Pharmaceutical & medical
Strict regulatory requirements for qualification and validation are aimed at supplying faultless medical devices and keeping patients safe. Credit: Kistler Group
The rapid route to transparent validation
temperature, so the curves are compared in a series of consecutive adaptation steps. As this sequential process proceeds, the operator can see whether and how individual machine setting values affect the cavity pressure. Process optimization continues until the new operating point precisely matches the reference cavity pressure, or until the user personally judges the result to be satisfactory.
Using cavity pressUre and statistics to define process windows
Once the process has been tracked back to the right machine, the search for a stable process window can be launched on the qualified machine. Finding a suitable window is the starting-point for
the final stage of process development: this is a very time-consuming stage of the overall validation procedure. The first step is to generate extensive test plans (known as DoE, or Design of Experiments) which are then loaded and worked through to determine how the machine settings influence conditions directly in the cavity – as expressed by the cavity pressure profiles. A vast body of data has to be recorded and statistically evaluated to identify the relationships between machine settings and part characteristics. Together with the Stasa QC software, technology from Kistler makes it possible to examine these process windows efficiently at shop-floor level. DoEs are then generated and transferred into the Stasa QC software. Automatic recording of the relevant cavity pressure curves is handled by the ComoNeoPREDICT functionality of the ComoNeo process monitoring system. The data is now fed
back into the Stasa QC software, which uses it to generate a statistical quality prediction model. The completed model simulates the relationships between machine parameters and expected part attributes. In conjunction with ComoNeoPREDICT, users can then have these expected quality characteristics specified directly on the machine without actually measuring them. Due to this approach, the part's quality can be predicted even before it has been manufactured. As well as its benefits for validation, this method yields a major advantage during production: with the help of the quality prediction model, automatic separation of good and bad parts can be implemented directly on the machine – together with all the documentation that is required. Monitoring of the injection molding process based on cavity pressure measurements has long been established in many industries; nowadays, use of this technology is also becoming more widespread in the medtech sector – especially in response to increasing regulatory requirements for documentation and traceability. Cavity pressure is a universal process variable that provides complete transparency about the process of creating the plastic parts. Thanks to the advantages it offers, manufacturers can use cavity pressure as a differentiation instrument in the various phases of validation, all the way through to production monitoring – helping them to meet demanding requirements with maximum efficiency.
Thanks to the ComoNeoPREDICT functionality, the quality of a part can be predicted even before it has actually been produced. Credit: Kistler Group
Instrumentation Monthly June 2021 Kistler Group
www.kistler.com 19
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