Laser Welding and Laser Marking of plastics

LASER WELDING

As a specialist in the conditioning of technical plastics, we are interested in innovative processing techniques for our products so that we can always offer our customers the best solution for the use case. Laser welding in an innovative joining technique for plastics and offer advantages that cannot be achieved with any other process at this time. In plastics, laser welding generates a very clean weld seam that does not leave behind any residues and loose particles around the seam. This fact makes the procedure especially interesting for the manufacture of medical devices where the highest demands are placed on material and function. In contrast to ultrasonic welding, laser welding procedures also permit the jointing of components with electronic parts, without compromising or destroying the properties of these parts. We test our products for their suitability for laser welding at our company innovation centre and so can always provide you with the optimal product for your use.

LASER MARKING

Laser marking is an innovative procedure for precisely labelling a wide variety of materials such as wood, paper or leather. In order to mark plastics with lasers, one needs as a general rule, depending on the use case, to develop the correct plastic compound for the end product, which will be subjected to the laser marking procedure in the course of constant development tests. Treffert here offers both the know-how for developing laser-markable plastics and the option of making extensive tests on the plastics at six different lasers in our own innovation centre. This makes it possible to considerably reduce the development time for laser markable plastics depending on the use case. If you are interested, just submit a query online or contact our application engineers and let them consult with you about the topic of laser marking at your business location.

 

Laser Welding for Plastics –

The Modern Joining Procedure for Many Areas of Application

Questions and answers about Laser Welding

Why Laser Welding?

Every new technology must have strong arguments to replace established methods. Why use lasers for plastic welding? There are four significant arguments:

  • Laser welded joints resist high mechanical loads, they are gas tight and often achieve the same strength as the base material.
  • With lasers, almost any kind of seam weld contour can be realized and there is a solution for nearly every workpiece geometry.
  • Minimal thermal and mechanical stress input is applied: What you weld is what you see. The welding is so precisely localized, that even
    sensitive components very close to the weld remain unaffected.
  • The results are surfaces with perfect quality, no micro particles, glue or roughness.
Four factors for success

As with any other process, laser welding of plastics needs specific conditions to be a success.
There are the following key factors:

  • Choice of suitable polymers, additives and pigments.
  • Use of the right laser source with suitable optics.
  • Appropriate joint configuration and small gap width.
  • Optimized clamping technology, allowing free access of the laser beam to the seam and applying sufficient pressure on the components.

What can be welded?
In summary, all thermoplastics and almost any thermo-plastic elastomer, unfilled or filled can be welded. For example, in current applications, polymers with a glass fibre percentage of up to 30% are laser welded. Also different kind of polymers can be joined without problems – provided they are chemically compatible and the two melting temperature ranges overlap sufficiently. Some examples of materials, which can be welded:

PE, PP, PS, ABS, SAN, PA6, PA6.6, PC, PMMA, PSU, PEEK, PET, PBT…

There is also a rule of thumb for natural materials: What you can weld ultra-sonically can also be laser welded… and many more.

Laserwelding of polymers is already successfully used in numerous applications: in the automotive, electronic and telecommunication industries, medical device technology, human care and household devices.

Process overview

Low heat conductivity and viscosity of polymers means that the most practical welding geometry is overlap welding. Here, the laser beam penetrates the upper material and is absorbed by the lower material. The heating of the latter leads to plastification which bridges the work-piece gap and melts the upper material by heat transfer. Therefore, having a small work piece gap is an important success factor.

Laser light penetrates the upper layer and is absorbed by the lower material (A). The melting of the latter transfers (B) the heat to the upperlayer (C). The mutual melting pool solidifies under external pressure to a high-quality weld (D).

Which laser source?

The wavelength is the decisive feature in determing which laser is the ideal one for polymer welding: diode lasers, Nd:YAG or fibre laser. Apart from the difference in wavelengths and the absorption behaviour of certain pigments, the following rules apply:

Nd:YAG lasers are particularly suitable for welding seam widths below 1 mm and for plane welding geometries with scanner head applications.

The new fibre laser demonstrates high reliability and long lifetimes along with high-energy efficiency in comparison to the YAG laser. Further advantages are
their compact size and there are also no consumable costs.

Diode lasers, however, are preferred for wider welding seams, circular seams and simple spot-welds.

Contour & quasi-simultaneous welding

These two processes show presently the best market presence. With contour welding, the laser beam follows the welding seam, similar to metal welding. Almost any work piece size can be welded. The limits for this technique are set by the tolerable gaps. With quasi-simultaneous welding, the laser beam passes over the entire welding contour several times very rapidly. Beam deflection is done using galvo scanning heads and therefore higher beam quality is essential. The entire welding path melts quasi-simultaneously due to heat buffering and allows the layers to move against each other easily. The pressure on both layers and a suitably designed sacrificial region can bridge larger gaps. On the one hand, quasi-simultaneous welding requires higher laser power; on the other hand, it allows even distortion-free energy input.

