Selecting a Rapid Prototyping Process
Compare manufacturing technologies to find a process best suited to your needs.
Prototyping is the starting gate in the race to improve and perfect products. Each iteration refines your parts to ensure fit, form, and function. The good news is that there are dozens of ways prototypes can be made. Moreover, as new prototyping processes emerge, product designers have the opportunity to choose which process or technology is best for their unique application.
This guide explores the advantages and shortcomings of the major prototyping processes now available to designers. It provides process descriptions and discusses material properties of parts made from each prototyping option. Ultimately, we want to help you select the best prototyping process for your product's development cycle.
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What is Rapid Prototyping?
Rapid prototyping is a common early step within the product development process during which design teams quickly iterate an initial model. Often, this design will become a minimum viable product (MVP) , since it contains only the essential features necessary to test and gain user feedback. Typically, speed is most valuable during this phase of product development, so quick‑turn or digital manufacturing processes like 3D printing or CNC machining are preferred. This allows product designers to test multiple iterations within a short period of time and finalise their parts more quickly.
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Advantages of Rapid Prototyping
Done right, rapid prototyping streamlines product development, providing wholly positive results.
Cost‑Effectiveness
Traditional prototyping for injection moulding often involves new tooling and moulds for each iteration – but creating multiple, expensive steel moulds to test a part may not be the best use of this technology. Rapid prototyping aims to save you money by altering that step. One way is to use injection moulding with comparatively inexpensive aluminium tooling, or prototyping using 3D printing, CNC machining, or sheet metal fabrication, depending on your part design. With any of these, you will be able to manufacture your prototype at a fraction of the cost. Depending on your needs, your final iteration can then use injection moulding for high‑volume production.
Enhanced Communication and Collaboration
Rapid prototyping typically involves digital manufacturing processes, which invite collaboration during the iteration phase, using a computer‑based model of a part called a digital twin – a virtual version of a physical part. The digital twin travels through a virtual version of the manufacturing floor, identifying potential manufacturability issues before the real work begins. Collective stakeholders can identify any issues in the digital version of the file, respond to that, and provide input before final manufacturing begins.
Accelerate Product Development
When prototyping, you want to use the fastest manufacturing method available to make your parts. That decision will be informed by your end part, but if you just need a part manufactured for which you can test form, fit, and function, it helps to choose the simpler/faster process to enhance iteration speed. There are solutions that not only speed development, but also reduce costs.
Greater Product Customisation
Rapid prototyping allows for fast tweaks to design so you can customise the parts you need. Whether you intend to offer end users variations of colour, material, or functionality, this method will speed manufacturing of individual parts for evaluation.
Improved Design Validation
No one wants to go to full production quantities without proper testing and validation. At the core of rapid prototyping is a process that can detect flaws early in the development process, either via user feedback or functional testing. This can help avoid issues later in your product's life cycle.
🔗 Related content: Design for Manufacturing toolkit → /resources/design-for-machining-toolkit/
Ways to Reduce the Cost of Rapid Prototyping
Something not often thought about is the fact that rapid prototyping gets you your parts faster. That reduces costs because you avoid the expense of waiting for parts and reduce go‑to‑market delays. Here are some additional ways to reduce costs:
| Strategy | Description |
|---|---|
| Use a digital manufacturer | Moves parts from CAD to prototype faster than traditional manufacturers, with DFM feedback to ensure manufacturability |
| Choose materials wisely | Remember, it is just a prototype. If your final product needs titanium, any other metal (or even plastics) will work well for basic fit testing |
| Drop surface finishes | Aesthetic or protective coatings are not necessary at this stage unless you need to validate finished part fit |
| Evaluate your design | Focus on the most critical elements. Define your minimum viable prototype (MVP) goal before starting |
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Comparing Prototyping Processes
| Process | Technology | Description | Layer Thickness (mm) | Example Materials |
|---|---|---|---|---|
| SLA | Stereolithography | Laser‑cured photopolymer | 0.051–0.152 | Thermoplastic‑like photopolymers |
| SLS | Selective Laser Sintering | Laser‑sintered powder | 0.102 | Nylon, TPU |
| DMLS | Direct Metal Laser Sintering | Laser‑sintered metal powder | 0.020–0.030 | Stainless steel, titanium, aluminium, Inconel |
| FDM | Fused Deposition Modeling | Fused extrusions | 0.127–0.330 | ABS, PC, PC/ABS, PPSU |
| MJF | Multi Jet Fusion | Inkjet array selectively fusing powder | 0.080–0.203 | Black Nylon 12 |
| PolyJet | PolyJet | UV‑cured jetted photopolymer | 0.015–0.030 | Acrylic‑based photopolymers, elastomers |
| CNC | CNC Machining | Subtractive machining (mills/lathes) | – | Most engineering‑grade thermoplastics and metals |
| IM | Injection Moulding | Moulded using aluminium or steel tooling | – | Most thermoplastics, LSR |
| SM | Sheet Metal Fabrication | Press brake forming, laser cutting | – | Aluminium, stainless, steel, copper, brass |
Pros and Cons of Each Process
3D Printing Processes (SLA, SLS, DMLS, FDM, MJF, PolyJet)
Pros:
Excellent for concept models and complex designs
Intricate geometries possible
Competitive cost
Fast turnaround
Cons:
Parts may not be as strong as engineering‑grade resins
Limited functional testing capability
UV and humidity exposure can cause degradation (SLA)
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CNC Machining
Pros:
Superior surface finish and strength
Full, homogeneous material properties
Wide range of engineering‑grade thermoplastics and metals
Good tolerances for fit and functional testing
Parts can be delivered in as fast as one day
Cons:
Geometry limitations (undercuts, deep pockets)
Sometimes more expensive than 3D printing for simple parts
🔗 Related content: CNC Design Guidelines → /services/cnc-machining-service/cnc-milling/design-guidelines/
Injection Moulding
Pros:
Parts made from engineering‑grade materials
Excellent surface finish
Excellent predictor of manufacturability for production
Almost any engineering‑grade plastic or LSR can be used
Cons:
Initial tooling cost (aluminium or steel)
Best used after one or two rounds of additive/subtractive prototyping
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Sheet Metal Fabrication
Pros:
High precision in a vast array of thicknesses and materials
Cost‑effective for enclosures and brackets
Cons:
Limited ability to produce stamped or curved bend lines
Linear bends only (press brake forming)
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Choosing a Process
Use the following framework to narrow down which factors are of highest importance based on where you are in the prototyping process:
| Priority | Factor | Recommended Process |
|---|---|---|
| Speed | Need parts in 1‑3 days | 3D Printing or CNC Machining |
| Material properties | Need engineering‑grade materials | CNC Machining or Injection Moulding |
| Complex geometry | Highly complex, organic shapes | 3D Printing (SLA, SLS, DMLS) |
| Functional testing | Need production‑like properties | CNC Machining or Injection Moulding |
| Cost sensitivity | Limited budget | 3D Printing or Sheet Metal (where applicable) |
| Production intent | Planning for high‑volume production | Injection Moulding with aluminium tooling |
Rapid Prototyping Applications
Definitions vary and may differ at different organisations, but the definitions below may be used as a starting point.
