| Fräser-Ø | Drehzahl | Vorschub pro Zahn | Zustellung (Tiefe) |
|---|---|---|---|
| 3 mm | 20.000–24.000 U/min | 0,05–0,10 mm | bis 1× D = 3 mm |
| 6 mm | 18.000–22.000 U/min | 0,08–0,15 mm | bis 1× D = 6 mm |
| 8 mm | 15.000–18.000 U/min | 0,10–0,20 mm | bis 1× D = 8 mm |
| 12 mm | 10.000–14.000 U/min | 0,15–0,25 mm | bis 0,5× D = 6 mm |
Aluminum is the king of materials in modern mechanical engineering. It is lightweight, strong, corrosion-resistant, and — with the right technique — excellent to machine. But here lies the catch: aluminum does not forgive mistakes in cutting data, tool selection, or cooling.
In this comprehensive practical guide, you will learn everything you need to know for successful aluminum milling on a CNC gantry milling machine — from alloy selection to surface quality.
Why Mill Aluminum?
Aluminum is one of the most frequently milled materials for good reason:
- Low weight: About 1/3 the density of steel
- Good strength: Especially high-strength alloys like AlMgSi or AlZnMg
- Corrosion resistant: Natural oxide layer provides protection
- Good machinability: Less tool wear than with steel
- Versatile: From front panels to prototypes to machine components
The Biggest Challenge: Built-Up Edge
The main problem when milling aluminum (especially soft alloys) is called built-up edge. The material becomes soft from frictional heat and sticks to the cutting edge of the milling cutter.
What Happens with Built-Up Edge?
- The cutter generates heat through friction
- Aluminum becomes soft and plastic
- Material welds itself to the cutting edge
- The cutter no longer cuts, but pushes and rubs
- Even more heat develops — a vicious cycle
- The cutter breaks or the workpiece is ruined
How to Prevent Built-Up Edge
1. Choose the right alloy
Not all aluminum is equally easy to mill:
| Alloy | Machinability | Typical Application |
|---|---|---|
| AlMg3 (5754) | Very good | Universal, signs, housings |
| AlMg4.5Mn (5083) | Very good | Shipbuilding, pressure vessels |
| AlMgSi (6060, 6082) | Good | Profiles, structural parts |
| AlZnMg (7075) | Good | High-strength parts, aerospace |
| Al99.5 | Poor (gummy) | Avoid for milling |
Tip: Ask your material supplier specifically for milling-suitable alloys.
2. Cooling and Lubrication
Without lubrication, aluminum milling is almost impossible. Minimum Quantity Lubrication (MQL) is the standard:
- Fine oil mist directly at the cutting edge
- Cools and lubricates simultaneously
- Prevents material adhesion
- Significantly improves surface quality
For heavy machining, emulsion cooling may be useful — but requires appropriate machine equipment.
3. The right tools
Special tool requirements apply for aluminum:
- Single-flute cutters: Large chip space, fast chip evacuation
- Polished flute: Material slides off better, less adhesion
- Sharp cutting edges: Less friction, less heat
- Coating: DLC (Diamond-Like Carbon) or uncoated — NO TiN!
Cutting Data for Aluminum
Aluminum likes speed — both spindle speed and feed rate.
Basic Rule: Cut Fast, Don't Rub
If the cutter moves too slowly through the material, more friction than cutting occurs. This leads to heat and built-up edge.
Reference Values for Aluminum
| Cutter Diameter | Spindle Speed | Feed per Tooth | Depth of Cut |
|---|---|---|---|
| 3 mm | 20,000–24,000 RPM | 0.05–0.10 mm | Up to 1×D = 3 mm |
| 6 mm | 18,000–22,000 RPM | 0.08–0.15 mm | Up to 1×D = 6 mm |
| 8 mm | 15,000–18,000 RPM | 0.10–0.20 mm | Up to 1×D = 8 mm |
| 12 mm | 10,000–14,000 RPM | 0.15–0.25 mm | Up to 0.5×D = 6 mm |
Note: These values are starting points. Optimize step by step based on chip formation, sound, and surface quality.
Climb Milling vs. Conventional Milling
Mill aluminum in climb milling mode (the cutting edge rotates in the feed direction). Advantages:
- Better surface quality
- Less burr formation
- Less vibration
- Longer tool life
Plunging (Ramping Instead of Drilling)
Never plunge vertically into the material! Aluminum is tough — with a plunging motion, enormous heat develops and the cutter can jam.
Instead:
- Ramp: Enter at an angle (2–5 degree angle)
- Helix: Spiral plunge entry
- Pre-drill: Entry hole with a drill bit, then mill
Which Machine for Aluminum?
Not every gantry milling machine is suitable for aluminum. The decisive factors are:
- Rigidity: Aluminum requires higher cutting forces than wood or plastic
- Spindle power: For efficient machining, at least 2–3 kW
- Cooling option: MQL connection should be available
BZT Recommendations by Application
For sheets, front panels, signs:
- PFU-S: Robust steel construction, ball screws. The all-rounder for aluminum up to 10 mm depth per pass.
