The benefits of designing medical devices for manufacture & assembly - an IVD case study

The benefits of designing medical devices for manufacture & assembly – an IVD case study

By 31 March 2021 News No Comments
A Design Engineer working on a computer with a CAD model of an IVD device on screen - he is optimising the design for manufacture and assembly.

When working under strict regulatory requirements such as in Medical Devices and IVD development, it’s critical that the manufacturability of each part of a device is considered for its intended purpose. Therefore, it is worthwhile involving people who have extensive experience in Design for Manufacture (DFM) and Design for Assembly (DFA) from the early stages of a project. Whilst a design may look beautiful in a sketch, if it isn’t manufacturable then it will never have its intended impact. Similarly, if a product looks fantastic but is badly assembled, that can lead to increased costs and lower quality, unreliable products.

Recently, we supported a client in the IVD industry needing help with the manufacturability and assembly of a portable device. Not only did our work allow the client to trial the device worldwide but, our materials knowledge and vast experience of DFM made for smarter assembly, reduced build time and, a higher quality product.

The project had already reached a good level of design with a working prototype before our involvement, but the core challenge for Haughton Design was to re-design the product’s housing and larger internal components, making all parts suitable for reliable manufacture and a higher quality look/feel for the device. Other considerations included making the device suitable for its various intended environments for use from rural Africa to fast throughput airport security points. Generally, all components needed to comply with low volume manufacturing requirements and we were tasked with reducing the overall mass of the device too. In addition, we were to make considerations for improved airflow and cooling while preserving the original aesthetic of the existing design.

Our approach began by undertaking a detailed immersion stage, focusing on the design provided to us. It was important for us to understand the role and function of each component before making any DFM changes. This included a site visit to the client’s laboratory, fully understanding the device function, as well as asking a number of exploratory questions to truly understand our client’s needs.

Having received the initial CAD models, we undertook a Critical Design Review (CDR) to identify each of the components requiring improvement. Through doing so, we were able to highlight areas of the design that required further attention for effective DFM. This included areas which required considerable redesign due to undercuts and insufficient mould tool draft etc. These are features which often lead to problems in the moulding process, assembly of components and the reliability of a product or medical device. There were also some bulky areas of plastic which we began questioning and making alternative suggestions for. Our brief was to enhance the product’s manufacturability while simplifying the design with the aim of creating one tool to suit different component configurations.  Achieving this, which we did, made tooling considerably simpler, more reliable and, cheaper to manufacture too.

Throughout this project, a large majority of the communication between ourselves and the client, was done remotely through detailed CAD models to demonstrate and discuss the purpose for our changes and how they would impact the DFM as a result. We also consistently performed FEA throughout the project, which allowed us to test a number of design changes to optimise and validate our design. Using FEA allowed us to demonstrate the extent of work done to eradicate unnecessary material and make the design as rigid and light as possible. During this process we constantly optimised the design to consider ease of build and appropriate manufacturing tolerances too.

Following general machining guidelines, elements of the previous design needed redesign for cost effective manufacture, which meant associated components were affected too. In most instances changes were required to suit standard machining tools. The previous design would have required the creation of multiple bespoke machining tools for no reason and therefore, unnecessary cost. We ensured that all clearances for components were enlarged and removed any legacy design features which were no longer necessary.

We also changed some of the materials and manufacturing processes from sheet metal to injection moulding, improving the assembly, reducing labour time and, improving the general quality of the product. Instead of manufacturing multiple parts, with different production processes, we were able to refine the key components to be moulded in one part. Through conversations with the client, we also recognised that poor access to key components within the product was a user frustration as they had to take the whole product apart. So, we built in an access panel, improving maintenance with no detriment to the assembly or cost of the product.

The existing design also required multiple cosmetic strips which were adhered to the body making them highly visual. Predicting that these would be difficult to fit accurately and to adhere reliably, we suggested they were made into one part to also act as a barrier to dust and water, again improving reliability and quality. This was a big manufacturing improvement, again made by just one tool rather than a number of parts which had to be manually positioned and stuck down.

As mentioned previously, the aesthetic of the initial design had already been signed off which meant it was necessary to work within certain parameters. One of which being a docking station which the battery powered device sat upon. It was important that the device not only matched the docking stations’ aesthetic but, fitted and located securely to enhance the perceived quality of the device.

Inside, the product was packed out with electronics – it was quite unbelievable how many components it contained! However, there had been no consideration for DFM in this area at all. So, we took this part, shelled out all of the unnecessary areas and designed in clips to improve and better utilise the space available. We applied even thicknesses, fixing points and with a lot of injection moulding experience, we were able to optimise the part for simplified tooling and manufacture.

Our understanding of design for manufacture and assembly (DFM & DFA) meant we were able to add significant value to the project in very compact and complex areas, densely packed with electronic components and wiring.  We were able to remove loose wiring clips and improve routing by providing additional features within the moulded parts to enhance wiring and assembly at no additional cost to the moulded components. Design for assembly (DFA) is something we also consider across all projects as it provides benefits beyond those listed and considers end of life for the product too.

Ultimately, our work provided a number of benefits for the client. Not only did it allow for the device to be manufactured in low volume for clinical trials but, our materials knowledge and experience of DFM made for smarter assembly, improved durability, reduced labour time and, a higher quality product of increased perceived value.

Hopefully, this insight shows the benefits of good DFM practice and, the importance of these considerations when designing IVD’s, medical devices and products too. Please get in touch if you’d like to discuss more about how we can help you.