IVD Device | Design Optimisation, DFM & DFA

The project had already reached a reasonable level of design with a 3D printed prototype produced, so the core challenge for HD was to re-design the product’s housing and larger internal components, making all parts suitable for reliable manufacture with a higher quality look and feel.

Other considerations included making the device suitable for its various intended environments of use from rural Africa to fast throughput airport security points. Generally, all components needed to comply with low volume manufacturing requirements. HD were also tasked with reducing the overall mass of the device. In addition, considerations were made to improve airflow and cooling while preserving the original aesthetic of the design.

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

Having received initial CAD models of the prototype, HD undertook a Critical Design Review (CDR) to identify each of the components requiring improvement. By doing so, areas of the design which required further attention for effective DFM (Design for manufacture) were highlighted. 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 HD questioned and made alternative suggestions for. Part of the revised 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 HD did, made tooling considerably simpler, more reliable and, cheaper to manufacture too.

Throughout this project, a large majority of the communication between HD and the client, was done remotely by using detailed CAD models in Teams to demonstrate and discuss the purpose for changes and how they would impact the DFM as a result. HD also consistently performed FEA throughout the project, which allowed the team to test a number of design changes allowing them to optimise and validate the design. Using FEA allowed HD to demonstrate the extent of work done to eradicate unnecessary material and make the design as rigid and light as possible. During this process, the design was constantly optimised 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 cutters such as routers and drill bits. The previous design would have required the creation of multiple bespoke machining tools for no reason and therefore add unnecessary cost. HD ensured that all clearances for components were enlarged and removed any legacy design features which were no longer necessary.

HD 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 assembly methods, key components were refined to be manufactured into one moulded part. Through conversations with the client, HD 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 prototype design also required multiple cosmetic strips which were adhered to the top and therefore highly visual. Predicting that these would be difficult to fit accurately and to adhere reliably, HD suggested they were made into one part to 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 crowded with electronics however, there had been little consideration for DFM in this area at the prototype stage. So, HD took this part, shelled out all of the unnecessary areas, then designed in clips to improve and better utilise the space available. Even thicknesses and fixing points were applied and with a lot of injection moulding experience, HD optimised the part for simplified tooling and manufacture.

HD’s understanding of design for manufacture and assembly (DFM & DFA) meant they were able to add significant value to the project in very compact and complex areas, densely packed with electronic components and wiring.  They 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 the HD team consider across all projects as it provides benefits beyond those listed and considers end of life for the product too.

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