Subtractive manufacturing
What is CNC and how does it work?
The traditional method of making parts by removing material from a block with cutting tools; included for comparison with 3D printing.
CNC Machining (for comparison)
CNC milling and turning are subtractive methods, the opposite of 3D printing: the part is obtained by removing material from a solid block or bar. They give very tight tolerances and excellent surface quality in metals and plastics. However, internal channels, lattice structures and geometries the tool cannot reach are not possible. Many projects combine them: 3D printing for prototypes and CNC for the final product, or CNC finishing on 3D printed parts.
| Typical tolerance | ±0.1 – 0.2 mm (ISO 2768-m, depending on size); precision ±0.025 mm |
|---|---|
| Minimum wall thickness | 0.8 mm (metal), 1.5 mm (plastic) |
| Surface | Ra 0.8 – 3.2 µm |
| Limitation | Internal geometry the tool cannot reach is not possible |
Process
CNC step by step
- 01
The stock is clamped in a vise.
- 02
CAM software generates the toolpaths.
- 03
Cutting tools remove material to create the form.
- 04
The part is flipped to machine the other faces.
- 05
Deburring and surface finishing follow.
Advantages
- Very tight tolerances
- Real engineering metals
- Excellent surface quality
- Fully isotropic material
Limitations
- Limited for complex internal geometry
- Material waste
- Expensive for one-off complex parts
Best suited for
- Mechanical parts with tight tolerances
- Metal end-use parts
- Precision surfaces and holes on 3D printed parts
Design
CNC design guidelines
- Minimum wall thickness0.8 – 1.5 mm
- Smallest detailDepends on tool diameter
- Minimum hole diameterØ 1 mm
- Overhang angleUndercuts require special tools
- Clearance for moving parts0.05 – 0.1 mm
- Text and logosEngraved ≥ 0.5 mm
Surface and assembly
Post-processing
- Anodizing (aluminum)
- Bead blasting
- Passivation
- Powder coating
Materials
Materials printed with CNC
Good to know
Frequently asked questions about CNC
What is CNC?
CNC milling and turning are subtractive methods, the opposite of 3D printing: the part is obtained by removing material from a solid block or bar. They give very tight tolerances and excellent surface quality in metals and plastics. However, internal channels, lattice structures and geometries the tool cannot reach are not possible. Many projects combine them: 3D printing for prototypes and CNC for the final product, or CNC finishing on 3D printed parts.
How does CNC work?
The stock is clamped in a vise. CAM software generates the toolpaths. Cutting tools remove material to create the form. The part is flipped to machine the other faces. Deburring and surface finishing follow.
What applications is CNC suitable for?
CNC is especially suitable for mechanical parts with tight tolerances, metal end-use parts, precision surfaces and holes on 3d printed parts.
How accurate are CNC parts?
Typical tolerance is ±0.1 – 0.2 mm (ISO 2768-m, depending on size); precision ±0.025 mm. The exact value depends on the machine, material and part geometry.
Other technologies
Let's talk about your project
Send us your idea and any design you have; our project support team will get back to you as soon as possible.