Milling Insert Minor Cutting Edge Geometry for Surface Quality
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Solution Overview
Problem
Existing indexable cutting inserts for milling face challenges in achieving high-quality machined surfaces due to the roughness caused by straight or circular minor cutting edges, which are sensitive to mounting orientation variations, leading to irregular feed marks and increased surface roughness.
Innovation Solution
A polygonal cutting insert with a minor cutting edge configuration featuring two circular cutting edge portions joined to straight major cutting edges and a straight cutting edge portion between them, where the straight cutting edge is tangent to the circular portions, allowing for precise edge runout measurement and reduced surface roughness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If straight minor cutting edges are used, then the cutting insert can be manufactured with simple geometry, but the machined surface quality deteriorates when the mounting orientation varies
Solution Approach 1:
The patent applies curvature to the minor cutting edge by forming it as a circular arc instead of a straight line. This curved geometry makes the cutting edge less sensitive to mounting orientation variations, as the arc can accommodate angular deviations while still effectively wiping the machined surface. The circular arc shape with radius R satisfies 0.01Ta ≤ R ≤ 0.05Ta, where Ta is the inscribed circle radius, allowing the cutting edge to maintain consistent performance across varying mounting conditions.
2Reliability
If circular minor cutting edges with large radius are used, then the cutting edge becomes less sensitive to tilt variations, but the height of ridges remaining on the machined surface increases
Solution Approach 1:
The patent optimizes the radius parameter of the circular arc minor cutting edge within a specific range (0.01Ta ≤ R ≤ 0.05Ta). By controlling the radius to be sufficiently small, the cutting edge can still effectively remove material and reduce ridge height, while the curvature provides enough tolerance to mounting variations. This parameter optimization balances the competing requirements of tilt insensitivity and surface quality.
3Reliability
If circular minor cutting edges are used, then the cutting edge is more tolerant of tilt, but the reference position for edge runout measurement becomes ambiguous
Solution Approach 1:
The patent introduces asymmetry by positioning the circular arc minor cutting edge at a specific corner of the polygonal insert, with the arc center located on the bisector of the corner. This asymmetric positioning within the symmetric circular geometry provides a unique reference position for measurement, as the arc's position relative to the corner and major cutting edges creates an unambiguous reference point for edge runout measurement.
4Measurement precision
If the straight cutting edge portion is made longer, then the reference for edge runout measurement is more stable, but the length of the circular portions is reduced
Solution Approach 1:
The patent defines specific parameter ranges for both the straight cutting edge length (0.05L1 ≤ L ≤ 0.4L1) and the circular arc radius (0.01Ta ≤ R ≤ 0.05Ta), where L1 is the length of the minor cutting edge. These parameter specifications ensure that the straight portion is sufficiently long to provide a stable measurement reference, while the circular portions retain adequate length to maintain their wiping function and tolerance to tilt variations.
Data Source
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AI summary
An object is to provide a cutting insert for milling that has a minor cutting edge for wiping to achieve improved machined surface quality. A minor cutting edge 3 at a corner includes two circular cutting edge portions 3a and 3a joined to major cutting edges 2 on both sides of the corner and a straight cutting edge portion 3b located between the two circular cutting edge portions. The cutting insert satisfies the following conditions: 0.05TA ≤ L1 ≤ 0.4TA, 0.1 L1 ≤ L ≤ 0.5L1, and h ≤ 15 µm, where TA is the radius of a circle inscribed inside the major cutting edges as viewed in the thickness direction of the cutting insert, L1 is the length of the minor cutting edge 3 in the longitudinal direction of the straight cutting edge portion, L is the length of the straight cutting edge portion 3b, and h is the height of the minor cutting edge 3.