| Done any remodeling lately? If you have, you’ve been faced with countless choices regarding design and materials. Even a relatively simple decision such as putting in hardwood flooring requires many considerations. What type of wood? What grade? How about the stain? Should it be factory stained and sealed, or should the flooring be installed by single board, then stained and sealed in place? Ultimately, your decision is based on your requirements with regards to cost, durability, and personal style.
Now imagine the decision making process that is required to produce a medical device. We’ve been discussing this complex process during our series on medical device design utilizing the systems engineering approach, a systemized approach to product development, design, and manufacture that is used within many manufacturing arenas. Its objective is to relate the requirements for manufacture, regulatory compliance, sale, use, and maintenance of the product to specific design criteria for functionality, durability, and safety. By doing so, the systems engineering approach ensures that the product meets or exceeds all requirements. Last time we wrapped up our discussion on the Development stage of systems engineering by discussing field testing of medical devices assembled during Preproduction. Problems encountered during this phase result in a comprehensive review of the device design and instructions. When all issues have been resolved, things move on to the manufacturing phase and full commercial production. During the Production stage, engineers make continual assessments of the manufacturing process and ongoing adjustments are made to the device design and manufacturing protocol as necessary, this due primarily to changing stakeholder requirements regarding cost reduction. In the competitive marketplace, cost reduction is a never-ending quest to maintain profitability in view of changing economic and market conditions, and this must be done without compromising the quality, safety, and effectiveness of the device. For example, suppose a medical diagnostic imaging machine was designed to be fitted with a machined metal gear in one of its mechanisms. The manufacturer specifies that a $10 decrease must be made in production costs so it can continue to be sold at an acceptable profit margin. After reviewing the design, engineers discover that substitution of a molded plastic gear would reduce manufacturing cost per machine by $12. This is a common scenario, as plastic parts are often substituted for metal to save on cost. Plastic versus metal? How can that be an acceptable swap? In many cases, it can be. Mechanical stressors are analyzed, and if the plastic gears meet durability requirements as well as their metal counterpart, they are substituted. During the Preproduction phase these plastic gears are used in both lab and field testing, where they are put through the rigors of real world use. If they perform acceptably, they are made a permanent part of the device’s design and used in commercial production. Next time we’ll continue our look at the Production stage to discover another way that systems engineering can facilitate cost reduction to meet stakeholder requirements. ___________________________________________
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Posts Tagged ‘functionality’
Systems Engineering In Medical Device Design – Finished Design
Sunday, December 30th, 2012 Last time we opened our discussion on the Development stage of the systems engineering approach to medical device design and discovered that the best design concept is the one that meets all stakeholder requirements. Let’s use the flow chart shown in Figure 1 to illustrate what comes next in this stage.
Figure 1To begin the transformation from concept to completed design, engineers review documentation created during the Concept stage, including design notes, concept sketches, and of course the final requirements specification which has been approved by all stakeholders. Once the review is completed, it serves as a guide to the creation of detailed design documentation, including mechanical drawings, electrical schematics, and wiring diagrams. A bill of materials, or BOM, is also created, listing all parts needed to produce the final product. Each part designated within the BOM is associated with a specific manufacturer or supplying vendor, and each has been qualified with regard to price, availability, functionality, and quality. The design documentation and BOM are also subject to a review by a fresh set of eyes, engineers who have no involvement in the project. If they should discover a problem, the design is rejected and sent back to the design engineers for revision. This process of evaluation and correction are repeated until the design successfully passes a final review. Only then can the fully approved finished design move on to the production stage. Next time we’ll continue our discussion of the Development stage, moving our concept medical device further along its journey to the Production stage. ___________________________________________ |
Systems Engineering In Medical Device Design – Concept and Communication
Monday, December 3rd, 2012| “Ask and you shall receive,” like “Make your thoughts known,” have the same objective, to initiate a dialogue between someone with a vision and those who can get the job done. In other words, if you don’t ask for it, you’re probably not going to get it, and the moving force behind it all is communication. Communication is as important in design engineering as it is in marriage.
Last time we learned that a system is a combination of interacting components organized to achieve one or more specific purposes and that communication is a key ingredient in the process. Now let’s see how the systems engineering approach is used within the medical device design process. The systems engineering approach consists of five key stages, the first being Concept. In this stage the objective is to identify all stakeholders, that is, those who have a stake in the outcome, then exhaustively define and capture their requirements. Crucial to this stage is a good line of communication between design engineers and stakeholders. This usually takes the form of brainstorming sessions in which all parties meet to toss around ideas. These ideas eventually solidify into design requirements. Once the design requirements are identified, they are incorporated into the first draft of a working specification. This specification will be written using plain English to minimize any potential misunderstandings. Within the specification each requirement is not only well defined, but traceable back to whoever proposed it. To this end, all requirements are listed in tandem with the names of stakeholders proposing them. Accountability is the main concern here. Next time we’ll talk more about these design requirements, and how they must serve the needs of functionality, performance, and constraint. ____________________________________________
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