Positive Geometry Turning Insert for Fine Machining
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Solution Overview
Problem
Existing double-sided turning inserts, such as those described in US 4411565, are not suitable for delicate fine turning operations like machining jet engine rings due to their negative cutting geometry, which leads to heat generation, adhesion, and abrasive wear, resulting in incomplete passes and surface defects.
Innovation Solution
A double-sided turning insert with a polygonal shape featuring a positive cutting geometry, where cutting edges have a nose edge and two main edges converging towards it, and a flank surface that slopes towards the chip surface, ensuring controlled chip removal and minimizing heat generation and adhesion by optimizing the level difference between the bearing surface and cutting edge.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If negative cutting geometry is used in turning inserts, then the cutting edge is stronger and more durable, but heat generation increases, causing adhesion and abrasive wear that lead to surface defects
Solution Approach 1:
The patent changes the cutting geometry parameters from negative to positive rake angle. The positive cutting geometry with rake angle greater than 0° reduces cutting forces and heat generation while maintaining sufficient edge strength through optimized edge configuration and support structure
Solution Approach 2:
The patent introduces a level difference between the bearing surface and the cutting edge, creating a three-dimensional configuration where the cutting edge is positioned at a different elevation. This dimensional change allows the chip to be directed away from the bearing surface, reducing heat transfer and adhesion while maintaining edge strength
2Duration of action of stationary object
If negative cutting geometry is used, then the cutting edge is more durable, but adhesion occurs between the chip and tool surface, causing abrasive wear
Solution Approach 1:
Changing from negative to positive rake angle reduces chip adhesion by altering the chip flow direction and reducing contact area between the chip and tool surface, thereby minimizing abrasive wear while extending service life
Solution Approach 2:
The level difference configuration creates spatial separation between the chip path and the bearing surface, preventing adhesion in the critical zone and reducing abrasive wear on the bearing surface, thus extending insert durability
3Adaptability or versatility
If the turning insert is designed for general-purpose use, then it can handle various turning operations, but it is not suitable for delicate fine turning operations requiring single-pass completion
Solution Approach 1:
The patent optimizes specific local features of the cutting edge geometry and level difference configuration to achieve superior chip control and surface quality, making the insert suitable for precision work while maintaining general applicability through standardized mounting interfaces
Solution Approach 2:
The level difference design provides enhanced chip directionality and control, ensuring that chips are consistently directed away from the bearing surface during delicate operations, enabling single-pass completion without surface defects while maintaining versatility
4Device complexity
If the cutting edge is positioned at the same level as the bearing surface, then the structure is simpler, but chip control is poor and chips may contact the generated surface
Solution Approach 1:
The patent introduces a vertical level difference between the bearing surface and cutting edge, creating a three-dimensional chip path that naturally directs chips away from the generated surface. This simple elevation change provides excellent chip control without complex additional structures
Solution Approach 2:
The level difference is applied locally at the cutting edge position rather than throughout the entire insert structure, providing enhanced chip control where needed while maintaining structural simplicity elsewhere in the insert design
Data Source
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AI summary
A double-sided, indexable turning insert having a polygonal basic shape comprises at least three corners and a pair of opposite, plane support surfaces (2) as well as a plurality of cutting edges, each one of which includes a nose edge (9) and two main edges (10) converging toward the same, all nose edges being situated in a common reference plane (RP) that is depressed in relation to the support surface (2). The individual main edge (10) is formed between a chip surface and a part (6) of a circumferential clearance surface extending between two corners, and the individual nose edge (9) between the chip surface and a convex part (7) of the clearance surface, a flank surface (13), which slopes toward the chip surface, extending from the outer contour line of the support surface (2), besides which the individual main edge - as viewed in side elevation - declines from a highest point (14) adjacent to the nose edge (9) toward a lowest point or section (15). According to the invention, the level difference (N1 + N2) between the support surface (2) and the lowest point (15) of the main edge (10) amounts to at most 0,5 mm, besides which the rake angle of the individual cutting edge is acute along the entire extension of the cutting edge.