CBN Turning Insert Curvature for Smooth Hard Steel Machining
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Solution Overview
Problem
Existing turning inserts for longitudinal turning of hardened steel fail to achieve a smooth machined surface finish and exhibit high wear, limiting their versatility and effectiveness, especially when machining materials with hardness above 55 HRc.
Innovation Solution
A turning insert design featuring a CBN cutting edge with a head portion and stem portion, where the cutting edge is straight or convexly curved with specific angles and dimensions, allowing for efficient machining in both directions and reducing wear by optimizing the cutting edge geometry and insert shape.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional turning insert geometry is used for longitudinal turning of hardened steel, then the insert can be manufactured and mounted, but the machined surface finish is rough and insert wear is high
Solution Approach 1:
The patent modifies the geometric parameters of the cutting edge, specifically setting the radius of curvature to 50-200mm and the angle relative to the longitudinal axis to 5-20 degrees. These parameter changes optimize both surface finish quality and reduce insert wear by creating a cutting edge that effectively shears the hardened material while maintaining stability.
Solution Approach 2:
The cutting edge is designed with a convex curvature (radius of curvature 50-200mm) rather than a straight or sharp edge. This curvature allows the cutting edge to gradually engage the workpiece material, distributing the cutting forces and producing a smoother surface finish while reducing shock loads that cause insert wear.
2Manufacturing precision
If the cutting edge geometry is optimized for smooth surface finish, then surface quality improves, but the insert becomes less versatile for different machining directions
Solution Approach 1:
The cutting edge is designed with asymmetric geometry relative to the longitudinal axis, forming a specific angle (5-20 degrees) with it. This asymmetric design allows the insert to effectively machine in both forward and reverse directions while maintaining optimal surface finish, as the angular configuration provides appropriate cutting angles regardless of direction.
Solution Approach 2:
The turning insert is designed with a symmetric overall shape and a cutting edge configuration that functions effectively in both forward and reverse machining directions. The convex curvature and angular orientation of the cutting edge enable it to perform the same cutting function regardless of the direction of feed, making the insert universal for bidirectional longitudinal turning.
3Productivity
If the cutting edge is made sharp for efficient cutting, then cutting performance improves, but the insert wear increases rapidly
Solution Approach 1:
Instead of a sharp cutting edge, the patent employs a convex curved cutting edge with a radius of curvature between 50-200mm. This curved geometry maintains cutting efficiency by gradually engaging the material and reducing shock loads, while simultaneously extending insert service life by distributing wear across the curved surface rather than concentrating it at a sharp point.
Solution Approach 2:
The patent changes the geometric parameters of the cutting edge from sharp (zero radius) to convex curved (50-200mm radius), and sets the angle to 5-20 degrees relative to the longitudinal axis. These parameter changes optimize the balance between cutting efficiency and wear resistance by creating a cutting edge that is effective without being overly sharp.
Data Source
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AI summary
The invention relates to a turning insert (1) comprising a head portion (9) connected to a stem portion (10). A CBN cutting edge (8) comprising a surface generating cutting edge (14) and two major cutting edge portions (17, 18). Each major cutting edge portion (17, 18) forming an angle (B1, B2) of 5-20° in relation to a tangent line (L1) of the cutting edge (8) at a forward point (13) of the cutting edge (8).