Segmented Cutting Insert Geometry for Stable Small-Diameter Milling
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Solution Overview
Problem
Small-diameter milling tools face challenges in maintaining machining accuracy and durability due to uneven cutting resistance and potential displacement of cutting inserts, particularly at corner cutting edges, where the contact area with the tool body is small, leading to reduced restraint force and increased likelihood of edge shaking.
Innovation Solution
A cutting insert design featuring a rake face, a bottom surface divided into two sections, and a circumferential side surface that secures a larger contact area on the tip side of the main cutting edge, with increased thickness on the end side for enhanced rigidity and durability, and a through hole that intersects the rake face and bottom surface diagonally, providing improved restraint against sliding forces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the bottom surface of the cutting insert is formed in a V shape to prevent displacement, then the cutting insert is securely fixed against sliding forces, but the contact area with the insert attachment seat is reduced by approximately half, decreasing restraint force and causing edge tip shaking
Solution Approach 1:
The bottom surface is divided into multiple inclined surfaces (first inclined surface, second inclined surface, third inclined surface, fourth inclined surface) with different slopes, allowing each segment to serve a specific function: the first and second inclined surfaces provide restraint against sliding forces, while the third and fourth inclined surfaces increase contact area and distribute stress, thereby resolving the contradiction between fixation stability and contact area
Solution Approach 2:
Different portions of the bottom surface are given different inclinations and functions: the first inclined surface has a specific slope for restraint, the second inclined surface has a different slope for additional restraint, and the third and fourth inclined surfaces are designed to increase contact area. This local differentiation allows the bottom surface to simultaneously achieve secure fixation and sufficient contact area
2Manufacturing precision
If the tool diameter is decreased for precision machining, then machining accuracy is improved, but the wall thickness of the tool body decreases, reducing support strength and increasing displacement risk
Solution Approach 1:
The cutting insert design incorporates local thickness variations with different inclined surfaces having different slopes and lengths. The first and second inclined surfaces provide restraint functionality, while the third and fourth inclined surfaces are designed to increase local contact area and thickness in regions where support strength is needed, allowing small-diameter tools to maintain both precision and strength
3Strength
If the radial rake becomes negative to increase wall thickness, then the wall thickness supporting the cutting insert increases, but the bottom surface becomes an outward slope, generating sliding force and increasing displacement likelihood
Solution Approach 1:
Instead of using a uniform negative radial rake, the invention applies different inclinations to different surfaces: the first inclined surface and second inclined surface are designed with specific slopes to provide restraint against sliding forces, while the third and fourth inclined surfaces compensate for the outward slope effect by creating additional contact areas that distribute and reduce sliding forces, thereby maintaining both wall thickness and displacement resistance
Data Source
AI summary
A cutting insert suitable for a small-diameter milling tool is provided. A cutting insert has a rake face, a bottom surface, a circumferential side surface, and a through hole. A first ridgeline at which the rake face and the circumferential side surface intersect each other includes a first main cutting edge, and a first corner cutting edge connected to a tip of the first main cutting edge. The bottom surface includes a first bottom surface that comes closer to the rake face gradually toward a side at which the first main cutting edge is located when viewed from a central axis of the through hole, and a second bottom surface that comes closer to the rake face gradually toward a side opposite to the first main cutting edge when viewed from the central axis. A distance between a virtual intersection line, at which a first virtual surface formed by extending the first bottom surface and a second virtual surface formed by extending the second bottom surface intersect each other, and the first main cutting edge decreases from a tip side, at which the tip of the first main cutting edge is located, toward an end side, at which an end opposite to the tip is located, in an extending direction of the first main cutting edge.