Prototype Development in Medical Device Design
Managing risk throughout product development processes
There are so many descriptions, purposes and uses for prototypes within product development, but the primary purpose of all remains unchanged: to prove a certain set of criteria at the earliest appropriate stage with the quickest and cheapest methods in order to push risk upstream. User Researchers often use storyboards to prototype workflow changes to help understand users’ tolerance to change and configurational mockups are created by Designers, which are used to help the Human Factors team prove out early ergonomic concepts. Likewise, in Engineering, there are so many different uses and formats for prototypes, but how do we know which kind of prototype to create and what is the value of each in the design process?
We’re here with Dan Greene, Insight’s Engineering Manager to take a deep-dive into the topic of prototyping:
So Dan, how are prototypes used in medical device design?
“Well, prototypes are primarily used throughout development to reduce risk as early as possible when changes can be made quicker and cheaper. In the initial stages of development, complex systems need to be broken down into smaller, less complicated subsystems and components.
As an example, in a drug delivery device there may be a dose counter that operates independently of the drug delivery mechanism. In this case we would want to prove we can count doses accurately, separately from proving proper delivery mechanism function. Each of these subsystems and components can then be evaluated to determine which contains the highest risk and prototyped to appropriately reduce that risk. As development progresses, these de-risked subsystems come together to create more complex assemblies which help us to understand the risk within the integrated system.”
What are the primary prototypes used in each phase of development and how are they different?
“First I’d like to clarify the word ‘prototype.’ It can mean a lot of different things at different stages. At Insight, we develop and utilize both computer, or digital models, as well as physical prototypes. Digital models are typically created using a 3D CAD program and utilize specialized software to analyze. They include things like Finite Element Analysis models to understand performance variables like strength and heat transfer or computational fluid dynamics to analyze fluid flow through a system. These are all done early to again help drive risk upstream. However, for the sake of this discussion, I am going to focus on physical prototypes.
Prototypes developed early can be used to de-risk the highest risk components and subsystems by helping to prove how well certain designs or technologies address the functional requirements. These are the first level of physical models which come about in Proof of principle prototype development. These demonstrate the feasibility of basic engineering principles when executed within individual components or subsystems. Here are a few basic characteristics of this level of prototype:
- They will not look like the specific device design and will likely use substitute materials and processes — for example, 3D printed materials instead of injection molded parts or hardwired electrical breadboards in place of printed circuit boards
- They are used to prove functionality of the high-risk subsystems and components
Once the basic functional principles are proven, the components or subsystems are brought together at a system-level within Proof of concept prototype development to evaluate how well they perform when working as an integrated system.
- Proof of concept prototypes allow for testing of the integrated system to see how or if any subsystem or component functionality may have changed when assembled as a complete system
- Production manufacturing processes aren’t typically used at this stage in order to save time and money
- They provide information on what may need to change or be incorporated prior to the detailed design phase
- This Proof of concept Prototype marks the end of the requirements generation phase and the point at which Design Inputs are finalized
To ensure confidence that the system will function appropriately in production, Proof of design prototype development is initiated during detailed design. This prototype is created from ground up CAD to represent the integration of production intent processes. It’s not a simple update of the proof of concept CAD and prototype. The preliminary CAD created earlier won’t include the finalized form, the intended manufacturing method nor any structure to facilitate easy adjustments later in production. These prototypes are created toward the end of development, as physical proof of the final design concept. This happens once the detailed design has been completed and will use production processes and materials as much as possible. Proof of design prototypes look and function like the production intent design, which represent the current engineering data developed for industrialization.
- Proof of design prototypes represent components at an appropriate fidelity necessary for testing to be a good predictor of performance of the production design when produced with production materials and processes
- They allow for confidence testing to be performed against a subset of design inputs which include critical to function or the highest risk design inputs
- They may be created with soft tools or, depending on the level of risk, with a single cavity of the production tooling to get one step closer to the eventual production part
Confidence testing results, risk and timeline can all be evaluated to determine if iterations of proof of design builds are warranted or if the industrialization phase can begin.
The final stage in the prototype development process is the Proof of manufacture build at the intended manufacturing site. These prototypes are produced by the manufacturer after production processes have been validated. They will also be used by Insight to perform design verification and usability validation. Proof of manufacture builds are made using validated production processes, production tooling and fixtures.”
How do you evaluate each prototype and how do the results affect later stage development?
“Prototypes are a great tool for helping confirm what is already understood and learning what was not. By breaking complex systems down into smaller, more manageable subsystems and components, we can quickly determine what works, what doesn’t and why. Iterations are common with early prototypes and since we’re dealing with smaller subsystems, these iterations can be done quickly and efficiently. We use a risk-based approach to evaluating the prototype to help us confirm performance of the higher risk items without spending time testing proven functionality. By the time we are evaluating the proof of concepts, our testing protocols help ensure we obtain relevant test data from a consistent testing methodology. This data informs any design changes that are captured for the next iteration or prototype build. It’s imperative to have confidence in a component or subsystem’s performance prior to integrating it with other systems or components because troubleshooting becomes much more time consuming as the complexity increases. Spending the time early in development to really understand the functional characteristics of the components and their interrelationships as they go from proof of principle, to proof of concept and proof of design ultimately gets robust products to market faster.”
When do you need to get a Contract Manufacturer involved to support prototyping?
“When a production partner is known early on, it makes sense to get them involved once the Proof of concept Prototype has been created and evaluated. The next step in prototype development will be the detailed design to embody the functional aspects of the integrated system in production-ready designs. During this phase of development, it’s important to discuss technical details like tooling strategies in collaboration with the CM to ensure that proof of design prototyping is done in a way that supports derisking of high-risk components and assemblies. These areas are where iteration is likely and collaboration with the CM on the design for manufacturing activities are important. Many decisions must be made with regard to manufacturing methods and assembly, so being able to tailor those decisions based on a particular CM’s capabilities and preferences can be a big help in smoothing the transition into production.
When it all comes down to it, all disciplines within product development have their own prototyping needs which provide different levels of feedback and information at each stage. For engineering in particular, it’s paramount to have a common understanding of definitions and outputs, given how critical prototyping is to managing risk. Ultimately, our team utilizes iterative prototyping to effectively push risk upstream which eliminates surprises as the design transitions from engineering into manufacturing.”