CNC Rapid Prototyping: The Complete Guide in 2022

by | Jan 12, 2022

Wouldn’t it be great if someone split such a complex topic as CNC rapid prototyping into simple sections and discussed them comprehensively? Well, we did.

This complete guide will detail the step-by-step process of CNC prototype machining and explain why it is the top-notch technique to apply.

For starters, it is essential to obtain a proper understanding of what is typically considered CNC prototype machining.

CNC is short for computer numerical control, i.e., any CNC-based machine is fully automated and does not require manual interventions. Certainly, some pre-adjustments and maintenance procedures are still needed. However, CNC machining is deprived of human factors deteriorating the quality of products manufactured.

CNC rapid prototyping product

At the same time, machining is the production of high amounts of components by manufacturing operations, e.g., milling, turning, drilling, etc. Thus, CNC machining is the use of complex automated machinery to manufacture batches of identical parts.

In the vast majority of cases, any manufacturer requires obtaining a sample of a product it wants to develop and produce. But before we go into that, let’s definitively polish insight into CNC prototype machining.

Considering that “prototype” is defined as an early model to test a concept or a process, it serves a particular purpose. It makes it easy to detect existing mistakes and problems in the preliminary stage and facilitates their further correction.

Finally, making prototypes is beneficial for the validation of machining operations. This strategy basically comprises all manufacturing processes where appropriate. Equipment units involved in rapid prototyping may differ from ones used for full-size batches of components.

Now you’re ready to discover more about why CNC rapid prototyping is frequently applied before actual large-scale production.

Why Choose CNC Rapid Prototyping

Let’s jump right into the reasons to apply techniques of CNC rapid prototyping.

1. Cost saving

Look at it this way. Besides all technical reasons detailed further, rapid prototyping is some form of fail-safe to prevent you from financial losses. It is frequent that an intricate design of a part does not succeed from a first attempt. It is much better to lose some materials and a bit of time instead of fully loading a manufacturer’s powers to produce sub-quality products. Instead, rapid prototyping enables the testing of a new design before custom machining.

Moreover, in most cases, you want parts produced to be tested for their mechanical properties before managing large-scale orders. Those properties may include harness, fatigue limit, elasticity, rigidify of the product, actual weight, etc. It is also possible that some complicated designs prove themselves to not be viable for the purpose they had been intended to. Launching a small batch of newly designed parts by means of rapid prototyping is a cost-effective intervention.

2. Precise tolerances

It may seem like any machining process is precise to a certain degree. The true value deviation offered by particularly prototype machining is extremely small. It is correct for comparison to other means of prototyping and larger versions of CNC machines used for large-scale orders. 

With rapid prototyping, the desired outcomes can be obtained with high precision. It creates solid ground for further manufacture of components.

precise CNC machining

3. Perfect mimic of a finished product’s design

I do not get tired of repeating the crucial point. It is vital to have a small batch of prototypes to launch manufacturing of a component with a new design.

From the quality assurance perspective, a batch of parts produced through rapid prototyping may serve as an object for further validation. It implies that testing of such prototypes can serve as documented evidence. It is proof that further manufactured parts have the same properties and are of the same quality as their samples tested.

So, what does all this mean? Rapid prototyping may help in obtaining quality certificates required to sell products in some countries. Overwise, samples made via prototype machining can be presented to customers or potential buyers. This way, prototypes also serve the proof of claimed features of a finished product.

4. Versatility

And the best part? You don’t need to choose from a range of options while deciding what prototyping suits your intended design better. CNC rapid prototyping is a highly versatile process, enabling the production of samples of desired complexity for further testing. Software-controlled manufacturing incorporates multiple machining operations. Rapid prototyping works similarly. As a result, you may receive any design you need. Most advanced equipment units for rapid prototyping are all-in-one solutions for your manufacture.

5. Wide range of applicable materials

The choice of a material depends on a part’s operating temperatures, properties requirements, and other factors. Therefore, you should be sure that rapid prototyping responds to your needs for a particular material.

