with cycle times of 2 seconds or less. Finally, it is a noncontact process that leaves no marks on the finished product and can reach recesses that are inaccessible to other welding methods.
To create a weld, a laser system uses a glass plate to hold two parts together, one on top of the other. The top part is made of a transparent material, while the bottom part is made of a material that absorbs near-infrared light. The laser light is then directed through the plate and the transparent upper part so that it strikes the near-infrared-absorbent part on the bottom. When this layer heats up, it melts the surrounding plastic and creates the weld.