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Perspectives on First Step in Design (Part IV)

Thu, 05/22/2008 - 11:40am
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?


John Gilligan
President, Boothroyd Dewhurst

John Gilligan .


Whether the device you are designing is for medical, aerospace, consumer, or automotive use, it is critical to understand if the parts in that design are absolutely necessary for its function.

This sounds basic, but more often than not engineers start their design by making the "best" individual components separately without looking at how the device will perform as a complete integrated assembly. One has to step back and interrogate the existence of every single part; it has to prove itself in the system of assembly parts before it should be included. When you do this exercise, you likely find that 40% to 50% of parts can be combined into single multi-functional components with higher quality, faster assembly times, and greater total cost efficiency.

When this first step is skipped, however, tremendous costs are almost automatically built into the design—and then production—of your device in warranty and service, inventory, engineering change orders, ERP, supply-chain management, and especially in the areas of production throughput and utilization of factory floor space. A device which has been analyzed correctly, for either manual or automated assembly, will reduce these total "downstream" manufacturing costs.

Most people think about design in CAD-centric ways and conceptualize the whole development process around geometry creation. But that's the stage where engineers should be detailing the features of designs that have been pre-optimized in Design for Manufacture and Assembly (DFMA) software—and then preparing their models for prototyping or FEA and eventual output to manufacturing systems.

So looking at parts for assembly efficiency and "should cost" manufacture is one of the very first critical steps in design. This can happen either at the napkin-sketch stage, or with rudimentary CAD geometries, or with existing products that have components with a long, unquestioned history.


Frank Rene
Vice President, Protek Power North America

Frank Rene .


The first step in designing any electronic medical device is to give considerable thought as to the power supply that will be required for the product. The power supply, in many cases, bears the critical responsibility for keeping the patient isolated from the incoming AC line.

The main factors to consider when selecting a power supply specific to a medical product are primary to secondary isolation and leakage current. In addition to this, the selected power supply must be approved to the relevant versions of the standard EN60601-1, depending on in which countries the end equipment will be used. Since power supplies that are certified to EN60601-1 are a small subset of the available power supplies in the market, careful consideration of the power consumption of the medical equipment must be examined, as well as whether or not the power supply will reside inside the equipment or outside.

If the power supply is determined to reside outside of the equipment, then power levels must be carefully considered as external/desktop type power supplies with EN60601-1 approvals are only available from a select number of power supply manufacturers, and are limited in total output power ratings. You would be hard pressed to find a readily available, medically approved desktop power supply above 200 watts, for example. If the equipment is to reside inside the equipment, the available power supply products in the market are much more plentiful, however, much more consideration must be taken as to the interaction (mechanically, electrically, thermally, etc) between the power supply and the end product.

In summary, the power supply, normally the last item thought of in a new design, should be prioritized as one of the first things to consider with a new medical product as it is critical to the end product design in numerous ways.



Mitch Free
CEO and President, MFG.com

Mitch Free .


Once a medical device is conceived, a "cost reward" approach to product development should be executed in the concept/design stage. Too often, companies are looking for profitability far too late in the cycle—at the production phase. Three proactive efforts can drive a company toward an innovative, cost-effective medical product.

Using rapid prototyping technologies, designers can produce numerous design iterations and prototypes to refine concepts. Today's prototypes are made from stronger materials and are produced more accurately and economically than ever before. With the speed and relatively low cost of rapid prototyping, the return on investment is rock solid. This process can eliminate potential problems in production and avoid warranty problems due to design flaws that quickly erode forecasted profits.

Deciding how a custom part will be made is a complex decision, and should be determined very early in the game. Will it be machined, molded, or cast? An engineer must weigh the design considerations or trade-offs with the cost of each process. Understanding all applicable manufacturing processes requires extensive domain expertise. Using the Internet, a design engineer can easily ask for price quotes and manufacturability suggestions from suppliers around the globe. This goldmine of knowledge enables an engineer to select a manufacturing process that will generate the highest return on investment.

By heading to an online marketplace, an engineer can discover competitive suppliers of electronics, materials, hardware, packaging, and other standard components. Sourcing online for custom manufacturers via a request for quote (RFQ) system will intelligently match your job to qualified shops with the necessary equipment, expertise, and capacity. Getting a reality check on product costs upstream in the development process enables a company to monitor and resolve design and production issues. Perfecting your design, pinpointing optimum manufacturing process(es), and identifying the right suppliers all translate to substantial "cost rewards."



Mark Yeager
Principal Engineer, Bayer MaterialScience LLC

Mark Yeager .


Like a successful play in football, successful medical product design requires team effort and a well-developed strategy.

Creating the best design requires optimization of the complete system—not just the individual elements. To accomplish this, the first step should be to assemble a team knowledgeable about the capabilities, limitations, and costs associated with the various elements that contribute to the device's performance, reliability, and manufacturability.

Together, this integrated team considers the impact of the various options of each element on the design of the other elements, evaluates the tradeoffs, and determines the set of options that result in the best overall device. Early input from all groups helps focus attention on total product cost, not just the costs of individual items or processes.

The team understands that adding cost in one area can reduce costs in other areas, subsequently translating into a net reduction in total device cost. For instance, adding snap latches and nesting features to the design may increase part and mold costs, but produce greater savings in assembly operations.

Another illustration of how the team's broader, more balanced perspective is beneficial pertains to materials selection. Plastics differ in their ability to hold tolerances and in the adhesives and welding techniques with which they can be used. Selecting a lesser (perhaps less expensive) resin may limit assembly options and create problems that ultimately increase device cost and reduce reliability.

Opportunities for device optimization, such as those described above, are often lost when design elements progress in a linear fashion, one after another, because molding and fabrication may be considered late in the design process when options are severely limited. This siloed approach can lead to molding and manufacturing problems that can translate into quality issues and elevated costs.

Simply put, for a winning product design, consider the team approach.



Steve Niedzielsi
Heaters Engineer, Minco

Steve Niedzielsi.


The first step in any thermal design process is to provide your vendors with the big picture of the installation. Key questions that can have serious implications later on include: "Where will the heater go?" "What are clearance issues?" "Where do power terminations need to route to?" "What type of heat sink metalwork is involved?" "Are there any thermal barrier conditions such as metal stand-offs, holes in the heat sink, airflow rates, or out-gassing issues?"

Here are several reasons why it's important to involve your vendors early in the process:
1. Heater manufacturers have optimum sizes for mass production
2. Conventional, lower cost and highest reliable termination methods use more than expected Z axis space
3. Heater element routing and mounting methods are key for optimal performance and reliability
4. Providing a sample idea or even a picture will help avoid miscommunications

Stepping back and giving these details will allow your vendor to recommend sizing of the heater to ensure it meets your performance needs. One of the more frequently overlooked issues is making sure there's adequate clearance for power terminations. Also, performance reliability due to high watt densities and/or poor heater installation in the field can drive multiple design iterations. Involving your vendor early in the design process may seem like adding an extra step, but in the long run, it can help you save time and money.

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