Indexable Rotary Cutting Insert With Variable Rake for Crack Resistance
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Solution Overview
Problem
Cutting inserts with inclined main cutting edges tend to crack due to thinning along the longitudinal direction, leading to increased cutting resistance and potential damage.
Innovation Solution
A cutting insert design with a rake angle that increases from a positive angle near the acute angle corner to a negative angle near the obtuse angle corner, with specific distance ratios and angles to reduce cutting resistance and prevent cracking, and an indexable edge rotary cutting tool incorporating this insert.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If the main cutting edge is inclined toward the seating surface along the longitudinal direction, then the cutting resistance is reduced, but the cutting insert becomes thinner and more likely to crack
Solution Approach 1:
The patent applies different rake angles to different regions of the main cutting edge. The acute angle corner portion has a positive rake angle to reduce cutting resistance, while the obtuse angle corner portion has a negative rake angle to increase strength and prevent cracking. This local differentiation resolves the contradiction between reducing cutting resistance and preventing cracks.
Solution Approach 2:
The rake angle is designed to dynamically change along the longitudinal direction of the main cutting edge, transitioning from positive at the acute angle corner to negative at the obtuse angle corner. This dynamic variation allows the cutting edge to adapt its geometry along its length, optimizing both cutting performance and structural integrity.
2Force
If the cutting insert is made thinner along the longitudinal direction, then the cutting resistance is reduced, but the thinnest portion on the diagonal line becomes vulnerable to cracking
Solution Approach 1:
The patent makes the insert thickness non-uniform along the longitudinal direction, with the thickest portion positioned at or near the obtuse angle corner portion. This local thickening at the vulnerable diagonal line region prevents cracking while maintaining thinner sections elsewhere to reduce cutting resistance.
3Manufacturing precision
If the rake angle is uniformly positive along the main cutting edge, then the cutting quality is improved, but the edge strength at the obtuse angle corner is reduced
Solution Approach 1:
The patent applies a positive rake angle at the acute angle corner portion to achieve good cutting quality, while applying a negative rake angle at the obtuse angle corner portion to strengthen the edge. This localized differentiation of rake angles resolves the contradiction between cutting quality and edge strength.
Data Source
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AI summary
A cutting insert includes a main surface formed in a substantially parallelogram shape in a plan view and having a pair of acute angle corner portions and a pair of obtuse angle corner portions, a seating surface that faces a side opposite to the main surface, a side surface that connects the main surface and the seating surface to each other, a corner cutting edge disposed in the acute angle corner portion, and a main cutting edge and a subsidiary cutting edge which are respectively disposed in a pair of side ridge portions of the main surface located each other across the acute angle corner portion. A mounting hole into which the fixing member is inserted penetrates the main surface and the seating surface. The main cutting edge is inclined at an inclination angle equal to or larger than 8° with reference to a plane perpendicular to an axial direction of the mounting hole so as to be closer to the seating surface side, as the main cutting edge is oriented from the acute angle corner portion toward the obtuse angle corner portion. The main surface has a region inclined in a direction away from the seating surface, as the main surface is oriented from the obtuse angle corner portion toward an edge portion of the mounting hole along a diagonal line connecting the pair of obtuse angle corner portion to each other.