CNC vs 3D Printing – How to Decide

Both technologies have their strengths and weaknesses when it comes to a product development and the manufacturing environment. There are certainly arguments to be made to determine which process is ideal for your business or application, but it’s important to note that these technologies are oftentimes complementary and can exist side-by-side.

You can identify ways for these technologies to benefit your department by looking at several factors, such as business model, company maturity, design development or production process. For example, a machine shop will use CNC machining for voluminous production requirements and alternatively, use 3D printing to produce parts that are designed with advanced complexities or geometries that are just not possible with subtractive technology.

One size does not fit all when it comes to fabrication technologies. Injection molding and CNC machining have been the most cost-effective mass production methods available to industry, while 3D printing adoption has grown significantly within the past decade. Amongst other variables, it’s important to compare size, quantity, functionality and purpose to establish what makes the most sense for you.

If you address these questions by industry, you may want to consider the following: The consumer product industry is experiencing massive growth with personalised footwear, accessories and electronics with the use of 3D printing. The automotive and transportation markets have invested significant time and resources to identify large format 3D printers that can replace bonding, welding and tooling requirements necessary on the production floor.

The basic difference between 3D printing and CNC is by its principles.  3D printing works on additive manufacturing principle. Whereas CNC works on subtractive manufacturing principle.

CNC machining is a subtractive process, starting with a chunk of metal and using programming controls (CNS Computer Numerical Control) which controls the machine tools movements in three dimensions, removing material until the object is complete. 

3D printing is additive, and the most common sort uses a plastic filament and melts it’s via a hot end extruder.  The movement of the extrude are controlled by the printer so that a line of plastic is laid down in a programmed shape, layer by layer.

Today, more companies in a variety of industries are embracing the 3D printing process as it presents many significant advantages over the more traditional manufacturing methods of subtractive manufacturing and injection molding:

1. Speed
2. Cost
3. Flexibility
4. Competitive advantage
5. Tangible design and product testing
6. Quality
7. Consistency
8. Risk Reduction
9. Accessibility
10. Sustainability

Though on average 3D printing is cheaper, costs depend on how many parts are required and how quickly you need them. For larger quantities (higher double digits to 100s) CNC is likely to be more appropriate. For low volumes, 3D printing is more appropriate and lower cost. 3D printing is also more appropriate if you need your prototypes or parts very quickly. There are additional factors however that make comparing the two technologies more difficult. These include materials varying in cost (from cheap materials like ABS to materials that can cost $500/kg like PEEK) and repairing and changing machinery (such as CNC heads).

3D printing is known to be simpler to use than CNC machining. This is because once the file is prepared, you just need to choose the part orientation, fill, and supports if needed. Then once printing has commenced, no supervisor is required, and the printer can be left until the part is finished. Post-processing requirements depends on the technology.

However, CNC machining is a far more labour-intensive process. A skilled operator is required to choose between different tools, rotation speeds of tools, the cutting path, and any repositioning of the material the part is being created from. There are also post-processing techniques which can require more time.

CNC and 3D printing use the same core technologies, so advances in one also pushes advances in the other. If considered whole manufacturing process of metal parts, it will appear that metal 3D printing and CNC machining are somehow two different things, and one cannot replace the other.

Metal 3D printing is constantly improving and can replace some of the processes but can still require CNC machining.

It depends on what you want to do. The short answer can be “3D printer”, because it is very versatile. Long answer is that there are dozens of factors that could affect your decision. In general, if you are undecided, you would probably be happier with a 3D printer.

CNC routers need highly skilled specialists, they produce a lot of noise and waste and can only be used in a workshop environment.

A 3D printer is slower, but producing low volumes is a lot cheaper. 3D printers can be operated after basic training and with lower emissions they can also be placed in an office surrounding.