AC Pulse Arc Welding Control for Stable Droplet Transfer
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Solution Overview
Problem
AC pulse arc welding becomes unstable when the electrode negative polarity current ratio exceeds conventional limits, leading to incomplete droplet transfer and random droplet formation due to large droplet size issues.
Innovation Solution
The method involves applying two successive peak periods, an electrode negative polarity peak period and an electrode positive polarity peak period, with the electrode negative polarity peak current having an absolute value greater than the critical value for negative polarity, and an electrode positive polarity peak current greater than the critical value for positive polarity, to facilitate stable droplet transfer even at high current ratios.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the electrode negative polarity current ratio is increased to reduce heat input and improve welding quality on thin plates, then welding quality and heat input control are improved, but droplet transfer stability deteriorates due to large droplet size and random droplet formation
Solution Approach 1:
The electrode negative polarity period is segmented into two distinct phases: a base period with base current (below critical value) and a peak period with peak current (above critical value). This segmentation allows the negative polarity period to be divided into functions: the base period controls heat input and the peak period ensures stable droplet transfer, resolving the contradiction between heat input reduction and droplet transfer stability.
Solution Approach 2:
The welding process uses periodic pulse current with alternating positive and negative polarity periods. Within the negative polarity period, periodic switching between base current and peak current creates a structured pattern that ensures droplet formation and transfer occur at controlled intervals, maintaining stability even at high negative polarity current ratios.
2Use of energy by moving object
If conventional AC pulse arc welding is used with high electrode negative polarity current ratio, then low heat input welding is achieved, but arc stability deteriorates due to large droplet size and random formation
Solution Approach 1:
The negative polarity period is segmented into base period and peak period, where the base period controls heat input and the peak period ensures arc stability through proper droplet transfer. This segmentation allows the system to maintain arc stability even at high negative polarity current ratios by ensuring droplet transfer occurs during the peak period.
Solution Approach 2:
Periodic switching between base current and peak current within the negative polarity period creates a structured pattern that maintains arc stability. The periodic peak current pulses ensure consistent droplet formation and transfer, preventing random droplet formation and maintaining arc stability during low heat input welding.
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 allows for setting the electrode negative polarity current ratio to higher values beyond the conventional range, ensuring stable welding with high-quality bead formation and low dilution rates, preventing spatter and maintaining arc stability.
Implementation Method 1
the applied peak current Ip generates an electromagnetic force or pinch that acts on an upper portion of the droplet, thereby producing a constricted part or a neck in the droplet
Implementation Method 2
AC pulse arc welding proceeds by repeating cycles each consisting of an electrode positive polarity period and an electrode negative polarity period
Data Source
Figure 1
Figure 2
Figure 3(A)~3(F)
AI summary
A control method for AC pulse arc welding performed upon application of cyclic AC welding current is provided. The welding current has a cycle including an electrode negative polarity period and an electrode positive polarity period subsequent to the electrode negative polarity period. In the control method, an electrode negative polarity base current (Ibn) and a subsequent electrode negative polarity peak current (Ipn) are applied during the electrode negative polarity period. The electrode negative polarity base current has an absolute value smaller than a first critical value, and the electrode negative polarity peak current has an absolute value greater than the first critical value. Then, an electrode positive polarity peak current (Ip) is applied during the electrode positive polarity period. The electrode positive polarity peak current has a value greater than a second critical value.