Resistance Welding Sandwich Plates with Insulating Plastic Layer
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Solution Overview
Problem
The challenge lies in efficiently resistance welding sandwich sheets with metallic components, as the thermoplastic layer acts as an electrical insulator, complicating the formation of a perfect welded connection and often requiring alternative joining methods like gluing or mechanical joining, which are not as efficient as desired.
Innovation Solution
A method using a second circuit to preheat the welding area via the metallic component, allowing for adjustable current strength and resistance measurement to optimize the welding process, enabling the use of conventional electrodes and reducing cycle times by controlling currents based on resistance measurements, and employing a welding gun or tongs for automated resistance welding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If the thermoplastic layer is present between metal cover layers, then the sandwich sheet provides lightweight construction and high strength, but the electrically insulating plastic layer prevents formation of perfect welded connection
Solution Approach 1:
The thermoplastic layer is heated and melted before the actual resistance welding process begins. This preliminary heating action removes the electrical insulation barrier, allowing subsequent electrical contact and welding between metal cover layers while preserving the lightweight sandwich structure
Solution Approach 2:
The electrical resistance of the thermoplastic layer is changed by heating it to its melting point. This parameter change transforms the layer from an electrically insulating state to a conductive molten state, enabling welded connection while maintaining the original lightweight construction
2Temperature
If temperature-controlled electrodes or pressing elements with heating elements are used, then the welding area can be heated and plastic layer displaced, but the structure of welding electrodes becomes relatively complicated
Solution Approach 1:
The thermoplastic layer itself serves as the heating element through resistive heating. When current passes through the molten thermoplastic layer, its electrical resistance generates heat that continues to melt and displace the material, eliminating the need for external heating elements in the electrodes
Solution Approach 2:
The mechanical heating system (heating elements in electrodes) is replaced by an electrical heating system where the thermoplastic layer's own electrical resistance generates the required heat, simplifying electrode design while maintaining effective heating
3Device complexity
If conventional welding electrodes are used without preheating, then the device structure remains simple, but the cycle time for welding increases
Solution Approach 1:
The heating and welding processes are combined into a continuous operation. The thermoplastic layer is heated and melted simultaneously with the welding process through continuous current application, eliminating separate heating and welding stages and reducing overall cycle time while keeping electrodes simple
4Productivity
If resistance measurement is carried out during welding, then the welding process can be optimized and cycle time reduced, but the measurement and control system becomes more complex
Solution Approach 1:
The welding electrodes serve dual functions: they apply electrical current for both heating/melting the thermoplastic layer and for the actual resistance welding. This multi-functionality eliminates the need for separate measurement and control equipment, reducing system complexity while enabling process optimization through resistance monitoring
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 approach simplifies the resistance welding process, reduces cycle times, and allows for a more economical and controlled welding of sandwich panels to metallic components, ensuring a robust and efficient joint formation.
Implementation Method 1
heating of the welding area can be achieved in a simple manner, which can also be variably adjusted via the current strength of the preheating current
Implementation Method 2
the cover layers of the sandwich sheet are pressed together by the application of force to the first and second welding electrodes
Implementation Method 3
a resistance measurement is carried out during the welding according to a further embodiment of the method, with the electrical resistance being measured between the two metal cover layers of the sandwich sheet
Implementation Method 4
the metallic cover layers are resistance-welded to the component 3 by the welding current
Data Source
Figure 1
Figure 2a~2c
Figure 3
AI summary
The invention relates to a method for resistance welding of a sandwich-type plate (2) to at least one further metallic component (3), the sandwich-type plate (2) having two metallic covering layers (2b, 2c) and a thermoplastic synthetic layer (2a) arranged between the metallic covering layers (2b, 2c). According to said method, at least the region (12) of the sandwich-type plate (2) that is to be welded is heated in such a manner that the thermoplastic synthetic layer (2a) softens and is displaced out of the welding region (12) by pressing the covering layers (2b, 2c) together, the covering layers (2b, 2c) are welded to each other and to the further component (3) by a flow of electrical current with a first electrical circuit (4a) via a first and a second welding electrode (6, 7), the second welding electrode (7) being in contact with the metallic component (3). A second electrical circuit (8a) is provided, which comprises the second welding electrode (7), the metallic component (3) to be welded to the sandwich-type plate (2), and an electrical bridge (10) that leads to the component (3). The second welding electrode (7) is arranged opposite the first welding electrode (6) on the side of the component (3) facing away from the lightweight plate (2), and at least the region (12) of the sandwich-type plate (2) that is to be welded is heated in the region of the second welding electrode (7) by a flow of current in the second electrical circuit (8a).