Cubic Boron Nitride End Mill Joint Edge Geometry
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Solution Overview
Problem
Cubic boron nitride radius end mills experience premature wear and reduced life due to damage at the boundary between the radius cutting edge and the end cutting edge during machining of high hardness materials, despite edge strengthening techniques like negative rake faces.
Innovation Solution
A cubic boron nitride radius end mill design featuring a negative rake face with a rake angle between -30° and -50°, a constant wedge angle, and a joint cutting edge with a concave angle smaller than the end cutting edge, which disperses load and enhances fracture resistance, combined with a non-helical cutting edge and specific width and wedge angle configurations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a chamfer with negative angle is disposed on the face along the cutting edge to strengthen the edge, then the edge strength is improved, but the depth of cut cannot be increased and the boundary between radius cutting edge and end cutting edge is still damaged
Solution Approach 1:
The invention applies different geometric characteristics to different parts of the cutting edge. The joint cutting edge has a specific concave angle (0.5°≦γ0≦2°) that differs from the end cutting edge concave angle, creating localized structural optimization at the boundary region to distribute loads and prevent damage while maintaining overall edge strength.
Solution Approach 2:
The cutting edge is divided into distinct segments: end cutting edge, joint cutting edge, and radius cutting edge. The joint cutting edge acts as a separate functional segment with optimized geometry to specifically address the boundary damage problem, rather than treating the cutting edge as a uniform structure.
2Strength
If the concave angle of the end cutting edge is increased to strengthen the boundary, then the edge strength is improved, but the load concentration at the boundary increases causing more damage
Solution Approach 1:
The invention optimizes the concave angle parameter of the joint cutting edge to a specific range (0.5°≦γ0≦2°), which is smaller than the end cutting edge concave angle. This parameter change creates a geometric configuration that strengthens the boundary while simultaneously reducing load concentration through improved stress distribution.
Data Source
AI summary
A cubic boron nitride radius end mill includes a sintered cubic boron nitride compact bonded to an end of a main body, and a cutting edge provided on the sintered cubic boron nitride compact. The wedge angle θt of the cutting edge is constant over the entire region of the cutting edge. A negative rake face is disposed on a face so as to extend over the entire region of the cutting edge, and the rake angle θn of the negative rake face satisfies the relationship −30°≦θn≦−50°. A joint cutting edge is disposed between an end cutting edge and a radius cutting edge in the cutting edge, the joint cutting edge having a concave angle γ0 which is smaller than the concave angle γ1 of the end cutting edge and which satisfies the relationship 0.5°≦γ0≦2°.