Coated Micro Ball End Mill Geometry for Stable Chip Evacuation
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Solution Overview
Problem
Ball end mills with small diameters face issues with hard coating film peeling and chipping due to high cutting loads, especially in the chisel portion, leading to unstable cutting performance over time.
Innovation Solution
The design includes chip discharge grooves that face each other without overlapping, with specific ratios for the chisel portion width and length, and a negative rake angle for the bottom blade, along with a hard coating film to enhance adhesion and durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional solid carbide ball end mills with 2-flute design are used, then rigidity and strength are improved, but chip evacuation capability deteriorates
Solution Approach 1:
The cutting edges are segmented into multiple flutes (3-5 flutes) along the mill length, with each flute acting as an independent chip evacuation channel. This segmentation allows chips to be efficiently removed through multiple pathways while maintaining structural integrity through optimized flute geometry and spacing.
Solution Approach 2:
Different sections of the mill body have different flute configurations optimized for local requirements. The land area between flutes is optimized for chip evacuation in specific zones, while maintaining varying flute angles and geometries along the length to balance rigidity in some areas with chip evacuation in others.
2Manufacturing precision
If conventional ball end mills with full radius ball section are used, then surface finish quality is improved, but material removal rate deteriorates
Solution Approach 1:
The mill transitions from a static full-radius ball section to a dynamic configuration where the ball radius varies along the length. The ball radius is reduced in certain zones to increase material removal rate, while maintaining adequate ball radius in finish-cutting zones to preserve surface quality. This dynamic variation allows optimization for different machining stages.
Solution Approach 2:
The ball radius parameter is changed along the length of the mill rather than maintaining a constant full radius. This parameter variation enables the mill to achieve both high material removal rates in roughing zones and good surface finish in finishing zones, eliminating the trade-off between productivity and precision.
3Device complexity
If conventional 2-flute solid carbide mills are used, then structural simplicity is improved, but chip packing and recutting deteriorates
Solution Approach 1:
The mill is segmented into multiple flutes (3-5 flutes) that create separate chip evacuation pathways. This segmentation prevents chip packing by distributing chips across multiple channels, reducing the likelihood of chip recutting while maintaining a relatively simple overall mill structure through standardized flute geometry.
Data Source
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AI summary
Provided is an end mill which includes an end mill main body having a bottom blade having a convex hemispherical shape, and a hard coating film coated on at least a surface of a distal end portion of the end mill main body. A diameter D (mm) of the bottom blade is 2 mm or less. A ratio W/D of a width W (mm) of a chisel portion to the diameter D (mm) is within a range of 0.020 to 0.060. A ratio L/D of a facing length L (mm) of chip discharge grooves to the diameter D (mm) is within a range of 0.014 to 0.090. A rake angle of the bottom blade in a range in which a chisel edge is formed in the chisel portion is within a range of-15° to -30°.