Laser transmission welding of plastics is dependent on a laser-transparent and laser-absorbing joining partner, which are connected in an overlap weld. Usually, the necessary optical properties are adjusted by additives. In the simplest case, carbon black is added to the absorbing component, while the transparent part remains unfilled.
What works simply and well in technical applications does not necessarily have to look appealing in design-oriented consumer goods or medical products – colour accents are required. Since the early days of laser material processing, colorant manufacturers have therefore been working on special additives that ensure the required optical properties of the joining partners in the range of the laser wavelengths used and at the same time enable a wide variety of colours in the visible range. Today, a wide range of colours is available – from laser-transparent black to laser-absorbing white.
Nevertheless, any deviation from the classic “natural – black” combination of the joined parts represents an increased complexity for the welding and manufacturing process of the components. In particular, combinations of the same colour are a challenge, which should convey exactly the same color impression and at the same time have different properties for the laser radiation. Laser-absorbing additives can also have an influence on the surface or the processability of the polymer and – like other material additives – must be approved, for example in medical technology. In order to circumvent these disadvantages, developments in laser systems technology make it possible to leave away laser-sensitive additives by a clever variation of the through transmission welding principle and under certain conditions. EVOSYS has been working on this for a long time and has already successfully implemented such colourful projects. But even if a laser-absorbing additive is necessary, we can fall back on a network of established colorant specialists – we are happy to provide you with competent and comprehensive advice.