Three-Way Indexable Milling Insert for Small-Diameter Stability
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Solution Overview
Problem
Existing insert-mills with three-way indexable cutting inserts face instability and design challenges for small diameter tool holders due to manufacturing inaccuracies, increased moment during cutting, and reduced core diameter, making them less competitive with solid end mills for diameters below 20 mm, especially in the range of 9 to 12 mm.
Innovation Solution
A single-sided three-way indexable cutting insert with a positive basic shape, optimized volume and thickness ratios, and a small edge circumscribed diameter is designed to minimize material usage while maintaining structural strength, allowing for economical production and improved performance in small diameter milling operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If three-way indexable cutting inserts are used, then the number of indexable positions is increased, but manufacturing inaccuracies have a greater effect on runout leading to greater instability during machining
Solution Approach 1:
The patent applies asymmetry by designing the tool holder with non-uniform flute spacing and corresponding non-uniform insert positioning. The flutes are spaced at different angular intervals (e.g., 90 degrees and 45 degrees) rather than uniform 120-degree spacing, which compensates for manufacturing inaccuracies and reduces cumulative runout effects while maintaining three indexable positions per insert.
2Adaptability or versatility
If three-way indexable cutting inserts are used, then the radial dimension is increased, but this creates greater moment when cutting forces are applied leading to greater instability
Solution Approach 1:
The patent transitions from traditional radial insertion to axial insertion by orienting the cutting inserts along the tool axis rather than radially. This dimensional change allows the inserts to be positioned closer to the tool center, reducing the radial dimension and consequently the moment arm for cutting forces, while still providing three indexable positions through axial spacing.
3Adaptability or versatility
If three-way indexable inserts are made wider to accommodate three edges, then they are more problematic to design for small diameter tools
Solution Approach 1:
The patent resolves the width conflict by moving the indexing mechanism from the radial plane to the axial direction. Inserts are spaced along the tool axis at different positions rather than being arranged radially, allowing three indexable positions to be achieved without increasing the insert's radial width, thus enabling use in small diameter tools.
4Loss of substance
If the core diameter of the tool holder is reduced to accommodate smaller inserts, then material usage is reduced, but this leads to unacceptable bending of the tool holder
Solution Approach 1:
The patent employs composite construction for the tool holder, combining different materials with complementary properties. The holder may use high-strength, low-density materials or composite structures (e.g., titanium alloy with optimized geometry, or hybrid material construction) that maintain adequate core diameter for structural integrity while minimizing overall material usage and weight.
5Loss of substance
If insert mills are used instead of solid end mills, then the cost of material is reduced, but the structural integrity and stability for small diameters is compromised
Solution Approach 1:
The patent applies segmentation by dividing the cutting tool into two separate components: a reusable tool holder and replaceable cutting inserts. This allows the expensive cutting insert material to be used only at the cutting edge where it is needed, while the tool holder can be made from more economical materials optimized for structural integrity and rigidity, achieving both cost efficiency and structural strength.
Data Source
Figure 1A~1C
Figure 2~4C
Figure 5A~6
AI summary
A single-sided three-way indexable milling insert for feed milling operations, includes a positive basic shape, a rake surface, a peripheral surface including side abutment surfaces, a base bearing surface and a screw hole connecting the rake and base bearing surfaces. The insert has a cutting edge including exactly three main cutting sub-edges and three secondary cutting sub-edges. A material volume VF of the cutting insert and a void volume VS of the insert fulfill the condition VS/VF ≥ 0.30.