Secondary Contact Current Limiting to Prevent Welding Wire Burn Back
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Solution Overview
Problem
Welding systems using soft electrode wires like aluminum face issues with 'burn back' due to unintentional arcing and melting at the contact tip during arc initiation, particularly when using hard wire wound liners, which can damage the torch and hinder the welding process.
Innovation Solution
Incorporating a current limiting device at a secondary contact point between the weld voltage and the welding wire to maintain the weld voltage without allowing sufficient current flow, preventing arcing by using a resistor, capacitor, or diode, and employing a non-conductive liner to reduce wire scraping.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a hard wire wound liner is used in the welding torch, then the liner can effectively guide and support hard wires like steel and stainless steel, but it causes scraping and damage to softer electrode wires like aluminum, leading to burn back and welding defects
Solution Approach 1:
The liner is designed with different material properties in different sections: the initial section uses a softer material to prevent scraping of soft wires during entry, while downstream sections maintain adequate structural support. This local differentiation of material hardness resolves the contradiction between needing liner strength and preventing wire damage.
Solution Approach 2:
The liner is constructed as a composite structure combining materials with different properties - softer materials (like plastic or Teflon) in contact with the wire to prevent scraping, potentially reinforced with harder materials in structural sections. This composite approach allows simultaneous achievement of wire protection and structural support.
2Object-affected harmful factors
If a softer liner material is used to prevent wire scraping, then the liner can protect soft wires like aluminum from damage, but it reduces the liner's ability to maintain voltage and guide the wire effectively
Solution Approach 1:
Different sections of the liner have different material properties optimized for their specific functions: the entry section uses softer material for wire protection, while downstream sections use materials with better electrical and mechanical properties for voltage maintenance and precise wire guidance.
Solution Approach 2:
The liner combines softer protective materials with materials having superior electrical conductivity and mechanical strength in different sections, creating a composite structure that simultaneously achieves wire protection and reliable voltage maintenance.
3Ease of operation
If aluminum wire is used as electrode material, then the wire can be fed smoothly through the torch, but it is prone to unintentional arcing and burn back at the contact tip during arc initiation
Solution Approach 1:
The system proactively prevents burn back by implementing multiple protective measures before arcing can occur: optimized contact tip geometry, controlled wire feed speed, proper liner material selection, and pre-arc circuit design that minimizes premature contact and arcing opportunities.
Solution Approach 2:
The invention optimizes critical parameters including contact tip to workpiece distance, wire feed speed, contact tip geometry, and liner material properties to create conditions that prevent premature arcing while maintaining smooth wire feedability for aluminum electrodes.
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 effectively prevents 'burn back' and maintains system performance by limiting current during arc initiation, reducing damage to the contact tip and drive roll, and ensuring consistent wire feeding.
Implementation Method 1
A current limiting device is coupled between the weld voltage and the secondary contact. The current limiting device is configured to maintain a voltage at the secondary contact at the weld voltage level while limiting the available current through the secondary contact to an amount insufficient to create an arc.
Implementation Method 2
employing a non-conductive liner to reduce wire scraping
Data Source
AI summary
A welding-type system includes a welding torch comprising a contact tip to provide an electrode wire. A secondary contact in electrical contact with the electrode wire, the secondary contact located along a length of the electrode wire and before the contact tip. Each of the contact tip and the secondary contact are connected to a welding-type power source. A current limiting device coupling located between the welding-type power source and the secondary contact and configured to limit a current at the secondary contact.