Hemming Method for Panel Assembly Bonding Strength
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Solution Overview
Problem
Existing hemming working methods fail to achieve sufficient bonding strength and are prone to sputtering during projection welding due to inadequate pressing of the flange portion on the projected portion, leading to a reduced contact area and compromised appearance of the panel assembly.
Innovation Solution
A hemming working method that includes a positioning step, a preparatory bending step, a regular bending step, and a finish bending step, where the flange portion is bent to be proximate to the outer side of the projected portion, expanding the contact area and reducing the radius of curvature, thereby enhancing bonding strength and preventing sputtering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the roller is rolled in roller hemming working to prevent the projected portion from being crushed by reducing press force, then the projected portion is protected from crushing, but the bonding strength is insufficient and the edge of bending is considerably bulged
Solution Approach 1:
The hemming working process is divided into two distinct stages: a first bending step that performs general bending while protecting the projected portion, and a second bending step that applies concentrated press force to the outer side of the projected portion. This segmentation allows each stage to optimize for its specific function without compromising the other.
Solution Approach 2:
The first bending step performs preliminary bending and positioning of the flange portion before the second bending step. This preliminary action prepares the workpiece by reducing the radius of curvature and positioning the flange, so that the subsequent concentrated pressing in the second step can achieve both strong bonding and good appearance without causing bulging.
2Strength
If the press force to the projected portion is reduced in roller hemming working, then the projected portion is not crushed, but the contact area between flange portion and projected portion is narrowed
Solution Approach 1:
The hemming process is segmented into two steps with different pressing strategies. The first bending step uses distributed press force to avoid crushing, while the second bending step uses concentrated press force on the outer side of the projected portion to maximize contact area and bonding strength.
Solution Approach 2:
The second bending step applies press force locally concentrated on the outer side of the projected portion rather than distributing it uniformly. This local concentration of quality creates optimal contact conditions at the critical bonding region, widening the contact area and promoting strong bonding.
3Productivity
If the contact region is narrowed in projection welding, then the welding range is reduced, but sputtering is easy to be brought about
Solution Approach 1:
The first and second bending steps perform preliminary shaping of the flange portion before projection welding. By reducing the radius of curvature and positioning the flange in advance, the workpiece is prepared in an optimal state for welding, ensuring wide contact area and preventing sputtering during the welding process.
Solution Approach 2:
The bending process changes the geometric parameters of the flange portion, specifically reducing the radius of curvature and adjusting the position. These parameter changes create optimal conditions for projection welding by ensuring adequate contact area between the flange and projected portion.
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
The method promotes bonding strength, reduces sputtering, and improves the appearance of the panel assembly by widening the contact area between the flange and projected portions, while allowing for efficient processing and cost-effective production using a single hemming roller.
Implementation Method 1
Projection welding is a kind of spot welding providing a plurality of projected portions at the inner panel, and a current is made to flow concentratedly to a position of the projected portion to thereby heat and press to bond.
Implementation Method 2
roller hemming working for bringing the flange portion into close contact with the inner panel
Implementation Method 3
press hemming working for bringing the flange portion of the outer panel into close contact with the inner panel by using press forming
Data Source
AI summary
A hemming working is performed by a positioning step of positioning a first panel formed with a projected portion for welding on a second panel formed with a flange portion; a first bending step of bending the flange portion; and a second bending step of pressing the flange portion on an outer side of the projected portion.