Rapid Prototyping for Medical Devices: 9 Decisions to Make Before You Build Again
We Can Build Prototypes Faster Than Ever. But Are We Learning Faster?
Once the first CAD is ready, the obvious next step is usually to get a prototype made.
It is an exciting stage of medical device development. An idea that has existed in conversations, sketches and CAD files suddenly becomes something you can hold, operate and put in front of a user.
And because technologies such as 3D printing have made prototyping significantly more accessible, it is also easier to move quickly from one iteration to another.
FDA notes that additive manufacturing allows manufacturers to create complex designs and make design changes without the conventional tooling required by many traditional manufacturing methods. The technology has also moved well beyond experimental prototyping: FDA says it has cleared more than 100 medical devices manufactured using additive technologies.
But faster iteration does not necessarily mean better product development.
Across 60+ healthcare product development projects at Inspire Design, we have seen that the useful question is rarely “How quickly can we make the next prototype?”
It is usually:
What do we need to learn from the next prototype?
That decision influences almost everything that follows - how detailed the prototype needs to be, which process makes sense, what material should be used, who needs to test it and how close it needs to be to the eventual manufactured product.
Here are 9 decisions we believe are worth making before building again.
1. Be Clear About What the Prototype Needs to Prove
“We need a prototype” sounds like a clear requirement. In practice, it leaves a lot unanswered.
Take a handheld medical device.
During early development, the team may need to understand whether the core mechanism works. Once that is established, the next concern might be whether the device feels comfortable in a clinician's hand. Later, the question could be whether the electronics and mechanical components fit within the intended form factor.
All three require prototyping, but not necessarily the same prototype.
This is why we prefer to define the question before deciding how the prototype should be built.
A useful starting point is to complete this sentence:
After testing this prototype, we need to know whether ______.
If that answer isn't clear, it may be worth spending a little more time on the design before spending on fabrication.
2. Don't Make an Early Prototype More Finished Than It Needs to Be
There is always a temptation to make a prototype look like the final product.
Sometimes that is exactly what is required. At other stages, it adds time and cost without answering the important engineering questions.
A team could spend considerable effort refining an enclosure only to discover in the next round of testing that the internal mechanism requires more space. The enclosure then needs to change anyway.
This becomes particularly important because early product-development decisions can have a significant impact downstream. Research in product development has estimated that approximately 70–80% of total product cost can be determined during the design and development stages.
Early prototypes should therefore help teams make better decisions while there is still room to change them.
A mechanism prototype can look like a mechanism prototype. An ergonomic model can focus on how the product feels in the user's hand.
The level of finish should follow what the team needs to learn at that stage.
3. A Simple Prototype Can Sometimes Give You the Better Answer
Suppose the team is deciding between several grip geometries.
Building one highly finished device may appear to be the obvious next step. But if the real question is simply which geometry clinicians find easier to handle, several simpler physical models may produce much more useful feedback.
This is one of the reasons rapid prototyping has become so valuable in medical device design and development It allows teams to compare alternatives before committing too much time and engineering effort to one direction.
It also changes how we should think about an unsuccessful prototype.
If an inexpensive early prototype shows that a mechanism is unreliable or an ergonomic direction doesn't work, it has still created value. The team has learned what not to carry into the next stage.
In our experience, the value of an early prototype is better measured by what the team learns from it than by how closely it resembles the finished product.
4. Choose the Process Based on What You're Testing
This is where prototyping discussions can quickly become technical.
FDM, SLA, SLS, CNC machining, silicone casting - each has advantages, but starting with the technology puts the decision in the wrong order.
If the team only needs to evaluate the overall size and form of a product, a relatively simple 3D print may be sufficient.
If fine features and surface geometry matter, a higher-detail process such as SLA may be more useful.
If the prototype needs to represent particular mechanical behaviour or tighter dimensional requirements, CNC machining or another functional process may make more sense.
For flexible components, seals or soft interfaces, a rigid 3D print could reproduce the shape while failing to reproduce the behaviour that actually matters.
FDA notes that different additive-manufacturing technologies and materials are used depending on the application; for example, powder-bed fusion can work with materials including nylon and titanium.
There is no single “best” prototyping technology for a medical device.
The right process depends on the question the prototype needs to answer.
5. The Prototype Material and Final Material May Have Different Jobs
Material selection creates similar confusion.
During early prototyping, the material may simply need to reproduce a shape.
At another stage, flexibility, strength, surface behaviour or dimensional stability may become important to what is being tested.
And as the product moves closer to its intended use, material decisions can become considerably more significant.
FDA makes an important distinction here: it does not generally approve materials for unrestricted use across medical devices. Materials are evaluated as part of the finished device and its intended use.
So using a particular material successfully in a prototype does not automatically mean that it is appropriate for the finished medical device.
For prototyping, we would start by asking which properties need to be realistically represented in the current build. That usually gives the team a much better basis for selecting the material.
6. Put the Prototype in the Hands of the People Who Will Actually Use It
This is often the point where assumptions begin to change.
A development team becomes very familiar with its own product. Everyone knows how to hold it, where the controls are and how much force needs to be applied.
An intended user does not have that familiarity.
A clinician may hold the device differently. They may try to operate it with one hand. Gloves may change how easily they reach a control. The device may also be used in an environment with limited space, different lighting, other equipment and frequent interruptions.
FDA's human-factors guidance specifically considers device users, use environments and user interfaces because these interactions can affect safe and effective use. FDA also identifies environmental factors such as lighting, noise, clutter and distractions as relevant considerations.
This is why user evaluation can be valuable well before a product looks finished.
A prototype that causes an intended user to behave differently from what the design team expected has given the team useful information. The next iteration can now be based on observed behaviour rather than assumption.
