Ball End Mill Gash Geometry for Edge Strength and Chip Flow
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Solution Overview
Problem
Existing ball end mills face challenges in maintaining cutting performance and preventing chipping or damage due to strength degradation of the bottom cutting edge, while also avoiding increased cutting resistance from chip clogging.
Innovation Solution
A ball end mill design featuring a chip discharge groove with a concave groove-shaped first gash and a second gash formed on the first wall surface, which increases the wedge angle of the bottom cutting edge and enhances chip discharge performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the radius of the cutting edge bottom roundness is increased to R=(0.15 to 0.3)×D and the rake angle is set to 5° or larger, then cutting performance is improved, but the wedge angle of the bottom cutting edge decreases, causing degraded strength and chipping or damage
Solution Approach 1:
The invention applies different geometric parameters to different regions of the bottom cutting edge. The cutting edge bottom roundness radius is set to R=(0.05 to 0.1)×D (smaller than conventional values) while the rake angle is specifically set to 5° or larger. This local differentiation allows the cutting edge to have both improved cutting performance through the rake angle and sufficient strength through the controlled roundness radius, resolving the contradiction between productivity and strength.
2Productivity
If the gash extends to the vicinity of the end mill rotation center to maintain the cutting edge bottom roundness radius and rake angle, then cutting performance is maintained, but the circumferential speed is close to zero, causing degraded strength and chipping or damage in the vicinity of the rotation center
Solution Approach 1:
The invention extends the gash to the vicinity of the end mill rotation center but applies localized geometric control: the cutting edge bottom roundness radius is limited to R=(0.05 to 0.1)×D and the rake angle is set to 5° or larger specifically in this region. This local quality approach ensures that even at low circumferential speeds near the rotation center, the bottom cutting edge maintains sufficient strength while still providing effective cutting performance.
3Strength
If the wedge angle of the bottom cutting edge is increased by reducing the rake angle and reducing the chip pocket, then the strength of the bottom cutting edge is ensured, but chip discharge performance is impaired, causing chip clogging and increased cutting resistance
Solution Approach 1:
The invention changes the critical parameters of the cutting edge geometry: the cutting edge bottom roundness radius is set to R=(0.05 to 0.1)×D and the rake angle is set to 5° or larger. These parameter changes optimize the balance between wedge angle (strength) and chip pocket geometry (chip discharge performance). The controlled roundness radius maintains wedge angle strength while the adequate rake angle ensures proper chip discharge, preventing chip clogging and maintaining productivity.
4Productivity
If the chip pocket size is increased to improve chip discharge performance, then chip clogging is reduced, but the wedge angle of the bottom cutting edge decreases, causing strength degradation and chipping or damage
Solution Approach 1:
The invention optimizes the chip pocket size through specific parameter settings: the cutting edge bottom roundness radius is limited to R=(0.05 to 0.1)×D while the rake angle is set to 5° or larger. These parameter changes create an optimized chip pocket geometry that provides sufficient chip discharge performance without excessively reducing the wedge angle. The result is adequate chip discharge capability while maintaining bottom cutting edge strength to prevent chipping or damage.
Data Source
AI summary
A ball end mill includes an end mill body; a chip discharge groove, a first gash, and a bottom cutting edge. A second gash is formed at an interval from the bottom cutting edge on at least a first wall surface of the first gash. A minimum curvature radius in a cross section perpendicular to an axis of the second gash is larger than a minimum curvature radius in a cross section perpendicular to an axis of a groove bottom portion of the first gash.