Plastic-welded component processed with the TRUMPF laser

Laser plastic welding

High-quality, reproducible, and completely without solvents – laser-based joining of plastics has many advantages and replaces traditional processes in many industries such as adhesive bonding and ultrasound or vibration welding. When joining using a laser, the weld seam can also be adapted to new component geometries as desired. Since the heat input is severely limited locally, delicate electronic components are protected effectively, for example. A distinction is typically made between four versions of laser welding for plastics: contour welding, quasi-simultaneous welding, simultaneous welding, and mask welding. When it comes to plastic welding, laser powers of up to approx. 300 watts are generally used.

High quality and reproducible

The weld seams are of a consistently high quality. The strength of the seams produced corresponds to that of the base material.

Flexible

The weld seam can be adapted to various component geometries as desired.

Residue free

Compared to adhesive bonding or vibration and ultrasound welding, no adhesive residues or plastic flakes are created when laser welding.

Gentle

The heat input is restricted locally and is gentle on delicate electronics.

Low noise and wear

Laser plastic welding is not just gentle for the material, but also for the environment.

How does laser plastic welding work?

When laser welding plastics using the transmission welding method, two types of thermoplastics are joined with one another: the laser passes through the transparent mating part and the absorbing mating part is heated. The absorbing plastic melts the transparent joining area. The mating parts must be pressed together using a suitable fixture in order to ensure sufficient heat transfer. As far as possible, the gap should be smaller than 150 μm here. In order to ensure a permanent connection, the melted plastic must solidify completely. The fixture therefore continues to press the two mating parts together for a given holding time after the actual welding process.

Which plastics can be welded using a laser?

The weldability of the various materials is shown in the material pairing matrix. Plastics of the same type have the highest level of connection stability after laser welding. If the plastic contains a high proportion of glass fibers, this may result in somewhat brittle welding connections. It is therefore recommended that a glass fiber content of 40% is not exceeded. A laser-transparent material with glass fiber should not be thicker than 2 mm.

What has to be taken into account when laser welding plastics?

Since many weldable thermoplastics only absorb a small proportion of the laser radiation from solid-state lasers, additives such as soot are added. The thermoplastics can therefore be melted and welded by the laser radiation. In order to ensure the reproducibility of the welding processes, a suitable receptacle also has to position components in a reproducible manner. The joining force is established by pressing the component against a conformal clamping device or a special glass. While exhibiting a high level mechanical stability, the glass has to let the laser light through.

The three laser transmission welding processes compared

Skizze Prozess Kunststoff Konturschweißen

Contour welding

During contour welding, round parts in particular are rotated at up to 25 m/min under a laser beam. The contour to be welded here is traveled along and heated up with the laser beam. Besides round parts, large three-dimensional components are also ideal for contour welding. The biggest problem with this process is that stresses may occur in very bulky components since the contour of the component to be welded is not heated up simultaneously.

Simultaneous welding

In the case of simultaneous welding, the laser beam is formed so that it adapts optimally to the component. In this manner, the contour to be welded is heated simultaneously. The result is very short process times of only around 100 ms. Components that have a low level of complexity and are produced in high quantities are particularly suitable for this process. However, if the component geometry changes, the form of the beam also has to be adapted.

Quasi-simultaneous welding

In the case of quasi-simultaneous welding, a scanning laser beam heats up the welding contour. Since the laser beam circulates at up to 15 m/s (900 m/min), it works so quickly that the contour is heated almost simultaneously before it has the chance to cool down. The programmable focusing optics allow you to react to changing welding contours quickly – this is a clear advantage compared to simultaneous welding.

Typical areas of application for laser plastic welding

TRUMPF plastic welding application filler cap

Contour-welded tank cap

In contour welding, a rotationally symmetrical component is rotated under the fixed laser beam. In this manner, a tank cap can be welded, for example.

TRUMPF plastic welding application quasi simultaneous buckle switch

Quasi-simultaneously welded seat belt buckle switch

In the case of quasi-simultaneous welding, contours are traveled along in rapid succession with scanner optics. This therefore means that each point along the contour is heated at almost the same time.

TRUMPF products for laser plastic welding

TRUMPF offers you the complete solution for plastic welding. You are provided with the laser, focusing optics with sensor system, and laser machine (with fixture upon request) all from a single source and perfectly adapted to your specific application.

TruDiode

The TruDiode diode lasers enable non-contact welding of thermoplastics by means of transmission welding.

To the product

Processing optics

TRUMPF provides the complete optics range: from fixed optics for contour welding and ring optics for simultaneous welding to scanner optics for quasi-simultaneous welding of plastics.

To the product

Temperature control

Our integrated temperature control ensures a consistently high heat input across the entire seam point.

To the product

Seam joint monitoring, TRUMPF sensor system

Melt travel monitor

The integrated seam joint monitoring monitors the lowering of the component during laser plastic welding. The laser is switched off after a defined melting of the material.

To the product

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Sensor system

As a complete system provider, TRUMPF also supplies process sensor systems. The continuous process monitoring increases quality and enables you to control your process accurately and reliably.

Processing optics

As a result of their modular system, TRUMPF processing optics can be adjusted to suit different applications and spatial conditions.

Laser welding

Laser beams open up new possibilities for joining metals and plastics. They can even weld materials with a high melting temperature and high heat conductivity with utmost precision.

Service & contact

Contact

Sales Laser Technology

Phone +1 734-454-7200

Laser plastic welding flyer

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