Sealing Screw Blank Undercut Forming by Blind Hole Deepening
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Solution Overview
Problem
Existing methods for producing screw elements with undercuts between the shaft and head using cold extrusion face limitations, such as requiring deformation of the shaft end face and complex machining steps, which restrict design freedom and material efficiency.
Innovation Solution
A method involving the formation of a blind hole on the head side of the screw element blank, which is deepened to create an undercut at the transition between the shaft and head through indirect material displacement, allowing for a flat end face and improved sealing without additional machining steps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of substance
If cold extrusion is used to create the undercut at the transition between shaft and head, then material efficiency is improved and machining steps are eliminated, but the shaft end face must be deformed and design freedom is restricted
Solution Approach 1:
The blind hole is divided into two sections: a first section with a larger cross-section for tool insertion and a second section with a smaller cross-section for forming the undercut. This segmentation allows the deformation to be concentrated in a specific region, preserving design freedom for the shaft end face while maintaining material efficiency through cold extrusion.
Solution Approach 2:
The deformation is localized to the second section of the blind hole and the adjacent shaft region, creating the undercut only where needed. The shaft end face remains undeformed and can be designed freely, while the local material displacement in the second section section forms the required undercut geometry.
2Adaptability or versatility
If machining steps are used to create the undercut, then design freedom is improved, but material loss occurs and process complexity increases
Solution Approach 1:
The formation of the blind hole and the creation of the undercut are merged into a single cold extrusion process. The multi-section blind hole design allows the same extrusion tool to first create the larger first section for access, then deepen it to form the second section that displaces material to create the undercut, eliminating separate machining operations.
Solution Approach 2:
The first section of the blind hole is formed first with a larger cross-section to accommodate the forming tool. This preliminary action prepares the path and space needed for the subsequent deepening of the blind hole to create the second section, which then forms the undercut through material displacement, streamlining the overall process.
3Reliability
If the blind hole is deepened to form the undercut through indirect material displacement, then sealing effect is improved and machining steps are eliminated, but the process complexity increases
Solution Approach 1:
The cold extrusion process uses indirect material displacement from the deepening of the second blind hole section to automatically form the undercut at the shaft-head transition. The material flow and displacement during the extrusion process itself create the sealing undercut geometry, making the process self-forming and eliminating the need for separate undercutting operations.
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
Enables the production of screw elements with enhanced sealing and securing effects while maintaining material efficiency and design flexibility, overcoming previous limitations of cold extrusion by allowing the screw element to be removed from the tool without deformation of the shaft end face.
Implementation Method 1
the shaft is expanded in sections by forming an undercut at the transition between the shaft and the head, by at least indirect material displacement from at least the second section of the blind hole
Data Source
Figure 1a~1b
Figure 2a~2b
Figure 3a~3c
AI summary
The invention relates to a method for producing a sealing screw or sealing screw blank (3), comprising a method step in which a blank (3) having a cylindrical shank (5) integrally formed on a screw head (4) is created, and wherein a bind hole (7) is formed in the blank (3) from a top side (11), facing away from the shank (5), of the screw head (4) in an, in particular further, method step, said blind hole (7) extending in the direction of the shank (5) and forming at least a first portion (13), in particular having a polygonal cross section (Q1), preferably for receiving a screwdriving tool, wherein, in a subsequent method step, the blind hole (7) is deepened, forming at least a second portion (14) adjoining the first portion (13), wherein the second portion (14) forms a cross section (Q2) that is preferably at least locally constant and is in particular smaller than the first cross section (Q1), wherein, in the subsequent method step, the shank (5) is locally widened, forming an undercut (15) at the transition between the shank (5) and screw head (4), in particular by at least indirect material displacement out of at least the second portion (14) of the blind hole (7).