Concept Model
A physical model made to demonstrate an idea. Concept models allow people from different functional areas to see the idea, stimulate thought and discussion, and drive acceptance or rejection.
Prototyping Considerations: Speed, appearance (colour, texture, size, shape)
Assembly/Fit Testing
Manufacturing some or all parts of an assembly, putting them together, and seeing if they fit properly. At the gross level, this checks for design errors. At the fine level, this is a matter of minor dimensional differences and tolerances.
Prototyping Considerations: Form (shape, features, size), Fit (how parts mate)
Functional Testing
Evaluating how a part or assembly will function when subjected to stresses representative of what it will see in its actual application.
Prototyping Considerations:
Chemical Resistance – resistance to acids, bases, hydrocarbons, fuels
Mechanical Properties – tensile, compressive, flexural, impact strength
Electrical Properties – dielectric constant, strength, dissipation factor
Thermal Properties – thermal expansion, heat deflection temperature
Optical Properties – refractive index, transmittance, haze
Life Testing
Testing properties that may change with time and that are important for a product to remain functional throughout its expected life. Often involves subjecting the product to extreme conditions (temperature, humidity, UV, etc.) to estimate long‑term performance.
Prototyping Considerations:
Fatigue Strength – ability to withstand repeated load cycles
Aging Properties – UV resistance, creep resistance
Regulatory Testing
Testing specified by a regulatory or standards organisation to assure parts are suitable for particular use cases (medical, food service, consumer applications).
Prototyping Considerations:
Flammability Properties – resistance to ignition
EMI/RFI Properties – shielding effectiveness
Food Rating – FDA/EC approval for food contact
Biocompatibility – ISO 10993 for medical devices
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Considerations for Transitioning to Production
Many engineers use 3D printing for prototyping and then switch to injection moulding for production quantities. It makes sense in terms of cost and time saved. Industries including aerospace and medical device typically take this path during their product's life cycle.
Define Your Part Before Designing
Put a lot of thought into your part's design, being cognisant of the different DFM requirements that 3D printing and injection moulding have. During prototyping, do not box yourself into a corner with fancy geometries that print beautifully but cannot be replicated via injection moulding. Our interactive DFM feedback during quoting can provide helpful guidance.
Using Multiple Prototypes
Designing and manufacturing multiple prototypes enables you to explore different design options, features, or aesthetic variations without committing to costly tooling too early. This allows for a more comprehensive understanding of what works best for the intended application and market.
Maneuvering Through Moulding
Transitioning to injection‑moulded parts requires specific design methods:
Uniform wall thickness – ensures the mould fills evenly, preventing defects
Draft angles – facilitates easy ejection of the part from the mould
These are considerations that must be included when moving to injection moulding, even if not present in a 3D‑printed prototype.
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Choosing Materials
Even the same material can act differently when printed vs. moulded. Material selection for injection moulding depends on various properties, including mechanical, physical, and thermal characteristics. Manufacturability, including resin flow and how well it fills the mould features, is essential. Cosmetic appearance and cost also play significant roles.
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Mitigating Costs and Timelines
Prototyping using 3D printing is often the fastest way to iterate. Changes can be made in a CAD model, leading to quick turnaround of your updated prototype. While cost and deadlines are crucial factors, using affordable production methods can help control costs. Digital manufacturing can also accelerate product development, shortening both prototyping and production timelines.
Summary
Prototype models help design teams make more informed decisions by obtaining invaluable data from the performance of, and the reaction to, those prototypes. The more data that is gathered at this stage of the product development cycle, the better the chances of preventing potential product or manufacturing issues down the road. If a well‑thought‑out prototyping strategy is followed, there is a far greater chance that the product will be introduced to the market on time, be accepted, perform reliably, and be profitable.
The right prototyping process depends on where you are in your process and what you are trying to accomplish:
Early in the design process – concept models are helpful
As the design progresses – a prototype that has the size, finish, colour, shape, strength, durability, and material characteristics of the intended final product becomes increasingly important
Three key elements to validate with your prototype:
| Element | Description |
|---|---|
| Functionality | Does the prototype faithfully represent the attributes of the end‑product? |
| Manufacturability | Can the design be repeatedly and economically produced? |
| Viability | Will anyone want to use it? Can it pass market and regulatory testing? |
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