Indexable Drill Insert Geometry for Chip Breaking and Center Drift
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Solution Overview
Problem
Conventional indexable drill inserts face issues with center drift due to uneven cutting forces, leading to narrow walls and insert breakage at corners, and inefficient chip formation and breaking, especially at high feed rates.
Innovation Solution
A quadrangular indexable drill insert with a segmented backwall for effective chip breaking and a top surface featuring a varying positive rake angle to direct cutting forces centrally and enhance cutting edge strength, comprising multiple cutting edge sections with transitional curves and a protruding portion for chip fragmentation and evacuation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If conventional rectangular cutting edges are used, then the drill structure is simple, but the cutting forces are uneven causing center drift
Solution Approach 1:
The cutting edge is divided into multiple segments including a first cutting edge section, a second cutting edge section, and a transitional cutting edge section. This segmentation distributes the cutting forces more evenly across the drill body, preventing center drift while maintaining structural simplicity.
Solution Approach 2:
Different sections of the cutting edge are designed with different geometries and orientations. The first cutting edge section has a specific angle configuration, the second section is tangential to an inscribed circle, and the transitional section connects them with convex and concave curves. This local differentiation optimizes force distribution without complicating the overall structure.
2Device complexity
If conventional convex-concave transition edges are used, then the insert structure is simple, but chip formation is unsmooth causing high stress areas
Solution Approach 1:
The transitional cutting edge section incorporates convex and concave curved surfaces that provide a gradual transition between cutting edge sections. This curvature eliminates sudden geometric changes, ensuring smooth chip flow and reducing stress concentrations that would otherwise lead to insert breakage.
Solution Approach 2:
The curvature parameters of the transitional section are specifically designed to control chip formation. By adjusting the radius and profile of the convex-concave curves, the system optimizes chip flow characteristics and stress distribution, improving reliability without increasing structural complexity.
3Ease of manufacture
If conventional uniform rake angle surfaces are used, then the manufacturing process is simple, but cutting forces are high and cutting edge strength is reduced
Solution Approach 1:
The rake surface is designed with a varying rake angle rather than a uniform angle. Different regions of the rake surface have different angles optimized for their specific functions: some regions have higher angles to reduce cutting forces, while other regions have lower angles to strengthen the cutting edge. This local optimization improves performance without significantly complicating manufacturing.
Solution Approach 2:
The rake angle parameter is varied across the rake surface to optimize both cutting performance and edge strength. By controlling the gradient and distribution of rake angles, the design reduces overall cutting forces while maintaining or enhancing cutting edge durability, achieving a balance between ease of manufacture and strength.
4Device complexity
If conventional single backwall design is used, then the structure is simple, but chip breaking is inefficient especially at high feed rates
Solution Approach 1:
The backwall is divided into multiple segmented portions rather than being a single continuous structure. These segments are positioned to effectively break chips at various stages of formation, particularly improving performance at high feed rates where chip control is critical. The segmentation enhances chip breaking efficiency without significantly increasing overall structural complexity.
Data Source
Figure 1~2
Figure 3A
Figure 3B
AI summary
An indexable drill insert (10) includes a top surface (12), a bottom surface (14), and a plurality of side surfaces (16) adjoining the top surface (12) and the bottom surface (14). A plurality of cutting edges (20) is formed by an intersection of a respective side surface (16) with the top surface (12). One aspect of the invention is that the top surface (12) includes a protruding portion (50) and a segmented portion (52) extending radially outwardly with respect to the protruding portion (50) for effective chip breaking. Another aspect of the invention is that a rake surface (48) has a positive rake angle that varies along a first cutting edge section (22) of the cutting edge (20) to lower cutting force.