- Ultrasonic welding. The thermal heating of the laser avoids the potentially destructive vibration from the ultrasonic process. SomeArial ultrasonic vibrations can damage sensitive electronic components that are part of the part. Other Arial, ultrasonic welding can melt polymers outside the weld zone through heating from standing waves that are generated in the part. Ultrasonic welding can also be inconsistent and very sensitive to part dimensions. Lasers and infrared sources are more consistent.
- Hot-plate or heated platen. Molten polymers stick to hot plates if they are welded above temperatures where release liners (Teflon) are used. Using very hot platens to vaporize any sticking polymer and increase the weld speed is a solution, but this creates fume. Some of these fumes may be hazardous. With laser welding, the light beam must not be impeded by dirt or fume. Adventitious dirt, either on the lasing surfaces or on the part, that absorbs much more strongly than the polymer itself can cause decomposition. Fume usually has a yellow color and on the next cycle it becomes brown and then black. At that point, the beam quality and power is often degraded.
- Electromagnetic radiation (induction, RF, microwave). Some sort of electromagnetic absorber must be present in the weld zone. If the polymer is the absorbing material, such as with RF welding, then there are limitations on the polymers that can be welded. Many are not sensitive to the wavelength of the radiation.
- Friction processes (spin and vibration welding). Parts that are much more delicate can be welded easier with laser than with friction processes. Since these processes depend on generation of heat through rubbing the parts together, the parts need to be fairly robust. However, friction processes are very useful for black parts that are commonly used in the automotive industry.
How Laser Compares
Laser welding compares favorably to traditional plastic joining techniques, such as: