CFRP Drill Geometry for Delamination-Free Hole Cutting
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Solution Overview
Problem
Conventional drills face challenges in effectively cutting carbon fiber reinforced plastic (CFRP) materials due to issues like delamination and uncut fibers, particularly at the cutting edge closer to the rotation axis, where cutting speed is lower and delamination occurs.
Innovation Solution
The drill design features a conical front end with pair of major cutting edges and a connection edge, along with chip discharge flutes and major rake surfaces, which enhance cutting balance and stability, reducing delamination and uncut fibers by maintaining a consistent helix angle and rake angle, and improving chip discharge performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional drill with S-shaped cutting edge is used for CFRP materials, then the drill can cut metal workpieces, but delamination and uncut fibers occur at the cutting edge closer to the rotation axis
Solution Approach 1:
The patent applies local quality by providing different rake angles at different locations of the cutting edge. Specifically, the first rake angle (α1) at the cutting edge portion closer to the rotation axis is set to 10° or more, while the second rake angle (α2) at the cutting edge portion farther from the rotation axis is set to 5° or more. This local differentiation ensures that the cutting edge near the axis, where delamination occurs, receives sufficient rake angle to prevent harmful effects, while maintaining appropriate geometry elsewhere.
Solution Approach 2:
The patent changes the geometric parameters of the cutting edge by specifying precise rake angle values (α1 ≥ 10° and α2 ≥ 5°) and their relationship (α1 > α2). This parameter optimization resolves the contradiction by adjusting the cutting edge geometry to prevent delamination and uncut fibers in CFRP materials while maintaining effective cutting performance across the entire edge.
2Object-affected harmful factors
If the cutting edge geometry is optimized for CFRP materials, then delamination is prevented, but cutting balance and stability may be compromised
Solution Approach 1:
The patent maintains cutting balance by applying local quality principles to the rake angle distribution. By setting α1 ≥ 10° near the rotation axis and α2 ≥ 5° farther from the axis, the design provides enhanced delamination prevention where needed while maintaining overall geometric balance. The gradual transition and specific angle relationships ensure stable cutting without compromising balance.
Solution Approach 2:
The patent optimizes cutting stability through precise parameter control, specifying that the difference between α1 and α2 should be 5° or more while maintaining α1 > α2. This parameter relationship ensures that the cutting edge geometry is optimized for delamination prevention without creating excessive asymmetry that would compromise cutting balance and stability.
3Ease of manufacture
If a single rake angle is used for the entire cutting edge, then manufacturing is simpler, but cutting performance varies along the cutting edge
Solution Approach 1:
The patent implements local quality by differentiating rake angles at different locations of the cutting edge. The first rake angle (α1 ≥ 10°) applies to the portion closer to the rotation axis, while the second rake angle (α2 ≥ 5°) applies to the portion farther from the axis. This location-specific geometry ensures consistent cutting performance throughout the entire cutting edge, preventing both delamination near the axis and other cutting issues at the outer portion.
Solution Approach 2:
The patent changes the rake angle parameter along the cutting edge length, specifying that α1 should be 10° or more and α2 should be 5° or more, with α1 > α2. This parameter variation along the cutting edge ensures that each portion is optimized for its specific cutting conditions, maintaining consistent performance across the entire edge while accommodating the varying cutting speeds and forces at different radial positions.
Data Source
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AI summary
There has been a demand for a drill capable of stably carrying out a cutting process even for a high-strength fiber composite material, such as a carbon fiber reinforced plastic (CFRP). A drill (1) according to an embodiment of the present invention includes a bar-shaped drill body (3), a major cutting edge (15) which is located at a front end of the drill body (3) and has a straight-line region (21) in a front view, a rake surface (9) located along the major cutting edge (15), and a chip discharge flute (7) being extended spirally around a rotation axis (X1) of the drill body (3) in a direction from the rake surface (9) toward a rear end of the drill body (3). The rake surface (9) has a flat region (27) located along the straight-line region (21).