As well as traditional CNC machines, software-based centers for prototypes incorporate a wide range of materials. It includes metals, woods, plastics, and even foams.

6. Fast turnaround

Rapid prototyping is not called “rapid” for nothing. Batches of custom samples are fairly small, and the process is focused on fast results delivery. As a result, it will not take long from setting an order to testing prototypes.

7. Short run

Rapid prototyping is also called “short-run production.” Allow us to explain. Short-run refers to a production cycle with at least one factor fixed. These input factors can be labor, capital, real property, equipment, materials, etc. While in long-run production, nearly all those variables can fluctuate, affecting the final cost of production, short-run manufacturing is less vulnerable to changes.

Let us give you some examples. A company produced a batch of components within half of a year. It is unlikely that something will change within this period. A supplier would not increase prices for materials, and the equipment involved would not require repair. However, further batches may have another net price per production unit. 

Ordering prototypes from a third-party service provider is also short-run production, executed in a period of six months or less. It is a predictable process, and the fixed terms of a contract give you confidence.

But how do you know when it is better to apply for short-run production and when for traditional large-scale CNC machining? As a rule of thumb, rapid prototyping is the most cost-effective alternative for the production of fewer than 10,000 parts or near that. For more exact calculations, you may use calculations for estimated net price per production unit, i.e., production cost formulas.

8. Wide range of finishing options

It is easy to forget about a component’s finishing while paying close attention to its fundamental design. Luckily, CNC rapid prototyping is known for incorporating a range of options to perfect an innovative sample.

The most obvious type of finishing is adding some surface texture and smoothness. Additionally, it may include removal of supports, sanding, or blasting. Then, you may be offered color matching, such as splay or hand painting. The other option available is coating. It may include plating, shielding, or durability coating. You can take it as an extra layer of protection. And the icing on the cake is the addition of inserts or functional assemblies. These make good designs even better.

Let me add another important piece of information, so you would not be confused if you were asked about whether basic, normal, or detailed finishing you need. The three types of finishing typically available offer the following. Basic – support removal only. In other words, it is simple surface finishing. Normal – removal of build lines and light bead blast (SLA only). Detailed – customized finishing in accordance with the specification, including painting, graphics, assemblies, etc.

9. No fixed tooling

It is a frequent difficulty of manufacturers of any size that their options for innovative solutions are limited. Indeed, having strictly defined sets of cutting tools for own production makes it difficult to eliminate errors that may arise during rapid prototyping. Thus, you may not be able to choose more appropriate tooling, as their range is limited. As a bonus of prototype machining, there is no fixed tooling by definition. It is highly appreciated if a company or a third-party provider is partnering with cutting tools suppliers. It enables us to involve any equipment needed fast. What is the purpose? To make absolutely any viable design possible to machine further.

Step-by-Step Process of CNC Rapid Prototyping

Do you need thoughtful insight into stages of prototype machining? We’ll walk you through the whole process of CNC rapid prototyping, explaining each step in great detail.

product ideation

1. Design Ideations

On the primary stage, product designers and engineers collaborate to create multiple designs of the same component. Varying factors are dimensions, materials, positioning of features, and others. Sometimes it happens that initially great ideations prove themselves to be not viable on this stage already. It is frequent that distinct ideations for manufacture and assembly (DFMA) and design for testing (DFT) are prepared. It ensures that the further production and current prototyping are optimal.

2. Generation of 3D files

You may have heard about computer-aided design (CAD) files and respective software. Well, in general, CAD design stands for digital modeling of parts. The highly advanced applications enable the creation of any design with consideration of the dimensions and features of an object required.

There is no other successful solution for drawing prototypes but CAD software. It is so because applications enabling the programming of CNC machines are based on CAD files. Therefore, The 3d files generation is convenient for designers to manifest their ideas fully, engineers to consider technical characteristics, and specialists to prepare computer-based machining centers.

product design

3. Identification of production sequence

CNC rapid prototyping, obviously, may include a number of manufacturing processes. Examples of them are cutting, milling, routing, turning, drilling, and others. To enable further production of innovative samples, it is vital to hand-pick processes that are to be implemented and their optimal sequence. It is another tricky stage to make sure that a production line comprising CNC machines has a well-defined set of machining operations for a particular component.  It may be that a single highly versatile equipment unit implements all the procedures. In any case, the production sequence is to be selected by respective specialists.

