3D Printing vs CNC Machining – How to Select a Rapid Prototyping Process?

CNC rapid prototyping is an important process for the product development. Manufacturers cannot mass-produce products with unproven or untested features and designs.

They can rely on traditional custom part prototyping methods, which are expensive and time-consuming. Unlike CNC prototyping, these methods can’t meet the requirement of the tight tolerances in today’s industry. There are many other advantages to CNC rapid prototyping that make it very attractive to custom prototype manufacturers.


What is Prototyping?

Prototyping is a process used in product development to create functional prototypes of designs before mass production. It involves using machining techniques to create a physical model or prototype of a product that can be tested and evaluated for function, fit, and form.

Computer-controlled machines carve out models from metal, plastic, or any other suitable solid material. Manufacturers use prototyping to identify design flaws before beginning full production.

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3D Printing vs CNC Machining: What’s the Difference?

3D printing is an additive manufacturing process. This means that the final product is created by the 3D printer placing successive layers of material on a work plate until the final shape of the product is achieved.

On the contrary, CNC machining is a subtractive manufacturing process. It starts with a piece of material called a blank, and then machine away or remove material to remain in the final product.


How do you select the suitable prototyping process for your project?

Material: CNC machining has a clear advantage when it comes to working with metals. 3D printing, in general, is more focused on plastics. There are 3D printing technologies that can print metals, but they can be very expensive from a prototyping perspective.

  1. Output and cost: If you are looking for a quick one-off prototype or very low quantities of prototyping, 3D printing will be cheaper. For higher production, CNC machining is the way to go.

For one-off prototypes, the upfront cost of additive manufacturing is generally lower than subtractive manufacturing. That said, all parts that do not require complex geometry can be made more cost-effectively using CNC machining.

  1. Design complexity: Both technologies have their limitations, but in this case, 3D printing has a clear advantage. CNC machining cannot handle complex geometries due to factors such as tool contact and clearance, tool holders, and mounting points. It also cannot machine square corners due to tool geometry. 3D printing offers more flexibility when it comes to complex geometries.

Another aspect to consider is the size of the part you are prototyping. CNC machines are better suited to handling larger parts. On the same cost condition, CNC machining can achieve the large parts but 3D printing cant.

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Size and accuracy: For parts that require tight tolerances, CNC machining is the best choice. CNC machining can achieve tolerance levels between ± 0.025 – 0.125 mm. Meanwhile, 3D printers generally have tolerances around ± 0.3 mm. Except Direct Metal Laser Sintering (DMLS) printers, which can achieve tolerances as low as ± 0.1 mm, this technology is too expensive for prototyping.

Surface treatment: If an excellent surface finish is an important criterion, CNC machining is a clear choice. 3D printers can produce a very good fit and finish, but if you need an excellent surface finish to fit with other higher-precision parts, CNC machining is the way to go.


3D printing is still a relatively new technology. There are expensive and state-of-the-art 3D printers that close the gap with CNC machining capabilities, but from a prototyping perspective, they cannot be considered here. How to select a suitable prototyping process for your parts depends entirely on the design specifications of your prototyping project. Both of them have advantages and disadvantages, if you can’t make the decision, welcome to check with us for getting more information.

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