Types Of Tool Wear During CNC Machining And How To Avoid Them

Thermal and mechanical stresses, particularly heat and abrasion, are the major factors contributing to tool wear. By understanding the common tool wear and their causes, machinists can swiftly remedy issues and extend the lifespan of their CNC machines. This proactive approach can help prevent premature or complete tool failure, minimize damage, and improve overall workpiece quality.

Here are our thoughts on the many forms of tool wear and how to recognize and mitigate them.

What we cover in this blog?

• Key Takeaways
• Types Of Tool Wear And Measures To Avoid Them

Key Takeaways

• Proper tool maintenance reduces the downtime of a CNC machine.
• Selecting the right cutting speed minimizes tool wear and premature tool failure.
• Efficient cooling systems enhance tool lifespan and reduce tool breakage.
• Regular monitoring ensures optimal tool performance and precision.

Types Of Tool Wear And Measures To Avoid Them

Tool wear is a pivotal factor during CNC (Computer Numerical Control) machining. It affects the quality of the machining process, tool life, and production costs. Below are the main tool wear types that occur during CNC machining.

Flank wear land

Cause:

Flank wear is a relatively uniform abrasion along the cutting edge on the tool’s relief or flank face caused by severe friction and continuous rubbing against the workpiece. It is generally caused by high temperatures, friction, and the hardness of the tool life of the material being cut.

Prevention:

• Use appropriate cutting speeds and feeds to reduce heat generated and friction.
• Apply cutting fluids to cool the tool and lubricate the cutting zone.
• Use wear-resistant grade tooling materials, such as carbide, ceramic, or coated tools.
• Regularly monitor tool wear and replace the tool before significant wear affects machining quality.

Crater wear

Cause:

Crater wear appears on the rake face of the cutting tool due to chemical reaction or diffusion between the tool and workpiece material at elevated temperatures. It is an abrasive wear that typically occurs in high-speed cutting operations.

Prevention:

• Reduce cutting speeds to lower the temperature at the tool-chip interface.
• Coated cutting tools (such as TiN or AlTiN) are used to provide a thermal barrier.
• Select cutting tools with a more appropriate geometry or tool diameter for the specific operation.
• Ensure optimizing coolant usage with high-quality cutting fluids.

Edge chipping

Cause:

Chipping occurs when small fragments break off the tool’s cutting edge, typically due to mechanical shock, uneven or shock loading, or interrupted cutting on a hard surface.

Prevention:

• Use tough and impact-resistant tools, like those made of cobalt-based alloys or certain carbides.
• Reduce feed rates or use a more gradual engagement with the workpiece to avoid excessive forces on the tool.
• Avoid machining hardened or abrasive materials without the proper tool material or coating.
• Implementing rigid machine setups and workpiece clamping is a proactive step to reduce vibrations and shocks.

Precision machined components in India establish the required control over the setup, preventing chipping and ensuring the efficiency of your operations.

Built-up edge (BUE)

Cause:

Built-up edge occurs when material from the workpiece’s surface finish adheres to the cutting tool, especially when machining softer materials like aluminum or low-carbon steel. BUE can alter the tool coating geometry and lead to poor surface finish.

Prevention:

• Increase cutting speed, proper cutting action, and temperature slightly to prevent material adhesion.
• Use tools with polished or anti-adhesive coatings, such as TiN or DLC (Diamond-Like Carbon).
• Apply cutting fluids that reduce adhesion and improve lubrication.
• Adjust the tool geometry to have a positive rake angle.

Thermal cracking

Cause:

Thermal cracking results from repeated heating and cooling cycles that cause the cutting tool to expand and contract, leading to microcracks. This cracking often occurs in interrupted cuts or when using improper coolant strategies.

Prevention:

• Maintain a consistent cooling strategy during machining (either use flood cooling or air cooling, but avoid switching frequently).
• Use ceramic or carbide tools that are more resistant to thermal shock.
• Adjust machining parameters to reduce temperature variations at the tool edge.

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Notch wear

Cause:

Notch wear occurs near the cutting edge, especially at the depth-of-cut line, and is typically caused by hard materials, stainless steels, abrasive workpieces, or work-hardened surfaces.

Prevention:

• Use harder, wear-resistant cutting tools for machining abrasive materials.
• Avoid machining work-hardened layers by using appropriate cutting depths.
• By applying cutting fluids, you can effectively cool the cutting area and reduce abrasive contact, thereby preventing notch wear.

Adhesive wear

Cause:

Adhesive wear occurs when there is welding or sticking between the tool and the workpiece material, typically in operations involving materials with a very high temperature and tendency for adhesion (like low-carbon steels).

Prevention:

• Use appropriate coatings like TiN or TiCN to reduce adhesion.
• Increase cutting speed to reduce the chances of adhesion at lower temperatures.

Deformation

Cause:

Excessive heat can soften any material, including cutting tools, and reduce hardness, leading to a faster dulling of the cutting edge.

Prevention:

It’s important to use cutting fluid properly to minimize deformation and choose a cutting tool material with higher wear resistance, additional coatings, and reduced cutting data.

Additionally, be mindful of conditions like tool rubbing that can create excess heat. It’s your responsibility to always ensure that you are using the proper feeds and speeds to address these issues and maintain your tool’s condition.

Implementing these strategies can significantly extend machine tool longevity, improve machining quality, and reduce production costs. These steps can be carefully performed under the supervision of contract manufacturers in India

Conclusion

Regularly monitoring and maintaining tools in good working condition is crucial for preventing downtime and cost savings. By utilizing appropriate running parameters and HEM toolpaths, wear caused by both thermal and mechanical forces can be minimized and spread evenly along the entire length of the cut.

To extend tool life, pay close attention to speeds, feeds, and depth of cut, even though wear is inevitable. Taking preemptive action to address potential issues before they escalate to entire tool failure is essential for efficient operations.

Frequently Asked Questions

What are the common tool wear types in CNC machining?

Common types include abrasive wear, adhesive wear, crater wear, and flank wear.

How can I identify tool wear during machining?

Signs of tool wear include changes in surface finish, increased cutting forces, and visible damage to the tool edge.

What causes tool wear in CNC machining?

Tool wear can result from factors like material hardness, cutting speed, feed rate, and insufficient lubrication.

How can I prevent tool wear in CNC machining?

Prevent tool wear by optimizing machining parameters, using appropriate cutting tools, and ensuring proper cooling and lubrication.