Cutting Insert Edge Geometry for Chipping-Resistant Drilling
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Solution Overview
Problem
Rotatable cutting tools, such as indexable-insert drills, experience issues with chipping and cracking due to the intersection of peripheral cutting inserts with previously generated groove surfaces, leading to potential drill breakdowns, especially when vibrating during operation.
Innovation Solution
The cutting insert design features two distinct chip surface sections with different cross-sectional shapes, forming part edges with varying angles relative to the clearance surface, providing a reinforced secondary edge to mitigate chipping and cracking risks by distributing stress more evenly and increasing the edge's strength at intersection points.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the peripheral cutting insert uses a positive cutting geometry with straight main edges, then chip removal is efficient, but chipping and cracking occur at the intersection with the groove surface
Solution Approach 1:
The cutting insert employs different edge geometries at different locations: the primary cutting edge has a positive geometry for efficient chip removal, while the secondary edge has a reinforced geometry with increased radius for resistance against chipping and cracking when intersecting the groove surface. This local differentiation of edge properties resolves the contradiction between productivity and reliability.
Solution Approach 2:
The main cutting edge is segmented into two distinct sections: a first section with positive cutting geometry for initial material removal, and a second section with reinforced geometry for stable intersection with the pre-formed groove. This segmentation allows each section to optimize its function, preventing crack propagation while maintaining cutting efficiency.
2Duration of action of stationary object
If hard and wear-resistant materials are used for the cutting insert, then service life is extended, but the material is more prone to cracking under stress
Solution Approach 1:
The patent modifies the geometric parameters of the cutting edge, specifically increasing the radius at the secondary edge and adjusting the angles of the cutting surfaces. These parameter changes create a reinforced edge structure that distributes stress more effectively, allowing hard materials to resist cracking while maintaining their wear resistance and extended service life.
3Productivity
If the main edge intersects the groove surface at an acute angle, then cutting action is effective, but stress concentration leads to crack development
Solution Approach 1:
The patent introduces curved transition surfaces and increased radii at critical intersection points instead of sharp acute angles. The secondary edge is formed with a larger radius that creates a more gradual transition when intersecting the groove surface, reducing stress concentration while maintaining effective cutting action through the curved geometry.
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
A tool (fig. 1) for chip removing machining, including a basic body (1) and two replaceable cutting inserts (2,3). Each insert (2,3) includes a chip-removing main edge (12,19) situated between a chip surface (38,29) and a clearance surface (39,27). The first insert (2) precedes the second insert (3) during machining of a workpiece. The cutting inserts (2,3) overlap each other in a zone (Z1, fig. 5) defined by a borderline (24) along which a surface generated by the main edge (12) of the first cutting insert (2), with a time delay, is intersected by the main edge (19) of the subsequent, second cutting insert (3). The main edge (19) of the second cutting insert (3) that afterwards intersects the already generated surface, is formed along a chip surface (29) including primary (29a) and secondary (29b) sections, which have different shapes in cross-sections (figs. 8-10) spaced apart along the main edge (19) in order to form a primary part edge (19a) and a secondary, reinforced part edge (19b) arranged to intersect the already generated surface.