Metals have been the basis of industrial construction for centuries. Their strength, conductivity, and workability make them indispensable in many applications.
In the manufacturing industry, “good quality” is no longer enough—today, micrometric precision, repeatability in every series, and flexibility in design changes are what count.
Under these conditions, traditional machining methods become a barrier to development. They are being replaced by solutions that combine automation with reliability, led by CNC machining, which we explain in detail in the article “What is CNC machining?”
Process flow – what does metal machining on CNC machines look like?
- From documentation to detail – what needs to be prepared
The process begins with the preparation of technical documentation in CAD (Computer-Aided Design) format, which is then converted into CAM (Computer-Aided Manufacturing) code.
This code contains instructions for the CNC machine regarding the tool trajectory, rotational speed, feed rate, and other parameters. The accuracy of this data is crucial to achieving the desired end result.
- What happens on the production floor?
At this stage, the actual metalworking on CNC machines takes place. The selection of tools, cutting parameters, and machining strategies depends on the geometry of the part, the material, and the type of technological operation.
Modern CNC centers are often equipped with automatic tool changers, cooling systems, and measuring sensors, which allow for high repeatability, shorter production times, and minimized risk of errors.
- Surface finishing – the final step that makes the difference
After the main cutting operations, the surface finishing stage follows, which may include:
- Deburring – removal of sharp edges and burrs.
- Grinding – achieving a smooth surface with low roughness.
- Polishing – giving the surface a shine and an aesthetic appearance.
Quality control at this stage is crucial to ensure compliance with technical requirements.
Challenges in CNC metalworking
Each material reacts differently to machining. What works for steel may be completely wrong for aluminum or brass. The right choice of tools and strategies is the key to quality, repeatability, and process durability.
Structural steel (e.g., S235, S355)
This is one of the simpler groups of materials in terms of machining. Both HSS (High-Speed Steel) and carbide tools can be used.
Structural steel can be machined quickly and without major restrictions, but for longer operations it is advisable to check the wear of the tool edges regularly.
Stainless steel (e.g. AISI 304, 316)
Requires a more thoughtful approach. It is hard and at the same time “stretchy” – it tends to stick to the cutting edge. This causes problems with chip removal and accelerated tool wear.
Blades with friction-reducing coatings, such as AlTiN (titanium and aluminum nitride), are usually recommended for machining this material.
Hardened steel (>45 HRC)
Hardened steel requires solid carbide tools (VHM – from German Vollhartmetall) and appropriate coatings, e.g. TiSiN (titanium and silicon nitride), which increase wear and temperature resistance.
The process must be stable – rigid clamping, short strokes, precise path. The parameters must be selected sensibly, depending on the tool diameter, geometry, and machine capabilities.
Aluminum
Aluminum is a machinable material, but due to its ductility and low hardness, it requires a specific approach. During machining, it produces long chips that easily clog the cutting space, and when working with thin-walled parts, there is a risk of vibration and deformation.
The best results are achieved with solid carbide (VHM) milling cutters with a large rake angle (approx. 45°) and a polished chip surface.
Brass and copper
These materials are very easy to machine and are often considered “easy” for CNC machining.
An overly aggressive rake angle or a rough cutting surface can lead to material tearing, local overheating of the cutting edge, and accelerated wear.
This is because the heat generated during machining is very quickly transferred to the workpiece, which in thin-walled components can result in deformation or dimensional changes.
For CNC machining of brass or copper, solid carbide (VHM) cutters with very sharp, precisely ground edges and a maximally smooth surface are recommended.
Understanding the physical and chemical properties of the material being machined and precisely adjusting the cutting strategy has a direct impact on the final quality of the component, the service life of the tools, and the efficiency of the entire cutting process.
What can go wrong with CNC metal machining – and how can it be prevented?
Three main problems can occur during CNC metal machining:
1. Chatter
This leads to an uneven surface, poorer accuracy, and faster wear of the cutting surfaces. The most common causes are excessive tool projection, lack of rigidity in the clamping, or incorrect cutting parameters.
2. Incorrect cutting parameters
Excessive speed, feed rate, or cutting depth can lead to blade overheating, tool breakage, and poor surface quality.
3. Tool wear
Every milling cutter, drill, and tap has a limited service life – if not checked regularly, it can damage the workpiece or cause errors in the entire series.
When is it worth outsourcing CNC metalworking to an experienced company?
For series production, complex geometries or high quality requirements, working with an experienced contractor helps to avoid errors and delays.
Not only is a precise machine park crucial, but also practical knowledge of different alloys, their behavior during processing, and possible design limitations.
Summary of CNC metalworking
CNC metalworking is more than just removing excess material. It is a complex technological process in which precision tools work together with computer control, and each stage is based on engineering knowledge and familiarity with the properties of materials. Thanks to this technology, it is possible to manufacture components with complex geometries, high quality, and repeatability in a fast, safe, and economical manner.
Behind the efficient CNC process is a team of specialists. The designer creates a model of the part, the programmer prepares the machining code, and the operator supervises the production process on the machine. It is the combination of human competence and the capabilities of modern machine tools that allows us to achieve a level of precision that cannot be guaranteed by traditional methods.