End Mill Cutting Edge Geometry for Chipping Suppression
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Solution Overview
Problem
Existing end mills, particularly those with CBN materials, suffer from chipping or fracture near the peripheral cutting edge tip, leading to reduced tool life, despite efforts to enhance edge tip strength.
Innovation Solution
The end mill design features a bottom cutting edge with a concave angle of 3° or less, a larger flank angle and width for the bottom cutting edge outer peripheral portion, and a gradual decrease in flank angle and width for the corner R cutting edge, aligning the cutting force direction closer to the central axis to reduce load on the peripheral cutting edge, thereby enhancing edge tip strength and rigidity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a minute flank face is provided on the flank face of the peripheral cutting edge to improve edge tip strength, then the edge tip strength is increased, but chipping or fracture near the peripheral cutting edge tip cannot be sufficiently suppressed
Solution Approach 1:
The invention applies different geometric parameters to different regions of the cutting edge. Specifically, the bottom cutting edge outer peripheral portion has a larger flank angle (5° or more) and larger flank face width compared to the peripheral cutting edge primary flank face. This local differentiation creates a load distribution optimization where the bottom cutting edge absorbs more load, reducing the stress concentration at the peripheral cutting edge tip and suppressing chipping or fracture while maintaining edge tip strength.
Solution Approach 2:
The invention changes the geometric parameters of the bottom cutting edge outer peripheral portion, specifically setting the flank angle to 5° or more and the flank face width to 0.05D or more (where D is the outer diameter of the end mill). These parameter changes create a concave angle of 3° or less at the bottom cutting edge, which redirects the cutting force direction closer to the central axis, thereby reducing the load acting from the bottom cutting edge toward the peripheral cutting edge and suppressing chipping or fracture.
2Reliability
If the flank angle of the bottom cutting edge outer peripheral portion is increased to reduce load on the peripheral cutting edge, then chipping or fracture is suppressed, but cutting force of the bottom cutting edge may increase excessively
Solution Approach 1:
The invention optimizes the flank angle parameter within a specific range (5° or more, but not excessively large) to achieve the right balance. This parameter setting creates an optimal concave angle of 3° or less, which is sufficient to redirect the cutting force direction closer to the central axis and reduce load on the peripheral cutting edge, while not being so large as to cause excessive cutting force from the bottom cutting edge.
3Strength
If the width of the bottom cutting edge outer peripheral portion primary flank face is increased to ensure rigidity, then sufficient rigidity is maintained, but the load on the peripheral cutting edge may not be reduced effectively
Solution Approach 1:
The invention sets the flank face width of the bottom cutting edge outer peripheral portion to a specific value (0.05D or more) that is larger than the peripheral cutting edge primary flank face width. This local differentiation in width creates both sufficient rigidity in the bottom cutting edge region and an appropriate load distribution that reduces the load on the peripheral cutting edge, effectively suppressing chipping or fracture.
Data Source
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AI summary
An end mill (1) includes a cutting edge portion (3) and a shank (2), which are rotated around a central axis (O), in which the end mill (1) includes a bottom cutting edge (11) located on a tip surface of the cutting edge portion (10), and a peripheral cutting edge (13) located on an outer peripheral surface of the cutting edge portion (10), the bottom cutting edge (11) has a bottom cutting edge outer peripheral portion (11a) that extends from an outer peripheral end of the bottom cutting edge to the shank side toward an inner side in a radial direction at an inclination angle (α) of 3° or less with respect to a plane orthogonal to the central axis (O), a flank angle of a bottom cutting edge outer peripheral portion primary flank face (14a) adjacent to the bottom cutting edge outer peripheral portion (11a) is larger than a flank angle of a peripheral cutting edge primary flank face (14a) adjacent to the peripheral cutting edge (13), and a width (W2) of the bottom cutting edge outer peripheral portion primary flank face is larger than a width (W1) of the peripheral cutting edge primary flank face.