In most industries, you can get away with testing early prototype using parts fabricated from various rapid prototype technologies. In medical device design, performance issues are often so critical and part features so small that early testing must be done using parts fabricated from the actual resin that will be used in the finished device. Sometimes raw sheet or rod stock can be used to machine-specific features that need to be tested, but usually adequate part geometry can only be achieved by using short-run injection mold tooling.
Though costly, this situation can be a blessing in disguise. The need for 50 parts to test often expands into a need for 5000 parts. These days, hardened steel tooling can be had for not much more than aluminum tooling. The increased quantities this allows provides an adequate supply of real parts that can be used very effectively in your marketing efforts. Just be sure to keep the tool “steel safe” so adjustments can be made with relative ease.
The prototype development stages and the effective uses of prototypes at each level are presented below. These prototype development phases must coordinate with design control documentation requirements.
Appearance Model : The appearance model may comprise rendered images from an industrial designer or a physical mock-up made from foam board or 3D printing. It may look like the final product. It is used to demonstrate the size, colors, control locations, actuator size/location, and other visual features. In some cases, the appearance model may be a series of drawings that explore a number of configurations for the product. It should be completed in weeks, rather than months, and may be used to gauge investor interest, as well as to garner end user feedback. The appearance model is part of the system’s concept design. The appearance model and concept drawings also may be part of the initial project proposal and user requirement overview.
Proof of Concept : Benchtop physical mock-ups and breadboards are proof of concept (PoC) prototypes. They are used for feasibility evaluation of the performance of a subsystem or technical component. For example, for pressure resistance or flow control capability, a tubing clamp design could be evaluated, or a dc-dc converter could be evaluated for heating under load, and for noise and line/load regulation.PoC prototypes are used to test the usability of a user interface, such as the functionality of an active mock-up graphical user interface (GUI) or the ease of loading the tubing kit onto a mock-up pump screen. These reviews and feasibility reports help with the creation of component selection and requirements and are part of the design history file of the unit (DHF).
For the final version, the PoC prototype designs are 40 percent to 80 percent stable. In a couple of months, the PoC prototype stage should be completed. To complement and refine the User Specifications Specification (URS), the Project Development Plan (PDP) and the Hazardous Situation List (HSL), which is part of the risk management process, the development of the PoC prototypes can be used.
Alpha: The Alpha prototype is the initial attempt to develop and produce the product to meet the specifications of the product specification (PRS). It is also the first attempt to build a prototype that both looks like the finished product and functions like it.Guidance for the next stage will be generated by the iterative method of developing and constructing the Alpha prototype. The Alpha can be designed for physical fit and performance assessment with 3D-printed enclosures and components. It will have initial designs of PCBs and enclosures for internal testing and performance, protection, EMC, usability, and appearance evaluation. Compared to previous phases, alpha production is costly and takes months to iterate and refine the design.
In recognising the product’s weaknesses and in optimising the concept, the Alpha design and testing are critical. The development process of the Alpha prototype will include development of hardware and software design specifications that identify performance specifications and implement safety mitigation for hazards defined in the HSL.
Device specifications, risk management, regulatory strategy, and V & V plan should be identified well enough at the end of the Alpha prototype development stage to have a pre-submission meeting with the FDA regarding the software and the expected regulatory strategy. The pre-sub meeting will include feedback from the FDA and, preferably, conclude that the regulatory direction and testing plan chosen are appropriate. Before embarking on Beta prototype creation, it is best to gather FDA feedback on any shortcomings.
Beta: The development of the Beta prototype integrates the design refinements contained in the development of Alpha and introduces them into production tools, moulds, PCBs, subassemblies, enclosures, GUI designs, etc. There are prepared test plans and verification protocols. The programme for the first release is refined and prepared. Documentation is being revised and prepared for the system master record release (DMR). Testing and assembly protocols are drawn up for development.
Beta prototypes are installed and tested according to manufacturing protocols, and in the risk management report, hazard mitigation is reported. To verify compliance with the PRS, the Beta prototypes are ready for verification and preliminary validation testing, security and EMC testing, and performance testing.
After assembling the Beta prototypes, refinements will be needed, and these refinements should be under configuration control to reflect the reasons for the modifications and how they make the Beta prototype resolve any limitations in meeting requirements and standards. Creation of beta prototypes will include the development of hardware and software verification specifications to ensure that the product meets design requirements.
Pilot Production: The pilot development stage is where the refinements from the verification and validation testing of the Beta prototype are integrated into the design and the production process. The DMR and RMR documentation will be revised. For pilot production, the concept transition to manufacturing and the implementation of the quality control system is completed.
These units can be used and are suitable for initial release to market for summative usability testing and clinical trials. The architecture and the method of production are reasonably stable. The application to the FDA for regulatory release to market [e.g., 510(k)] will be completed during this process depending on when the verification and validation testing is completed.
Matured Product: The matured product requires refinements from user input and monitoring of output. The design and the assembly process are robust, have high yields and cost-saving measures are implemented. With input from complaints, customer demands and manufacturing experience, postmarket surveillance of the product is introduced. To fix any problems, the feedback can result in the initiation of a CAPA project.