What is rapid prototyping?

In manufacturing, rapid prototyping refers to technologies and methods for quickly fabricating prototype parts or scale product models from computer-aided design (CAD) for evaluation, testing, and refinement before final production.

Rapid prototyping was introduced in the mid-1980s with the invention of stereolithography (SLA), and grew increasingly popular and more accessible with the emergence of other 3D printing technologies. Today, rapid prototyping is an integral part of the product development process, used for everything from generating physical models for product design evaluation and proof of concept to producing parts and product models for stakeholder input, user validation, and functional testing in real-world use.

How rapid prototyping works: the basics

Rapid prototyping is an iterative process with four basic steps.

Step 1: Design. Every rapid prototyping cycle starts with a part or product design executed as a CAD model or other three-dimensional digital design file.

Step 2: Prototyping. This is the quick generation of a physical prototype part or product model based on the data in the design file. The technology used to generate the prototype depends on the stage of product development or the purpose for the prototyping (see ‘Rapid prototyping technologies, below).

Step 3: Testing and validation. In this step, one or more stakeholders (e.g., customers, partners, engineers, regulatory experts) evaluate the prototype and provide feedback—e.g., design changes, test results, new feature ideas—or final approval.

Step 4: Refinement (repeat). The cycle begins again, starting with a new design that incorporates stakeholder feedback to the previous prototype.

There’s no specified or recommended number of rapid prototyping iterations in a product design process. In fact, today many product development organizations iterate constantly, prototyping incremental part and product improvements on a weekly or even a daily basis.

Rapid prototyping technologies

Fused deposition modeling or FDM

FDM technology is what most people today understand as a 3D printer: It ‘prints’ in three dimensions instead of two, by putting down multiple layers of plastic instead of one layer of ink.

Specifically, FDM deposits melted thermoplastic (such as acrylonitrile butadiene styrene or ABS) layer by layer, hardening the plastic between layers, to build a part from the bottom up. Typically, FDM machines also add struts to support delicate or projecting structures during the build; these struts need to be removed once the build is complete.

While FDM technology is always improving, it still builds in thicker layers compared to other rapid prototyping technologies, and FDM models tend to have a rougher surface finish and fewer fine details. This makes FDM best suited to creating fast, early-stage, low-fidelity prototypes, such as models for initial design reviews (e.g., product shape and size reviews), proof-of-concept, or initial functional review.

Stereolithography (SLA)

Stereolithography (SLA) builds parts using a laser to solidify and bind layers of plastic resin—a process called photopolymerization. (SLA is actually the acronym for stereolithography apparatus, the device that builds or ‘prints’ the parts, but the acronym is also used as shorthand for the stereolithography process.)

While somewhat slower than FDM, SLA can build parts using a wider range of plastics, including elastomers (for rubber-like parts) and plastics that can withstand higher physical stress and temperatures. It enables high-fidelity prototypes with thinner build layers, sharper details, smoother surface finish, more intricate part structures and geometries, and greater overall accuracy.

As a result, SLA is suitable for a wider range of rapid prototyping use cases than FDM—everything from high-fidelity proof-of-concept models, to parts for functional testing in production assemblies, to masters for injection-molding short runs of end-use parts.

SLA’s chief drawback is slower build speed, making it less suitable than other methods (such as ‘Digital light processing (DLP)’ below) for producing significant runs of final production parts.

Selective laser sintering (SLS)

Selective laser sintering (SLS) is also a laser to builds parts layer by layer, but from a nylon or polymer powder instead of a resin. A roller spreads a layer of powder on the build platform; the laser ‘draws’ the part in the powder and fuses the powder to create the first powder layer; then the roller spreads the next layer of powder, and the process repeats, until the part is built.

SLS is very popular with engineers and well-suited to prototypes for functional testing: it creates prototype parts that are even more accurate, intricate, and durable than SLA parts, and that require less post-production finishing (because they don’t require support struts). But the material choices are more limited—primarily to nylon and thermoplastic polyurethane (TPU)—and SLS parts can have a grainier surface finish than SLA parts.

Direct metal laser sintering (DMLS)

DMLS is basically SLS using metal powder. It can produce prototypes and final production parts in just about any type of metal or metal alloy. The downsides are that DMLS is more costly than SLS or SLA, especially for large quantities of parts, and the post-processing required to smooth the grainy surface finish is expensive.

