Perspectives on Prototyping, Part II
Has design software reached the point where it can serve as an acceptable replacement for physical prototypes in medical device manufacturing?
Gregory L. Horton
President, Stellar Microelectronics
Properly utilized design software can eliminate much of the need for physical prototypes, and can increase the degree of success of First Article Inspection (FAI). However, many companies do not take advantage of all the benefits design software offers. Electrical, mechanical, structural, and thermal analysis software all assist in Design for Manufacturability (DFM) optimization. Design Rule Checking (DRC) analysis software is another must-have for a first-run design.
While design software has made great strides in replacing the need for physical prototypes, a related way to further enhance the probability of product success is to put design and build in the same facility. At Stellar Micro, our design engineers observe and apply lessons learned. We use a combination of Cadence and Valor Trilogy software to manage our PCB design process and meet time-to-market demands. Our engineers design labor out of the product, collaborating with our clients, detecting issues early in the process, making it more cost-effective, and optimizing quality. In addition, our domestic, single-site production helps protect IP.
That said, regardless of whether you use a physical prototype or the virtual prototyping of design software, we recommend a small lot for the first time build. There are always refinements that can be applied once the first run is complete. For instance, while your design may be functional, you may opt to revise your component sourcing due to supply or cost logistics. This is essentially outside the realm of actual design, but can substantially impact production and, therefore, the success of your program.
No, and it never will. No matter what technical innovations today or tomorrow brings, software can’t fully replicate the experience and the interaction of people with devices. While we do all kinds of functional testing with software and CAD, it will never be able to predict the complete scope of human behaviors. The Mindray V Series are the first bedside monitors that can be disconnected for use during patient transport. We needed to understand people’s perception of the proposed latching system. While software allowed us to confirm that the tolerances would be appropriate to guarantee a secure lock, physical prototyping was the only way to assess the perceptive aspect of user confidence. Our approach is human-centered, and time and time again, we’ve gleaned critical insights when we put our medical devices into physical prototypes.
Technical and Design Services Manager, Value Plastics
No. Perpetual software innovation has no doubt provided increasingly accurate predictions of what might be expected from a physical part, and in turn, is helping to feed good design and expedite development. However, nothing truly replaces the benefits of having physical parts in your hands, particularly with those designs that factor usability into the specifications. The often elusive benefits of grasping something tangible provides essential insight into the user interface and, therefore, is key to developing a product to which people will relate well. Physical prototypes remain paramount in achieving a feel for how the ergonomics of a design coalesce with difficult-to-define dynamics, such as the interplay of molded part properties and the application of compound, non-linear forces. Even given the magnitude of technical advances in software, at the end of the day, there is no truly effective computing means to extrapolate feel.
Engineer, Cyth Systems Inc.
Design software cannot yet replace physical prototypes in medical device manufacturing because they are often complex systems interacting with delicate parts and substances. The software model is not optimized for testing materials or the fitting and interaction of materials and parts. Some materials may expand or change with temperature, while others may change size or strength when contacted with fluids. Surface friction is a frequent issue with interacting parts that design software would not often be able to detect. Tolerance is not free and the design software may give a false preview of the final costs of the medical device. Depending on how fine and polished a prototype needs to be, the surface finish and tolerances between each part cannot be accurately depicted by design software.
More importantly, humans interact differently with each medical device. In order to test these products with humans, prototypes must be tangible. There are design errors that engineers can make in the software that would not be possible when building the physical model. There are some simple designs that may get by without needing to build a prototype, but design software cannot acceptably replace a physical prototype at this point.
President, bleck design group
We have been designing very small assemblies with dynamic interactions of parts driven by hand action. Design software is extremely useful in modeling what you know and is predictable. It is not good at discovering design issues where materials are pushed past published standards, or many moving parts interact, and especially where humans never act the same. For example, we could be designing a disposable device with limited cycles and plan to use materials at thickness below what the material manufacture has tested. We do the analysis with available standard data, but only testing tells us if the design will perform, plus we discover properties not otherwise published. Computer models of very small part assemblies tend to look more accurate than the actual parts. Staying with the computer model too long before prototype modeling gives a false impression of accuracy. When a feature is only two-thousands of an inch, the surface is far more significant than any computer model can show. Further, you can't model the real variation in human behavior. Nothing replaces a model in hand and the multiple reactions to the design. Finally, we find the inspection of parts is really the third leg of the process. Intricate small designs require computer modeling, prototype testing, and careful inspection to improve design and innovation productivity.
Program Manager, RKS
Though design software (e.g., 3D CAD, finite element analysis, thermodynamic analysis, mold flow analysis, etc.) has made the design process more accurate and faster, it is still not a replacement for a physical prototype. Design software can certainly show potential problems and help to drive the number of revisions down on the prototype, perhaps to even just the first round that simply proves out the design, but the prototype is still necessary to ensure that nothing was missed.
Even if all the stake holders are 100% sure there are no mechanical problems with the design, there are things that a prototype can show you that are impossible to demonstrate in software—things like the human interface with the device. Are things positioned in a way the operator can access them as planned? Is the push of the button correct and giving the proper tactual feedback? Is the unit blowing hot air out on the feet of the patient or user that no one even thought to think about?
No matter how good design software is, we live in a real world and not a virtual one. And as long as we do, we will need to confirm things in that world.