Drill Holder Axial Rake Angle Optimization for Chip Discharge
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Solution Overview
Problem
Drills with inner and outer cutting edges face challenges in smoothly discharging chips, especially when machining ductile materials like stainless steels or low carbon steels, as the chips generated by the outer cutting edge tend to extend and cling to the holder due to high rotational speed, leading to poor chip discharge performance.
Innovation Solution
A drill design with a holder featuring a first insert pocket with a larger axial rake than a second insert pocket, where the first cutting edge and second cutting edge are attached to protrude from the tip end, allowing for effective chip discharge through strategically formed breaker grooves and apex portions, ensuring smooth discharge of chips generated by either cutting edge.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the outer cutting edge operates at high rotational speed to improve productivity, then the chip discharge performance deteriorates because chips extend and cling to the holder
Solution Approach 1:
The patent applies different axial rake angles to different insert pockets: the first insert pocket (inner cutting edge) has a larger axial rake angle while the second insert pocket (outer cutting edge) has a smaller axial rake angle. This local differentiation optimizes chip curling characteristics for each cutting edge's specific operating conditions, particularly addressing the chip discharge problem at high rotational speeds for the outer cutting edge.
2Ease of manufacture
If the inner cutting edge and outer cutting edge use the same insert shape to simplify manufacturing, then the chip discharge performance deteriorates because chips from different cutting edges have different shapes and cannot be smoothly discharged
Solution Approach 1:
The patent uses identical insert shapes for both inner and outer cutting edges, but differentiates the axial rake angles of their respective insert pockets. This approach maintains manufacturing simplicity while achieving locally optimized chip discharge performance for each cutting edge's specific rotational speed and chip formation characteristics.
Solution Approach 2:
The patent changes the axial rake angle parameter for different insert pockets while keeping the insert shape standardized. The first insert pocket has a larger axial rake angle and the second has a smaller axial rake angle, allowing the same insert design to produce appropriately curled chips for both inner and outer cutting edges operating at different speeds.
Data Source
AI summary
A holder of the present invention has a first insert pocket and a second insert pocket at the tip end thereof. The first insert pocket is located closer to the central axis thereof than the second insert pocket. The axial rake of the first insert pocket is larger than the axial rake of the second insert pocket.