| How many times have you bought something and lugged it home, only to discover that it didn’t work as advertised? These days this scenario is all too common. Chances are it was developed haphazardly and rushed into production without adequate research and testing. A chief contributor to the product’s not living up to expectations is very often the result of a poor beginning. In its concept and development stages, design engineers failed to use a systems engineering approach.
Last time our discussion of the Concept stage of systems engineering identified stakeholder requirements as being of three basic types, serving the needs of functionality, performance, and constraint. Once identified, these requirements were incorporated into a detailed specification that is approved by all stakeholders involved, then used to devise alternate medical device concepts in order to really size things up. Let’s now move on to the Development stage of the design process to see how the alternate concepts are evaluated. The Development stage of the systems engineering approach to medical design begins with research and development of alternate device concepts. Stakeholder requirements as defined in the original product specification are used to guide the process, then mockups and prototypes of the alternate concepts are built, tested, and analyzed in view of the requirements. Considerations such as cost, ease of manufacture, operation, durability, and potential risk of harm to users are evaluated. As often happens, the best alternate concept satisfies all but a few of the specified requirements, resulting in a “good enough” scenario. That is to say, if stakeholders can agree the requirements not met aren’t all that important in the scheme of things, they may be willing to remove them from the specification, thus approving the concept for further development. If an agreement such as this cannot be reached, it may be necessary to return to the Concept stage and begin the entire process again. This re-evaluation of the process should result in a set of requirements that are further refined and from which better options in alternative concepts can be developed. Next time we’ll continue our discussion of the Development stage and see what it takes to finalize design and begin manufacture. ____________________________________________
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Posts Tagged ‘validation testing’
Systems Engineering In Medical Device Design – Concept Evaluation
Monday, December 17th, 2012
Food Manufacturing Challenges – HACCP Design Principle No. 4
Sunday, November 6th, 2011| Imagine going on a diet and not having a scale to check your progress, or going to the doctor and not having your temperature taken. Feedback is important in our daily lives, and industry benefits by it, too.
Generally speaking, feedback, or monitoring, is a tool that provides relevant information on a timely basis as to whether things are working as they were intended to. It’s an indispensable tool within the food manufacturing industry. Without it, entire plants could be erected exposing workers to injury and consumers to bacteria-laden products. It’s just plain common sense to monitor activities all along the way, starting with the design process. Now let’s see how monitoring is applied in HACCP Design Principle No. 4. Principle 4: Establish critical control point monitoring requirements. – Monitoring activities are necessary to ensure that the critical limits established at each critical control point (CCP) established under Principle 3 discussed last week are working as intended. In other words, if the engineer identifies significant risks in the design of a piece of food processing equipment and establishes critical limits at CCPs to eliminate the risk, then the CCPs must be monitored to see if the risk has actually been eliminated. Monitoring can and should be performed in food manufacturing plants by a variety of personnel, including design engineers, the manager of the engineering department, production line workers, maintenance workers, and quality control inspectors. For example, engineering department procedures in a food manufacturing plant should require the engineering manager to monitor CCPs established by the staff during the design of food processing equipment and production lines. Monitoring would include reviewing the design engineer’s plans, checking things like assumptions made concerning processes, calculations, material selections, and proposed physical dimensions. In short, monitoring should be a part of nearly every process, starting with the review of design documents, mechanical and electrical drawings, validation test data for machine prototypes, and technical specifications for mechanical and electrical components. This monitoring would be conducted by the engineering manager during all phases of the design process and before the finished equipment is turned over to the production department to start production. To illustrate, suppose the engineering manager is reviewing the logic in a programmable controller for a cooker on a production line. She discovers a problem with the lower critical limits established by her engineer at a CCP in the design of a cooker temperature control loop. You see, the time and temperature in the logic is sufficient to thoroughly cook smaller cuts of meat in most of the products that will be made on the line, however the larger cuts will be undercooked. The time and temperature settings within the logic are insufficient to account for the difference. This situation illustrates the fact that monitoring does no good unless feedback is provided with immediacy. In our example, the design engineer who first established the CCP and the critical limits was not informed in a timely manner of the difference in cooking times that different size meats would require, resulting in the writing of erroneous software logic. Fortunately, continued monitoring by the engineering manager caught the error, leading her to provide feedback about it to the design engineer, who can then make the necessary corrections to the software. Next week we’ll see what design engineers do with the feedback they’ve received, as seen through the eyes of HACCP Principle 5, covering the establishment of corrective actions.
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Medical Device Design Controls – Transfer, Changes, and History
Sunday, September 12th, 2010| Did you ever hear the saying, “garbage in, garbage out?” Perhaps you’ve used it yourself at times, as when your teenager insists on writing their 20-page term paper the night before it’s due. Parents, having the benefit of decades of life experience, know that the outcome of a last ditch effort of this type will most likely not turn out well.
