High-speed machining (HSM) revolutionized roughing. The technique uses LIGHT radial engagement at HIGH feed and speed.
The HSM Principle
Traditional: 50-100% radial engagement, conservative feed. Heat-limited at full engagement.
HSM: 5-15% radial engagement, full axial depth (1-2× diameter), 3-5× normal feed rate. Heat dissipates between engagements.
Toolpath Methods
- Trochoidal milling — Tool follows circular path while advancing. Best for slot roughing.
- Adaptive clearing — Modern CAM (Fusion, HyperMill, Mastercam). Best for pockets.
- Peeling/dynamic milling — Mastercam Dynamic Mill
Tool Selection
- Solid carbide end mill, 4-7 flutes
- Variable helix preferred (anti-chatter)
- Coating: AlTiN/AlCrN for steel, ZrN/DLC for aluminum
- Corner radius: 0.5-1.0mm minimum
- Maximum L:D = 3
Parameters Example (1018 Steel, 12mm 5-flute)
| Parameter | Traditional | HSM |
|---|---|---|
| Vc | 200 m/min | 250 m/min |
| Feed/tooth | 0.10 mm | 0.15 mm |
| Axial depth | 6mm (0.5×D) | 20mm (1.7×D) |
| Radial | 50% (6mm) | 10% (1.2mm) |
MRR per pass lower with HSM, BUT tool life 5-10× longer. Net production: 3-5× traditional.
Machine Requirements
- High-acceleration servos (1g+)
- Modern CNC with look-ahead (Fanuc 30i, Siemens 840D)
- Through-spindle coolant or air blast
- Spindle speed range: 12,000+ RPM helpful
See end mill selection for HSM-rated tools.
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