Rotary Cutting Tool with Variable Helix Pitch and Rake Angles
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Solution Overview
Problem
Conventional end mills experience excessive chatter during cutting operations, leading to poor surface finish, increased costs, and reduced tool life due to harmonics, which existing variable helix and pitch end mills have not adequately addressed without compromising stability.
Innovation Solution
A rotary cutting tool with diametrically-opposed, symmetrical, helical flutes having variable pitch and radial rake angles, where at least one peripheral cutting edge has a different radial rake angle than others, and all peripheral cutting edges have a positive radial rake angle, improving stability and reducing chatter.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional end mills with equal pitch helical flutes are used, then manufacturing is simple and stable, but excessive chatter occurs leading to poor surface finish
Solution Approach 1:
The patent applies asymmetry by varying the pitch between adjacent helical flutes, creating unequal spacing between cutting edges. This asymmetric pitch distribution prevents harmonics and regenerative vibration by ensuring cutting edges engage the workpiece at different intervals, thereby eliminating chatter and improving surface finish quality.
Solution Approach 2:
The patent implements local quality by assigning different pitch values to different pairs of helical flutes. Specifically, first and second pairs of diametrically opposed flutes have a first pitch, while third and fourth pairs have a second pitch different from the first. This localized variation in pitch along the axial length optimizes cutting performance at different positions.
2Manufacturing precision
If variable helix end mills are used to reduce chatter, then surface finish improves, but tool stability is compromised
Solution Approach 1:
The patent segments the helical flutes into distinct groups with different pitch characteristics. By dividing the four pairs of flutes into two sets (first and second pairs with first pitch, third and fourth pairs with second pitch), the tool achieves variable pitch benefits while maintaining structural stability through systematic segmentation rather than random variation.
Solution Approach 2:
The patent changes the pitch parameter between different pairs of helical flutes to optimize performance. By varying the pitch while maintaining consistent helix angles and radial rake angles, the tool achieves chatter reduction through parameter modification without compromising overall tool stability or balance.
3Reliability
If all peripheral cutting edges have the same radial rake angle, then manufacturing is consistent, but chatter vibration increases
Solution Approach 1:
The patent applies asymmetry by assigning different radial rake angles to different peripheral cutting edges. Specifically, cutting edges on first and second pairs of flutes have a first radial rake angle, while cutting edges on third and fourth pairs have a second radial rake angle. This asymmetric configuration disrupts harmonic patterns and reduces chatter-induced vibration, extending tool life.
4Productivity
If aggressive cutting feed rates are used to increase productivity, then material removal rate improves, but regenerative vibration and chatter increase
Solution Approach 1:
The patent implements periodic action through the structured variation of pitch and radial rake angles across different pairs of helical flutes. This periodic variation in cutting edge geometry creates non-uniform engagement intervals that disrupt the feedback loop of regenerative vibration, allowing aggressive feed rates to be used without triggering chatter.
Data Source
AI summary
A rotary cutting tool or end mill is provided, the tool comprising a plurality of pairs of diametrically-opposed, symmetrical, helical flutes formed in a cutting portion of the tool body, wherein the pitch between at least one pair of adjacent helical flutes is less than or greater than the pitch of at least one other pair of adjacent helical flutes in at least one radial plane along the axial length of the flutes, a plurality of peripheral cutting edges, wherein at least one of the peripheral cutting edges has a radial rake angle different from radial rake angle of a peripheral cutting edge of a different helical flute.