Spot Welding Pressure Control for Uneven Plate Thickness
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing spot welding methods face challenges in achieving consistent weld quality due to variations in pressure distribution between electrodes, leading to uneven current density and reduced weld strength, especially when welding plates of different thicknesses.
Innovation Solution
A pressure control method for a spot welding apparatus that uses a combination of a pressure actuator and a sub-pressure actuator to apply preset pressures and sub-pressures to the workpiece, allowing for precise control of the contact pressure between electrodes, thereby ensuring consistent current distribution and improved weld quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a single pressure actuator is used to apply pressure to the workpiece, then the device complexity is reduced, but the manufacturing precision of pressure distribution is insufficient leading to uneven current density
Solution Approach 1:
The pressure control system is segmented into a main pressure actuator and a sub-pressure actuator. The main pressure actuator applies overall pressure to the workpiece, while the sub-pressure actuator specifically adjusts pressure at the thin plate portion. This segmentation enables precise pressure distribution control without requiring complete redesign of the entire pressure system.
Solution Approach 2:
The sub-pressure actuator is positioned to apply pressure locally at the thin plate portion of the workpiece. This local quality approach allows differential pressure control where the thin plate receives additional sub-pressure to compensate for its lower rigidity, while other portions receive only the main pressure, achieving uniform current density through localized pressure adjustment.
2Strength
If pressure is increased to improve contact between plates, then weld strength is improved, but the thin plate bends more causing gaps and uneven current density
Solution Approach 1:
The system changes the pressure parameter distribution by introducing a sub-pressure component specifically at the thin plate portion. Instead of uniformly increasing pressure across the entire workpiece (which causes bending), the sub-pressure actuator locally adjusts the pressure parameter at the critical thin plate area, maintaining contact stability without inducing excessive bending.
Solution Approach 2:
The control system uses feedback from pressure sensors to monitor the actual pressure distribution and workpiece state. Based on this feedback, the sub-pressure actuator dynamically adjusts the local pressure to maintain optimal contact between the thin plate and adjacent plates, preventing gap formation while avoiding excessive bending that would disrupt current density uniformity.
3Strength
If the thickness of thick plates is increased to improve structural strength, then overall strength is improved, but it becomes more difficult for the nugget to reach the joint section between the thin plate and first thick plate
Solution Approach 1:
By applying sub-pressure to the thin plate portion, the system changes the pressure parameter to increase contact resistance at the thin plate interfaces. This generates additional heat at these interfaces, facilitating nugget formation and penetration through the thick plates. The parameter change in pressure distribution compensates for the increased thickness barrier, enabling the nugget to reach the joint sections effectively.
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 achieves high welding quality by accurately applying preset pressures and sub-pressures, reducing mechanical resistance effects and maintaining stable contact resistance, resulting in enhanced weld strength and consistency across varying plate thicknesses.
Implementation Method 1
a movable electrode 111 and a fixed electrode 112 hold the workpiece 100 therebetween such that the thin plate 101 is in tight contact with the first thick plate 102
Implementation Method 2
when a power source 113 applies a current to the workpiece 100 through the movable electrode 111 and the fixed electrode 112, the current density in an electric path between the movable electrode 111 and the fixed electrode 112 becomes substantially uniform
Implementation Method 3
The spot welding technique involves using a pair of welding electrodes to hold and apply pressure to the stacked plates, and applying a current between the welding electrodes for a predetermined time period
Data Source
AI summary
There is provided a pressure control method for a spot welding apparatus. Upon spot-welding a workpiece while applying a preset pressure to the workpiece by a pressure actuator through a movable electrode and a fixed electrode holding a workpiece and applying a preset sub-pressure by a sub-pressure actuator through a sub-pressure unit, the workpiece is pressed with an initial pressure by the movable electrode and the fixed electrode, and an initial sub-pressure is applied through the sub-pressure unit. After that, the setting pressure is applied to the workpiece by the pressure actuator through the movable electrode and the fixed electrode, and the setting sub-pressure is applied by the sub-pressure actuator through the sub-pressure unit.