Laser plastic welding

Laser plastic welding

Laser plastic welding – Contour welding

During laser transmission welding, a transparent covering material is pressed onto an absorbent base material. The laser beam penetrates the upper transparent joining material and is completely absorbed by the lower, dark material. The absorptive material starts to melt at its surface. The molten mass expands a little bit and coats the transparent covering material. The joining of the transparent material with the absorptive is based on a diffusion process of the both molten materials.The laser head is conducted by a robot along the contour and produces an uniformly welded seam.

Most important requirements for laser welding of plastics:

  1. The two components must be thermoplastic and chemically equal or very similar, otherwise the adhesion is merely based on indenting of the components – Table for possible material combinations

  2. The transparent material can also be milky (glass fiber reinforced). The scattering of the laser light does not make the welding process impossible.

  3. The transparent material can also contain special pigments, which cause a coloured or black effect, but which are transparent to the laser.

  4. Reliable and reproducible results are only produced with exact temperature control with LASCON®

Advantages:

  • No waiting times as with adhesives
  • No dosing problems as with adhesives
  • Exact process control with on-line monitoring
  • Short processing times – high production cycle

Simultaneous welding

The goal of simultaneous welding is to weld the whole contour with one laser shot instead of having a robot traverse along the entire contour. Various processes are available for this:

  1. In simple cases, the contour can be generated using laser beam shaping (for example ring-shaped optics)

  2. Creating a mask, which is illuminated by a laser

  3. The laser beam is scanned by a galvo optic mirror along the welding seem very fast and high frequently, so that the whole seam simultaniously starts to melt.