As a product designer or engineer, you often face countless choices in the product design process. For example, when selecting appropriate engineering materials or manufacturing methods for prototype (and production) parts, you may be at a crossroads.

CNC machining and 3D printing - two popular manufacturing methods today - can save you a lot of time and money while still ensuring high-quality parts. But these methods are not one size fits all. They all have many different functions, making them very suitable for different engineering design scenarioses.

This article introduces some key areas that you need to evalsuate before choosing between CNC machining or 3D printing for prototype design or production projects.

Five key areas that must be evalsuated before selecting CNC machining and 3D printing

To make the right choice between 3D printing and CNC machining, you need to evalsuate the following five key areas:

Small feature size

geometry

tolerant

engineering material

Cost and delivery time

#1 Small feature size

The small feature size describes the small scale at which you can create features on a workpiece using machining equipment. Due to CNC machining being a material reduction manufacturing technology, the tool diameter determines the feature size. By contrast, the nozzle size determines the small features you can generate using a 3D printer.

Usually, if you want to create parts with small feature sizes between 0.25 millimeters and 0.8 millimeters, you should choose 3D printing technology. The small feature size of CNC machines ranges from 1 millimeter to 3 millimeters - approximately four times the size of 3D printing technology.

#2 Geometry

Due to the CNC tool coming into contact with the workpiece from the top, you may encounter difficulties when machining certain shapes. For example, creating hidden features and undercutting using CNC machines is particularly challenging. In this case, you can rely on additive manufacturing processes such as 3D printing.

However, if you do your homework well and realize that CNC machining is suitable for your design, then it is important to choose the correct CNC equipment. CNC milling machines are very suitable for creating cavities and oblique cutting on workpieces with regular shapes, while CNC lathes are more suitable for processing complex cylindrical shapes. (Related post: Here are 5 CNC machine tools that you should definitely know)

#3. Tolerance

Now that you know that 3D printers can create almost any design, you can continue with 3D printing prototypes and production design, right? Wrong!

An important factor you need to consider before 3D printing parts is tolerance. If you are interested in± 0.1 mm and± If you are satisfied with the tolerance between 0.3 millimeters, you can continue to 3D print your design. But if your design requires stricter tolerance requirements, such as± 0.04 mm, then you must use a CNC machine tool.

The tolerance of CNC machines is between± 0.025mm and± Between 0.125mm, it is superior to all 3D printing technologies, including SLS, FDM, and DMLS metal 3D printing.

At this point, you may want to know if it is possible to machine extremely complex geometric shapes with hidden cavities through CNC while meeting strict tolerance requirements. Yes, it's definitely possible; What you need to do is to use auxiliary cutting tools instead of standard CNC cutting tools.

#4 Engineering materials

One of the significant advantages of CNC machines compared to 3D printers is their compatibility with a wider range of materials. With CNC, you can manufacture almost any material block, including plastic, metal, and composite materials.

In contrast, 3D printers are only compatible with thermoplastic plastics (ABS, PLA, nylon, etc.) and a few metals (such as aluminum and stainless steel).

However, you need to know one thing: because a 3D printer builds parts layer by layer, it changes the properties (or the way parts respond under pressure). Therefore, you must confirm that the 3D printing process will not change the properties required for your design to run as expected.

#5 Cost and delivery time

We can talk all day about small feature sizes, geometric shapes, tolerances, and a lot of other things that need to be considered. However, these are not as important to businesses as manufacturing costs and delivery times. Fast and cost-effective manufacturing technology is the dream of every product designer.

CNC machining is usually cheaper and faster than 3D printing, especially when you want to create over 100 identical parts. This is mainly because CNC machining eliminates the post-processing operations required for 3D printed parts, such as removing support structures and surface finishing operations.