Patient safety is the highest priority when developing medical devices and therefore thoroughly testing a device to understand how it performs, what its limitations are, and when it will fail are very important.

There are several ways a device can be understood; from using well understood legacy components, to physical testing and more recently computer simulation (FEA).

Physical testing can provide limited insight into what is happening within a device. For example, during drop testing the device needs to be fully assembled, so if an internal component is breaking or the device is disassembling it can be difficult to understand what has happened. With FEA the outer components can be hidden, or the device sectioned so that internal components are clearly visible. 

Time saving due to quick iteration in FEA prior to getting components manufactured: by analysing multiple design variations quickly through FEA simulations, medical devices can be optimized for enhanced performance, durability, and patient safety before physical production of components to do physical testing with. 

On top of iteration is the requirement to understand how device components will function at the upper and lower bounds of their tolerance range. To do this with physical testing would require components to be manufactured at upper, lower and nominal design limits, likely requiring a tool to be manufactured for each size which takes considerable time and expense to do. Instead, we could test the components in FEA and quickly adjust geometry sizes to understand what effect the variation has on the device performance. 

Medical Device Design Engineer conducting finite element analysis study on autoinjector medical device component (FEA)

For complicated materials such as polymers, material models are notoriously difficult to find with some suppliers not publishing any data other than yield. For accurate FEA results it’s best to develop your own material models or benchmark the study against existing physical data. Something to be aware of is even though a detailed datasheet may exist for a material, when a component is moulded the layout of molecules may produce different results to a common tensile test sample. 

FEA can help find small areas of the design that can lead to large failures. Such as corners requiring radiuses where without, stress concentrations occur. It maybe that due to tooling limitations radiused corners in some areas may not be possible, therefore a redesign may be required or discussions with the tooling manufacture to understand how the tool itself can be redesigned to allow for stress reducing features to be added. 

It’s important to remember the limitations of your manufacturing processes and design for manufacture even when using FEA to iterate your design. When stresses are high in areas it’s natural to think that thickening that area will solve this issue. However, with some injection moulded plastics this may actually lead to a weaker component, either due to residual stress after moulding, or because voids have formed within the component as the area was too large to fill properly. There are lots of tricks our engineers use for reducing stress in components for increased safety and life without introducing manufacturing issues. 

FEA and simulation tools are valuable to ensuring patient safety in the design of medical devices. By predicting and evaluating device performance, assessing material properties and durability, optimizing design for safety and reliability, simulating worst-case scenarios, and validating design changes and regulatory compliance, FEA and simulation can help prevent failures, minimize risks, and accelerate the development program.

Get in touch to learn more and discuss how HD can help accelerate your medical device development through FEA.

Jack Dunkley CEng - Medical Device Engineering Director at Haughton Design Jack Dunkley CEng 31 July 2023

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Get in Touch with Jack Dunkley CEng

Engineering Director

Jack is a chartered engineer who holds a Master’s degree in Mechanical Engineering from Cardiff University. He has experience working with design for injection moulding, machining and sheet metal as well as design for assembly and serviceability. Prior to HD, he worked at metrology company Renishaw for 6 years where he led several complex mechanical projects from initial concepts through to production. He has also worked at electrosurgical medical device manufacturer Olympus Surgical Technologies Europe (Gyrus ACMI).

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