This wisdom also applies particularly well to the medical manufacturing process. The FDA is like the parent in this instance, mandating that Design Transfer Procedures be in place to avert the types of disasters which might ensue if the “garbage” philosophy were carried out. Meant to ensure that medical device designs are correctly translated into production specifications for manufacturing, Design Transfer Procedures keep those directly involved with the manufacturing process in check. It is absolutely vital that those involved in manufacturing receive accurate and complete information. Imagine what would happen if an engineer provided a manufacturer with faulty design information. Components could be made to the wrong specifications or of a material that proves toxic to the application. These errors range in negative effect from being costly in terms of dollars wasted to perhaps costing someone their life. A Design Transfer Procedure would ensure that a variety of mishaps do not occur during the transfer process. The procedure is typically overseen by the medical device company’s management. For example, a Design Transfer Procedure would lay out responsibilities of supervisors and managers to make sure the latest revision of electrical schematics, bills of materials, Gerber files, and quality testing procedures are received by the manufacturer of a device’s printed circuit boards. It’s important that the order is received in a timely manner so as not to hold up the manufacturing process. However, it’s much more important that the printed circuit board is made properly, the correct electrical components are placed on it in the correct orientation, and it is tested to make sure it doesn’t malfunction after assembly. Design Change Procedures basically ensure that when changes are necessary, the medical device company follows all the procedures for Design and Development Planning, Design Input, Design Output, Design Review, Design Verification, and Design Validation. Once the changes are reviewed, validated, verified, and approved, they can be incorporated into the original device design. This is where the Design Change Procedure must dovetail with the Design Transfer Procedure to make sure the correct information is provided to the company’s management staff in the procurement, manufacturing, product service, and warehouse departments. This is to make sure they can keep component vendors on track with the changes, maintain sufficient inventory of the changed components, put the right components in the device during assembly, and properly support repair technicians in the field. Yet another aspect of Design Controls promulgated by the FDA comes into play with the establishment of procedures for maintaining a Design History File (DHF). This DHF contains all documentation created during the life cycle of the project, meaning, movement from creation to completion and on into market introduction, sometimes beyond. DHF Procedure sets up protocols for collection and organization of information about the medical device design, starting with design documentation and covering the gamut from design changes, to validation testing, to design verification, and on to design review. All this is done to ensure that the initial product design was developed in accordance with the original design plan and overall product design requirements. _____________________________________________ |
Medical Device Design Controls – Output, Verification, Review, and Validation
Sunday, September 5th, 2010| Recently my wife was on a quest to make the perfect pound cake, but before she put butter to flour she did her research. What’s the best butter? Best flour? Eventually she came up with a recipe she felt would prove to be the Queen of all pound cakes. After the recipe came reviews by her test panel, or family members, including myself. Questions were asked, such as, When you first bite into a pound cake, do you want to be aware of vanilla or lemon? It was only then that she would begin to combine ingredients for the final mouth watering product. Very much this same procedure is used when coming up with a new medical device.
Previously we’ve discussed FDA requirements for medical devices as they concern design controls with respect to design and development planning and design input procedures. We’ll now focus on requirements for Design Output, Design Verification, and Design Review Procedures. Design Output and Design Verification Procedures go hand in hand to ensure that design output is properly documented, organized, reviewed, and evaluated in light of design input. What this means is that medical device companies must scrutinize and evaluate what is going into the design process, then make a comparison to what is coming out. The design is ultimately verified when all requirements for the medical device as previously set out have been met. “Design output” is just another name for work product after major phases of the design project are completed, such as when my wife determined which butter would produce the best pound cake. Design output typically takes the form of specifications, notes, calculations, computer programs, mechanical drawings, electrical schematics, printed circuit board (PCB) layouts, bills of materials (BOM), mockups, prototypes, test data, and test reports. These are then utilized by people outside engineering circles to manufacture components and assemble them into a final product. Design Review Procedures ensure that the design output is evaluated by others not directly involved in or responsible for the design work product, much as when family members served as a reviewing committee for my wife’s inquiries into taste preferences in pound cake. Sometimes she’d even ask a friend or neighbor to put their two cents in, and companies, too, will at times go outside and hire consultants to perform this function. By so doing, unbiased opinions are sought out, in the hopes that this fresh set of eyes will be more likely to spot errors, omissions, and misinterpretations that could prove disastrous if put into play. Design reviews are typically conducted after each major phase of a design project is complete. Just as a recipe that looks good on paper may not necessarily taste good, a device design will often seem to work perfectly on paper, then prove otherwise when its manufacture begins or it’s used in the field. Ideally bugs are worked out before the product hits production and, later, the marketplace. Design Validation Procedures make use of prototypes for testing and careful evaluation under simulated or actual use conditions. Does the design safely meet requirements for intended use? Does it conform with industry standards? If not, there’ll be a lot of wasted “dough” going into the trash — pun intended! Next time we’ll explore FDA requirements for Design Transfer and Design Changes. We’ll also talk about procedures for Design History Files. _____________________________________________ |
