When it comes to the world of medical device design, there is always a concern about how different technologies will perform under various environmental conditions. Will your wearable device perform well in high temperatures? Will your latest implantable device withstand the harsh conditions of the human body? Whether it’s high temperatures, high humidity rates, or just a sensitivity to electrical voltages, device makers have to account for a bevy of different environmental conditions when evaluating device performance.
For many device makers, evaluating performance means researching all the requirements needed for the device to perform in any environment—which could take some time. This can often lead to lengthy testing phases where design teams can get overwhelmed with different variables and performance metrics. So how can device makers be more proactive when it comes to predicting and solving issues to help boost product performance?
Perry Parendo has spent the last 30 years developing a series of Design of Experiments (DOE) techniques, a method that runs all the way back to his days working for General Motors Research Labs in 1986. Parendo eventually began to use these DOE techniques to help solve complex problems that would arise during the product and process development phase for international design teams tasked with new product development.
These DOE techniques are what eventually led to the founding of Perry’s Solutions LLC in 2006, when Parendo began helping organizations and companies with critical product development activities. Parendo has spent countless hours consulting with design teams from different organizations to help them maximize product performance to take their product to the next level. He will be speaking on the subject November 1 at MD&M Minneapolis in the session, “Getting Your Product Performance to the Next Level.”
Parendo recently spoke with MD+DI ahead of his MD&M talk to discuss some of the nuances of evaluating and improving product performance. He shares a few tips on how device makers and design teams can predict and stay ahead of issues that can affect device performance in various environmental conditions.
MD+DI: For starters, can you talk about the process of evaluating your product during design characterization? What are some of the things that are important to look for to help boost product performance?
Parendo: The process starts with knowing your requirements and which ones may be challenges. Then, assemble potential input variables that may influence those outcomes. This includes any noise factors or environmental conditions. This can all happen at the beginning of the project. Characterize these items and then “confirm” the next tier requirements are working as expected. If not, then more characterization work is needed to reduce project risk.
It is important to look beyond the obvious design factors. It is easy to identify 30 or more factors that could impact performance. I am not suggesting to go crazy with it during a test, but limiting ourselves to the easy and obvious 2-3 variables is clearly limiting. Being in an unstable operating zone with one input variable can make the entire design/product unreliable. By taking advantage of hidden replication, we can ensure our sample size is still manageable.
MD+DI: When it comes to evaluating a product’s ability to perform in different environmental conditions, what are some basic barometers for success that you look for?
Parendo: Success depends on understanding the sensitivity of the key design requirements. How much shift in performance is going to be noticed by a user? Any noticeable change is likely going to be considered bad. How can we operate in a stable performing region? How do we know where it is at? Once these answers are determined, the design tradeoffs can be made. It is one thing to create a capable design, but it really takes no more effort to find a level of robust design.
MD+DI: What are some ways that designers can accelerate the evaluation and testing process, and how will that benefit the product in the long run?
Parendo: We need to understand which design parameters may interact together and make sure to test them together. Design of Experiments (DOE) is the only technically and statistically efficient way I know to do that. When I ask people which variables may interact, it is a complex set of possibilities. It is rarely a clear cut answer. However, those same variables are often tested in isolation, which does not allow us to extract the information. We assume, or hope, that the interactions are small, but the truth is some of them are not. We do not know which one it is without performing efficient tests of the combinations. This is considered strategic testing.
MD+DI: What are some tips that you could share with design teams when it comes to selecting the best combination of variables for short-term testing?
Parendo: Testing in isolation is bad because we lose combination effects. However, testing everything together is too complex and inefficient. The best tip is to group our tests with variables that may interact together. As a simple example, in one test, combine mechanical variables together, and in another test combine the electrical variables together. I have heard it called testing within the “energy bands” and is something I consider on every test I set up.
MD+DI: In your experience, how can designers try to be more proactive when it comes to both predicting and addressing issues in a fast and effective manner?
Parendo: It is not easy, but we need to be honest about our designs. Be up front about risks and uncertainty. This does not make you a bad designer. Instead, it makes you realistic. We get surprised at times, and that is okay. Ensure we evaluate our higher-risk items deeper than our lower-risk items. Unfortunately, many designers test everything to a similar level, regardless of the risk involved. We are optimistic that things will work out, and we end up doing inadequate work.
MD+DI: Finally, if you could give one piece of advice to designers when it comes to taking product performance to the next level, what would it be? In essence, what’s a good piece of advice that you’ve picked up over the years that many design teams often overlook?
Parendo: Be humble in design. Testing is intended to help us learn, so a “failure” can be a good thing early on. Use early tests to make a better design, not just prove that you were right. It is a subtle, but very important difference.
Join Parendo November 1 at MD&M Minneapolis in the session, “Getting Your Product Performance to the Next Level." The session is part of the MD&M MInneapolis Technical Solutions track, which Parendo is chairing.