Variable-Rake Cutting Insert for Stable Chip Flow Into Flutes
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Solution Overview
Problem
Existing drill bits face challenges in controlling chip flow, leading to unstable chip direction and potential damage to the workpiece surface, as chips often fail to flow into the flute and instead move towards the outer peripheral direction.
Innovation Solution
The cutting insert features a rake face with varying rake angles, including a first, second, and third surface region, where the second and third rake angles are smaller than the first, facilitating chip curling and directing chips towards the flute, which is positioned closer to the second end and has a helical shape for smooth discharge.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional rake face with uniform rake angle is used, then the structure is simple, but chip flow control is poor and chips may jump out damaging the workpiece surface
Solution Approach 1:
The rake face is segmented into three distinct surface regions (first, second, and third surface regions) with different rake angles. This segmentation allows each region to perform a specific function in controlling chip flow at different stages, from initial curling to final discharge, thereby improving chip flow control while managing structural complexity through functional division.
Solution Approach 2:
Different regions of the rake face are assigned different local properties (rake angles) to optimize chip control at each stage. The first surface region has a larger rake angle for initial chip engagement, the second surface region has a moderate rake angle for chip curling, and the third surface region has a smaller rake angle for guiding chips into the flute. This local differentiation improves overall chip flow control.
2Reliability
If the rake angle is large throughout, then chip curling is easier, but chips may not flow into the flute and move towards the outer peripheral direction
Solution Approach 1:
The rake angle parameter is varied across different surface regions of the rake face. The first surface region has a larger rake angle to facilitate chip curling, while the second and third surface regions have progressively smaller rake angles to guide chips toward the flute. This parameter variation ensures that chips are curled effectively while being directed into the flute for discharge, preventing them from moving toward the outer peripheral direction and damaging the workpiece surface.
3Productivity
If the flute is positioned closer to the first end, then chip discharge path is shorter, but chip flow stability is reduced and chips may jump out
Solution Approach 1:
The third surface region with a smaller rake angle is positioned adjacent to the flute rearward in the rotational direction, creating a preliminary guiding action that directs chips toward the flute before they reach it. This preliminary action ensures that chips flow stably into the flute, maintaining chip flow stability while the flute's position closer to the first end provides a shorter discharge path for improved productivity.
Data Source
AI summary
An insert includes a main body extending from a first end toward a second end. The main body includes a cutting edge, a rake face, and a flute. In the rake face, a second rake angle of a second surface region positioned closer to the second end than a first surface region connected to the cutting edge is smaller than a first rake angle of the first surface region. A third rake angle of a third surface region is smaller than the second rake angle, the third surface region being adjacent to the flute rearward in a rotational direction and on an outer peripheral side of the main body.