- PFE: Affordable entry for engraving, thin sheets, and light aluminum work.
For heavy machining (volume removal):
- PFH: Heavy — heavy steel construction, optionally with servo motors and HF spindles up to 15 kW. Here you can really remove material.
- PFX: HSC machine for high-speed cutting — highest precision for 3D machining.
For profile machining:
- PFS: Open frame construction, specially designed for long aluminum profiles (window construction, trade show construction). Face and surface machining possible.
Surface Quality on Aluminum
With the right technique, you can achieve excellent surfaces on aluminum:
What Affects the Surface?
- Tool condition: Only sharp tools deliver good surfaces
- Feed rate: Slower finishing feed = finer surface
- Depth of cut: Small finishing allowance (0.2–0.5 mm)
- Cooling: MQL significantly improves the surface
- Machine rigidity: No vibrations = no chatter marks
Achievable Surface Roughness
| Process | Roughness Ra | Appearance |
|---|---|---|
| Roughing | 6.3–12.5 µm | Visible milling marks |
| Finishing | 1.6–3.2 µm | Fine milling marks |
| Fine finishing | 0.4–0.8 µm | Nearly mirror finish |
Typical Applications
Front Panels and Housings
The classic: engraved front panels for measuring instruments, control panels, HiFi equipment. Typical: anodized aluminum with through-engraved lettering.
Prototypes and One-Off Parts
Rapid production of functional samples, brackets, adapter plates. Aluminum is ideal for prototypes: lightweight, strong, fast to machine.
Machine Components
Base plates, angles, brackets, motor mounts. Anywhere lightweight construction and corrosion resistance matter.
Model Making
Molds for deep drawing, casting patterns, lamination molds. Aluminum can be polished well and withstands thermal loads.
Practical Tips for Aluminum Machining
Chip Control
Aluminum chips are long and like to wrap around the cutter. Watch out for:
- Adequate dust extraction
- Single-flute cutters (better chip evacuation)
- Regular monitoring during machining
Workpiece Clamping
Aluminum is soft — clamping devices quickly leave pressure marks. Use:
- Vacuum table for thin sheets
- Soft jaws in the vise
- Sufficient support surface
Post-Processing
Aluminum is easy to post-process:
- Deburring: Chamfer cutter or manual
- Polishing: Polishing paste for mirror finish
- Anodizing: For protection and appearance
- Blasting: Matte finish for industrial look
Advanced Techniques
HSC Machining (High Speed Cutting)
With HSC, higher spindle speeds and feed rates are used, but with reduced depth of cut. Advantages:
- Better heat removal through the chips
- Reduced thermal load on the workpiece
- Excellent surface quality
- Higher productivity for finishing operations
Pocket Milling with Adaptive Toolpaths
Modern CAM software offers adaptive toolpaths (e.g., Fusion 360, Mastercam). These keep the tool load constant and enable:
- Greater depths of cut (up to 2× diameter)
- Higher feed rates
- More even tool wear
- Less tool breakage
FAQ — Frequently Asked Questions About Aluminum Milling
Can I mill aluminum without cooling?
Only very limitedly. For thin engravings or minimal material removal, compressed air might work in a pinch. For real milling work, MQL is strongly recommended — otherwise you risk tool breakage and poor surfaces.
Which cutter for aluminum — single or multi-flute?
For most applications: single-flute cutters. They have more space for chip evacuation and are less prone to clogging. Multi-flute cutters only with very rigid machines and good cooling.
How do I know if the cutting data is correct?
Watch the chips: short, comma-shaped chips with slight discoloration (silver to gold) are good. Long strings or blue chips (too hot) are bad. Listen to the sound: consistent cutting sound is good, squealing is bad.
Can my wood CNC also handle aluminum?
To some extent. Many machines designed for wood can handle light aluminum work (engraving, thin sheets). For serious aluminum machining, you need a more rigid construction and adequate spindle power.
What tolerances are achievable?
With a rigid BZT machine and careful workmanship, tolerances of ±0.05 mm are easily achievable. Under optimal conditions (temperature-controlled workshop, precision tools), even ±0.02 mm is possible.
Conclusion: Aluminum Milling — No Problem with the Right Setup
Aluminum milling is not rocket science if the setup is right. With a rigid BZT machine (preferably steel frame), minimum quantity lubrication, the right tools, and adapted cutting data, you achieve mirror-smooth surfaces and H7 fits.
The short formula for successful aluminum milling:
- Choose a milling-suitable alloy (AlMg3, AlMgSi)
- Use MQL cooling
- Use single-flute, polished cutters
- Run fast (high spindle speed, high feed rate)
- Mill in climb milling mode
- Never plunge vertically
Planning aluminum machining on your CNC? Our technical team is happy to advise you on the optimal machine configuration and accessories. Contact us!
Recommended Products for Aluminum Machining
- CNC Gantry Milling Machines — Machines with sufficient rigidity for aluminum
- HF Spindles — High-frequency spindles for high speeds on aluminum
- Minimum Quantity Lubrication — Indispensable for aluminum machining
- Carbide Cutters for Aluminum — Single-flute and polished two-flute cutters
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