Rapid prototyping is a set of techniques that quickly turn a CAD model into a physical part ready for evaluation and testing. It lets design teams check concepts, find errors and make changes before a company starts production. In this guide we explain how prototyping works, which technologies are used and when CNC machining is the right choice.
Table of contents:
- Rapid prototyping – definition
- What are prototypes?
- How the prototyping process works
- Rapid prototyping technologies
- Materials for prototypes
- Benefits of rapid prototyping
- Limitations and challenges
- CNC prototypes at Sacher CNC
- Rapid prototyping – FAQ
Rapid prototyping – definition
Rapid prototyping (RP) covers the fast production of models and parts directly from digital data. The starting point is a 3D model prepared in CAD software. Based on it, a physical object is made that can be inspected, measured, assembled and tested.
Rapid prototyping allows engineers to go from an idea to a physical object within days rather than weeks. It can be used at every stage of product development – from the first concept to pre-production samples.
What are prototypes?
A prototype is an early version of a product or part used to check the design before production starts. Depending on its purpose, there are several types of prototypes:
- concept and visual models – show the shape and proportions and help visualise the idea,
- functional prototypes – make it possible to check operation, strength and fit with other parts,
- pre-production prototypes – made from the target material and with the target technology, used for final verification.
A physical model also makes communication easier. The customer, the designer and the process engineer evaluate the same object rather than an image on a screen, which helps to spot errors quickly.
How the prototyping process works
Prototyping is an iterative process, and at every stage of the process the team learns something new about the product. The basic cycle is: idea, prototype, test, feedback and correction. The team can repeat it several times until the design meets all requirements.
In practice, the process includes several stages:
- development of the concept and 3D model in CAD software,
- choice of technology and prototype material,
- production of the first prototype,
- tests, measurements and collecting user feedback,
- making changes and producing the next version.
This approach resembles the MVP (Minimum Viable Product) method: first the simplest version is made to check the key assumptions, and the following iterations develop it. Finding an error at the prototype stage is much cheaper than after production has started and the tooling is already in place.
Rapid prototyping technologies
Rapid prototyping uses additive technologies, i.e. 3D printing, and subtractive ones, i.e. CNC machining. The choice of technology depends on the purpose of the prototype, the complexity of the part, the required accuracy and the material.
3D printing
3D printing builds a part layer by layer. It is the most popular rapid prototyping technology because it requires no tools or fixtures. The most common printing technologies are:
- FDM – fused deposition modelling; molten material is extruded through a nozzle and laid down layer by layer,
- SLA – stereolithography; resin is cured with light, which gives very accurate reproduction of details,
- SLS – selective laser sintering of powder, most often nylon, without the need for supports.
3D-printed models are ideal for assessing shape and ergonomics. However, their strength and surface often differ from a production part, and FDM models usually need additional finishing. We write more about combining these technologies in the article How to use 3D printing for CNC machining.
CNC machining
CNC machining removes material from a solid block or bar by milling and turning. When a prototype has to work like a finished part, CNC machining gives the most reliable result, because it is made from the same material as the series product. It allows tight tolerances and good surface quality to be achieved. Cutting tools can also produce threads, fits and sealing surfaces just as on a series part. A CNC prototype can undergo functional and load tests as well as trials under temperature changes or vibration.
Compared with 3D printing, CNC machining requires programming and preparation of fixtures. For a single piece this extends the time needed, but in return it delivers a part close to the production version.
Materials for prototypes
The choice of material depends on what the prototype is meant to check. For assessing appearance, 3D-printed plastics are sufficient, often combined with simple finishing. For functional tests, it is worth choosing the target material.
The materials most often used in CNC prototyping are:
- aluminium, e.g. the popular 6061 alloy – light, easy to machine and strong,
- steel and stainless steel – for parts exposed to loads and wear,
- titanium – for aerospace and medical applications,
- engineering plastics such as PEEK, polycarbonate or nylon.
Metal prototypes have better mechanical properties than plastic models, so they better reflect the durability of the finished part. Making samples from several materials allows them to be compared before the decision to go into production is made.
Benefits of rapid prototyping
Rapid prototyping matters to every company that develops new products. The most important benefits are:
- shorter time to market – successive versions are created quickly,
- lower development costs – errors come to light at the prototype stage, not in production,
- better communication – teams, customers and manufacturers evaluate the same physical model,
- tests in real conditions – a functional prototype checks how the part works and fits,
- the possibility to compare materials and finishes before series production.
Prototyping is widely used in automotive, aerospace, medical and mechanical engineering, where shortening the development cycle has a real impact on competitiveness.
Limitations and challenges
Rapid prototyping also has limitations worth keeping in mind:
- some printing technologies give a rough finish and require post-processing,
- a prototype made from a material other than the target one will not fully reflect the part's behaviour,
- some materials are difficult to obtain in small quantities,
- part size may be limited by the size of the printer or machine,
- with tight tolerances, not every technology will deliver the required result.
That is why it is worth defining exactly what the prototype should check before choosing a method.
CNC prototypes at Sacher CNC
At Sacher CNC we make prototypes by CNC machining – from design analysis and material selection to the finished part. We work from customer documentation and also help develop the model from scratch. We use CAD/CAM software and modern machining centres for milling and turning. We make single prototypes as well as small series, which are a natural next step after the prototyping phase.
Every prototype undergoes dimensional inspection. If the part requires hardening or grinding, we can carry out these operations in our own plant. You will find more information on our page about CNC prototyping.
Do you have a design to check? Send an enquiry with a 3D model or drawing.
Rapid prototyping – FAQ
What is rapid prototyping?
It is a set of techniques for quickly producing physical models and parts directly from CAD data. It lets you check the design before a company starts production.
How does prototyping work?
By creating successive versions of a product and testing them. The cycle includes the idea, making the prototype, testing, feedback and a corrected design.
What is rapid?
"Rapid" comes from rapid prototyping. The word emphasises the short time from a digital model to a physical part.
What are prototypes?
They are early versions of a product: concept models, functional prototypes or pre-production prototypes. They make it possible to assess the appearance, function and manufacturability of a part.
Is rapid prototyping the same as 3D printing?
No. 3D printing is one of the rapid prototyping technologies. Prototypes are also made by CNC machining, especially when accuracy and a material close to the production one matter.