Perspectives on First Step in Design (Part II)
The idea has been thought up, the “napkin sketch” has been made, and the project is ready to move forward. So what’s the first “real” step in the design process? This was the question for the participants in this month’s Perspectives feature. Ideally, you will be able to take away a tip or two before embarking on your next project.
Q: Once the general idea for a new device is formulated, what aspect should first be addressed in the design process and why is this the critical first step?
Donald L. Sweeney
EMC Engineer and President, D.L.S. Electronic Systems Inc.
Donald L. Sweeney.
Designers often fail to take EMC (electromagnetic compatibility) in mind when formulating the idea of a new device. Emissions from the newly designed product can easily cause the malfunction of other medical devices. The newly designed product must also be protected from outside electrical interference. Therefore, medical products are required to comply with many regulatory and operational EMC requirements, from the simplest requirement that the product operate in its intended environment to often meeting very strict requirements of the FDA and European Union. Compliance to these requirements will not occur by accident. From the beginning, mechanical, electrical, and software engineers need to discuss the intended operating environment, need to know the agencies or authorities that determine legal requirements for their product, and need plan their product accordingly.
Finding that the medical device is out of limit or failing immunity during compliance testing of the final product can be very costly in both time and dollars. To add filters or shielding or redesign a circuit board may cost from a few cents to hundreds of dollars per unit. When manufacturing large quantities, any increase in cost may be substantial. Yet returning to the design table at this stage may cause extensive delay in getting the product to market, which once again is very costly.
To address EMI issues at the beginning of the design stage instead of at the final product stage would therefore be extremely beneficial. I would therefore conclude that the first item to be addressed in the design process of medical devices is to be aware of electromagnetic compatibility and know how to design the electrical system to control both emissions and susceptibility.
Dale Henson, P.E., BSME
President, Engineering By Design
Since the general idea for a new device is formulated, it is assumed that the device has already been established as being technically feasible and financially viable. If not, it should not go forward. Any general idea should be broken down into parts and each evaluated individually as to value, risk, resources and timeline to develop. Some aspects may not fit into the overall project guidelines and need to be revised, like parts that need specialized development, hard tooling, or other features that push it beyond the project scope. The most difficult, risky, and/or time-consuming aspects must be considered first because those are the ones that could threaten the entire project. In some cases, a “proof of concept” prototype or some other special evaluation should be done immediately. Many parts of the project will have to be done in parallel to meet the overall schedule and those that involve multiple disciplines are first on the list. Mold-related tooling may take a long time but at least the timelines are predictable. A mechanism that requires electronics and software generally comes first as it involves the most diverse disciplines. Often, a complex mechanism design cannot even start until the control functions and ergonomics are considered. It is conceivable that something as obscure as canned software needed for components to communicate could change the project scope beyond acceptable limits. Breaking down the project and looking at the aspect(s) that can become the greatest risk of overall project failure is always the “critical first step.” A serious problem late in a project can be catastrophic while early problems might be considered “challenges.”
Kaushik (Kosh) Ghosh
Director, Product Strategy Formulation, Battelle Medical Device Solutions
Kaushik Ghosh .
A medical device concept is usually born when a compelling clinical need meets an enabling technology. This “concept” is most typically captured in a marketing document such as a Market Requirements Document (MRD). However, before investors (internal or external) will release the major funding required for full-blown design and commercialization, they will likely need the basic risks identified, and some retired, based on their investment criteria.
Therefore the first step in the design process must be a structured risk assessment and retirement method that we call Applied Research. In the Medical Device Solutions group at Battelle, we have integrated business and technical thinking into a succinct set of tools to facilitate this step. First, we list the risks in various categories (Technical, Market, Regulatory, Reimbursement, and Intellectual Property) and choose a few of them as Key Performance Indicators (KPIs). We then qualify the status of the KPIs as Red, Green, or Yellow using a signal chart tool. Then, we codify the desired future status of the KPIs as another set of “signals.” This second set of signals is indicative of the investor’s risk tolerance: the more they desire green, the less is their tolerance!
The gap between the current and future status of the KPIs becomes a powerful guide for planning and executing a series of experiments of either a scientific or business nature. Scientific experiments could include a technical feasibility demonstration using breadboard prototypes, while business investigations could include regulatory path determinations or reimbursement analysis. At the end of these experiments, the signal chart is updated and presented to the investors.
Applied research is a way to increase the predictability of the scope, time, and cost of full-blown design and commercialization. Without this structured step, the downstream activities run the risk of stalling in unforeseen ways.
Product Manager, FasTest Inc.
The cost of not testing, or ensuring product quality, is too great for most manufacturers. So why is there so little emphasis given during this critical first stage of product design? Why are we not asking, “How will we test this product?” Is it that we feel we have the best workers and we make the best product, so testing is just to “rubber stamp” what we already believe? All too often, how a product is tested is left until the eleventh hour when production is ready to run.
During the product design stage, slight design considerations may be possible which can significantly improve the process of product verification and testing, thus reducing your overall manufacturing costs. Such consideration at this point may seem premature, but may pay big dividends once the product goes into production.
Developing an understanding of various testing methods and the connection tools available which can seal your part is not overly complicated or time consuming. A vast amount of information is available over the internet. But I suggest trade magazines and trade shows as excellent sources. By looking through various trade magazines, find advertisements for manufacturers that appear to have experience with your product or industry. Then pick up the phone and call that company. Ask to speak to one of their product/application specialists. In just a few minutes, you may gain an understanding on testing and connection tools that may significantly improve your overall manufacturing process.
Division Fellow, Analog Devices Inc.
Innovative advancements in chip technology and architecture often enable “breakthrough” products at the medical system level. An important first step in the design process is for the designer to partner with a semiconductor vendor that has historically demonstrated innovation, offers a proven track record of product reliability and robustness, as well as applications engineering experience. A development team that brings the semiconductor vendor into the design cycle early will leverage the advances in IC technology to deliver a product that differentiates itself in performance, ease of use, and manufacturing cost.
Integration of key functionality on a single chip, small IC packages, and new technologies (for example, internal self-calibration, very low power data acquisition, galvanic isolation, or capacitance sensing) can introduce levels of performance and functionality to a portable device beyond what was previously possible. This, in turn, supports an improved diagnostic process for the physician, a better user experience for the patient, and greater market potential for the device.
You (the system designer) know what you need. We (the IC technologists) know how to do many new things at the chip level. Together, we find the intersection that defines a successful product. What we can accomplish together is limited not by our engineering expertise, but rather by our imagination: "If we can agree on what we want, we can build it!"