CBN Cutting Insert Groove Structure for Crack Containment
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Solution Overview
Problem
Conventional cutting inserts made of CBN sinter are prone to cracking due to their brittleness, leading to breakage of cutting edges and propagation of cracks across principal surfaces when cutting high-hardness materials, resulting in reduced tool life and efficiency.
Innovation Solution
Incorporating a recessed groove in the side surface of the cutting insert to absorb cracks, preventing them from reaching the opposing principal surfaces, while maintaining the cutting edge formed by the boundary between principal and side surfaces, which is made of CBN sinter for cost-effectiveness and high hardness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the entire cutting insert is formed of CBN sinter to reduce cost and provide high hardness, then manufacturing cost is reduced and hardness is improved, but the brittleness increases making the material inferior in ductility and prone to cracking
Solution Approach 1:
The side surface is divided into a groove portion (recessed) and a non-groove portion, creating a segmented structure that isolates cracks to specific regions. The groove acts as a separate zone that captures and contains cracks, preventing them from propagating across the entire insert.
Solution Approach 2:
The groove serves as an intermediary structure between the cutting edges on opposite principal surfaces. It acts as a buffer zone that intercepts and contains cracks, preventing direct propagation from one cutting edge to the opposite cutting edge.
2Productivity
If a cutting edge on one principal surface breaks causing a crack in the side surface, then the cutting edge functionality is compromised, but the crack may develop to the other principal surface disabling the other cutting edge
Solution Approach 1:
The groove converts the harmful effect of crack propagation into a beneficial containment mechanism. By providing a recessed zone, the groove captures cracks and transforms them from a threat to the opposite cutting edge into a contained feature that does not compromise overall tool functionality.
Solution Approach 2:
The groove is pre-formed as a cushioning zone before any cracking occurs. This recessed structure is designed in advance to absorb and contain potential cracks, protecting the opposite cutting edge from damage even before the cracking event happens.
3Ease of manufacture
If the side surface is made entirely of CBN sinter without grooves, then the structure is simpler and manufacturing is easier, but cracks can freely propagate across the side surface
Solution Approach 1:
The side surface is segmented into groove and non-groove portions, creating a simple yet effective structure that divides the continuous side surface into functional zones. This segmentation is achieved through straightforward machining or forming processes.
Solution Approach 2:
The groove portion has a different local quality (recessed geometry) compared to the non-groove portion (flat surface). This local variation in geometry provides crack containment functionality only where needed, while maintaining the simple CBN sinter construction elsewhere.
Data Source
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AI summary
A cutting tool includes a cutting insert 4 that is held in a holder in a detachable manner. The cutting insert 4 has a substantially regular quadrangular shape in plan view and includes four round corners 4a. The cutting insert 4 is formed of CBN sinter as a whole. The cutting insert 4 includes two principal surfaces 6 that are upper and lower surfaces opposite to each other, and four side surfaces 7 that are arranged so as to connect the principal surfaces 6 to each other. A boundary portion (ridge line portion) between each of the principal surfaces 6 and each of the side surfaces 7 forms a cutting edge 8. In a central portion of each of the side surfaces 7 of the cutting insert 4, a groove 10 for absorbing a crack, having a substantially V-shape in cross section, is formed all around the cutting insert 4 so as to be recessed with respect to the side surfaces 7.