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On-Ramp to Design Engineering: Prototypes Are Made for Breaking!

Design engineers are always looking for a challenge, which is why we love tackling problems requiring highly optimized designs.

Optimization can take many forms: minimizing weight, maximizing strength, or minimizing cost. Often it requires squeezing every last drop of performance from a part or removing every bit of extraneous material. These decisions are engineering-driven, but we always keep the user and our clients front and center.

For example, a client might ask us to use as little plastic as possible in a disposable syringe, but the syringe still has to feel strong enough to earn a user’s confidence.

Finding the Starting Point

We start by establishing a thorough understanding of the product’s real-world requirements. Sometimes we already have a specification for a part or product, but most of the time we need to establish the applied forces by testing a mockup or quick prototype in the lab and measuring what happens using instrumentation.

We might take a similar product that’s commercially available and put force gauges on it to figure out how hard a user might push it — in what direction and for how long. That information gives us a starting point for optimization.

Testing, Testing

Once we’ve fully defined and engineered the product with these real-world conditions in mind, we use finite element analysis (FEA) to predict the behavior of a part as we look to shave material here and there, working to achieve the most refined design possible. Both CAD packages we use (PTC Creo 2.0 and Solidworks 2013) let us quickly create variants and seek an optimum trade-off in terms of part geometry, wall thicknesses, and material usage.

We can also analyze the part as if it were made with different materials, perhaps swapping a weaker material for a more svelte part made of a higher performance material. Will swapping in 20% talc-reinforced polypropylene let us reduce how much plastic we use? Can we replace an aluminum part with something less expensive?

Pushing Parts To Their Limits

Software tools are indispensable for this kind of work, but in the end we always need to take it into the real world and see how the optimized design performs versus the baseline. Thanks to all the great advances in rapid prototyping, we can source the same part very quickly in different critical versions and compare them. We will test a part, remove material, then test it again, and iterate that process until it eventually breaks.

Make It to Break It Process Illustration

At that point, you know just how thin, light, or inexpensive a part can be. This might seem a bit brute force, but the analysis we do beforehand gives us a very strong sense of where to start and how to incrementally hone in on the goal. There are subtle differences between what you thought was going to happen and what actually goes on once everything is connected together. Only through these hard fought iterations can the final result be a design that is as good as it can possibly be.

(On-Ramp is an ongoing series illuminating engineering techniques for product development.)