Spot Welding Apparatus with Differential Pressure Control
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Solution Overview
Problem
Spot welding of stacked plates with differing rigidities often results in unstable weld quality due to uneven current density and heat distribution, leading to defects such as holes, cracks, and reduced joint strength, especially when thicker plates are stacked on top of thinner ones.
Innovation Solution
A spot welding apparatus with a base unit, receiving unit, and movable welding electrodes that adjust pressure to ensure consistent contact resistance across the joint, allowing for controlled current density distribution by varying the welding pressure applied to each plate, thereby stabilizing the weld quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a large current is applied to achieve sufficient joint strength, then the nugget diameter increases, but expulsion occurs due to superheating and molten metal is expelled from between the plates
Solution Approach 1:
The patent applies different welding pressures to different regions of the stacked plates. Specifically, a larger welding pressure is applied to the thicker plate while a smaller welding pressure is applied to the thinner plate. This creates localized pressure distribution that compensates for the rigidity differences between plates, ensuring uniform contact pressure and current density across the joint zone, thereby preventing expulsion while achieving sufficient joint strength.
Solution Approach 2:
The patent dynamically adjusts the welding pressure parameter during the spot welding process. By varying the welding pressure applied to each plate based on their respective rigidities and thicknesses, the system optimizes current density distribution and heat generation, preventing superheating and expulsion while maintaining adequate joint strength.
2Object-generated harmful factors
If a small current is applied to avoid expulsion, then the nugget diameter remains small, but sufficient joint strength is not achieved
Solution Approach 1:
The patent applies different welding pressures to different regions of the stacked plates. Specifically, a larger welding pressure is applied to the thicker plate while a smaller welding pressure is applied to the thinner plate. This creates localized pressure distribution that compensates for the rigidity differences between plates, ensuring uniform contact pressure and current density across the joint zone, thereby preventing expulsion while achieving sufficient joint strength.
Solution Approach 2:
The patent dynamically adjusts the welding pressure parameter during the spot welding process. By varying the welding pressure applied to each plate based on their respective rigidities and thicknesses, the system optimizes current density distribution and heat generation, preventing superheating and expulsion while maintaining adequate joint strength.
3Area of stationary object
If low welding pressure is applied, then the contact area between plates increases, but current density increases due to reduced contact resistance, causing expulsion
Solution Approach 1:
The patent applies different welding pressures to different regions of the stacked plates. Specifically, a larger welding pressure is applied to the thicker plate while a smaller welding pressure is applied to the thinner plate. This creates localized pressure distribution that compensates for the rigidity differences between plates, ensuring uniform contact pressure and current density across the joint zone, thereby preventing expulsion while achieving sufficient joint strength.
Solution Approach 2:
The patent dynamically adjusts the welding pressure parameter during the spot welding process. By varying the welding pressure applied to each plate based on their respective rigidities and thicknesses, the system optimizes current density distribution and heat generation, preventing superheating and expulsion while maintaining adequate joint strength.
4Area of stationary object
If high welding pressure is applied, then the contact area at the joint increases, but current density decreases, resulting in small nugget and reduced weld strength
Solution Approach 1:
The patent applies different welding pressures to different regions of the stacked plates. Specifically, a larger welding pressure is applied to the thicker plate while a smaller welding pressure is applied to the thinner plate. This creates localized pressure distribution that compensates for the rigidity differences between plates, ensuring uniform contact pressure and current density across the joint zone, thereby preventing expulsion while achieving sufficient joint strength.
Solution Approach 2:
The patent dynamically adjusts the welding pressure parameter during the spot welding process. By varying the welding pressure applied to each plate based on their respective rigidities and thicknesses, the system optimizes current density distribution and heat generation, preventing superheating and expulsion while maintaining adequate joint strength.
5Device complexity
If uniform welding pressure is applied to all plates, then the setup is simple, but uneven current density occurs due to rigidity differences, leading to unstable weld quality
Solution Approach 1:
The patent applies different welding pressures to different regions of the stacked plates. Specifically, a larger welding pressure is applied to the thicker plate while a smaller welding pressure is applied to the thinner plate. This creates localized pressure distribution that compensates for the rigidity differences between plates, ensuring uniform contact pressure and current density across the joint zone, thereby preventing expulsion while achieving sufficient joint strength.
Solution Approach 2:
The patent employs a dynamic pressure control system that adjusts welding pressures independently for each plate based on their rigidity characteristics. The pressure control unit varies the welding pressure applied to each plate during the welding process, transforming the static uniform pressure approach into a dynamic differentiated pressure approach, thereby achieving consistent weld quality across plates with different rigidities.
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 solution achieves uniform penetration and high weld strength across the joint from the thinner to the thicker plates, improving the overall quality of the spot weld by managing current density and heat distribution effectively.
Implementation Method 1
a first welding electrode and a second welding electrode that are movable toward and away from each other in an opposing relationship. The workpiece is clamped between a combination of the second welding electrode that abuts against the thinner plate and the receiving unit that is adjacent to the second welding electrode and abuts against the thinner plate, and the first welding electrode that abuts against the second thicker plate, a pressure is applied to the workpiece by the first welding electrode
Implementation Method 2
a current is passed between the first welding electrode and the second welding electrode while the workpiece is clamped under pressure to spot weld the workpiece
Implementation Method 3
heat the joint zone to substantially a melting temperature, thereby joining the plates together
Implementation Method 4
allowing for controlled current density distribution by varying the welding pressure applied to each plate, thereby stabilizing the weld quality
Data Source
AI summary
There are provided a spot welding apparatus and a spot welding method. A workpiece is clamped between a combination of a second welding electrode and a receiving unit that abut against a thinner plate, and a first welding electrode that abuts against a second thicker plate, a pressure is applied to the workpiece by the first welding electrode, and a current is passed between the welding electrodes. Consequently, a satisfactory nugget is formed over from the thinner plate to the second thicker plate. Similarly, a workpiece is clamped between a combination of the first welding electrode and the receiving unit that abut against a thinner plate, and the second welding electrode that abuts against a second thicker plate, a pressure is applied to the workpiece by the second welding electrode. Consequently, a satisfactory nugget is formed over from the thinner plate to the second thicker plate.