Buttressed PCD Drill Bit Notches for Chip Breaking Precision
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Solution Overview
Problem
Polycrystalline diamond drills face challenges with chip control during drilling of composite and metal airframes, particularly with Titanium, as the stiff metal swarf oversizes holes in the composite layer due to the brittle nature of PCD materials, making it difficult to maintain precision fit and tolerance.
Innovation Solution
The introduction of asymmetrical buttressed notches on the drill cutting edges, which distribute cutting forces through a buttressed region, enhancing the strength of the notches and allowing for effective chip breaking and control, thereby preventing oversized holes by splitting chips into smaller pieces that can easily exit through the drill flutes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If asymmetrical notches are added to the cutting edge to break chips into smaller pieces, then chip control and hole precision are improved, but the brittle PCD material chips and fails due to cutting forces concentrated on the notch edges
Solution Approach 1:
The notch is segmented into multiple regions: a cutting edge region for chip breaking and a buttressed region for force distribution. This segmentation allows each region to perform its specific function - the cutting edge region breaks chips into smaller pieces for better control, while the buttressed region with increased material thickness distributes cutting forces to prevent PCD material failure
Solution Approach 2:
The notch design implements local quality by providing different structural properties in different regions. The cutting edge region has sharp geometry for effective chip breaking, while the buttressed region has increased material thickness and modified geometry to distribute stresses. This localized variation in structural quality allows the notch to simultaneously achieve chip breaking functionality and resistance to material failure
2Manufacturing precision
If PCD drills are used to maintain tight tolerances in dissimilar materials, then manufacturing precision is improved, but chip control deteriorates due to the brittle nature of PCD material
Solution Approach 1:
The cutting edge is segmented with multiple notches that divide the chip into smaller segments. This segmentation of the chip structure allows stiff metal swarf to break into manageable pieces that can exit through the drill flutes without oversizing the hole in the composite layer, thereby maintaining the precision fit while using brittle PCD material
Solution Approach 2:
The notches act as intermediary structures between the cutting edge and the chip flow path. These notches provide controlled locations for chip breaking and redirection, serving as mediators that manage the interaction between the brittle PCD material and the chip flow, enabling effective chip control without compromising the integrity of the PCD drill
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 solution enables consistent drilling within a tolerance of plus or minus twenty microns, improving the mechanical properties of the combined materials by effectively managing chip exit and maintaining precision fit between the hole and fastener.
Implementation Method 1
This region may transition between the rake face and the cutting edge of each notch to distribute the cutting forces over the buttressed region, thereby strengthening the notch and improving the strength of the resulting cutting edge
Implementation Method 2
The notches act to break the chips into smaller pieces that can more easily transit the composite layer though the drill flutes without creating an oversized condition
Data Source
AI summary
Drilling tools and/or drill bits having notches with buttressed regions and/or notches therewithin to improve notch strength. In some embodiments, the drill/drill bit may comprise a shank comprising a cutting face, the cutting face terminating in a cutting edge. A notch may be formed along the cutting edge, which may be configured to separate chips formed by the drilling tool during operation. A buttressed region may be formed within the notch and may terminate along the cutting edge. The buttressed region may expand a size of the notch in one or more dimensions.