4. CNC programming

Both the production sequence and the design created will be integrated into a CNC machine’s control panel’s software. It is done by using G-coding to program cutting depths, feed rate, tool travel time, etc.

Learn more about pre-programming and preparation of components. Also, read our other blog posts about CNC machining.

Complex software solutions enable automatic transfer of CAD files into G-code-based ones. They incorporate machining operations intended and exploit ideation. Such a procedure makes it possible to command a machining center to move, turn, and feed cutting tools and/or workpieces. This stage requires a complete understanding of processes to eliminate all potential errors. 

A manufacturer rarely employs specialists capable of perfecting CNC machine programming. This part is frequently done by third-party service providers, such as ones offering rapid prototyping.

5. Prototyping

Without further ado, we are reaching the core of CNC rapid prototyping. It is the production of multiple samples per the 3d file coded. The numeric control panel of a CNC machine receives signals, dictating the movements of spindles along a center’s axes. As a result, the material is cut off a workpiece, and the desired product is achieved. It may take a while to eliminate all potential errors preventing the CNC machine from delivering repeatable outcomes. At this stage, both machining processes and the ideations designed should be finally optimized.

6. Testing

Here’s the kicker. The essential goal of rapid prototyping is to ensure that a component of a required design complies with requirements. For this purpose, innovative samples are tested for functionality, defects, durability, overall performance, physical suitability for a complex part they are intended for, etc. To satisfy a customer’s requirements and prove the viability of ideation, experts conduct multiple tests, generating respective data. It is to be analyzed further, and a suitable prototype to be chosen.

Limitations of CNC Rapid Prototyping

Let’s be honest. None of the machining or any other manufacturing techniques and processes are deprived of all the disadvantages.

Here is the list of ones relevant to CNC rapid prototyping.

1. Production costs

It was mentioned above that rapid prototyping is cost-effective. But the truth? It is more expensive to produce a single prototype than a single component finished by regular means of CNC machining. It is so because of the focus of rapid prototyping on in-detailed replication of a design rather than on cost-optimization. It is why many companies prefer not to make prototypes on their own, letting third-party service providers do the job. A manufacturer may require only one or two prototypes a year. But companies offering CNC rapid prototyping exploit their equipment fully, thus justifying initial capital investments.  Therefore, rapid prototyping cannot serve as a replacement for traditional methods of CNC machining. It is mainly intended for producing small batches of samples for testing.

2. Wastage of materials

You should take that it is unlikely that a prototype will be perfect from a first attempt. Typically, it requires a set of tries to receive the first viable component. Then, a certain amount of resources is needed to polish the machining technology. Kerf and subtracted materials and inevitable. It is also a con that you are unlikely to sell prototypes, even if they comply with all technical requirements. It is so because they may not have a serial number engraved and may not have proper packaging. They are not considered parts of a production batch. However, you may present prototypes to potential buyers to interest them in your products even more.
CNC machining labor

3. Require skilled labor

Basically, this disadvantage is not such if a third-party provider handles most designing, pre-programming, and testing. But what if you decided to create prototypes on your own? It is not like we warn you not to, but even if your specialists managed the creation of CAD/CAM files and CNC machines adjusting, they would not necessarily succeed in prototyping. The strategy requires innovative approaches, creative vision, substantial experience, knowledge of the procedures for testing and errors finding, etc. Likely, even masters of CNC machining cannot make prototypes without previous training. Isn’t it more cost-effective to let already trained teams do their job?

Final Word

In a nutshell, rapid prototyping is a pre-manufacturing process, vital to create and test a particular design. Besides the generated data for newly obtained components, rapid prototyping polish sequence of production steps required further. It is cost-effective for manufacturers to collaborate with a third-party provider to make prototypes or small batches of components.

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