Laser welding plastic

The laser welding of plastic using diode lasers supplement traditional welding methods such as ultrasound, vibration, or hot plate welding. It combines the advantages of contact-free welding, without fluff formation or excessive melting, with the possibility of welding with a measurable setting path.

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Diode lasers with low and medium laser power are perfect for creating a high-quality, durable connection between thermoplastic polymers using the transmission welding method. Different special optics and additional components, such as pyrometers for temperature-controlled contour welding or CMOS cameras, can be adapted for process visualization. For quasi-simultaneous welding, scan systems with highly dynamic deflection mirrors guide the laser focus along every desired 2D contour.

Plastic welding systems – the method

Laser beam transmission welding always involves a component that is transparent for the laser and a laser absorbing component being merged. Before they are welded, the join partners are positioned and then pressed together. In the actual fusion process, the laser beam passes through the transparent component without significantly heating it up, before the absorbing component takes the laser energy, which heats up its surface. This energy is transferred via heat conduction onto the surface of the transparent component. The energy that has been absorbed plasticizes the plastic which, with pressure and heat conduction, leads to the components being joined. The existing joining pressure results in a substance-to-substance bond for both parts. The firmness of the resulting weld is typically within the region of the base material’s strength.

Polymer Welding: Advantages of diode lasers

The diode laser has the edgecompared to conventional solid-state lasers because of its wavelength spectrum and “top hat” steel profile without an intensity peak. In this way, local temperature peaks (which could damage the join partners) are avoided. Because of the diode laser’s local energy input, the plastic in the join zone is heated very quickly, without damage to the material, resulting in a homogeneous melt and zero fluff formation due to dry friction. Setting path monitoring systems, or temperaturemonitoring systems, can record the plastic welding process and pass the result to a higher-level control system. Functional changes to the component or new design ideas for the welding contour can be programmed flexibly. In particular, the laser protects interior and vibration-sensitive components or complex electrodes from damage by means of its contact-free heat input. The even energy distribution at the laser focus melts the welded joint without overheating the material, thereby preventing pores from being formed. The outstanding feature of thelaser is that it gives rise to much greater freedom of design in terms of the development of new components and housings. Plastic laser welding services make it possible to join plastic housings with inner electronic components (which are often damaged or dirtied by conventional methods such as vibration welding or ultrasonic welding)with a low thermal and mechanical impact and zero contact.

Examples of application

Quasi-simultaneous welding in the electronics industry

A typical application, for example, is quasi-simultaneous welding – a form of transmission welding that is mainly used for the durable closure of plastic housings in the electronic industry. Highly dynamic scanner systems with a homogeneous circular focus lead to optimum beam guidance and correspondingly high-quality results. The contact-free heat input protects the sensitive components, while the quick heating, which is gentle on the material, leads to a homogeneous melt.

Transmission welding of automobile tailgates

Lightweight automobile tailgates made from plastic are produced via transmission welding using Laserline’s diode lasers. Their unique feature: the weld seams for laser welding plastic are not visible, and post-processing in the inner visible areahas become completely obsolete.