Tool breakage during CNC machine tool processing: causes and solutions

Tool breakage during CNC machining can be caused by a variety of factors. These factors generally relate to the material being processed, the tool itself, the machine's settings, or external influences. Understanding these causes and implementing solutions is essential for maintaining productivity and reducing downtime.

Summary Table of Causes and Solutions

Detailed reasons and solutions

1. Excessive Cutting Force

Cause:

• High cutting forces can cause tool wear and ultimately lead to breakage. This can occur when the feed rate or cutting depth is too high, or when the material being machined is too tough for the chosen tool.

Solution:

• Reduce the feed rate or depth of cut.
• Use tools with higher strength and wear resistance.
• Choose appropriate cutting parameters based on the material properties.
• Use a more powerful CNC machine if necessary.

2. Incorrect Cutting Parameters (Speed, Feed, Depth of Cut)

Cause:

• Incorrect speeds, feeds, or depths of cut can cause excessive stress on the tool. Too high speeds or feeds can lead to overheating, while too low can result in poor chip removal and increased tool wear.

Solution:

• Ensure that cutting parameters are optimized for the specific material being machined (e.g., use recommended cutting speeds and feeds from the tool manufacturer).
• Adjust settings based on real-time monitoring, ensuring optimal chip removal and preventing excessive heat buildup.

3. Tool Material Incompatibility

Cause:

• If the tool material is not suited for the workpiece material (e.g., using a tool with insufficient hardness for a hardened steel part), it can wear out quickly or break under pressure.

Solution:

• Choose the right tool material for the application (e.g., carbide, ceramic, high-speed steel).
• For tough materials, use cutting tools with higher toughness and wear resistance, such as carbide with a coating (e.g., TiN or TiAlN).

4. Improper Tool Setup

Cause:

• Incorrect tool installation, poor alignment, or improper tool mounting can result in misalignment during machining, causing uneven cutting forces, vibration, and eventual tool failure.

Solution:

• Ensure proper tool setup by carefully checking tool installation and alignment.
• Use precision tool holders and verify that the tool is firmly secured in the CNC machine.
• Regularly check the tool for wear and replace it as needed.

5. Insufficient Coolant or Lubrication

Cause:

• Lack of sufficient coolant can cause excessive heat buildup during cutting, which can soften the tool, cause thermal shock, or increase friction, leading to breakage.

Solution:

• Ensure that the coolant is applied correctly and in sufficient quantity. Choose the right type of coolant (e.g., oil-based or water-based) for the material being cut.
• Maintain proper coolant pressure and flow to cool both the tool and workpiece.
• In some cases, use air blasts to remove chips and reduce heat buildup.

6. Vibration or Chatter

Cause:

• Vibration or chatter during machining can cause uneven cutting forces, leading to tool breakage. This is typically due to improper machine settings, tool geometry, or workpiece instability.

Solution:

• Minimize vibration by adjusting cutting parameters such as feed rate and speed.
• Use rigid tool holders and ensure the workpiece is securely fixtured to reduce any movement.
• Consider using vibration-damping tooling or using higher-rigidity CNC machines.
• Use smaller depth of cuts or alternating cutting paths to reduce the chance of chatter.

7. Tool Wear and Dulling

Cause:

• Over time, cutting tools naturally experience wear, which can cause them to lose cutting effectiveness. This wear can lead to excessive heat generation, poor chip removal, and eventually tool failure.

Solution:

• Regularly monitor and replace worn tools to prevent catastrophic failure.
• Use tools with appropriate coatings for wear resistance.
• Set up tool wear detection systems (if available) on CNC machines to help identify when tools need replacing.

8. Overheating

Cause:

• Excessive heat generated by high cutting speeds, insufficient cooling, or hard-to-machine materials can cause the tool to soften, crack, or break.

Solution:

• Reduce cutting speeds and optimize cutting parameters to prevent overheating.
• Ensure adequate cooling (use proper coolant or lubrication systems).
• For high-temperature applications, consider using tools made of heat-resistant alloys or coated tools designed to handle extreme temperatures.

9. Incorrect Tool Geometry

Cause:

• Incorrect tool geometry, such as an incorrect rake angle, clearance angle, or tool shape, can lead to improper cutting behavior, excessive forces, or tool breakage.

Solution:

• Select tools with the correct geometry for the material and type of cut.
• Consult with the tool manufacturer or cutting tool experts to select the optimal geometry for your application.

10. Improper Part Fixturing or Setup

Cause:

• If the workpiece is not securely fixtured or positioned correctly in the machine, it can move during machining, leading to tool impacts, misalignment, and potential breakage.

Solution:

• Use high-quality, rigid fixturing systems to securely hold the workpiece in place.
• Double-check the alignment and positioning of the workpiece before starting machining operations.
• Ensure the part is properly balanced and supported throughout the entire machining process.

11. Tool Defects or Manufacturing Flaws

Cause:

• Occasionally, a tool may have inherent defects or flaws (e.g., cracks, microfractures, or improper heat treatment) that can lead to premature failure under load.

Solution:

• Purchase tools from reputable manufacturers with stringent quality control processes.
• Inspect tools before use, especially if they have been in storage for an extended period.
• Replace defective tools immediately.

12. Intermittent Contact or Interrupted Cuts

Cause:

• In operations where the tool experiences intermittent contact with the material (e.g., slotting or machining castings), this can create sudden shock loads that cause tool breakage.

Solution:

• Use tools designed for interrupted cuts, such as those with reinforced bodies or inserts that can withstand shock loads.
• Reduce cutting speeds and feeds when machining interrupted cuts to reduce impact forces.