Four-Way Positive Cutting Insert for Small-Diameter Shoulder Milling
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Solution Overview
Problem
Existing small diameter end mills, particularly those with diameters of 20 mm and less, face challenges in competing with solid end mills due to limitations in design features and material usage, leading to inefficiencies in 90° shoulder milling operations and increased costs.
Innovation Solution
A single-sided four-way indexable cutting insert with a basic square shape and specific design features such as a rake surface, unground lower sub-surface, and overhanging portions, allowing for four indexable positions and reduced material usage, which enables efficient 90° shoulder milling operations in small diameter tool holders.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If four-way indexable inserts are used in small diameter tool holders, then productivity and cost-effectiveness are improved, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The insert is divided into functionally distinct zones: a wiper portion with positive relief angle for finishing operations and a relieved cutting edge portion with negative relief angle for roughing operations. This segmentation allows each zone to be optimized for its specific function while maintaining four-way indexability in small diameter applications
Solution Approach 2:
Different portions of the cutting edge have different geometric properties: the wiper portion has positive relief angle (5-15 degrees) for smooth finishing, while the relieved cutting edge portion has negative relief angle (0-5 degrees) for aggressive material removal. This local quality variation enables multi-functionality within a single insert design
2Reliability
If the cutting edge is designed with wiper portion and relieved cutting edge portion, then cutting performance is improved, but the overall cutting edge length is reduced
Solution Approach 1:
The patent optimizes the proportional distribution between the wiper portion and relieved cutting edge portion to maximize effective cutting length. By carefully controlling the extent of each portion and their respective relief angles, the design achieves both high-performance cutting and adequate edge length within the constraints of small insert diameters
3Adaptability or versatility
If inserts are made with smaller diameters to compete with solid end mills, then adaptability to small locations is improved, but manufacturing precision and distortion control become more difficult
Solution Approach 1:
The insert geometry is designed with predetermined compensation features that account for expected sintering distortion. The asymmetric distribution of material and strategic placement of voids create internal stress patterns that counteract the convex bulging tendency, pre-compensating for distortion before the insert is even installed
4Loss of substance
If the volume ratio of void volume to material volume is increased, then material usage is reduced and cost is decreased, but structural strength may be compromised
Solution Approach 1:
The insert incorporates a controlled void volume (Vs/Vf ≥ 0.25) strategically positioned within the insert structure. These voids reduce material consumption and cost while being located in areas that minimize impact on structural integrity. The voids are positioned to avoid critical load-bearing zones while still achieving significant material reduction
Data Source
Figure 1A~1C
Figure 2~3
Figure 4~5C
AI summary
A single-sided four-way indexable cutting insert (14) includes a positive basic shape, a rake surface (24), a peripheral surface (28) including four side abutment surfaces (38A, 38B, 38C, 38D), a base bearing surface (26) and a screw hole (30) connecting the rake and base bearing surfaces (24, 26). The insert (14) has an imaginary square frustum which defines a square base containing the cutting insert's base bearing surface (26), and further defines four isosceles trapezoid side surfaces (54A, 54B, 54C, 54D) respectively containing the cutting insert's (14) four side abutment surfaces (38A, 38B, 38C, 38D). A material volume VF of the cutting insert (14) and a void volume VS of the insert (14) fulfill the condition VS/VF ≥ 0.25.