Drill Clearance Surface Geometry for Lower Friction Loads
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Solution Overview
Problem
Conventional drills experience high frictional and thermal loads during drilling due to high stresses and friction, particularly at the clearance surfaces adjacent to the main cutting surfaces, which affects chip removal efficiency.
Innovation Solution
The drill design features a clearance surface with varying clearance angles, transitioning from a near-center section with a constant angle of 8-10° to an outer section with increasing angles from 10° to 40°, and a curved progression to minimize friction and thermal loads by aligning with higher circumferential velocities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the clearance surface has a constant clearance angle, then the structure is simple and easy to manufacture, but high frictional and thermal loads occur during drilling
Solution Approach 1:
The clearance surface is divided into multiple sections with different clearance angles: a first section with a first clearance angle, a second section with a second clearance angle greater than the first, and a third section with a third clearance angle greater than the second. This local differentiation allows each section to be optimized for its specific functional requirements, reducing overall frictional and thermal loads while maintaining manufacturability.
Solution Approach 2:
The clearance angle parameter is varied along the length of the clearance surface. By increasing the clearance angle from the first section to the second section and then to the third section, the design adapts to changing operational conditions, effectively reducing frictional and thermal loads in different regions of the drill.
2Object-affected harmful factors
If the clearance angle is increased to reduce friction, then frictional load decreases, but the structural complexity increases
Solution Approach 1:
The clearance surface is segmented into three distinct sections, each with a different clearance angle. This segmentation allows the complex geometry to be broken down into manageable parts that can be manufactured using standard processes, reducing overall structural complexity while achieving the friction reduction goal.
Solution Approach 2:
The transition between different clearance angle sections is achieved through curved surfaces rather than sharp edges. This curvature creates a more complex three-dimensional geometry that smoothly transitions between angles, reducing stress concentrations and simplifying the manufacturing process compared to abrupt angular changes.
Data Source
AI summary
The drill extends along an axis of rotation and has a radius (r) as well as a plurality of main cutting surfaces, which each extend in the direction of the axis of rotation from a cutting corner situated on the radius (r), wherein a respective clearance surface adjoins the main cutting surfaces in a circumferential direction (U), forms a clearance angle (α, β1, β2) with respect to a horizontal plane (H) oriented perpendicular to an axis of rotation, and transitions along its further progression into a flute. When viewed in a vertical section parallel to the axis of rotation, an outer section of the clearance surface in the region of the cutting corner has a curved progression, and a near-center section in the region of the axis of rotation has a linear progression. A low frictional load on the front face of the drill is achieved as a result.