Carbon-Fiber Composite Drill Geometry for Low-Defect Hole Making
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Solution Overview
Problem
Conventional drills used for carbon fiber composite materials often result in defects such as burrs, delaminations, carbon fiber splinters, or mounds around the hole due to high cutting resistance and inadequate cutting edge geometry.
Innovation Solution
The development of a drill with two cutting edges symmetrically formed around a rotation axis, featuring forward-end small-diameter portions with inclination portions that gradually increase in diameter, and relief surfaces to provide sharp cutting edges and reduce cutting resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional drills are used for carbon fiber composite materials, then drilling operation can be performed, but defects such as burrs, delaminations, carbon fiber splinters, or mounds around the hole are generated due to high cutting resistance
Solution Approach 1:
The drill is divided into multiple functional zones: a chisel portion at the center, inclined portions on the drill body, and cutting edges at the periphery. Each zone performs a specific function - the chisel portion creates an initial pilot hole, the inclined portions gradually expand the hole diameter, and the cutting edges finish the hole. This segmentation allows progressive material removal with reduced cutting resistance and prevents defects in carbon fiber composite materials.
Solution Approach 2:
The drill performs preliminary actions by first using the chisel portion to create a small pilot hole at the center, then gradually expanding the hole diameter through the inclined portions before the main cutting edges engage. This preliminary hole creation reduces the cutting resistance encountered by the main cutting edges and prevents burrs and delaminations.
2Force
If a drill with narrow chisel width and thinning web is used, then thrust resistance is reduced and less operator force is required, but the forward end of the drill is likely to be chipped since the chisel width is very narrow
Solution Approach 1:
The drill separates the functions of force reduction and strength provision into different portions. The thinned web and narrow chisel width at the forward end reduce thrust resistance and operator force requirements, while the reinforced body structure and inclined portions provide the necessary strength to prevent chipping.
Solution Approach 2:
The drill has different structural properties in different locations: the forward end has a thinned web and narrow chisel for reduced cutting resistance, while the body has adequate thickness and strength. The inclined portions gradually transition between these regions, providing local optimization of both force requirements and structural strength.
3Manufacturing precision
If the rake angle formed by thinning is set to be greater than 90° for high hardness steel plate, then cutting ability is improved, but the drill requires significant force when the center to the outer peripheral edges reach the workpiece
Solution Approach 1:
The drill separates the cutting function into multiple stages: the chisel portion with high rake angle creates the initial hole with good cutting ability, while the inclined portions and peripheral cutting edges complete the hole with reduced force requirements. This segmentation avoids the need for the entire drill to withstand high forces simultaneously.
Solution Approach 2:
The chisel portion performs preliminary cutting action with a high rake angle (>90°) to create an initial hole in hard materials. This preliminary action reduces the force required by the subsequent inclined portions and peripheral cutting edges, allowing the use of high rake angle geometry without requiring the entire drill to withstand excessive forces.
Data Source
AI summary
The drill of the invention has: two cutting edges, each having a main cutting edge and a thinned cutting edge, wherein two relief surfaces formed symmetrically around rotation axis, first and second margin portions are formed, the first margin portions have a forward-end small-diameter portion with diameter smaller than the drill diameter, that is formed from the side of the drill forward-end toward the drill rearward-end, the second margin portions have a second forward-end small-diameter portion with diameter smaller than the first forward-end small-diameter portion, that is formed from the side of the drill forward-end toward the side of the drill rearward-end, the first forward-end small-diameter portion and the second forward-end small-diameter portion have inclination portions, the diameters of which gradually increase from the side of the drill forward-end toward the side of the drill rearward-end, and the inclination portions of the first forward-end small-diameter portion have relief surfaces.