Many stainless steel medical devices are used repeatedly. For tracking and traceability, they must be permanently marked with a contrasting mark. This mark is usually created by laser marking.

The basic requirements for standard laser marking are demanding. Laser marking can meet many demanding requirements:

Marking of medical devices using nanosecond lasers

Nanosecond fiber lasers are commonly used for marking metals. These lasers allow fast and inexpensive metal marking, but do not provide ideal results for medical applications. The classical ns laser marks metal using heat. This means that the laser beam creates a liquid metal phase on the surface of the product in which chromium diffuses. On the surface of the material, chromium (Cr) and iron (Fe) are oxidized to form various oxides. This will separate the different elements of the alloy and change it irreversibly.

Advantages and disadvantages of nanosecond lasers for marking stainless steel

Advantages

Disadvantages

The intensive change in material properties also leads to a reduction in the ability to resist corrosion.

Reference samples created using a nanosecond fiber laser system. Samples of steel types 1.4301 and 1.4016 after 72 h at 50 °C after spraying with a 5% NaCl (salt water) solution. Without passivation step. Laser settings: pulse length 200 ns, max. average power 20 W.

The use of USP lasers allows the limits to be overcome.

USP lasers are the solution to corrosion and marking legibility problems. Ultra-Short-Pulse lasers minimize the thermal impact on the product and create changes in the surface structure by the LIPSS (Laser Induced Periodic Surface Structure) method. The very short pulse duration limits the liquid phase of the marking, thus limiting the diffusion of elements and therefore no oxidation of Cr and Fe on the product surface or changes in the surface structure. The structure is formed as a result of the high peak power of the laser.

Advantages and disadvantages of USP lasers for marking stainless steel

Advantages

Disadvantages

Scanning electron microscope (SEM) view of laser markings created by picosecond laser. The dark mark is created by a combination of nanoscale surface structuring and oxides.

Corrosion behaviour ps USP of laser marks on SuS

Different marks formed by picosecond laser after 72 h at 50 °C after spray test with 5% NaCl (salt water) solution. Initial passivation has no effect on marking contrast or corrosion behaviour. A wide range of parameter sets can be used for marking.

For markings made with a picosecond laser, passivation is also not a problem.

The UDI mark easily survives the passivation process (7% Citrisurf 2250, 20 min at 50 °C) and repeated sterilization in an autoclave (50 cycles)

For marking medical devices, complete laser systems can be used, i.e. complete laser workstations or laser subsystems. Laser subsystems contain only the laser source, the process laser head and other necessary components. This makes them suitable for easy integration into larger production lines.

Examples of applications in medical device manufacturing

Ready for the future

Coherent Black Marking lasers are ready for unique identification of each device using UID codes. A complete system can include creating databases of codes and importing them into the laser, actual marking of the codes on the product, and subsequent verification of the marked code including archiving of the report.

Not only medical device applications...

... and not just stainless steel. However, USP lasers can find applications not only in medical device manufacturing, but also where precision marking is required with minimal heat impact on the material. The USP laser can also be used to mark:

The same laser and optical configuration can also be used for marking other materials, saving costs and increasing laser usage and efficiency.