CBN Cutting Tool Negative Land Geometry for Chipping Resistance
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Solution Overview
Problem
Conventional CBN cutting tools face challenges in maintaining durability and surface quality during high-efficiency machining of hard ferric workpieces, particularly in resisting chipping and achieving superior surface roughness and fatigue life, especially at high feed rates and with complex shapes.
Innovation Solution
A CBN cutting tool design featuring a negative land between the arcuate nose and rake face, forming obtuse cutting edges that rise from the apex, with specific inclination angles and dimensions, and a method of using it at controlled feed rates to enhance durability and surface finish.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the radius of curvature of the nose is increased to improve durability against cutting load in high-efficiency machining, then the durability against chipping improves, but the brazing area decreases and brazing strength becomes insufficient
Solution Approach 1:
The invention applies a negative land (a localized geometric feature) specifically at the nose portion of the cutting tool. This local modification creates a wiper edge that concentrates the beneficial effect where it is most needed - at the cutting edge - without requiring a global increase in nose radius that would reduce brazing area. The negative land has specific dimensional parameters (width W, downward distance h, inclination angle β) that are optimized to provide durability while maintaining adequate brazing area.
Solution Approach 2:
Instead of increasing durability by increasing the nose radius in the horizontal plane (2D approach), the invention introduces a vertical dimension by creating a negative land that extends downward from the rake face. This three-dimensional feature creates a wiper edge that provides both cutting and burnishing functions, improving durability without compromising the horizontal brazing area.
2Productivity
If conventional cutting tools are used for high-efficiency machining at high feed rates, then productivity increases, but the resistance to chipping and surface quality deteriorate
Solution Approach 1:
The negative land is pre-formed on the cutting tool before machining operations. This preliminary geometric feature is designed to create a wiper edge that will automatically perform burnishing action on the workpiece surface during high-feed machining, providing chip resistance and surface quality improvement without requiring additional processes or tool adjustments during operation.
3Manufacturing precision
If conventional cutting tools are used for finishing operations, then machining is performed, but surface roughness and fatigue life are insufficient
Solution Approach 1:
The cutting tool with the negative land performs multiple functions simultaneously: it acts as both a cutting tool (removing material through the main cutting edge) and a burnishing tool (improving surface quality through the wiper edge). This multi-functionality allows the same tool to perform both roughing and finishing operations, achieving superior surface roughness and fatigue life without sacrificing machining efficiency.
4Strength
If the nose radius is increased to improve durability in high-feed machining, then chip resistance improves, but the tool cannot be used for copying and recess forming of complex shapes
Solution Approach 1:
The negative land provides the durability-enhancing wiper edge feature locally at the cutting point, without requiring a large overall nose radius. This localized approach maintains the adaptability needed for copying and recess forming operations on complex shapes while still providing the burnishing action and chip resistance benefits for high-feed machining.
Data Source
AI summary
It is an object to provide a CBN cutting tool using cBN-based sintered bodies which shows high resistance to chipping even when a hard ferric workpiece which is difficult to cut is cut at a high feed rate for high-speed, high-efficiency machining, and which can provide a machined surface that shows superior surface roughness, and improved fatigue life and sealability. A cBN-based sintered body of a cutting tip has an arcuate nose 5, a rake face 6, flanks 7 and a negative land 9. One of the cutting edges 10 defined between the negative land 9 and the flanks 7 that serves as an end cutting edge forms an inclination angle 6′ of not less than 20 degrees and not more than 35 degrees with respect to the rake face. Further, the cutting edges 10 are positioned such that they are the lowest at the apex P of the arcuate nose and gradually rise from the apex P toward two points Q1 and Q2, respectively.