Webinar follow-up with Medagent: Questions and answers around the validation of a laser marking system

What to consider when validating my UDI marking laser system to be compliant with the regulations?" was the topic of our UDI Expert Talk on March 18, 2021 with Wolfgang Hirschauer from the consulting firm Medagent and Christian Söhner from FOBA. The speakers gave a comprehensive overview of all aspects concerning a validation of a marking system, a marking software and an entire marking process as well as of the quality management.

The large number of questions asked at the end of the presentation reflected the great interest of the participants. Unfortunately, due to time constraints, some questions remained unanswered. Therefore, we summarize questions and answers in this webinar follow-up.

A recording of the webinar from March 18, 2021 (in German language) is available at


Why isn't the complete reprocessing validated?

Wolfgang Hirschauer: The reprocessing must be included in the validation of the marking. FOBA has a case study on the durability of laser marking after multiple reprocessing. For reusable products, the IFU* should include information on the procedures for cleaning, disinfection, packaging and, if applicable, on the validated procedure for re-sterilization according to the country in which the product was placed on the market. This procedure must also be followed when validating the labeling.


*Instruction for use

Before verifying the process, the laser must be qualified. How can I perform the OQ if I cannot measure parameters such as laser intensity?

Christian Söhner: For the OQ (Operational Qualification) you need a power measuring device. Our service technician can perform the measurement, or you can purchase an appropriate device through FOBA.

Does laser marking always have to be validated, or is 100% verification sufficient?

Christian Söhner: It does not always have to be verified according to the standard. Reading back through the camera secures the process, and the code is verified online and permanently in the process. I also don't have to verify according to the standard every time: It is sufficient to verify at the beginning of a new product series and then at defined regular intervals in order to validate the entire process at the end.


Does the laser already have to be qualified for the process studies?

Wolfgang Hirschauer: Yes, definitely, otherwise the results may be subject to appeal.

How long does it take to validate instrument cleaning (disinfection/sterilization)?

Wolfgang Hirschauer:  That depends on the laboratory and would also have to be requested from the laboratories. It can take about four to five weeks.

At what interval should instrument cleaning validation be repeated?

Wolfgang Hirschauer:  If nothing changes in the process, the reprocessing does not have to be revalidated.

Does the UDI readability have to be revalidated, or is the first validation permanently valid for the scope under consideration?

Christian Söhner: Yes, that is correct, it must be revalidated.

What is the best way to prove the reprocessing cycles in terms of UDI durability? And is this part of the validation?

Christian Söhner: This can be proven, for example, by 25 cleaning cycles in steam sterilization or autoclave or also by reprocessing. And yes, such proof is part of the validation.

How can I ensure that a marking is still legible after more than 200 reprocessings if I do not know the reprocessing media of the "users"?

Christian Söhner: In this case, I can only be assured by unambiguous, clearly described instructions for use.

Can I also use the marking laser as a verifier?

Christian Söhner: No, the integrated camera can only verify whether the code is readable, not how qualitatively good the code is. Nevertheless, such a verification serves to make the process stable and secure – this is also important for a complete Trace & Track.

How are the parameters from the parameter overview from the application lab to be understood? There, line spacing and label repetition "S2" can be read out.

Christian Söhner: S2 means hatch fill with an angular offset. For example, the laser beam marks with the angle 0 degrees in the first step, then it has an angular offset in the second step "2".


Is scanning with commercially available scanners not considered in validation? Because sometimes it is the case that verified UDIs cannot be scanned in practice due to size or reflection, etc.

Christian Söhner: A classifier or, even better, a verifier is needed. How this will look later in practice is still an open question. Aesculap, for example, offers hospitals a verifier – I think it's from Steritrack.

Wolfgang Hirschauer: Verification of the code by the verifier assesses the quality of the code. By approving only a very good quality, the readability is ensured even with "normal" scanners in most cases. The minimum size of the code is prescribed by the guidelines (GS1).

To verify according to the standard, one would have to verify all items after the labeling process. Could FOBA's camera system be validated as a verifier for code readback, thus qualifying the camera system itself?

Christian Söhner: You don't have to verify all items individually, it's enough to verify the first "shot" of a new product, for example. The integrated camera verifies the UDI code online and continuously: This then serves as reliable proof of the entire code verification – and you can detect, document and react to ad hoc changes vs. the verification.

Is there any experience of the influence of EO sterilization on the quality of the UDI code or is it necessarily required to validate this?

Wolfgang Hirschauer: There are no known influences of EO sterilization* on the properties and durability of laser markings in the literature. Therefore, consideration of the marking can be dispensed with when selecting the worst-case product for EO sterilization validation. Only products that are very sensitive to temperature and humidity should not be sterilized using this sterilization method.


*Ethylene oxide sterilization (EO or ETO sterilization): In this process, EO gas penetrates both the packaging and the product itself and destroys all viable microorganisms. Applicable here is DIN EN ISO 11135:2020-04 (Requirements for the development, validation and control of the application of a sterilization process for medical devices).

Is there something like a "template catalog" in which parameter range I can start – depending on the material?

Christian Söhner: Yes, for this we have the Parameter Expert in the MarkUS marking software with reference values for each parameter. In general, I recommend selecting one to two worst-case products (three pieces each) for testing in our lab: The parameters determined by our team of experts in the application can then be loaded onto your marking system, so that you already have the first values stored in your MarkUS software upon delivery.


Is it necessary to specify the service life/autoclave cycle in the instrument IFU?

Christian Söhner: The precise description in the instructions for use of how the medical devices are to be reprocessed is important.

Wolfgang Hirschauer: For reusable products, the IFU* should contain information on the procedures for cleaning, disinfection, packaging and, if applicable, on the validated procedure for re-sterilization, according to the country in which the product has been placed on the market. It must be mentioned that the product may no longer be used if, for example, there are signs of material wear, or the maximum permissible number of reuses has been reached.

*Instruction for use

Is the laser marking compatible with the high pH values during cleaning? Is a defect catalog (e.g. corrosion) necessary?

Christian Söhner: In our six-month test with 500 autoclaving cycles, we selected the pH value of 14 in order to expose the material – in this case, stainless steel 1.4021 – to maximum stress. Result: The marking could be classified with an A throughout the process.

What is the influence of marking with a fiber laser on general biocompatibility as opposed to "engraving" with a laser. We have a FOBA system in use and are currently evaluating this point.

Christian Söhner: We clearly recommend annealing. This has a very positive effect on biocompatibility, but at the same time also on the readability and durability of the UDI code.

What standards apply to validating the readability of a UDI code?

Christian Söhner: For readability, we refer to ISO 29158 for Direct Part Marking (DPM) and to ISO 15415 for labeling. The minimum module size for GS1 codes is specified as 0.1 mm in order to obtain an AIDC machine readable code. The minimum size for clear text (HRI) is not defined in standards, but it should be documented how the readability has been tested.

Does the validation have to be repeated when the laser system is moved internally, or is that also covered by the risk assessment?

Wolfgang Hirschauer: For the most part, this is covered by a risk assessment. However, if components of the system are dismantled and reassembled after the move, or if the environmental conditions change, a risk assessment may no longer be sufficient. Re-qualification and/or re-validation should be examined.