LASER WELDING PLASTICS

After countless applications in joining metal elements, laser is now becoming popular even in the field of thermo-plastic materials, as a substitute for traditional methods. Laser systems for joining this kind of materials are commercial machines of high productivity and reliability which require reasonable investments, within reach of most small-sized enterprises. They may need the use of sensory systems to monitor weld temperature or part dimension and, upon request, they can be fully automated.
They are divided into two categories:
- Systems based on anthropomorphic and cartesian robots, suitable for 3D welds and large areas
- Galvanometric systems, suitable for flat elements of small/medium-sized components.

Laser enables welding of nearly any kind of thermoplastic material:

PC, PMMA, ABS, PA, SAN, PE, PP... even with glass fibre reinforcement

LASER WELDING ADVANTAGES
High process speed (up to some m/s)
Good quality, precision and repeatability
High flexibility and easy change of weld configuration
High mechanical strength of joints, up to that of base material
Sealing joints
Lack of contact and no mechanical stress or wear on welded parts
Very low and localized thermal input
High precision in welding dimension and deepness
Working selectivity
Possibility to perform the welding of dissimilar materials
New potentialities in the aesthetical field because of the inside welding
No or little dross, always well attached
Very low fume emission


















The most interesting and versatile process is welding in transmission, by means of lasers emitting in the near infrared, between 800 and 1100 nm, a wavelength interval at which most non-pigmented polymers are transparent to light. The process takes place in an overlap configuration: a transparent thermoplastic layer is superimposed to a properly pigmented (absorbing) layer. The laser beam passes the first layer without interaction, and interaction happens at the interface of the two layers, when the beam reaches the absorber. Thus interface welding between the two materials is possible and the weld is totally invisible. Any type of IR laser can join thermoplastic materials, though CO2 cannot be used in transmission welding. Generally, power level is low, between 50 and 200 Watt, welding width between 1 and 3 mm and welding speed in the range 0.5 to 10 m/min.

A different matter is laser processing of films of plastic material, on which also cutting can be performed by the same source. CO2 lasers are used, by which it is possible to weld any kind of film (PE, PP, PVC, PS...), with thickness that may reach hundreds of micron. By a few hundreds watt, it is possible to attain processing speed of some hundreds metres per minute.

FIELDS OF APPLICATION
Automotive
Household appliances
Sensoristica
Electronic
Packaging
Telephony
Textile
and all the fields in which are moulded and assembled polymeric materials.