Using drop test simulation to de-risk a drug delivery device

Challenge

Our engineering team used finite element analysis (FEA) to improve the understanding of a drug delivery device during a drop test and build confidence in the design. This would allow for cost-saving before prototyping and tooling.

Approach

Our mechanical engineering team used the ‘explicit dynamics’ functionality of the Ansys FEA software to investigate a typical device robustness challenge. We simulated a drop using a 3D model of a prefilled syringe. The team later compared the predictive results of this simulation to high-speed video footage of a real device.

Outcome

The simulation predicted the drop test performance accurately which was validated by the high-speed video footage. The simulation technique was used to build confidence in the design, saving cost in the long run.

Cost efficient simulation of a medical device drop test

Drop test performance is an important aspect of medical device robustness and reliability. Physical prototypes can be costly, especially if they need to be produced by injection moulding to reflect true physical properties, so simulation allows project teams to de-risk the design before a significant cost investment is made.

Historically, simulating complex issues with devices was time consuming and produced results of questionable accuracy. So the application of simulation techniques needed careful consideration, it was important to avoid simulating everything you could. Recently, advanced simulation techniques, such as ‘explicit dynamics’ (which simulate very short, highly transient events), are less time consuming and more accessible. This is opening new areas of investigation in the development of medical devices such as drop test simulation. These kinds of analysis techniques – in silico representations of physical systems – are sometimes referred to as ‘digital twinning’.

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Demonstrating a drop test for a prefilled syringe

Our simulation experts performed a drop test of a prefilled syringe. The key risks we wanted to qualify were:

• would the glass vial experience cracking under stress?
• would the locking mechanism auto-trigger on impact if it experienced enough deformation?

The team created a 3D CAD model specifically optimised for this analysis and applied relevant loads and constraints. We performed a simulated drop from one metre and observed the stresses and deflections in the 5-millisecond time period immediately after impact.

The explicit dynamic analysis can reveal a huge amount of detail about how your device behaves. However, even a simple simulation model can take hours to solve per millisecond of simulation time, so you have to apply these techniques appropriately. Part of the skill of engineering analysis is getting the most out of the tools for the least effort and minimum cost.

Charlie Lowndes, Senior Engineering Consultant, Team Consulting

To prove the accuracy of the simulation, we validated the result by carrying out a physical experiment in the lab. Our team dropped the same prefilled syringe used in the 3D model using a bespoke test rig which allows precise control of the drop orientation. The test was filmed at 10,000 frames per second so that the behaviour of the syringe could be visualised. The results of our simulation matched the high-speed video very closely.

Outcome

This demonstration showed that drop test simulation can be used to de-risk designs much earlier in a project than was previously possible. The benefit of FEA is that a wide variety of scenarios and design concepts can be tested quickly which is cost-effective in the long run.

 

 

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