Spot Welding Sub-Pressure Control for Plate Rigidity Mismatch
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Solution Overview
Problem
Existing spot welding techniques face challenges in achieving high welding quality when joining plates of varying rigidity, as the uneven pressure distribution leads to inconsistent current density and reduced weld strength, particularly when thick plates are involved, causing deformation and instability in the workpiece.
Innovation Solution
A spot welding apparatus with a sub-pressure applicator that allows for adjustable pressure settings between the welding electrodes and a sub-pressure unit, enabling selective application of pressure to achieve balanced current density across the joint sections, thereby ensuring high welding quality by controlling the sub-pressure positions and actuator movements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a pair of welding electrodes is used to clamp and apply pressure to stacked plates with varying rigidity, then the plates can be joined through spot welding, but the thin plate and thick plates bend upward causing gaps to form between joint sections, leading to reduced contact area at joint sections and increased current density at thick plate sides
Solution Approach 1:
The welding pressure application is segmented into two independent systems: a main pressure applying mechanism that applies overall pressure to hold the workpiece, and a sub-pressure applying mechanism that applies localized sub-pressure at specific joint sections. This segmentation allows independent control of pressure at different locations, enabling compensation for deformation and gaps at joint sections while maintaining overall workpiece stability.
Solution Approach 2:
The sub-pressure applying mechanism applies localized sub-pressure specifically at the joint sections between plates of different thicknesses. This local quality adjustment compensates for the reduced contact area caused by bending and gap formation, ensuring uniform current density distribution across all joint sections and consistent weld quality throughout the assembly.
2Ease of operation
If pressure is applied uniformly by welding electrodes to stacked plates of different thicknesses, then the welding process can be simplified, but the contact area at joint sections is reduced due to bending, causing uneven current density and variable weld strength
Solution Approach 1:
The pressure control system is divided into main pressure application (for overall workpiece holding) and sub-pressure application (for localized joint section support). This segmentation enables the system to maintain simplicity in overall operation while adding localized intelligence at critical joint sections, ensuring reliable and consistent weld strength without significantly complicating the welding process.
3Strength
If the thickness of thick plates is increased to meet structural requirements, then the structural strength is improved, but it becomes more difficult for the nugget to reach the joint section between the thin plate and first thick plate, reducing weld penetration and quality
Solution Approach 1:
The sub-pressure applying mechanism applies localized sub-pressure at the joint sections, particularly at the interface between the thin plate and first thick plate. This local pressure application ensures adequate contact area and current density at these critical locations, enabling the nugget to penetrate through increased plate thickness and achieve reliable weld penetration and quality throughout the multi-plate assembly.
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 apparatus achieves consistent and high welding quality by maintaining balanced current density across the joint sections, reducing variations in weld strength and ensuring stable contact resistance, even with plates of different rigidity, thus improving the overall welding process.
Implementation Method 1
a sub pressure applying actuator 31 configured to move the sub pressure unit 35 so as to selectively apply a sub pressure to the workpiece
Implementation Method 2
applying current between the first welding electrode and the second welding electrode
Data Source
AI summary
There is provided a spot welding apparatus. The apparatus includes fixed and movable electrodes to hold and press a workpiece therebetween, and a sub pressure force applicator having a sub pressure unit that moves and selectively stops at a plurality of positions including a sub pressure position where the sub pressure unit is adjacent to the fixed electrode and in contact with the workpiece so as to apply a sub pressure, and a sub-pressure-non-requiring position where the sub pressure unit is located away from the workpiece. Spot welding is performed by applying current between the electrodes while holding the workpiece between the fixed electrode together with the sub pressure unit located in the sub pressure position and the movable electrode. Spot welding is also performed by applying current between the electrodes while holding the sub pressure unit in the sub-pressure-non-requiring position and holding the workpiece between the electrodes.