KEVOS® MAKEOS · Manufacturing
Ball-Nose Finishing Plan (Stepover, Speed, Feed and Time)
What stepover gives my target cusp height with this ball-nose cutter, what speed suits its effective diameter, and how long will finishing the area take?
Plan of ball-nose finish milling on a flat or gently curved area: stepover for the target scallop height, or the scallop for a stepover you set (as the scallop height tool), effective cutting diameter at the axial engagement and the spindle speed for the cutting speed there (as the ball nose diameter tool), held to the machine maximum, the feed rate, number of passes and finishing time for the area.
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How this tool works
Inputs, units and where to find them
| Input | Unit | Typical source |
|---|---|---|
| Ball-nose diameter | mm | Diameter of the ball-nose cutter. |
| Flutes | Number of flutes. | |
| Axial engagement | mm | Depth of the ball in the material (sets the effective diameter). |
| Scallop height wanted | µm | Largest scallop (cusp) height the surface may have. |
| Stepover chosen (0 = from the scallop) | mm | Stepover you intend to program; 0 uses the stepover for the scallop target. |
| Cutting speed at the effective diameter | m/min | Cutting speed wanted at the effective diameter. |
| Feed per tooth | mm | Feed per tooth. |
| Largest spindle speed | rpm | Highest spindle speed. |
| Area length (pass direction) | mm | Length of each finishing pass. |
| Area width (stepover direction) | mm | Width of the area across the passes. |
Method and formulas
- Stepover for scallop h: s = 2√(2Rh − h²); scallop for stepover s: h = R − √(R² − s² ÷ 4) (as the scallop height tool).
- Effective diameter D_e = 2√[a_p (D − a_p)]; n = min(1000 v_c ÷ π D_e, n_max) (as the ball nose diameter tool).
- Feed = n z f_z; passes = width ÷ stepover (rounded up); time = passes × length ÷ feed.
- Example: a 0.28281 mm stepover leaves 2 µm; at 15,000 rpm and 1,500 mm/min the 100 × 80 mm area takes 18.867 min.
Limitations
- Flat surface normal to the tool; slopes change the scallop and effective diameter.
- Stepover moves and lead-in time are not included.
- Example values are illustrations. Replace them with values for your actual task.
Typical uses
- Program a finishing pass for a mould or die surface
- Trade surface finish against machining time
- Set spindle speed for a small effective diameter
Who it is for
- CNC programmers
- Mould makers
- Manufacturing engineers
What you get
- Stepover and scallop height
- Effective diameter, spindle speed and feed
- Passes and finishing time
Interpreting the result
- Halving the scallop height only shortens the stepover by about 30%, but the time rises in the same proportion.
References
- Machinery’s Handbook, 29th edition (Industrial Press, 2012), printed pp. 1039–1058, 1279–1300. Topic reference; no source tables or recommended settings are reproduced.
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