Through-Transmission Infra-Red Welding

As the name indicates, this welding process depends on transmission of IR energy to the weld interface through one of the parts being welded.  Process is ideally suited for two thermoplastics components that can be brought into intimate contact at the weld locations and where at least one of the components is transparent to IR energy; plastics that are transparent to visible light are also transparent to IR energy.  Simple configurations include a sandwich of two flat sheets of plastic or two pieces of plastic butting against each other.

The IR energy, once it is transmitted through the transparent component, has to be absorbed at the interface on the other component.  Hence it helps if the other component is not transparent; any colored plastic works but black colored plastic would be ideal.  If both plastics are transparent, one can add a thin layer of black plastic sheet as an "braze" between the two.  The absorbed energy melts the plastic surface and then by conduction also melts the transparent plastic which has to be held in intimate contact during the whole process.

IR energy can be delivered over an area with halogen lamps or can be focused to a spot with a laser fiber.  Laser energy sources can include YAG or Diode lasers.  Depending on the part geometry, a direct diode source can also be used.  For seam welding applications, such as enclosures or other containers, the laser energy can be delivered at a spot and the spot is then moved along the required trajectory to form a seam weld.

Other sources of energy such as CO2 laser light (10.64 microns) does not transmit through any plastic thus making it difficult to heat the interface.  However, such light can be used if the interface is directly exposed to the light or if the parts being welded are very thin sheets and absorption on the exposed surface is sufficient to generate the welding heat.

For additional information or consulting services, please contact us.