Multi Jet fusion (MJF)

Invented by Hewlett-Packard in 2016, Multi Jet Fusion (MJF) is also similar to SLS. Instead of using a laser as a binder between layers, MJF uses inkjet-like print heads to ‘print’ a fusing agent on thin layers of thermoplastic powder. It also prints a detailing agent on the surface to enhance the resolution of small details.

MJF yields parts better suited to functional testing or end use than parts created with FDM, SLA, or SLS. But parts require time-consuming post-processing to remove excess powder and improve the surface finish, and one step of the post-processing—bead blasting, in which the part is blasted with tiny glass beads—can sometimes damage fine details.

PolyJet (PJet)

PolyJet (PJet) is kind of a cross between SLA and Multi Jet Fusion: It uses an inkjet-like print head to print very thin layers of resin, and cures and bonds each layer with ultraviolet (UV) light.

PJet’s thin build layers—as thin as 6 ten-thousandths of an inch—yield parts with the finest surface finish of any 3D printing method described here, and unlike the other 3D printing methods, PJet can also yield parts with elastomeric (rubber-like) flexibility. But PJet parts aren’t sufficiently strong or heat-resistant for functional testing.

Digital light processing (DLP)

Digital light processing is also similar to SLA—but instead of using a laser to ‘draw’ part layers in resin, DLP uses a UV projector to ‘snapshot’ each layer. As a result, DLP is considerably faster than SLA, making it more suitable for shops that do lots of prototyping or for producing end-use parts.

CNC machining

The 3D printing prototyping technologies described above are called additive manufacturing technologies, because they build prototype parts by adding layer after layer of material.

In contrast, computer numerical control machining, or CNC machining, is a subtractive technology: it mills, carves, drills, or grinds a solid piece of material into the shape of the prototype part.

CNC machining works with any type of material that can be milled—virtually any metal and hard plastic, but also glass, stone, composites, and even wood. It produces prototype and production parts with a superior surface finish and, because they can be milled from industrial-grade materials, superior strength.

But CNC may not be able to create complex part designs, particularly designs with complex internal structures. And CNC prototyping can be expensive and slow when performed in-house. CNC was invented in 1952 and dominated rapid prototyping until the late 1980s, when 3D printing technology emerged and gained popularity as a faster and more affordable alternative for many use cases.

Sheet metal fabrication

For manufacturers that build products from sheet metal, the latest technologies used for manufacturing final products—press brake forming (for bending metal), rolling, punching, and laser cutting—are equally well suited to rapid prototyping. In fact, many sheet metal manufacturers prototype constantly (between or coincident with production runs) to continually refine or improve their products or product features. Any approved prototype can quickly be integrated into the production process.

Sheet metal fabrication does limit product design possibilities (for example, press brake machines can only make straight-line bends), but these are the same limitations inherent in the final production method. In this sense, sheet metal prototyping is the rare rapid prototyping method that provides 100% visibility into the final production process.

Injection molding and vacuum casting

Technically, injection molding (injecting plastic or metal into a mold) or vacuum casting (molding plastic parts in a vacuum chamber) aren’t rapid prototyping technologies—they require a prototype part as a master in order to create the mold. But because they are relatively fast and inexpensive ways to create small runs of parts, they are often complements to the rapid prototyping process, particularly in the latter stages of the product design. For example, a product team might use injection molding to create 20 concept models to share with multiple stakeholders or manufacturing partners.

Rapid prototyping applications

Proof-of-concept (PoC) models

Product designers and engineers use proof-of-concept (PoC) models (also called concept and communication models) to determine if an initial product or part idea is worth pursuing.

PoC models needn’t be very detailed or accurate; frequently, they combine prototype parts with off-the-shelf components, such as readily available hinges or bolts, that communicate assembly requirements, basic movement, or some other aspect of the concept.

What PoC does require is lots of rapid iteration—including iterations of multiple design variations—that enable teams to compare, test, and refine different ideas. As a result, this prototyping is typically done using faster, lower-cost rapid prototyping technology, such as FDM 3D printing or very basic CNC machining.

Looks-like prototypes

Looks-like prototypes are just what they sound like: Primarily cosmetic, high-fidelity prototypes or mockups that look exactly or almost exactly like the final product will look, without necessarily having any working parts, features, or functionality.

Typically, a looks-like prototype is created by industrial design teams, who are focused on the outward physical form and appearance of the product. They may start with a clay or foam model, then transition to CAD-driven prototypes featuring the same colors, finishes, and even materials used in the final product. Not surprisingly, looks-like prototyping leverages high-fidelity prototyping technologies, including stereolithography, SLS/DLMS, and more advanced CNC machining.

