WhatisCNCMilling?
Everything about the most important subtractive process in metalworking.
Milling — Definition and Principle
Milling is a subtractive manufacturing process in which a rotating, multi-tooth tool (milling cutter) removes material from the stationary workpiece. Unlike turning, the tool rotates rather than the workpiece.
Milling is classified under DIN 8589 as a process with geometrically defined cutting edges. The cutter has defined edges that engage the material and produce chips. Modern CNC milling machines move the tool and/or the table in up to 5 simultaneous axes — enabling virtually any conceivable geometry.
Milling Methods Overview
Different milling methods are used depending on the task:
| Milling Method | Description | Typical Application |
|---|---|---|
| Face milling | Creating flat surfaces | Mounting surfaces, sealing surfaces |
| Peripheral milling | Contours cut with the cutter shank | Pockets, grooves, external contours |
| Pocket milling | Enclosed recesses | Housings, lightweighting |
| Drill milling | Drilling with milling tools | Precision holes with chamfers |
| Thread milling | Internal and external threads | Metric threads, trapezoidal threads |
| 3D freeform milling | Complex surfaces | Mold making, turbine blades |
Climb vs. Conventional Milling
A fundamental distinction in milling technique:
- Climb milling — Tool and feed move in the same direction. Result: better surface finish, less wear, longer tool life. This is the standard for CNC today.
- Conventional milling — Tool rotates against the feed direction. Result: rougher cut, more heat, but more stable tool engagement. Used for unstable workpieces or cast skin.
At Strobel Industry, we mill in climb mode by default. Our CNC machines have backlash-free ball screws, which are a prerequisite for this.
3-Axis vs. 5-Axis Milling
The number of axes determines which geometries are possible:
- 3-axis milling (X, Y, Z) — The cutter moves in three linear axes. Suitable for prismatic parts, plates, and simple pockets. Multiple setups needed for complex parts.
- 5-axis milling (X, Y, Z + A, B) — Additional rotary axes enable machining from virtually any angle in a single setup. Benefits: fewer re-clamping errors, shorter machining times, better surface quality on inclined surfaces.
Strobel Industry offers 5-axis simultaneous machining for demanding geometries — from turbine blades to medical implants. → More about 5-axis milling
Typical Milling Materials
Any machinable material can be milled. The most common:
- Aluminum — High cutting speeds (up to 800 m/min), easy machining process. Ideal milling material. → Aluminum machining
- Structural steel (S235, S355) — The all-rounder. Moderate cutting parameters, good machinability.
- Stainless steel (1.4301, 1.4571) — Challenging: high cutting forces, built-up edge formation, heat accumulation. Requires special geometries and coatings. → Stainless steel machining
- Plastics (PEEK, POM, PA) — Low cutting forces but risk of melting. Sharp tools and cooling strategy are critical. → Plastic machining
Frequently Asked Questions
What is the difference between milling and turning?
In milling, the tool rotates and the workpiece is stationary. In turning, the workpiece rotates and the tool is stationary. Milling is suited for prismatic parts (housings, plates), turning for rotationally symmetric parts (shafts, bolts).
How much does CNC milling cost?
Hourly rates typically range from €60–90/h for 3-axis and €80–120/h for 5-axis. The total price depends on geometry, material, tolerances, surface finish, and quantity.
What accuracy is possible with milling?
CNC milling machines achieve standard accuracies of ±0.01 mm and up to ±0.005 mm for precision machining. The achievable tolerance depends on the machine, tool, and clamping setup.
What is 5-axis milling?
5-axis milling uses 3 linear axes (X, Y, Z) plus 2 rotary axes (A, B or C). This allows the workpiece to be machined from virtually any angle in a single setup — ideal for complex geometries.
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