Variable Hold-Down Force for Direct Screw Joining
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Direct screwing methods using hole-forming and thread-forming screws can lead to undesirable gaps between components due to plastic deformation, and existing solutions like hold-down devices apply constant pressure, which may damage sensitive materials or cause surface damage.
Innovation Solution
A method where the hold-down force applied by a hold-down device varies during the screwing process, with maximum force applied only when necessary to prevent gap formation, and reduced or zero force applied during other phases to protect components, particularly using a device with an adjustable actuator and controlled force-displacement profile.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a hold-down device applies constant maximum force during the entire screwing process, then gap formation between components is prevented, but surface damage and material deformation occur on sensitive components
Solution Approach 1:
The hold-down force is made variable rather than constant. The device adjusts the clamping force dynamically during the screwing process, applying maximum force only during the critical flow-hole formation phase when gap formation risk is highest, and reducing or releasing force during other phases to prevent surface damage on sensitive components like CFRP.
Solution Approach 2:
The hold-down device applies force in periodic cycles corresponding to different stages of the screwing process. Force is applied during flow-hole formation, released during thread formation, and potentially reapplied during final tightening if needed. This periodic action pattern matches the varying risk of gap formation at different process stages.
2Productivity
If direct screwing is performed without pre-drilling, then manufacturing efficiency is improved and pre-hole alignment is eliminated, but plastic deformation causes gap formation between components
Solution Approach 1:
The hold-down device is positioned and pre-loaded before the screwing process begins. During the flow-hole formation phase, the device actively presses components together to prevent material displacement and gap formation. This preliminary and active hold-down action compensates for the lack of pre-drilling while maintaining component alignment.
3Stability of the object's composition
If hold-down force is applied throughout the entire screwing process, then component alignment is maintained, but unnecessary pressure damages sensitive materials like fiber-reinforced plastics
Solution Approach 1:
The hold-down force magnitude is dynamically adjusted based on the screwing phase. The device applies high force during flow-hole formation when alignment is critical, then reduces or releases force during thread formation and final tightening phases, preventing unnecessary stress on sensitive materials while maintaining alignment when needed.
Solution Approach 2:
The hold-down device changes the force parameter throughout the screwing process. By varying the clamping force according to process stage requirements, the device maintains component alignment during critical phases while avoiding excessive pressure that would damage sensitive materials during other phases.
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
Prevents gap formation and minimizes damage to sensitive materials by applying the necessary hold-down force only when required, effectively joining components without pre-drilling and maintaining structural integrity.
Implementation Method 1
As a result of the resulting friction, the connection point is heated locally, which enables plasticization of the component materials
Implementation Method 2
which enables plasticization of the component materials, which are then plastically deformed in the radial direction and in the axial direction
Implementation Method 3
the components being pressed against one another during the screwing-in process by means of a hold-down device
Data Source
Figure 1
AI summary
The invention relates to a method for directly screwing together at least two components (310, 320) using a self-drilling and tapping screw (200) which has a head (210) and a shank (220) formed onto the head (210) with a self-tapping thread section (221) and a punching section (222) for flow punch forming, wherein the components (310, 320) are held pressed against one another by a holding down clamp (120) while the screw is screwed in. According to the invention, the holding down force (P), with which the holding down clamp (120) presses the components (310, 320) against one another while the screw is screwed in, is varied. The invention further relates to a device (100) for performing the method.