CBN Cutting Edge Geometry for High-Speed Alloy Machining
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Solution Overview
Problem
Cubic boron nitride cutting tools used for high-speed cutting of heat-resistant alloys face issues with chipping and wear due to their low toughness, and edge toughening processes that prolong tool life also reduce sharpness and increase cutting heat.
Innovation Solution
A cubic boron nitride cutting tool with an edge tip made of a sintered cubic boron nitride compact having low thermal conductivity and a positive rake angle, which reduces lateral cutting edge wear and flank face wear, thereby prolonging tool life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a cubic boron nitride cutting tool is used for high-speed cutting of heat-resistant alloys, then cutting speed can be increased to 200 m/min or higher, but the cutting edge becomes chipped due to low toughness
Solution Approach 1:
The invention uses a composite structure consisting of a cubic boron nitride compact (providing hardness and heat resistance) combined with a specific rake face geometry (positive rake angle) to create a tool that maintains both high-speed cutting capability and cutting edge integrity. The composite nature addresses the toughness deficiency of pure cBN material.
Solution Approach 2:
The invention changes the geometric parameter of the rake face from negative or zero angle (conventional) to a positive rake angle of 5-20 degrees. This parameter change fundamentally alters the stress distribution at the cutting edge, preventing chipping while maintaining the high-speed cutting performance enabled by the cBN material's thermal properties.
2Duration of action of moving object
If edge toughening process is applied to the cutting edge, then tool life can be prolonged, but the edge sharpness is reduced and cutting heat increases
Solution Approach 1:
Instead of applying conventional edge toughening methods (negative rake angle, edge blunting) that reduce sharpness, the invention inverts the approach by using a positive rake angle. This inverted geometry naturally strengthens the cutting edge through favorable stress distribution while maintaining sharpness, thereby reducing cutting heat and eliminating the trade-off between tool life and temperature.
3Reliability
If a negative rake face is formed to toughen the cutting edge, then chipping is prevented, but the edge becomes blunted and produces larger cutting heat
Solution Approach 1:
The invention inverts the conventional negative rake angle approach and applies a positive rake angle of 5-20 degrees. This inversion achieves chip resistance through a different mechanism: the positive angle creates compressive stresses at the cutting edge that prevent chipping, while simultaneously maintaining edge sharpness that reduces cutting heat generation.
Solution Approach 2:
The invention changes the critical geometric parameter of the rake angle from negative values (conventional) to positive values (5-20 degrees). This parameter change fundamentally transforms the stress state at the cutting edge, achieving both chip resistance and reduced cutting heat without the blunting effect of conventional toughening methods.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The tool with a positive rake angle exhibits lower wear rates compared to edge-toughened tools, significantly extending the life of cubic boron nitride cutting tools during high-speed cutting of heat-resistant alloys.
Implementation Method 1
an edge tip made of a sintered cubic boron nitride compact having a low thermal conductivity
Implementation Method 2
a cutting edge formed on the edge tip has a positive rake angle... exhibits lower lateral-cutting-edge-portion boundary wear or flank face wear
Data Source
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AI summary
An object is to prolong the life of a cubic boron nitride cutting tool used for cutting a heat-resistant alloy. A cubic boron nitride cutting tool includes an edge tip made of a sintered cubic boron nitride compact having a thermal conductivity within the range of 20 to 70 W/m·K and including cubic boron nitride particles having an average particle diameter within the range of 0.5 µm to 2 µm; and a base metal that holds the edge tip at a corner portion of the base metal, wherein a cutting edge formed on the edge tip of the tool has a positive rake angle.