Double-Step Sawtooth Cutter for Burr-Free Composite Stack Drilling
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Solution Overview
Problem
Existing drilling technologies face challenges in preparing high-quality holes in composite materials and hybrid stack structures due to issues like layered damage, fiber tear, burrs, and metal chip accumulation, which result in low interlayer bonding strength and poor hole precision.
Innovation Solution
A vertical-edge double-step sawtooth cutter with a right-hand helix design, featuring a double-step structure and sawtooth cutting region, includes a negative step angle and a vertical chip breaking edge to inhibit inlet and outlet layering, reduce burrs, and effectively break and crush metal chips, preventing scratch damage to composite materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional drilling is used on composite material, then hole preparation can be achieved, but axial force is large and interlayer bonding strength is low causing layered damage and fiber tear
Solution Approach 1:
The cutter employs a double-step structure that segments the cutting process into two distinct stages: a first step for initial material removal and a second step for final hole formation. This segmentation reduces the axial force required at each stage compared to single-step drilling, preventing interlayer bonding failure and layered damage in composite materials.
Solution Approach 2:
The cutter features different geometric parameters at different locations: the first step has specific helix angle and tooth geometry optimized for initial cutting, while the second step has different parameters optimized for final hole quality. This local differentiation allows each step to perform its function optimally, reducing overall axial force and preventing fiber tear.
2Manufacturing precision
If conventional drilling is used on composite material, then hole preparation can be achieved, but inlet and outlet positions have weak constraint effect resulting in layered damage
Solution Approach 1:
The first step of the double-step structure performs preliminary cutting and material removal, creating a pilot hole that strengthens the constraint effect at inlet and outlet positions before the second step completes the hole. This preliminary action prevents layered damage by establishing structural integrity early in the cutting process.
3Ease of manufacture
If metal is drilled in hybrid stack structure, then connection can be achieved, but continuous ribbon chips are produced that scratch composite material
Solution Approach 1:
The vertical chip breaking edge extracts the harmful continuous ribbon chips from the cutting zone by actively breaking and crushing them as they are formed. This removal of harmful chips prevents them from scratching the composite material surface while maintaining the connection capability of the hybrid stack structure.
Solution Approach 2:
The vertical chip breaking edge converts the harmful continuous ribbon chips into beneficial small granular chips. By breaking and crushing the long chips vertically, the structure transforms a harmful factor (scratching chips) into a beneficial outcome (clean hole surface without scratches) while maintaining manufacturing capability.
4Productivity
If sawtooth structure is located at final cutting edge, then cutting function is achieved, but small tear damage occurs at outlet and inlet reducing hole wall smoothness
Solution Approach 1:
The sawtooth structure is segmented and distributed around the drill axis rather than concentrated at the final cutting edge. This segmentation allows multiple sawtooth elements to perform cutting functions simultaneously at different angular positions, maintaining cutting efficiency while distributing the mechanical stress to prevent tear damage at inlet and outlet positions.
Solution Approach 2:
The sawtooth structure is arranged in a three-dimensional configuration around the drill axis with specific helical distribution, rather than being confined to a two-dimensional cutting edge. This spatial distribution allows the sawtooth elements to engage material progressively, reducing tear damage while maintaining cutting efficiency.
Data Source
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AI summary
The present invention belongs to the technical field of drilling tools in machining, and relates to a vertical-edge double-step sawtooth cutter for preparing high-quality holes of composite material and thereof hybrid stack structure. The vertical-edge double-step sawtooth cutter for preparing high-quality holes of composite material and laminated structure thereof comprises three parts which are a major cutting edge region A, a minor cutting edge region B and a shank region C, wherein the minor cutting edge region B comprises a step vertical-edge region D and a sawtooth cutting region E. The vertical-edge double-step sawtooth cutter for making high-quality holes of composite material and laminated structure thereof in the present invention has the step structure and the sawtooth structure which is distributed in the first step, has a recutting function at the inlet and a reverse cutting function at the outlet in the direction opposite to the main cutting motion and effectively inhibits damage such as inlet and outlet layering and burr of the composite material. The cutter has the vertical edge structure distributed in the second step, and the angle of the second step is a negative value, thereby realizing chip breaking and crushing, reducing scratch to the upper-layer composite material and metal hole walls, removing the metal outlet burr and outlet burr of the composite material from roots and improving outlet quality of the metal and the composite material.