Drilling Tool With Dual Helix Angles For Chip Evacuation
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Solution Overview
Problem
Conventional drilling tools for small-diameter deep holes in PCBs face challenges in achieving both rigidity and effective chip evacuation, often resulting in chip clogging and poor hole wall roughness due to conflicting factors like web thickness taper and helix angle, which can lead to drill breakage and inaccurate hole positioning.
Innovation Solution
The drilling tool features a dual helical region design with varying helix angles and web tapers, where the helix angle is reduced near the drill point to prevent chip coiling and increased near the base for efficient evacuation, along with strategically placed taper regions to maintain rigidity and flute capacity, ensuring better hole position accuracy and wall roughness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the web thickness is increased to improve drill rigidity and hole position accuracy, then the drill becomes more rigid, but the flute capacity decreases causing chip clogging and poor hole wall roughness
Solution Approach 1:
The chip-evacuating flute is divided into a first helical region with a first helix angle and a second helical region with a second helix angle greater than the first. This segmentation allows different sections to perform different functions: the first region maintains rigidity while the second region enhances chip evacuation, resolving the contradiction between drill rigidity and flute capacity.
2Productivity
If the helix angle is increased to improve chip evacuation through pump action, then chip evacuation improves, but the cutting edge becomes sharply pointed causing excessive chipping and decreased torsional rigidity
Solution Approach 1:
Different helix angles are applied to different regions of the flute. The first helical region has a smaller helix angle to maintain torsional rigidity and prevent excessive chipping, while the second helical region has a larger helix angle to enhance chip evacuation through pump action. This local differentiation resolves the contradiction between chip evacuation efficiency and drill reliability.
3Volume of stationary object
If the web taper is increased to maintain flute capacity at the base end, then the flute capacity is preserved, but chips produced at the point end are not smoothly evacuated causing clogging
Solution Approach 1:
The flute is segmented into two helical regions with different helix angles. The first region with smaller helix angle ensures smooth chip evacuation from the point end, while the second region with larger helix angle provides sufficient flute capacity at the base end. This segmentation resolves the contradiction between flute capacity and chip evacuation smoothness.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration prevents chip coiling, enhances drill rigidity, and improves hole wall roughness and position accuracy, effectively addressing the contradictions in conventional tools for small-diameter drills of 0.4 mm or less.
Implementation Method 1
A method often adopted to improve on both of these contradictory factors is to generally increase the helix angle so as to make use of the pump action involved in the rotation of the drill and forcibly push out the chips
Data Source
Figure 1~2
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Figure 5~6
AI summary
To provide a far more practical drilling tool that is capable of drilling holes having good hole position accuracy and hole wall roughness using a small-diameter drill of 0.4 mm or less. A drilling tool in which helical chip-evacuating flutes (2) are formed in the outer circumference of a tool main body (1), wherein the chip-evacuating flutes (2) have a first helical region (3) with a first helix angle α1 and a second helical region (4) with a second helix angle α2 greater than the first helix angle α1, being provided on the tool base side of the first helical region (3); the tool main body 1 has a first taper region (6) with a first web taper and a second taper region (7) with a second web taper smaller than the first web taper, being provided on the tool base side of the first taper region (6); and a portion (8) where the first taper region (6) and the second taper region (7) are connected in a row is located more toward the tool base side than the portion (5) where the first helical region (3) and the second helical region (4) are connected in a row.