Plastic welding

Menu :

• Laser principle
• Laser sources
• Applications
  • Cutting
  • Metallic welding
  • Plastic welding
  • Soldering
  • Brazing
  • Marking, engraving
  • Cleaning and surface preparation
  • Cladding
  • Surface alloying
  • Laser assisted machining
  • Laser machining

Plastic welding :

In the middle of the 90's a true interest for the use of laser sources in plastic welding emerges. The arrival on the market of new irradiation sources like laser diodes has contributed to the present research works. Their small size, the constant decrease of their prices and above all the new possibilities they offer make them one of the future solutions for the welding of polymers.

Principle :

Laser welding is based upon the behaviour of plastic under irradiation. In near infrared, most plastics are transparent. The laser beam goes through without interaction. The addition of additives or colorants into the plastic can change this transparency. For polymers, the welding characteristics only depend on the interface temperature, the heating time and the holding pressure. With a laser source the energy supply is always controlled, the welds are perfectly homogeneous and the mechanical resistance usually higher to those obtained with other processes.

	Laser beam	Beam moving
Clamping
			Absorbing polymer
	Heated and welded volume	Transparent polymer

By stacking a transparent material with an absorbing material and irradiating the whole we create a local melting of the absorbing material at the interface. By thermal conduction the transparent material rises in temperature. Interpenetration and tangle of the macromolecular chains will give after cooling a solid bond between both parts.

Characteristics

Beyond the ability to make nearly invisible welds and the precise control of the energy supply, laser has following advantages

Welding with diode laser of a decorative part in polyamide.

• a great flexibility in the process with the possibility of changing at any time the sizes of the welding zones
• cycle time often lower than with traditional processes
• no contact between energy source and plastic
• less constraints of implementation than with other processes
• no moves of the part to be welded (rotation...)
  

Industrial applications :

At the present time thanks to research works, plastic welding has left its experimental stage. The results as a whole, particularly the comprehension and the control of the interaction phenomena between plastics and a laser irradiation, not only proved the technological potential of theprocess but also are the basis fr further industrial applications.

Watertight box in polyamid(transparent/black and black/black assembling)