Variable-Helix Milling Tool for Surface Error Reduction
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Solution Overview
Problem
Milling tools struggle to produce completely smooth and straight surfaces due to force variations during machining, leading to form errors in machined surfaces, despite optimal cutting conditions.
Innovation Solution
A milling tool design featuring a cutting portion with teeth following a curved helical path, where the helix angle transitions from a first angle to a second angle, with the second angle being greater by at least 2° and up to 15°, located within a specific distance along the cutting portion, to balance cutting forces during entry and exit phases, reducing surface errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a conventional milling tool with constant helix angle is used, then the tool structure is simple and easy to manufacture, but the cutting force varies significantly during machining, causing form errors and poor surface quality
Solution Approach 1:
The patent applies local quality by varying the helix angle along the axial length of the cutting portion. Different axial positions have different helix angles (first helix angle in the first axial region, second helix angle in the second axial region), allowing each region to be optimized for its specific function: the first region controls entry force while the second region controls exit force, thereby reducing overall force variation and improving surface quality
Solution Approach 2:
The patent changes the geometric parameter of the helix angle along the axial direction. By transitioning from a constant helix angle to a variable helix angle profile, the tool optimizes cutting forces at different axial positions. The helix angle varies between 30°-60° in the first region and 40°-70° in the second region, creating a controlled force variation that reduces form errors and improves machined surface quality
2Manufacturing precision
If the helix angle is increased to reduce form error, then the cutting force variation decreases, but the tool deflection and vibrations increase
Solution Approach 1:
The patent uses local quality by assigning different helix angles to different axial regions. The first helix angle (30°-60°) in the first axial region provides moderate cutting action for entry, while the second helix angle (40°-70°) in the second axial region provides stronger cutting action for exit. This localized optimization reduces form error without causing excessive overall deflection, as no single region has an excessively high helix angle that would cause instability
3Productivity
If optimal cutting conditions are applied, then productivity is maximized, but form errors still occur due to periodic force variations
Solution Approach 1:
The patent changes the helix angle parameter along the axial direction to decouple productivity optimization from surface quality optimization. This allows the tool to operate at optimal cutting conditions for high material removal rate while the variable helix angle profile simultaneously compensates for periodic force variations, reducing form errors and improving surface flatness without sacrificing productivity
Data Source
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AI summary
The invention relates to a milling tool (1) having a front end (2), a rear end (3), and a longitudinal axis (C) extending therebetween, wherein the milling tool comprises a shank portion (4) and a cutting portion (5). The cutting portion extends along the longitudinal axis from the front end towards the shank portion, and comprises a plurality of teeth (6) separated from each other by a corresponding number of flutes (7), wherein the teeth (6) extend axially along the cutting portion (5) following a curved helical path around the longitudinal axis. Each tooth (6) extends at a first helix angle (α) from the front end (2) to a helix transition (8), and at a second helix angle (β) from the helix transition towards the shank portion. The second helix angle (β) is greater than the first helix angle (α) by at least 2° and at most 15°. The first helix angle (α) fulfills 33° ≤ α ≤ 50°, whereas the second helix angle (β) fulfills 40° ≤ β ≤ 55°, and the helix transition (8) is axially located within a distance, from the front end (2), of 0.2 to 0.7 of the longitudinal length of the cutting portion (5).