Pulsed Spot Welding Waveform for Mixed-Thickness Laminates
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Solution Overview
Problem
In spot welding of laminates with varying metal plate thicknesses, excessive nugget growth on thicker plates leads to expulsion, while insufficient growth on thinner plates results in incomplete welding, making it challenging to achieve successful welding without expulsion.
Innovation Solution
A spot welding method using pulse current with a pulsed waveform, where the peak state and no-peak state are alternately set, with a peak duration of 0.9 ms or less and a no-peak duration between 4 ms to 13.6 ms, and an upper limit peak current of 10.6 kA or more, to control nugget growth and prevent expulsion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the current value is increased to ensure nugget growth on thin plates, then welding success is improved, but expulsion occurs on thick plates
Solution Approach 1:
The patent applies periodic pulsed current with alternating peak and no-peak states. The pulse current creates periodic heating cycles that allow controlled nugget growth on thin plates while preventing excessive growth and expulsion on thick plates. The cyclic nature of the current enables differential thermal accumulation across plates of varying thicknesses.
Solution Approach 2:
The patent employs dynamic current control by adjusting peak current magnitude (10.6 kA or more), peak duration (0.9 ms or less), and no-peak duration (4 ms to 13.6 ms) based on plate thickness variations. This dynamic parameter adjustment optimizes nugget growth rate for each plate thickness, ensuring reliable welding without expulsion.
2Object-generated harmful factors
If the current value is decreased to prevent expulsion on thick plates, then expulsion is inhibited, but nugget growth is insufficient on thin plates
Solution Approach 1:
The periodic pulsed current creates alternating heating and cooling phases. During peak current states, nugget growth is promoted on thin plates; during no-peak states, heat dissipation prevents excessive growth on thick plates. This periodic action resolves the contradiction by providing temporal separation of growth promotion and expulsion prevention.
Solution Approach 2:
The patent changes current parameters dynamically by setting specific peak current values (10.6 kA or more), peak durations (0.9 ms or less), and no-peak durations (4 ms to 13.6 ms). These parameter changes enable the system to achieve both insufficient growth prevention on thin plates and excessive growth prevention on thick plates simultaneously.
3Reliability
If continuous energization is used to ensure nugget growth, then welding success is improved, but nugget excessively grows and protrudes from corona bond
Solution Approach 1:
The patent replaces continuous energization with periodic pulsed energization. The alternating peak and no-peak states create cyclic nugget growth and cooling phases. This periodic action ensures nugget growth reaches sufficient size for welding success while the cooling phases prevent excessive growth and protrusion from the corona bond.
Solution Approach 2:
The patent maintains continuous useful action through repeated pulse cycles. Multiple peak-no-peak cycles continue the nugget growth process until sufficient size is achieved, ensuring welding success while preventing excessive growth through the interspersed no-peak cooling phases.
4Object-generated harmful factors
If short period energization is used to prevent nugget protrusion, then expulsion is inhibited, but nugget cannot grow to required size
Solution Approach 1:
The patent uses extended periodic pulsed energization with multiple peak-no-peak cycles. Each peak state contributes to nugget growth, and the cumulative effect of repeated cycles ensures nugget reaches required size. The no-peak states prevent excessive growth, maintaining the balance between sufficient growth and protrusion prevention.
Solution Approach 2:
The patent ensures continuous useful action by implementing multiple successive pulse cycles. The repeated peak current applications continuously drive nugget growth over an extended period, ensuring the nugget reaches the required size for successful welding while the interspersed no-peak phases prevent excessive growth.
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 method allows for successful welding while inhibiting expulsion, providing a wide welding current range that accommodates errors in current values, enabling continuous welding of car bodies for mass production.
Implementation Method 1
energizing between a pair of electrode chips in a state where the plurality of metal plates are sandwiched between the pair of electrode chips. Consequently, a nugget is generated among the plurality of metal plates
Data Source
AI summary
Provided is a spot welding method by which welding can be performed successfully while inhibiting occurrence of expulsion. First to third metal plates W1 to W3 were welded in which a ratio of a total thickness to a thickness of the first metal plate W1 is 7. In Example 1, a peak current value A1 is 14.6 kA, an effective current value A2 is 7.8 kA, a peak duration T1 is 0.1 ms, and a no-peak duration T2 is 5.9 ms. As a result, a lower limit current value A3 is 6.9 kA, an upper limit current value A4 is 8.42 kA, a difference A5 between A4 and A3 is 1.52 kA, T2/T1 is 59.0, A2/A1 is 0.53, and rising time T3/falling time T4 is 0.53, furthermore, no expulsion occurs, and a welding result was determined to be OK.