7. A Working Prototype Does Not Automatically Mean You Have the Right Product
There is a point in many projects when everything appears to be working.
The mechanism functions. The electronics fit. The enclosure closes. The prototype survives basic testing.
That is an important milestone.
But it doesn't answer every question.
The device may still take too many steps to operate. Cleaning could be difficult. Assembly may be unnecessarily complicated. The user may need two hands for a task that is typically performed with one.
Or the product may work technically without improving the original clinical problem enough to justify the change.
That is why medical device prototype testing needs to keep coming back to the problem that started the project.
Technical feasibility answers whether the concept can work.
Product development has to go further and determine whether it works in a way that is genuinely useful for its intended application.
8. The Moment You Move From 1 Unit to 1,000, the Questions Change
A working prototype is built individually.
Manufacturing has to produce the product repeatedly.
That difference affects almost every engineering decision.
A 3D-printed enclosure, for example, may work perfectly during development. If the intended production process later becomes injection moulding, the design may need to account for wall thickness, draft, tooling, tolerances, material selection and assembly.
The user may eventually see almost the same product, while the engineering behind it has changed considerably.
This is why we believe Design for Manufacturing (DFM) should enter the conversation before the design is treated as completely finished.
The earlier statistic becomes particularly relevant here: if a significant proportion of eventual product cost is influenced during design and development, waiting until the end to think about manufacturing limits the team's room to improve those decisions.
At this stage, the question is no longer simply whether the product can be made.
It is whether it can be made consistently, at the required quality and at a commercially sensible scale.
9. Before Building the Next Version, Write Down What Changed
Once a prototype has been tested, teams are naturally eager to move on.
But before updating the CAD, it is worth documenting what the previous version actually taught you.
Perhaps the mechanism worked and stays unchanged.
The grip needs modification.
One component can be eliminated.
A control needs repositioning.
A material needs further evaluation.
An assembly step is creating unnecessary complexity.
Now there is a clear brief for the next prototype.
We find this much more useful than iterating simply because another version feels like the natural next step.
A good prototyping cycle is relatively simple:
Question → Prototype → Test → Learn → Decide → Next iteration
Each prototype should leave the team knowing something it did not know before.
Which Rapid Prototyping Method Should You Use for a Medical Device?
There is no universal answer, but this is a useful starting point:
What you need to understand | Method you may consider |
Overall size, form and fit | Basic 3D printing |
Fine features and surface geometry | SLA/high-detail additive process |
Complex functional polymer geometry | SLS or suitable additive process |
Precision or material-dependent behaviour | CNC machining/functional prototyping |
Flexibility, compression or sealing | Silicone/elastomer prototyping |
Small batches of similar parts | Casting/appropriate low-volume process |
Manufacturing assumptions | More production-representative processes |
The final choice depends on the product, development stage, material requirements and what is being evaluated.
9 Questions to Answer Before Spending on Your Next Prototype
Before the CAD file goes out for another build, ask:
1. What exactly do we need this prototype to prove?
2. Which parts of the design are still uncertain?
3. Are we building it to a higher level of finish than we currently need?
4. Is the prototyping process appropriate for what we're testing?
5. Are the relevant material properties represented adequately?
6. Have the intended users evaluated the aspects that matter at this stage?
7. What did the previous prototype teach us?
8. Have we started considering how this design will eventually be manufactured?
9. What decision will we make once this prototype has been tested?
If several of these questions are difficult to answer, it may be worth reviewing the product before committing to another build.
That review can sometimes be more valuable than another prototype.
Sometimes the Next Step Isn't Another Prototype
It may be a design change.
It may be user feedback.
It may be an engineering calculation.
It may be a conversation about manufacturing.
And sometimes another prototype is exactly what the product needs.
Across 60+ healthcare product development projects, this is how we approach prototyping at Inspire Design. Before deciding how to build the next version, we first try to understand what the team still needs to learn.
That makes the prototype part of the development process rather than simply another deliverable.
Already Have a CAD Model or Working Medical Device Prototype?
If you've already gone through a few iterations and aren't sure what should change next, you don't necessarily need to start over.
At Inspire Design, we work with clinicians, healthcare startups and medical-device companies across industrial design, engineering, rapid prototyping and Design for Manufacturing.
Share the stage your product is at and the problem you're currently trying to solve. We can start the conversation there.
FAQs About Rapid Prototyping for Medical Devices
1. What is rapid prototyping for medical devices?
Rapid prototyping for medical devices involves creating physical versions of a device during development to evaluate questions around form, fit, function, ergonomics, mechanisms, user interaction or manufacturability before progressing further.
2. Is 3D printing the same as rapid prototyping?
No. 3D printing is one rapid-prototyping method. Depending on the device and development question, teams may also use CNC machining, casting, silicone/elastomer prototyping and other low-volume fabrication methods.
3. Which prototyping process is best for a medical device?
There is no single best process. The choice depends on the design, material behaviour, geometry, accuracy, surface requirements and what the prototype is intended to evaluate.
4. How many prototypes are needed to develop a medical device?
There is no standard number. The number of iterations depends on the complexity of the product, technical uncertainty, user requirements, risk and what each prototype reveals.
5. Can the material used for a prototype be used in the final medical device?
Possibly, but successful prototype use alone does not establish suitability for the finished medical device. Final material selection depends on intended use, performance, manufacturing and applicable safety and regulatory requirements.
6. When should Design for Manufacturing begin?
DFM should be introduced early enough for manufacturing considerations to influence the design before major decisions become difficult or expensive to change. The level of detail increases as the product architecture matures.
7. Is a working medical device prototype ready for manufacturing?
Not necessarily. A working prototype can demonstrate feasibility, while manufacturing introduces additional considerations around repeatability, tolerances, tooling, assembly, materials, suppliers, quality and economics.
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