End Mill Core Geometry for Chatter-Resistant Roughing
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Solution Overview
Problem
End mills experience chatter and vibrations during roughing operations, leading to noise, reduced accuracy, and shortened tool life due to inadequate resistance to bending moments and vibrations.
Innovation Solution
The end mill features at least two flutes with varying shortest distances to the axis of rotation along the axial direction, creating an irregular core cross-section that reduces chatter by phase-shifting and canceling out vibration waves, while maintaining desired stiffness and tool stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the end mill uses a conventional core design with uniform cross-section, then the structure is simple and manufacturing is easy, but chatter and vibrations occur during roughing operations
Solution Approach 1:
The core cross-section is designed to be irregular rather than uniform, with varying distances from the axis of rotation to the flutes at different axial positions. This asymmetric geometry creates varying stiffness characteristics that disrupt the regularity of vibration waves, causing them to cancel each other out and reduce chatter during roughing operations.
Solution Approach 2:
The core is designed with locally varying properties - the distance from the axis of rotation to the flutes changes at different axial portions of the cutting section. This creates zones of different stiffness along the core length, which helps to dampen vibrations locally and prevent the propagation of chatter waves throughout the tool.
2Strength
If the core diameter is tapered towards the tip to resist bending moments, then resistance to bending moments improves, but chatter and vibrations still occur during roughing
Solution Approach 1:
Instead of simple tapering, the core uses an irregular cross-sectional design where the distance from the axis to flutes varies in a non-uniform pattern. This creates complex stiffness variations that not only provide bending resistance but also actively disrupt vibration patterns through phase shifting and cancellation of chatter waves.
Solution Approach 2:
The core design introduces dynamic characteristics by creating varying stiffness zones along its length. This makes the vibration response of the tool more complex and less predictable, preventing the establishment of regular chatter patterns while maintaining the necessary structural strength for roughing operations.
3Object-affected harmful factors
If irregular core cross-sections are used to reduce chatter, then vibration cancellation improves, but manufacturing complexity increases
Solution Approach 1:
The invention changes the geometric parameters of the core - specifically the distance from the axis of rotation to the flutes - in a controlled manner along the axial direction. By systematically varying these parameters rather than using complex irregular shapes, the design achieves chatter reduction through stiffness modulation while keeping the manufacturing process relatively straightforward.
Data Source
Figure 1~3b
Figure 4~7
AI summary
The application concerns an end mill having a shank section (2) and a cutting section (4) connected thereto. The cutting section comprises a core (5) supporting at least two spaced apart teeth (6-9) which have a cutting edge (10-13) extending in the axial direction with respect to the axis of rotation (3) of the end mill. Each cutting edge has a flute (15-18) associated therewith and each flute has for each cross-section of the end mill perpendicular to the axis of rotation thereof a bottom point on said core at a shortest distance to the axis of rotation. At least two flutes have a said shortest distance varying differently with the distance to a cutting end (14) of the end mill.