Guide to Preventing CNMG Insert Chipping in CNC Machining

In precision manufacturing, CNC (Computer Numerical Control) machining plays a pivotal role. However, tool chipping remains a persistent challenge for many CNC operators. This issue not only leads to scrapped workpieces but can also cause potential damage to machine tools, resulting in significant economic losses. This article focuses on CNMG inserts, exploring how proper selection can effectively prevent chipping while enhancing machining efficiency.

During CNC operations, inserts directly contact workpieces to perform cutting operations, with their performance directly impacting machining quality, efficiency, and costs. Tool chipping can occur due to multiple factors:

• Substandard insert material: The hardness, toughness, and wear resistance of insert materials determine their lifespan. Inferior materials cannot withstand the high temperatures, pressures, and impacts during cutting operations.
• Inappropriate insert selection: Different insert types suit different materials and machining conditions. Improper selection prevents optimal performance.
• Improper cutting parameters: Cutting speed, feed rate, and depth of cut significantly affect tool stress. Incorrect settings may overload the insert.
• Insufficient cooling/lubrication: Cutting generates substantial heat. Inadequate cooling raises insert temperatures, reducing hardness and strength.
• Machine tool inaccuracy: Machine precision directly affects cutting paths. Poor accuracy causes vibration during operations.
• Operator error: Technical skill and operational habits impact tool life. Improper handling can lead to premature failure.

The consequences of tool chipping are severe:

• Workpiece rejection: Chipped tools create surface defects requiring material scrappage.
• Machine damage: Chipping may damage tool holders, spindles, or other components.
• Production delays: Tool replacement and parameter adjustments cause downtime.
• Safety hazards: Flying fragments may injure operators.

CNMG inserts are widely used in CNC turning operations, with their alphanumeric designation indicating specific characteristics:

• C: 80° diamond shape
• N: 0° clearance angle
• M: Tolerance class
• G: Insert with hole and clearance

Key advantages include:

• Versatility: Suitable for various materials including steel, stainless steel, cast iron, aluminum, and copper alloys.
• Wide applicability: Effective for roughing, semi-finishing, and finishing operations.
• Cost-effectiveness: Provides excellent value through extended tool life.
• Easy replacement: Standardized dimensions and interfaces simplify changes.

To maximize CNMG insert effectiveness and prevent chipping, consider these technical recommendations:

• Steel machining: Select carbide grades based on material hardness. Higher cobalt content suits hard steels; tougher grades handle high-strength steels.
• Stainless steel: Choose chemically stable, tough carbide grades with PVD coatings or ceramic options.
• Cast iron: Opt for wear-resistant carbides with CVD coatings.
• Aluminum: Select uncoated carbide or diamond inserts with sharp cutting edges.
• Copper alloys: Use corrosion-resistant carbides with TiAlN coatings.

• CNMG120404: Finishing/semi-finishing with sharp edges for superior surface finish.
• CNMG120408: Roughing/semi-finishing with robust edges for heavier cuts.
• CNMG120412: Heavy roughing with maximum edge strength.

• F-type: Finishing with excellent chip control.
• M-type: Semi-finishing with balanced performance.
• R-type: Roughing with efficient chip evacuation.

• Cutting speed: Excessive speeds cause overheating; insufficient speeds reduce productivity. Match to material and conditions.
• Feed rate: Excessive feeds overload inserts; insufficient feeds lower efficiency.
• Depth of cut: Excessive depths stress tools; insufficient depths waste capacity.

Effective cooling reduces temperatures and friction while extending tool life. Select appropriate fluids with adequate flow/pressure.

Regularly inspect inserts for wear, chipping, or cracks. Replace compromised tools immediately to prevent further issues.

Secure inserts correctly using specified clamping methods and torque values to prevent vibration or loosening.

Wear protective equipment during tool changes and adhere to all machine safety protocols.

A manufacturer producing high-strength cast iron engine blocks achieved 30% longer tool life and 20% higher productivity after implementing optimized CNMG inserts, significantly reducing production costs.

A surgical instrument manufacturer requiring exceptional surface finishes achieved Ra0.2μm surface quality using specialized CNMG inserts, meeting stringent medical requirements.

An aerospace parts producer machining aluminum components attained ±0.01mm dimensional accuracy and mirror-like finishes using precision CNMG inserts, satisfying aviation standards.

Through proper selection and application of CNMG inserts, manufacturers can significantly enhance machining efficiency while reducing tooling costs and improving product quality. Continuous innovation in insert technology promises further advancements in CNC machining capabilities.