Transparent-to-transparent laser welding: wavelengths, additives and joint geometries

Introduction to laser welding of transparent plastics

Laser welding of transparent plastics is a highly precise process that requires specific technologies and materials to achieve optimum results. This article highlights the essential aspects such as wavelengths, additives and joint geometries that influence the process.

Wavelength options: 1.94 µm and 2.1 µm

Choosing the right wavelength is crucial for successful laser welding of transparent plastics. While conventional wavelengths in the range of 800 to 1100 nm are used, specific wavelengths such as 1.94 µm and 2.1 µm offer clear advantages. Both wavelengths enable better penetration without the need for additional additives.

Advantages of the 1.94 µm wavelength

This wavelength is distinguished by its ability to penetrate deep into transparent materials and create uniform joints. It is particularly effective with plastics that have low absorption in the visible spectrum.

Advantages of the 2.1 µm wavelength

2.1 µm offers an improved absorption rate without colour additives. This wavelength is optimal for applications where absolute clarity and stability of the weld seam are required.

Additives for improving absorption

Additives play an essential role in increasing the absorption of the laser light. They enable the welding of transparent to transparent materials by efficiently absorbing the light energy and converting it into heat.

• Absorber additives: These additives are specially developed to absorb the wavelengths mentioned and thus facilitate welding.
• Nanoscale additives: By using extremely fine particles, the optical properties of the plastic can be modified without significantly impairing its transparency.

Joint geometries and their influence on weld quality

The design of the joint geometry is crucial for the quality of the weld seam. Round groove and V-groove designs are common geometries that promote an even distribution of energy.

Round groove design

This geometry enables an even distribution of energy and minimises stresses within the weld seam.

V-groove design

The V-groove design offers precise control over the penetration depth of the laser beam and is often preferred for complex components.

Test methods and leak-tightness verification

Specific test methods are required to ensure the quality of the welded components. Reliable seam inspections include both optical and physical tests.

• Optical test methods: Use of infrared cameras to analyse the temperature distribution and detect weak points.
• Leak-tightness testing: Pressure tests to confirm the integrity of the seam and ensure fault-free application.

Conclusion

Laser welding of transparent plastics requires a deep understanding of the processes and materials. By choosing the right wavelength and the targeted use of additives, production quality can be significantly increased.

Further information on plastics in industry.

Frequently asked questions

What advantages do the wavelengths 1.94 µm and 2.1 µm offer in laser welding?

These wavelengths enable deep penetration without the need for colour additives, which leads to a clearer and more stable seam.

Which additives are used in laser welding of transparent plastics?

Typical additives are absorber additives and nanoscale additives that increase light absorption without significantly affecting transparency.

What are typical joint geometries in laser welding?

Round groove and V-groove designs are common geometries that support efficient energy distribution and high seam quality.

How is the quality of the weld seam checked?

The quality is checked by optical test methods such as infrared cameras and physical leak-tightness tests.

Why are additives important in transparent to transparent laser welding?

Additives increase the absorption of the laser in the material, which is essential for seam formation in transparent plastics.