From Dozens of Prints to One Decision

How Iterative 3D Printing Helped Us Converge on the Right Medical Device Design

In early-stage medical device development, it’s easy to mistake progress for clarity. Every iteration looks better than the last, every prototype feels closer to “final,” and momentum builds quickly. But speed without direction can be deceptive.

This case study reflects a project where 3D printing played a critical role—not because it helped us move fast, but because it helped us slow down, observe carefully, and make one informed design decision that ultimately shaped the entire product.

The Context

The project began with a client developing a compact, handheld medical device intended for repeated use in a clinical environment. The core technology was already validated at a conceptual level, but the physical form, internal layout, and user interaction were still open questions.

The initial goal was straightforward: create a functional prototype that could be used for early evaluation and discussion. The assumption-common in early development was that a few iterations would be enough to converge on a workable design.

That assumption turned out to be wrong.

The First Few Prints: Confidence Without Certainty

The earliest 3D prints focused on overall form and size. Using rapid additive manufacturing allowed us to quickly explore different enclosure geometries and internal layouts.

At this stage, the feedback was mostly positive. The device fit in the hand, the components fit inside, and the assembly sequence appeared logical. From a distance, the design seemed “almost there.”

But something felt unresolved.

When the device was handled repeatedly, picked up, rotated, set down, and reassembled, subtle issues began to surface. The grip felt secure in some orientations but awkward in others. Internal clearances were technically sufficient but left little margin for variation. Assembly worked, but only when done carefully.

None of these issues were severe enough to fail a prototype review. But together, they suggested that the design was still fragile.

When Iteration Becomes Exploration

Instead of pushing forward prematurely, we decided to lean into iteration.

Rather than refining one design incrementally, we deliberately printed multiple divergent versions in parallel. Each version exaggerated or minimized a specific aspect of the design: grip angle, wall thickness, button placement, internal spacing, or seam location.

Over time, the number of prints grew, not because of indecision, but because each print answered a narrow, specific question.

Some prints existed only to test how the device behaved when held with gloves. Others were printed to examine how assembly felt when visibility was limited. A few were intentionally “wrong,” designed to push limits and reveal failure modes.

This phase produced dozens of physical parts. Not all were assembled. Not all were functional. But every one of them taught us something.

What the Prints Revealed That CAD Did Not

One of the most valuable outcomes of this process was how quickly physical models exposed assumptions that had gone unnoticed in CAD.

For example, a particular internal feature looked perfectly reasonable on screen. In reality, it forced the assembler to flex the enclosure slightly during closure. The deformation was minor and temporary but it introduced stress that would accumulate over repeated assembly and disassembly.

Another version revealed that a seemingly insignificant change in wall thickness altered how the device felt in the hand. It shifted the perceived balance just enough to affect confidence during use.

These were not issues that would have triggered alarms during a design review. They only became apparent through repeated physical interaction.

The Turning Point: Recognizing the Real Decision

After many iterations, it became clear that the project was not converging on a single “best” design automatically. Instead, the team was circling around a fundamental architectural decision that had not yet been made.

The question was not about aesthetics or minor geometry changes. It was about how the device should be fundamentally structured: how the internal components were anchored, how the enclosure carried load, and how assembly forces were managed.

Once this realization surfaced, the earlier prints took on new meaning. They were no longer just variations they were evidence.

Looking across all the printed versions side by side, patterns emerged. Certain configurations consistently felt more robust. Others repeatedly introduced small but persistent issues.

The dozens of prints narrowed the decision space from “many possible designs” to “one clear direction.”

Making the One Decision That Mattered

The final decision involved rethinking how the internal structure and enclosure interacted. It required accepting trade-offs: slightly more material in one area, a small change in assembly sequence, and a shift in how the device was opened for servicing.

On paper, the change looked modest. In practice, it transformed the design.

The next printed version-built around this decision-stood out immediately.

Assembly felt easier. The device felt more solid in the hand. Small inconsistencies that had appeared across earlier versions simply disappeared.

Importantly, this version was not perfect. But it was coherent. It behaved predictably, and its remaining issues were clearly defined rather than ambiguous.

That clarity allowed the project to move forward with confidence.

Why Fewer Prints Would Have Been Riskier

Looking back, it would have been tempting to stop iterating earlier. Several earlier prototypes were “good enough” by most standards.

But stopping early would have meant committing to a design without fully understanding its weaknesses. Those weaknesses would likely have resurfaced later, during manufacturing, testing, or clinical evaluation, when changes are far more expensive.

The value of 3D printing in this project was not speed alone. It was the ability to explore uncertainty safely and visibly.

Each print reduced risk by making assumptions tangible.

Lessons Learned

This project reinforced several principles that now shape how we approach early medical device design:

First, iteration is only valuable when it is intentional. Printing many versions without clear questions leads to noise, not insight.

Second, physical interaction reveals things that digital tools cannot. Ergonomics, assembly behavior, and perceived quality are difficult to judge on screen.

Third, convergence often depends on recognizing the right decision to make. Once that decision is clear, progress accelerates naturally.

And finally, additive manufacturing is most powerful when used as a thinking tool not just a prototyping tool.

Outcome

The final design moved forward with significantly fewer downstream changes than initially anticipated. Manufacturing discussions were more focused, and testing revealed fewer surprises. While 3D printing did not eliminate all challenges, it helped ensure that the remaining ones were manageable and expected.

Most importantly, the team reached a design decision grounded in observation, not assumption.

Closing Thought

From the outside, dozens of 3D prints can look like indecision. In reality, they can be the clearest path to certainty.

In medical device design, where late-stage changes are costly and risky, taking the time to learn early, through deliberate, physical iteration can make all the difference.

Sometimes, it takes many prints to arrive at one good decision.