Cutting Head Rake Angle Layout for Wear, Stability, and Chip Flow
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Solution Overview
Problem
Cutting heads used in drilling operations face issues with wear resistance at radially outer edges and stability at radially inner edges, as well as inefficient chip evacuation, particularly at high feed rates.
Innovation Solution
A cutting head design featuring radially outer cutting edges with a positive rake angle and radially inner cutting edges with a negative rake angle, along with extended gash paths for efficient chip evacuation, is implemented. The cutting head is rotatable and includes a tip portion with axially forwardmost tip points and front surfaces, with each outer cutting edge extending radially inwardly and inner cutting edge adjoining the outer cutting edge at a transition point, where the rake angles change from positive to negative, enhancing wear resistance and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If radially outer cutting edges use positive rake angle for wear resistance, then wear resistance improves, but cutting forces increase
Solution Approach 1:
The cutting head applies different rake angles to different radial positions: positive rake angles at radially outer portions for wear resistance, and negative rake angles at radially inner portions for stability. This local differentiation resolves the contradiction by optimizing each region for its specific operational requirements rather than using a uniform rake angle throughout.
2Stability of the object's composition
If radially inner cutting edges use negative rake angle for stability, then stability improves, but wear resistance decreases
Solution Approach 1:
The cutting head applies different rake angles to different radial positions: negative rake angles at radially inner portions for stability, and positive rake angles at radially outer portions for wear resistance. This local differentiation resolves the contradiction by optimizing each region for its specific operational requirements.
3Productivity
If gash paths are extended axially rearward for chip evacuation, then chip evacuation efficiency improves, but device complexity increases
Solution Approach 1:
The gash paths extend axially rearward from the tip portion along the first axis, utilizing the axial dimension for chip evacuation rather than relying solely on radial or circumferential paths. This dimensional approach improves chip evacuation efficiency while maintaining a relatively simple gash configuration that integrates with the existing cutting head structure.
Data Source
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Figure 5~6
AI summary
A cutting head (20) rotatable about a first axis (Al), comprising an intermediate portion (22) and a tip portion (24). The intermediate portion has a plurality of leading edges (28) defining a cutting diameter (DC), and the tip portion has an axially forward most tip point (NT) and a plurality of front surfaces (30) with outer (32) and inner (34) cutting edges. An outer rake surface (40) adjacent to each outer cutting edge has a positive outer rake angle, and an inner rake surface (42) adjacent to each inner cutting edge has a negative inner rake angle. Each outer rake surface is disposed on a head flute (44) intersecting one of the leading edges, and each inner rake surface is disposed on a gash (46) intersecting one of the head flutes. Each gash extends to a gash path end point (NP) located a first distance axially rearward of the tip point, and the first distance is greater than thirty percent of the cutting diameter.