CNC Machining Common Issues and Improvement Methods（二）

Seven, Edge Chipping.

Causes and Improvements:

1. Feeding too fast
   • Slow down to an appropriate feed rate.
2. Rapid feed at the beginning of cutting
   • Slow down the feed speed at the beginning of cutting.
3. Loose clamping (tool)
   • Tighten the clamp.
4. Loose clamping (workpiece)
   • Tighten the clamp.
5. Insufficient rigidity (tool)
   • Use the shortest allowable tool, clamp the shank deeper, and consider climb milling.
6. Cutting edge of the tool is too sharp
   • Change the brittle cutting edge angle to a less fragile one; consider using a single edge.
7. Insufficient rigidity of the machine tool and tool holder
   • Use a machine tool and tool holder with better rigidity.

Eight, Wear.

Causes and Improvements:

1. Machine speed is too fast
   • Slow down; ensure sufficient coolant.
2. Hardened materials
   • Use advanced tool materials, tools, and increase surface treatment methods.
3. Chip adhesion
   • Change feed speed, chip size, or use coolant or an air gun to clean chips.
4. Improper feed speed (too low)
   • Increase feed speed; try climb milling.
5. Inappropriate cutting angle
   • Change to a suitable cutting angle.
6. Tool relief angle is too small
   • Change to a larger relief angle.

Nine, Breakage.

Causes and Improvements:

1. Feeding too fast
   • Slow down the feed speed.
2. Excessive cutting volume
   • Use a smaller per-edge cutting volume.
3. Blade length and overall length are too large
   • Clamp the shank deeper, use a shorter tool, try climb milling.
4. Excessive wear
   • Re-grind in the early stages.

Ten, Chatter Marks

Causes and Improvements:

1. Feed and cutting speed are too fast
   • Adjust feed and cutting speed.
2. Insufficient rigidity (machine tool and tool holder)
   • Use better machine tools and tool holders or change cutting conditions.
3. Relief angle is too large
   • Change to a smaller relief angle; process the blade edge (grind once with an oilstone).
4. Loose clamping
   • Clamp the workpiece.

Consideration of Speed, Feed, and Depth of Cut

The interplay of speed, feed, and depth of cut is the most crucial factor in determining cutting effects. Inappropriate feed and speed often lead to reduced production, poor workpiece quality, and significant tool damage.

1. Use the low-speed range for:

• High-hardness materials
• Ductile materials
• Hard-to-cut materials
• Heavy cutting
• Minimal tool wear
• Maximum tool life

2. Use the high-speed range for:

• Soft materials
• Better surface quality
• Smaller tool diameters
• Light cutting
• Brittle workpieces
• Manual operations
• Maximum processing efficiency
• Non-metallic materials

3. Use high feed rates for:

• Heavy, rough cutting
• Rigid structures
• Easily machinable materials
• Coarse processing tools
• Flat cutting
• Low tensile strength materials
• Coarse-tooth milling cutters

4. Use low feed rates for:

• Light, precision cutting
• Brittle structures
• Hard-to-machine materials
• Small tools
• Deep slotting
• High tensile strength materials
• Precision machining tools.