CFRP Drill With Side-Through Grooves for Delamination Control
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Solution Overview
Problem
Drilling through CFRP materials is challenging due to delamination, surface peeling, burrs, and increased machining torque, primarily because of the low glass transition temperature of the resin and the tendency of fibers to break, leading to uncut fibers and reduced machining efficiency, along with issues like heat generation and chip pulverization.
Innovation Solution
A drill design without margins on the pilot blade, diameter-enlarging spiral thread portion, and finishing spiral thread portion, featuring side-through grooves for coolant supply and communication between cutting portion grooves to prevent chip pulverization and delamination, allowing for granulated chip formation and efficient discharge.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a drill with conventional margin portions is used for drilling CFRP, then the drill structure is simple and easy to manufacture, but the cutting edge sharpness deteriorates rapidly due to heat and friction, causing delamination and poor machining quality
Solution Approach 1:
The drill is divided into multiple functional portions: a pilot blade portion for initial cutting, a diameter-enlarging spiral thread portion for expanding the hole, and a finishing spiral thread portion for final surface finishing. Each portion has optimized features (no margins, specific helix angles) to perform its function while reducing overall heat generation and improving machining quality.
Solution Approach 2:
The pilot blade portion performs preliminary cutting to create a pilot hole before the diameter-enlarging portion acts. This preliminary action reduces the cutting resistance and heat generation for subsequent portions, preventing delamination and maintaining machining quality throughout the drilling process.
2Temperature
If cutting is performed without coolant supply (dry machining), then the drill structure is simpler, but the cutting temperature increases rapidly causing resin softening, blade sharpness loss, and delamination
Solution Approach 1:
A coolant supply system uses hydraulic principles to deliver coolant through channels in the drill shank to the cutting edges via communication grooves. This controlled fluid delivery effectively manages cutting temperature without requiring complex external cooling systems, preventing resin softening and maintaining blade sharpness.
3Duration of action of stationary object
If the drill has margin portions for structural stability, then the drill is easier to manufacture, but the entire blade tip experiences friction and heat causing rapid wear and thrust force increase
Solution Approach 1:
The drill features localized quality variations: the pilot blade and diameter-enlarging portion have no margins to minimize friction and heat, while the finishing portion has optimized margins for surface quality. This local differentiation extends blade tip durability in critical areas without compromising manufacturability overall.
4Manufacturing precision
If conventional drilling is used on CFRP, then the process is simpler and faster, but fibers break and form uncut fibers causing burrs and fluffing
Solution Approach 1:
The drill utilizes dynamic helical spiral threads with specific lead angles that create progressive cutting action. The rotating spiral threads dynamically engage the CFRP fibers, pulling them through the cutting edge at optimized angles to prevent breakage and uncut fibers, ensuring both precision and efficiency.
Solution Approach 2:
The drill itself is designed as a composite tool with multiple material portions (pilot blade, spiral threads, finishing portion) each optimized for specific functions. This composite structure enables precise cutting of CFRP while maintaining the productivity needed for efficient machining.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The design results in high-quality hole machining with reduced delamination, surface peeling, and burrs, maintaining the sharpness of the cutting edge, and effectively managing heat generation, enabling precise cutting through CFRP and similar materials.
Implementation Method 1
side-through grooves for coolant supply
Implementation Method 2
finishing spiral thread portion
Data Source
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AI summary
A drill capable of efficiently performing high-quality drilling machining on a material which is hard to be cut such as CFRP and the like is provided. The drill includes a drill body 4 having a shank portion 2 at a rear side of the drill main body and a cutting portion 3 at a front side of the drill main body, a first land A to a fourth land D at the cutting portion 3, a first cutting portion groove 5a to a fourth cutting portion groove 5d provided between the lands of the first land A to the fourth land D, a pilot blade 6 formed at the tip of the cutting portion 3, a diameter-enlarging spiral thread portion 9 having a group of threads of diameter-enlarging spiral threads AK1-DK4 continuously following the pilot blade 6, a finished spiral thread portion 12 having a group of threads of finishing spiral threads AF1-DF5, which have the same height, and continuously following the diameter-enlarging spiral thread portion 9, a diameter-enlarging spiral blade portion 18 having a group of blades of the diameter-enlarging spiral threads AK1-DK4, and a finishing spiral blade portion 19 having a group of blade of the finishing spiral threads AF1-DF5. A cutting feed rate is set to an amount so that a spiral convex part will not be formed on the wall surface of a cutting hole formed in a material to be machined, and therefore the wall surface will be finished as a flat wall.