Spot-Welding Device With Control-Pressure Unit For Stacked Plates
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Solution Overview
Problem
Spot-welding of stacked plate materials with varying thicknesses often results in uneven weld quality due to differences in current density and pressure distribution, leading to issues like expulsion, surface flash, and reduced weld strength, especially when clamping and pressing mechanisms fail to maintain uniform contact pressure across the joint sections.
Innovation Solution
A spot-welding method and device that uses a combination of welding electrodes and a control-pressure applying unit to manage pressure distribution, ensuring that the pressure from the second welding electrode is set to be smaller than that from the first welding electrode, thereby maintaining a higher current density at the joint section between the thin plate and the first thick plate, and adjusting pressure settings to balance contact resistance across the stacked plates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If high current is applied to increase nugget size, then weld strength is improved, but expulsion and surface flash occur due to excessive calorific value
Solution Approach 1:
The patent applies different pressures to different regions of the stacked plates by using a control-pressure applying unit that selectively presses the thin plate at specific locations. This creates local variations in contact pressure that compensate for the non-uniform current density distribution, ensuring that the calorific value remains within optimal ranges across all joint sections while maintaining sufficient nugget size for weld strength.
2Object-generated harmful factors
If low current is applied to prevent expulsion, then harmful factors are reduced, but nugget size becomes too small for sufficient joint strength
Solution Approach 1:
The control-pressure applying unit creates localized high-pressure zones on the thin plate where needed, which increases contact area and reduces current density in specific regions. This allows the overall current to be reduced to prevent expulsion while maintaining sufficient local calorific value for nugget formation through the pressure-induced contact resistance adjustments.
3Ease of operation
If uniform pressure is applied by welding electrodes, then ease of operation is improved, but current density becomes non-uniform due to plate bending, reducing manufacturing precision
Solution Approach 1:
The control-pressure applying unit acts as an intermediary device between the welding electrodes and the thin plate. It provides additional localized pressure control that compensates for the non-uniform pressure distribution caused by plate bending, thereby maintaining uniform current density across all joint sections without requiring complex adjustments to the welding electrode pressure mechanism.
4Stress or pressure
If pressure is increased to reduce contact area and maintain current density, then current density is improved, but contact area decreases leading to overheating and expulsion
Solution Approach 1:
The control-pressure applying unit applies pressure selectively at specific locations on the thin plate rather than uniformly across the entire contact area. This creates a non-uniform pressure distribution that increases contact area where needed to prevent overheating, while maintaining sufficient current density at critical joint sections to ensure proper weld formation and prevent expulsion.
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 ensures uniform and stable weld quality by maintaining consistent current density and pressure distribution, preventing expulsion and surface flash, and enhancing weld penetration and strength across the stacked plates.
Implementation Method 1
applying high current between the welding electrodes for a predetermined time, and then increasing the temperature at a joint section to substantially a melting temperature so as to form a nugget
Implementation Method 2
clamping and pressing the stacked-plate workpiece by using a first welding electrode that is brought into contact with a second thick plate, a second welding electrode that faces the first welding electrode and is brought into contact with a thin plate, and a control-pressure applying unit that is set adjacent to the second welding electrode and is brought into contact with the thin plate
Data Source
AI summary
When spot-welding a workpiece including a thin plate, a first thick plate, and a second thick plate, the workpiece is clamped by a fixed electrode in contact with the second thick plate, a movable electrode in contact with the thin plate, and control-pressure applying unit set adjacent to the movable electrode and in contact with the thin plate. Pressure is applied to the second thick plate by the fixed electrode, and pressure and control pressure are respectively applied by the movable electrode and the control-pressure applying unit to the thin plate. The pressure from the fixed electrode is controlled to be smaller than the pressure from the movable electrode. The current density between the thin plate and the first thick plate increases.