Hard-Film-Coated Drill Edge Geometry for Adhesion and Sharpness
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Solution Overview
Problem
Existing hard-film-coated drills face challenges in maintaining uniform radius of curvature for round chamfers across different drill sizes, leading to issues such as chipping and wear, especially as drill diameter increases.
Innovation Solution
Optimizing the round-chamfering process by adjusting the radii of curvature of specific ridgelines on the drill body and controlling the thickness and hardness of the hard film, within specific ranges, to enhance adhesion and reduce film destruction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the radius of curvature of the round chamfer is increased to prevent film destruction at the cutting tip, then film adhesion is improved, but the cutting resistance increases and cutting sharpness deteriorates
Solution Approach 1:
The patent applies different radius of curvature values to different ridgelines based on their specific locations and functions. The first ridgeline (between flank and chamfer surfaces) has a smaller radius (0.05-0.5mm) to maintain cutting sharpness, while the second ridgeline (between chamfer and margin) has a larger radius (0.1-1.0mm) to prevent film destruction. This localized differentiation resolves the contradiction by optimizing each region's radius according to its specific requirements.
Solution Approach 2:
The patent changes the parameter of radius of curvature from a uniform value to specific differentiated values for different ridgelines. By establishing specific parameter ranges for different locations (first ridgeline: 0.05-0.5mm, second ridgeline: 0.1-1.0mm), the patent optimizes both film adhesion and cutting sharpness simultaneously, resolving the contradiction between these two opposing requirements.
2Adaptability or versatility
If the drill diameter is increased to handle larger workpieces, then cutting resistance and force on the cutting tip increase, but this makes it more difficult to maintain uniform round chamfer geometry
Solution Approach 1:
The patent identifies specific ridgelines that require round chamfering and assigns different radius ranges to different locations. The first ridgeline (closer to the cutting edge) uses a smaller radius (0.05-0.5mm) while the second ridgeline (further from the cutting edge) uses a larger radius (0.1-1.0mm). This localized approach ensures that even as drill diameter increases, each region maintains its optimal geometry for both film adhesion and cutting performance.
3Strength
If the radius of curvature is made small to maintain cutting sharpness, then film destruction occurs at the ridgeline, but if made large to prevent film destruction, then cutting resistance increases
Solution Approach 1:
The patent applies different radius of curvature values to different ridgelines based on their specific locations and functions. The first ridgeline (between flank and chamfer surfaces) has a smaller radius (0.05-0.5mm) to maintain cutting sharpness, while the second ridgeline (between chamfer and margin) has a larger radius (0.1-1.0mm) to prevent film destruction. This localized differentiation resolves the contradiction by optimizing each region's radius according to its specific requirements.
Solution Approach 2:
The patent performs round chamfering with specific radius values as a preliminary action before hard film coating. By pre-forming the ridgelines with optimized radii, the patent prevents film destruction from occurring in the first place, eliminating the need to increase radius afterward which would compromise cutting sharpness.
Data Source
AI summary
In a hard-film-coated drill having a cemented carbide drill body coated with a hard film, the drill body is provided with a smooth region at a boundary between a flank surface and a rake surface. The surface hardness of the hard film is within 2000 to 2500 HV in Vickers hardness. A radius r1 (μm) of curvature of the first ridgeline L1 where the smooth region and the flank surface intersect is represented by r1=0.45×D+a1 (10≤a1≤25), where D is the diameter (mm) of the body. A radius r2 (μm) of curvature the second ridgeline L2 where the flank surface and a margin intersect is represented by r2=0.65×D+a2 (39≤a2≤67). A thickness t1 (μm) of the hard film is represented by t1=0.8×ln(D)+a3 (0.7≤a3≤3.0).