Ball End Mill Tip Geometry for Cutting and Polishing
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Solution Overview
Problem
Ball end mills with hemispherical tip parts suffer from shallow cutting depth and high cutting resistance due to the absence of a ball-nosed end cutting edge, leading to tool damage and poor workpiece surface quality.
Innovation Solution
A ball end mill design featuring a flank connected to the tip surface oriented rearward with respect to the tool-rotation direction, including a center-nearing ball-nosed end cutting edge positioned closer to the rotation center and another edge positioned further away, which reduces cutting resistance and enables both cutting and polishing with a low edge-perpendicular width of 0.5-25% of the tool's outer diameter.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a hemispherical tip part is provided for polishing, then surface finish quality is improved, but cutting depth becomes extremely shallow and cutting cannot be substantially performed
Solution Approach 1:
The tool tip is segmented into distinct functional zones: a hemispherical tip surface for polishing and ball-nosed end cutting edges for cutting. This segmentation allows each zone to perform its specific function effectively, with the cutting edges providing substantial cutting depth while the tip surface provides polishing quality.
Solution Approach 2:
Different parts of the tool tip are given different local qualities: the tip surface is made hemispherical for polishing contact, while the crossing ridgeline portion is equipped with ball-nosed end cutting edges for cutting. This local differentiation enables the tool to perform both cutting and polishing functions simultaneously with optimal performance in each zone.
2Manufacturing precision
If the tip part does not have a chisel edge, then polishing surface quality is improved, but cutting resistance becomes high resulting in tool damage
Solution Approach 1:
The tool structure is segmented to separate the polishing function (tip surface) from the cutting function (ball-nosed end cutting edges). The cutting edges are positioned on the crossing ridgeline and perform the cutting action, while the hemispherical tip surface performs polishing, preventing excessive cutting resistance at the tip.
Solution Approach 2:
The ball-nosed end cutting edges act as an intermediary element between the hemispherical tip surface and the workpiece. They perform the initial cutting action that reduces material removal burden, thereby lowering cutting resistance at the tip surface while maintaining polishing quality.
3Productivity
If ball-nosed end cutting edges are positioned away from the center, then cutting performance is improved, but rigidity near the center decreases
Solution Approach 1:
The ball-nosed end cutting edges are positioned at specific locations on the crossing ridgeline that optimize both cutting performance and structural rigidity. The cutting edges are located away from the center to provide effective cutting action, while the overall tool geometry and support structure maintain rigidity near the center.
Data Source
Figure 1
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Figure 3~3(c)
AI summary
Provided is a ball end mill which is capable of performing both cutting and polishing well and in which cutting resistance at a tip part is low. A ball end mill formed with a plurality of chip discharge grooves 2 on an outer periphery of a tool body 1 from a tool tip toward a proximal end side, and provided with ball-nosed end cutting edges 5, 6 on a crossing ridgeline part between a rake surface 3 of the chip discharge grooves 2 and a spherical tip surface 4 of the tool body 1, said ball end mill having a tool rotation center O on the spherical tip surface 4 and a center-nearing ball-nosed end cutting edge 5 set so that a distance X from the tool rotation center O to the point closest to the tool rotation center O on one ball-nosed end cutting edge 5 in a view of the tool tip is shorter than a same distance Y to the other ball-nosed end cutting edge 6.