Self-Drilling Screw Tip Geometry for Chip Removal and Low Resistance
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Solution Overview
Problem
Conventional self-drilling screws face issues with cutting performance and screwing resistance due to the included angle of the tip, leading to improper positioning, increased friction, and chip accumulation, which can cause the workpiece to crack during screwing.
Innovation Solution
A self-drilling screw design featuring a leading section with a drilling portion having a first included angle between 30 degrees and 60 degrees, two blade portions, and concave surfaces, along with discharge grooves and cutting edges, allowing for accurate positioning, sharp cutting, and efficient chip removal to reduce screwing resistance and prevent workpiece cracking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If the included angle of the tip is made smaller to increase sharpness, then the tip becomes sharper and easier to puncture the workpiece surface, but the cutting edge area is reduced which decreases cutting effect
Solution Approach 1:
The drilling portion is divided into multiple functional sections: a tip section with a smaller included angle for puncturing, and a cutting section with blade portions for cutting. This segmentation allows each section to have optimized geometry for its specific function, resolving the contradiction between tip sharpness and cutting effectiveness.
Solution Approach 2:
Different sections of the drilling portion have different included angles tailored to their specific functions. The tip section has a smaller included angle for sharpness and puncturing, while the cutting section has optimized blade portions for effective cutting. This local differentiation resolves the contradiction by applying different geometric qualities to different locations.
2Productivity
If the included angle of the tip is increased above 120 degrees to improve cutting edge area, then the cutting effect is improved, but the tip sharpness is reduced which is unfavorable for positioning
Solution Approach 1:
The drilling portion is segmented into a tip section for positioning and a cutting section for material removal. The tip section maintains a smaller included angle for sharpness and accurate positioning, while the cutting section provides sufficient cutting edge area for effective cutting, thus resolving the contradiction between positioning accuracy and cutting effect.
3Force
If the tip is not sharp enough, then the friction between the tip and the workpiece increases, but the tip cannot stand upright on the surface efficiently causing deviation from the screwing path
Solution Approach 1:
The drilling portion is segmented with a distinct tip section that has optimized sharpness for reliable positioning and upright standing on the workpiece surface. This ensures the screw follows the correct screwing path while the cutting sections handle material removal, resolving the contradiction between friction force and path stability.
4Productivity
If chips are generated between the bevel surfaces during cutting, then the cutting operation proceeds, but the entrance to the flutes becomes blocked by chip accumulation causing high screwing resistance
Solution Approach 1:
The invention extracts the chip removal function from the flute structure by adding dedicated discharge grooves on the cylindrical surface of the drill body. These grooves provide alternative chip egress paths that prevent blockage at the flute entrance, resolving the contradiction between cutting operation and screwing resistance.
Solution Approach 2:
Instead of relying solely on the internal flute structure for chip removal, the invention adds discharge grooves on the external cylindrical surface, creating a third-dimensional chip egress path. This dimensional addition allows chips to be removed from multiple directions, preventing blockage and reducing screwing resistance.
5Productivity
If excessive chips accumulate during cutting, then the cutting operation continues, but undue pressure is added to the workpiece causing it to crack
Solution Approach 1:
The invention extracts chips from the cutting zone through dedicated discharge grooves before they can accumulate and create excessive pressure on the workpiece. This continuous chip removal prevents workpiece cracking while maintaining productive cutting operation.
Solution Approach 2:
The invention converts the potentially harmful chip accumulation into a beneficial continuous removal process. By providing discharge grooves that actively evacuate chips during cutting, the system transforms what would be a harmful accumulation into a controlled removal process that protects workpiece integrity.
Data Source
Figure 1
Figure 2~2A
Figure 3
AI summary
A self-drilling screw (3) includes a leading section (33) having a drill body (331) and opposite discharge grooves (332) formed on the drill body (331) . The drill body (331) and the discharge grooves (332) meet at cutting edges (333) . On the drill body (331) are formed two blade portions (3331) connected to the cutting edges (333) and tapering at respective second tips (3331a). The blade portion (3331) has a second included angle (a2) of not more than 50 degrees. Between the blade portions (3331) is formed a drilling portion (3311) terminating at a first tip (3311a) and having a first included angle (a1) of not more than 60 degrees. Two opposite concave surfaces (334) each extend from the drilling portion (3311) to each blade portion (3331). The first tip (3311a) and the second tips (3331a) are situated at different places. Accordingly, the end of the leading section (33) presents a shape of a curved bow riser to cut quickly and help quick removal of chips, thereby decreasing resistance and preventing the cracking problem.