From Light to Lettering: Laser Marking on Silicones
The lettering remains even after the light has faded away: the use of a laser beam for purposes of marking and labeling – or simply laser marking – is an excellent method for high-precision, permanent marking on silicone products. Among its several applications, laser marking is used, for instance, on medical devices, cables or household goods – in other words, wherever distinct, razor-sharp and permanent labeling is required.
Series and batch numbers, machine-readable QR codes or barcodes, manufacturing and expiration dates are but a few examples of the various types of information that is to be included in the labeling on silicone products. The reasons for labeling are as varied as the products themselves. While shelf life, distinctiveness and preventing mix-ups are top priority for medical devices, the focus in other businesses may be on aspects such as tracking options, streamlined logistics, or ensuring copy protection and preventing counterfeiting and tampering. The marking itself, however, must always meet the same set of requirements: it should be easily readable by a human or a machine, and, above all, it should be permanent and durable.
Printing Does Not Always Serve the Purpose
Though silicone elastomers have many outstanding properties, they also have a weak point, and labeling by means of conventional printing techniques soon reaches its limit. In principle, it is possible to implement inkjet or pad printing techniques. Under certain circumstances, however, they may deliver poor results, for example blurred outlines, abrasion or dissolution of the ink upon contact with chemicals and exposure to UV light. In some cases, regular printers cannot reach the intended surface or, in other situations, the surface is totally unsuitable because it is too uneven, soft or flexible.
Light Is the Answer: Laser Marking
Laser marking is an excellent alternative for permanent, razor-sharp labeling of silicone parts. Laser marking is a non-contact process, whereby heat generated by the laser beam triggers a chemical reaction in the material. As there is no mechanical interaction with the target surface, marking thus takes place within the material itself and is therefore less sensitive to abrasion, heat, UV rays or chemicals. The process can be implemented even for translucent silicone products or curved surfaces, for instance on cables.
Advantages of Laser Marking:
- Non-contact, high-speed marking process that uses a laser beam to deliver precise and sharp outlines
- High-precision, high-contrast marking is achieved on a wide range of colored and translucent silicone products
- Excellent readability, even with small font sizes and intricate graphics or QR codes
- Permanently low level of sensitivity to wear, heat and chemicals
- Suitable for a wide range of shapes; can be implemented even on uneven surfaces, flexible components and hard-to-reach areas
- Requires no labels or solvents
The Lettering Remains Even After the Light Has Faded Away
All that is required for laser marking is a special polymer and a suitable laser. Generally, laser systems with an emission wavelength of approximately 1,064 Nm are used. Labeling is performed in a non-contact process, whereby the laser beam is directed onto the target surface for a short while. The heat generated by the laser beam triggers a chemical reaction which, depending on the composition of the laser-sensitive pigment, leads to discoloration or foaming of the substrate.
Laser systems with an emission wavelength of approximately 1,064 Nm (near-infrared range)
| Marking Laser Type | Typical Power Range | Typical Beam Speed | Typical Frequency Range | Typical Applications/Remarks |
|---|---|---|---|---|
| Vanadate (YVO4) | 6–40 W | 500–10,000 mm/s | 20–100 kHz | Marking stations, static marking |
| YAG | 6–40 W | 500–10,000 mm/s | 20–100 kHz | Marking stations, static marking |
| Fiber | 20-300 W | 500-60,000 mm/s | 20-400 kHz | High-speed marking, marking on the fly, easy integration in production lines |
Watch the time-lapse video demonstrating the laser marking process:
Laser marking on a 21 x 21 cm silicone panel (laser speed shown in time-lapse)
Not All Silicones Are the Same
Not every elastomer is automatically suitable for laser marking. Rather, special masterbatches developed specifically for laser marking systems are required. They contain laser-sensitive pigments that, for example, enhance the definition and contrast of the marking and thus improve readability. WACKER’s ELASTOSIL® portfolio includes three laser-compatible, ready-to-use masterbatches:
- ELASTOSIL® COLOR PASTE Laser Marking White – for white markings on dark substrates
- ELASTOSIL® COLOR PASTE Laser Marking Black – for black markings on light-colored substrates
- ELASTOSIL® COLOR PASTE Laser Marking Black TRL – for markings on transparent substrates
All ELASTOSIL® COLOR PASTE masterbatches can be combined with pigment pastes from the ELASTOSIL® FL and PT series so as to produce a wide range of colors for laser-marking silicone products.
Find Out More in Our “Laser Marking on Silicones” Webinar
In collaboration with Merck Electronics KGaA and König & Bauer Coding GmbH, WACKER conducted the “Laser Marking on Silicones” webinar in February 2023. Find out more about the latest developments in materials engineering and the application of laser marking technology in the webinar recording or download the presentation booklet.
Topics:
- Silicone elastomers and their properties
- ELASTOSIL® COLOR PASTE Laser Marking Masterbatches by WACKER
- Merck Iriotech® 8000 laser-sensitive pigment series
- Integration of laser marking in production processes