This is the fourth in our Reducing your COGS series detailing how KMC Systems reduces customer Cost of Goods Sold during the medical device manufacturing process through its Design-for-Manufacturability software. The DFMA® software is just one aspect of KMC's cost-saving Design for X (DFx) process.
In our previous posts, we looked at the importance of Design for Manufacturability and Design for Assembly, and how to implement both in the medical device manufacturing process. In this post, we'll examine overall DFx principles, why they're important for reducing Cost of Goods Sold and how to apply them when manufacturing your own medical device.
The Boothroyd and Dewhurst concept of DFMA (the result of combining DFM and DFA) is one aspect of Design for X, also referred to as Design for Success.
Other DFx practices include design for:
- Reliability: The instrument should function properly for its intended lifetime, and all parts should meet the life expectancy of the instrument.
- Testability: Design the product so testing requires minimal effort.
- Serviceability: Parts should be easily accessible for repair and replacement.
- Usability: Consider the ease, comfort and safety of the end user when designing a medical device.
- End-of-life processing: How will the device be broken down and disposed of? Consider using recyclable materials and reduce the possibility of contamination.
Design for reliability
Use the appropriate design margins when considering product reliability goals.Durability andperformance are key trade-offs made during part selection and design.
What’s the right balance between design margin and performance? Jerry Sevigny, Senior Principal Systems Engineer, says the appropriate design margin is typically two to three times what’s required.
Your medical device’s operating environment also impacts the selection of materials to meet the reliability goals. What chemicals will the instrument be exposed to for cleaning? What is the operational ambient temperature and humidity range of conditions? For example, Sevigny explains that the use of a 10% diluted bleach cleaning solvent on instrument surfaces not only can damage the surface finish but can also produce vapors that compromise the reliability of plastic connectors., Consideration of the cleaning solvents used in the operating environment is an important consideration when selecting appropriate plastic polymers and surface finishes.
According to the AMSAA Design for Reliability Handbook, a system block diagram can be created to investigate the reliability of interconnectivity of assemblies and components, in turn allowing for the examination/analysis of cause and effect relationships inherent in complex multi-level systems. The proposed system level electrical/mechanical/software architecture is evaluated through FMEA to identify an optimum instrument module strategy for manufacturability, testability, serviceability, as well as reliability.
Early in the design processes, Highly Accelerated Life Testing (HALT) is utilized to expose early prototypes and existing components to the full range of expected operating conditions within a controlled environment to identify design failures. This allows the design team to re-evaluate/redesign for deficiencies in performance before the product is launched.
Design for testability and serviceability
Design logical, modularized breakups and locations in the hardware and software architecture for optimal testability and serviceability of your medical device.
Modularization eases testability in manufacturing and serviceability in the field. Not only should medical device components be easily accessible with minimal tools, but they should also include on-board diagnostics when possible. On-board diagnostics in the medical instrument and its modules tell the operator when there’s a problem and what modules need testing. Optimally, the instrument can self-test those modules at the operator’s command through “Built In Test” (BIT) software.
Sevigny touts the benefits of modularization coupled with on-board diagnostics, which allows the field service technician to identify and isolate the faulty module, remove it and replace it with a working module. The field service technician can then ship the faulty module back to the manufacturer for diagnostics testing, depot repair and design-improvement feedback.
Design for usability
The entire user interface should accommodate the skill of the user as well as ergonomic factors for comfortable, safe and efficient use of the instrument.
The usability design should ensure that the user can accurately input reagents and consumables, add samples and collect output results/reports, in a safe and efficient manner across all instrument use cases.
Ideally, the instrument is designed with a simple and intuitive graphical user interface for ease of use and prevents user error.
KMC partners with Farm Product Development to provide design input that addresses instrument usability in compliance with FDA regulations and IEC 62366.
Conduct usability testing with actual end users operating the instrument in real life situations in all use cases to identify potential design improvements.
Farm gives some examples of refined usability requirements that improved the intended use case as a result of user testing:
- The display shall be visible at a distance of one meter to three people standing side-by-side, with all able to detect color and read text.
- The medical device, when being carried, shall have no edges, corners or protrusions that catch on clothing.
- The stylus shall activate software controls on the screen when used at an angle between 20 and 90 degrees.
Design for end-of-life processing
Review the age of the technology you’re using and its updates during the design process to combat obsolescence. Consider the technology and parts availability in your design and seek parts with multiple suppliers. When that is not possible, have a backup plan - especially for critical components.
DesignNews shares some other end-of-life design techniques:
- Choose recyclable materials: Eliminate materials that will end up in landfills and this will most likely minimize toxic materials.
- Minimize the use of permanent fastening methods like adhesives or welding for ease of disassembly
- Reduce the number of dissimilar materials to make materials separation easier and reduce chances of cross-contamination
Build electronics and software to monitor the performance of your medical instrument as it performs in the field. This, of course, feeds back into reliability and serviceability because you’re able to monitor how much longer a part should last and replace it before the part stops functioning.
Ultimately, avoid a medical device shutting down in the field with a scheduled preventative-maintenance program.
Design and COGS: Final tips for cost-reducing DFx success
Find the right balance between cost to design and manufacture, and reliability and performance.
Try to include all of the Design for X “-ilities” in the product-definition phase so engineers know all of the performance expectations up front. Put all requirements in writing so that the design team knows what flexibility they have in recommending a solution. There are times when conflicting constraints between performance goals and cost goals arise, and a trade-off results.
In the development process, build prototypes and perform testing not only for functionality verification but also to determine the reliability of the design. If you find that the design intent is not met then you can modify the design.
Accelerated life testing is invaluable in identifying failures early so that design improvements can be incorporated before shipping the product to the customer. Uninterrupted instrument run time, mean time between failures and allowable maintenance intervals all influence appropriate materials and parts selection, and testing to meet your instrument cost and reliability goals.