Variable-Rake Finish End Mill for Deep Shouldering Stability
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Solution Overview
Problem
Conventional end mills face challenges in achieving effective deep shouldering milling due to increased vibration and reduced tool life when milling high hardness materials, as they tend to bend and experience chip evacuation issues with longer cutting lengths.
Innovation Solution
The end mill design incorporates varying radial rake angles and helix angles, along with increased flute depth and relief surface width variations, to reduce vibration and enhance chip evacuation, allowing for effective cutting lengths greater than 2.5D while maintaining a good surface finish.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If the effective cutting length of the end mill is increased to enable deep shouldering milling, then the milling depth capability is improved, but vibration increases and tool life decreases
Solution Approach 1:
The patent applies local quality by varying the radial rake angle and helix angle at different axial locations along the effective cutting length. Specifically, the radial rake angle changes from a first value near the cutting end face to a second value at greater axial distances, and the helix angle varies to optimize chip evacuation. This localized geometric variation allows each section of the end mill to be optimized for its specific function, reducing overall vibration while maintaining deep cutting capability.
Solution Approach 2:
The patent implements parameter changes by modifying the geometric parameters of the teeth and flutes along the axial length. The radial rake angle is changed from approximately 10-15 degrees near the cutting end face to 0-5 degrees at greater axial distances. The helix angle is also varied, with the flute depth increasing from 0.1D to 0.3D of the end mill diameter. These parameter changes reduce vibration and improve tool life while enabling deep shouldering milling.
2Length of moving object
If the effective cutting length is increased to achieve deeper milling, then the milling depth capability is improved, but surface finish quality deteriorates
Solution Approach 1:
The patent applies local quality by providing different radial rake angles at different axial locations. The teeth near the cutting end face have a larger radial rake angle (10-15 degrees) for efficient cutting, while teeth at greater axial distances have a smaller radial rake angle (0-5 degrees) for reduced vibration and improved surface finish. This localized geometric optimization ensures high surface finish quality even at deep milling depths.
Solution Approach 2:
The patent employs periodic action through the alternating pattern of teeth and flutes with varying geometries along the axial length. The periodic variation in radial rake angle and helix angle creates a rhythm in the cutting action that reduces vibration and improves surface finish quality during deep shouldering milling operations.
3Productivity
If the flute depth is increased to improve chip evacuation, then chip removal capability is improved, but vibration increases due to chip abutment
Solution Approach 1:
The patent applies local quality by varying the flute depth and helix angle at different axial locations. The flutes near the cutting end face have a depth of 0.1D to accommodate initial chip formation, while flutes at greater axial distances have increased depth of 0.3D for enhanced chip evacuation. The helix angle is also varied to optimize chip flow and reduce abutment against the workpiece, improving both chip removal capability and vibration control.
4Force
If the radial rake angle is decreased to reduce radial cutting force, then cutting force is reduced, but tooth strength decreases
Solution Approach 1:
The patent applies local quality by providing different radial rake angles at different axial locations along the effective cutting length. Teeth near the cutting end face have a larger radial rake angle (10-15 degrees) for efficient cutting with lower radial forces, while teeth at greater axial distances have a smaller radial rake angle (0-5 degrees) for increased tooth strength. This localized geometric variation allows each section to be optimized for its specific mechanical demands.
Solution Approach 2:
The patent implements parameter changes by systematically varying the radial rake angle from 10-15 degrees near the cutting end face to 0-5 degrees at greater axial distances. This parameter change reduces radial cutting forces in the critical cutting zone while maintaining tooth strength in the support zones, resolving the contradiction between force reduction and strength maintenance.
Data Source
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AI summary
A finish end mill configured for rotating about a central rotation axis (AR) with teeth having an average radial rake angle value, with one or more teeth having a smallest radial rake angle value and one or more teeth having a largest radial rake angle value wherein at an axial location in a front half of the effective cutting length at least three teeth having different radial rake angles, at least some of the different radial rake angle values being different from all other non-identical values by 2° or more, and the flutes having a helix variance of 6° or less.