Works-like prototypes

Works-like prototypes are just what they sound like: Part or product models created specifically for functional testing. Engineering teams create work-like models to test and refine mechanical functions (such as movement or action), electrical features, internal structures (e.g., fluid channels), ergonomics, or resistance to temperature or chemicals

Works-like prototypes can be created before looks-like prototyping, to validate functional viability before investing in product design, or in parallel to looks-like prototyping, to streamline production. They tend to be rough or unfinished compared to look-alike prototypes. Often, engineering teams create work-like prototypes to test the parts or subsystems before incorporating them into a larger product prototype.

Another use case for works-like prototyping is usability testing or user research. For example, an engineering team working on a new television remote might create a working-like prototype of a new and (hopefully) more intuitive button layout, and connect it to existing remote electronics for user testing.

Engineering prototypes

Engineering prototypes—also called functional prototypes or pre-production prototypes—are used for several later-stage prototyping purposes:

• Assembly and fit testing: This involves iterating on components or parts to ensure they fit or connect properly with other parts or with the rest of the product.
• Late-stage functional testing: Engineering teams produce prototypes that look like the end product, work like the end product and are built using the same or functionally equivalent materials as the end product, for testing by real users or in real world This testing is especially important for products that need to tolerate special or extreme conditions (high or low temperatures, high pressure, etc.).
• Manufacturability: Here, rapid prototyping is used to create tooling—injection molds, dies, etc.—to create small runs of parts using the same (or an effectively similar) manufacturing process used to create the final product. This allows engineers to identify design flaws (e.g., wall thickness, inflexibility, material tolerances) or geometries that might not stand up to the rigors of mass production, while these flaws can be addressed inexpensively.

Engineering prototypes are typically produced using high-fidelity prototyping technologies—such as SLA, SLS/DMLS, MJF, or PJet—that can produce detailed, accurate prototypes from the same or equivalent materials used in the finished product. But in certain cases, they can also be created with FDM, followed by appropriate post-processing (e.g., surface finishing, plating, etc.).

Prototyping for regulatory compliance

Rapid prototyping is becoming increasingly critical for demonstrating and maintaining legal and standards compliance for products that target highly regulated industries. For example, in the medical device industry, rapid prototyping supports compliance with

• The FDA’s Quality Management System Regulation (QMSR). Published by the U.S. Food and Drug Administration (FDA) and scheduled to take effect on February 6, 2026, the QMSR incorporates much of the ISO 13485 standard, which (among other things) requires rigorous documentation of the design, manufacture, risk management, and ongoing maintenance procedures involved in the development and lifecycle of any medical device.
• IEC 60601. Published by the International Electrotechnical Commission (IEC), IEC 60601 lays out safety requirements for electric medical devices, addressing both electrical safety issues (such as electrical shock, fire, and electromagnetic interference) and mechanical safety issues (sharp edges, pinch points, tipping potential).

Prototyping for compliance throughout the product development cycle results in safer products and helps prevent costly time-to-market delays and regulatory fines.

Benefits of rapid prototyping

The two chief advantages of rapid prototyping, compared to traditional prototyping, are significantly faster time to market and dramatically lower preproduction costs.

This is because rapid prototyping tools eliminate the slower, more costly tooling, moldmaking, and casting of traditional prototyping workflows, which rely primarily on manual or traditional manufacturing methods. They also enable stakeholders to identify mistakes, manufacturing issues, and potential compliance problems earlier, when they take less work and cost less money to address.

There are no formal studies available, but manufacturing organizations and experts routinely estimate that rapid prototyping can speed time to market as much as 40 percent, and cuts overall product development costs by as much as 90% compared to traditional prototyping.

Other benefits of rapid prototyping include:

• Improved communication and collaboration. Rapid prototyping makes it much easier for all stakeholders—designers, engineers, manufacturers, supply chain partners, end users—to convey product and feature ideas and feedback.
• Higher sustained product quality. Because rapid prototyping enables more and more cost-effective testing and feedback loops, product teams catch more quality issues that might otherwise not be identified until the product is in market. It’s worth noting that many general and industry-specific quality management standards and frameworks specify rapid prototyping, including ISO 9001, ISO 13485 (for the medical device industry), NADCAP (automotive industry), and AS9100 (aerospace industry).
• Continuous improvement and innovation. Rapid prototyping gives product development teams more time and opportunity to explore and test additional features or optimize features in response to user feedback. Many manufacturers use rapid prototyping technology to prototype and release new features continually (in much the same way as software developers using Agile or DevOps methodologies), instead of grouping new features into periodic product releases.