Ball Nose End Mill Feeds And Speeds

Factors Affecting Feeds and Speeds

1. Workpiece Material: Different materials require different cutting speeds and feed rates. For example, softer materials like aluminum allow higher speeds, while harder materials like stainless steel or titanium require lower speeds.
2. Tool Material and Coating: Carbide tools generally allow higher speeds compared to high-speed steel (HSS) tools. Coatings like TiAlN or PVD can also enhance tool performance.
3. Depth of Cut and Stepover: Shallow depths of cut (typically 0.01" to 0.1") and smaller stepovers help reduce tool engagement and improve surface finish.
4. Machine Capabilities: Ensure that the machine can handle the required spindle speeds and feed rates.

Calculating Feeds and Speeds

1. Cutting Speed (Vc): This is typically expressed in surface feet per minute (SFM) or meters per minute (m/min). The recommended cutting speed depends on the workpiece material. For example:
   • Aluminum: 500-1000 SFM (150-300 m/min)
   • Stainless Steel: 100-200 SFM (30-60 m/min)
   • Titanium: 50-150 SFM (15-45 m/min).
2. Spindle Speed (RPM): Use the formula:

   RPM=(SFM×3.82)/Tool Diameter​

   For metric units:

   \text{RPM} = \frac{\text{Vc (m/min)} \times 1000}{\pi \times \text{Tool Diameter (mm)}} \][^3^][^7^].

3. Feed Rate (Vf): This is calculated based on the feed per tooth (fz) and the number of flutes (z):

   $$\text{Vf (mm/min or IPM)}=\text{RPM}\times \text{Number of Flutes}\times \text{Feed per Tooth}$$

   Typical feed per tooth values range from 0.001" to 0.010" (0.025mm to 0.25mm) depending on the material.

General Recommendations

• Feed Rates: For ball nose end mills, start with a moderate feed rate (e.g., 50-300 IPM for metals, 100-300 IPM for plastics) and adjust based on the desired surface finish.
• Coolant: Use appropriate coolant or lubrication to reduce heat and improve tool life. For plastics, air blasts or mist coolants are preferred.
• Toolpath Strategy: Use climb milling (down milling) whenever possible for better surface finish and tool life.

Example

• Recommended Vc: 800 SFM (240 m/min)
• RPM calculation:

  RPM=(800×3.82)/0.5​=6112 RPM

• Feed per tooth (fz): 0.005"
• Number of flutes: 4
• Feed rate (Vf):

  \text{Vf} = 6112 \times 4 \times 0.005 = 122.24 \text{ IPM} \][^3^][^7^].