cBN Cutting Insert Geometry for Small-Bore Chip Discharge
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional cutting tools have inaccuracies in forming the rake face and a small chip pocket under the first flank face, which hinders precise processing of holes with very small inner diameters due to inadequate chip discharge properties.
Innovation Solution
A cutting tool design featuring a cutting tool insert with a cBN material tip and a shank, where the second flank face is tilted relative to the center axis by an angle greater than 0°, increasing the chip pocket volume without reducing the brazing interface, and incorporating a negative rake angle to enhance chip discharge and abrasion resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the rake face is formed conventionally with a 0° alignment to the centre axis, then the manufacturing process is simple, but the chip pocket volume is insufficient and chip discharge properties are poor
Solution Approach 1:
The patent applies asymmetry by tilting the rake face relative to the centre axis by an angle of 5° to 15°. This asymmetric configuration creates additional chip pocket volume behind the cutting edge while maintaining manufacturability. The tilted rake face allows chips to be discharged more effectively from the narrow borehole without requiring complex multi-component structures.
2Volume of moving object
If the second flank face is tilted by an angle greater than 0°, then the chip pocket volume increases, but the brazing interface area may be reduced
Solution Approach 1:
The patent optimizes the tilt angle of the second flank face to be greater than 0° but less than 10°, and the rake face tilt angle to be 5° to 15°. These parameter ranges are carefully selected to maximize chip pocket volume while preserving sufficient brazing interface area. The specific angular parameters balance the competing requirements of chip discharge capability and joint strength.
3Strength
If cBN material is used for the cutting tip, then abrasion resistance is high, but the material cannot be easily processed and requires expensive sintering
Solution Approach 1:
The patent segments the cutting tool into distinct functional zones: a sintered cBN cutting tip for abrasion resistance, a transition zone with gradient composition for stress distribution, and a carbide base for mechanical strength and ease of manufacturing. This segmentation allows each zone to be optimized independently, making the overall tool manufacturable despite the difficulty of processing pure cBN.
Solution Approach 2:
The patent employs composite material construction with a sintered cBN tip bonded to a carbide base through a transition zone. This composite structure combines the high abrasion resistance of cBN with the manufacturability and toughness of carbide, resolving the contradiction between material performance and ease of manufacture.
4Productivity
If the cutting tool insert is designed with a negative rake angle, then chip discharge properties improve, but the cutting edge may become more vulnerable to chipping
Solution Approach 1:
The patent specifies a negative rake angle range of -5° to -15° for the cutting edge. This parameter optimization balances chip discharge efficiency with cutting edge stability. The negative rake angle promotes effective chip evacuation from narrow boreholes while the controlled magnitude prevents excessive vulnerability to chipping.
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 design improves chip discharge properties and abrasion resistance, allowing for more precise and efficient processing of holes with small diameters by increasing the chip pocket volume and maintaining a stable brazing interface, thus enhancing the cutting tool's performance.
Implementation Method 1
cBN is the second hardest material after diamond, while showing a chemical and thermal stability that is even greater than that of diamond. A high abrasion resistance and defect resistance is particularly desirable
Implementation Method 2
The cutting tool insert 110 is fixed to the shank body 120 by brazing
Implementation Method 3
The cutting tool insert 110 is formed by a base 111 and a cutting part 113 sintered together to form a sintered body composition
Data Source
Figure 1~3
Figure 4~6
Figure 7~9
AI summary
The present invention provides in various aspects a cutting tool which comprises a cutting tool insert (210) with a tip portion of cBN material having a cutting edge (216) formed therein and a base portion forming a sintered composition with the tip portion, and a body portion (220) coupling the cutting tool insert with a shank of the cutting tool, wherein the cutting tool insert (210) has a rake face (212) and a first flank face (214) defining the cutting edge (216). In one aspect, the rake face (212) has a negative rake angle relative to an axis parallel to a centre axis of the body portion. In another aspect, a second flank face (218) defining a further edge with the first flank face is formed such that the cutting edge (216) and the further edge do not have a common vertex. Herein the second flank face (218) is tilted with respect to an axis parallel to a centre axis of the body portion (220) by an angle greater than 0o.