Transparency and absorption

All commonly used polymers are more or less trans-parent in undoped condition in the infrared wavelength range of the laser sources (except CO2 lasers). Filler materials, like pigments, provide for the absorption of laser energy. Many colour pigments absorb within the infrared range and can be used for laserwelding. Even simpler, and therefore most common, is the use of carbon black particles acting as absorbers, typically in a concentration of 0.05 – 0.5 %. However, this results in darker colours. There are already standard solutions for black-black and transparent-black welding availabe.
For clear and bright colours, colorants, which are flexible in use, are also available. They absorb only within a certain wavelength range and have no significant influence on the colour. The slight colour changes due to the additives can be adjusted by colour matching.

Most polymers (lighter blue curve) are usually transparent or translucent in the visible and near IR range. By adding pigments (darker blue curve), suitable absorption of the laser wavelength is achieved.

Even colored and also transparent
Black, colored, transparent, white … In this order, the complexity of process requirements for laserwelding of polymers increases. Applications with black material, acting as absorber, are usually easy to realise or already available as a standard solution. For welding of colored polymers, the necessary pigment combinations are customised in laser transparent and laser absorbing form – a typical task for the experienced masterbatcher.

Welding of light-colored or transparent polymers, which is particularly required in the medical device industry, is successfully achieved with CO2 laser in the case of welding thin films or more general by using the above mentioned laser absorbing high performance additives.

Those have to exhibit high absorption efficiency at the appropriate wavelength and low color impression in the visible range as well as various additional
characteristics: the know-how of an innovative worldwide operating masterbatcher ensures optimum results. Titanium dioxide presents particular problems in relation to beam scattering and low transparency and requires customised solutions for white-white welding.

Increasing degree of complexity in overlap welding of polymers. For many applications an experienced partnership between additive producer and masterbatcher is of great advantage.

Easy to compensate residual color with high NIR absorption efficiencies
With its tailormade surface properties, the hybrid nano-pigment Lumogen® IR 1050 gives perfect migration stability and matrix compatibility in all thermoplastic polymers. Its supply form as a pre-dispersed suspension in a thermally and chemically inert carrier guarantees perfectly homogeneous distribution and extremely low scattering values in every polymer.

Another highlight of this innovative product family is the weak, easy to compensate residual color in the visible, in combination with very high absorption effi-ciencies in the Near Infrared (NIR). All members of the Lumogen® IR product line are non-ionic, free of halogen and heavy metals, and toxicologically harmless: excellent preconditions for their use in the medical device industry and other sensitive applications.

Coloring: a factor of success
To find the ideal color formulation, the desired color together with perfect laserwelding characteristics are the two key factors. For that, it takes a specialist with the knowledge and experience of hundreds of thousands of formulations and with a sophisticated laboratory equipped with modern extrusion lines. Color samples submitted by the customer are the basis for the creation of masterbatches. The masterbatch is easy to process, optimally dispersed and identical in color. If requested, the original material can be conditioned, which means it is used as the carrier material for the masterbatch. The characteristics and the authorization of the original material are thus retained to a large extent.

You can call up the information from question and answers here as a brochure:

Laser Welding (PDF, ca. 0,5 MB)

Sample products for laser welding and laser marking

Contact Person

Our Application Engineers


Germany


for the regions of Rhineland-Palatinate, Saarland and Baden-Wurttemberg:

Eric Strauß
Dipl.Wirt.Ing. (FH)
phone: + 49 (0) 67 21 403-78
‣ Contact


for the regions of Nordrhein-Westfalen, Lower-Saxony and Bremen:

Martin Ebenhög
Dipl.-Ing. Chemieingenieurwesen
phone: + 49 (0) 67 21 403-69
‣ Contact


for the regions of Bavaria and Hesse:

Sascha Klamp
Technischer Betriebswirt
phone: + 49 (0) 67 21 403-80
‣ Contact


other regions:

phone: + 49 (0) 67 21 403-24
‣ Contact


France


for the region of Eastern and Northern France:

Guillaume Fenyes
Technico-commercial
phone: + 33 (0) 3 87 31 84 85
‣ Contact


for the region of South France:

Richard Renaudin
phone: + 33 (0) 3 87 31 84 82
‣ Contact


other regions and export:

Marc Marchand
Ingénieur A. et M.
phone.: +33 (0) 3 87 31 84 87
‣ Contact


for the regions of Western France and Île-de-France:

Murielle Berthier-Heinle
phone: + 33 (0) 3 87 31 84 86
‣ Contact