Short Circuit Welding Stick Out Control via Cycle History
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Solution Overview
Problem
Existing short circuit transfer welding power supplies face challenges in accurately controlling the burn-off rate on a short-by-short basis, leading to increased spatter and instability due to inadequate control of arc length and wire pre-heating, with prior solutions being complex, inaccurate, and prone to false predictions and excessive pre-heating or under-heating.
Innovation Solution
A method and apparatus for short circuit welding that involves sensing stick out length, adjusting welding parameters, and using real-time feedback from arc current and voltage to control the burn-off rate, detecting imminent short clearing through derivatives of power and voltage, and adjusting current profiles based on welding cycle history to maintain consistent arc length and reduce spatter.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If secondary switchers are used to control the output, then fast control is achieved, but cost increases and peak current capacity is insufficient
Solution Approach 1:
The patent extracts the control function from complex secondary switchers and implements it through simpler means: using a current sensor to detect wire current and a controller to generate control signals based on detected values and reference values. This removes the need for complex secondary switching circuitry while maintaining fast control response.
Solution Approach 2:
The patent replaces the mechanical/electrical secondary switcher system with an electronic control system using current sensors and digital controllers. The control is achieved through electronic signal processing rather than mechanical switching, reducing complexity while maintaining speed.
2Manufacturing precision
If arc power is used to control the burn-off rate, then control is implemented, but the control scheme becomes complex and inaccurate
Solution Approach 1:
The patent extracts the essential control parameter from arc power (which requires both voltage and current measurements) to wire current alone. By controlling burn-off rate through wire current only, the system eliminates the complexity of calculating and controlling arc power while achieving more precise and reliable burn-off rate control.
Solution Approach 2:
The patent changes the control parameter from arc power (a composite parameter requiring voltage and current) to wire current (a single parameter). This parameter simplification makes the control scheme less complex and more accurate, as wire current directly correlates with burn-off rate without the complications of voltage variations.
3Measurement precision
If arc voltage is used to determine arc length, then control is implemented, but the control is inaccurate due to voltage variations
Solution Approach 1:
The patent implements feedback control by continuously detecting wire current, comparing it to a reference value, and adjusting the wire feed speed based on the difference. This closed-loop feedback system provides reliable and precise arc length control by responding to actual process conditions rather than relying on potentially misleading voltage measurements.
Solution Approach 2:
The patent substitutes voltage-based arc length measurement with current-based measurement and control. By using wire current as the primary feedback parameter, the system achieves more reliable and accurate arc length control, eliminating the inaccuracies inherent in voltage-based methods.
4Temperature
If wire feed speed is increased to compensate for under-heating, then pre-heating is improved, but spatter increases due to excessive burn-off rate
Solution Approach 1:
The patent uses feedback control to dynamically adjust wire feed speed based on actual wire current measurements. When under-heating is detected (current below reference), wire feed speed is increased to improve pre-heating. When over-heating is detected (current above reference), wire feed speed is decreased to prevent excessive burn-off and spatter. This closed-loop control balances pre-heating and spatter prevention.
Solution Approach 2:
The patent dynamically changes the wire feed speed parameter in response to detected wire current conditions. Rather than using a fixed feed speed, the system adjusts this parameter in real-time to optimize both pre-heating and minimize spatter, achieving a balance that static parameters cannot provide.
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 provides precise control over the short circuit welding process, reducing spatter and maintaining consistent arc length by using real-time feedback and adjusting welding parameters, thereby improving the accuracy and stability of the welding process.
Implementation Method 1
During the arc state the wire melts, and during the short circuit state the metal further melts
Implementation Method 2
Short circuit transfer welding generally consists of alternating between an arc state and a short circuit, non-arc state
Data Source
AI summary
A method and apparatus for short circuit welding includes providing welding power suitable for short circuit welding, sensing the stick out length, and adjusting the welding speed, such as wire feed speed or travel speed, adjusting a welding parameter, or adjusting the gas mixture in response thereto. Stick out is preferably determined by measuring a welding parameter, and performing an FFT on the parameter, and then calculating stick out, in one embodiment. Stick out can be either CTTWD or CPTPD. The system can determine when a short is about to clear by calculating a value Vc defined by Vc=d/dt(k1*dp/dt), and comparing Vc to a Vthreshold, which varies in response to welding cycle history.