Engineering Review: Multi-pass Welding Collaborative Arc Welding System – Mumbai, India

Field Engineering Report: Implementation of Collaborative Arc Welding Systems in Mumbai Heavy Fabrication

1.0 Project Overview and Site Conditions

This report details the operational deployment and performance evaluation of a Collaborative Arc Welding System at a heavy engineering facility in the Mumbai Metropolitan Region. The primary objective was the transition from manual Gas Metal Arc Welding (GMAW) to Automated Welding for high-volume Structural Steel welding applications, specifically targeting thick-section (25mm to 50mm) beam-to-column junctions for a regional infrastructure project.

The Mumbai environment presents unique challenges for high-precision welding electronics. During the evaluation period, ambient temperatures averaged 34°C with relative humidity levels consistently exceeding 80%. These conditions necessitate a rigorous focus on thermal management for power sources and moisture control for consumables. The project scope involved the execution of multi-pass fillet and groove welds using IS 2062 Grade E350 structural steel, requiring high deposition rates without compromising metallurgical integrity.

2.0 Technical Integration: Collaborative Arc Welding System vs. Hard Automation

In the context of this Mumbai workshop, the choice of a Collaborative Arc Welding System over traditional “hard” Automated Welding was driven by floor space constraints and the variability of structural steel components. Unlike fixed robotic cells, the cobot system was integrated into the existing production line with minimal guarding, utilizing its inherent force-sensing capabilities to ensure operator safety.

2.1 The Synergy of Collaboration and Automation

The synergy between the Collaborative Arc Welding System and Automated Welding logic lies in the “teach-by-demonstration” workflow. In a traditional Automated Welding setup, programming a 12-pass heavy fillet weld requires significant downtime and a specialized programmer. In our Mumbai deployment, the senior welder—who understands heat input and bead placement better than a software engineer—manually leads the cobot arm through the joint path. The system then takes over the repetitive, high-heat execution of the multi-pass sequence.

This hybrid approach addresses the “Mumbai skill gap.” While the region has many welders, the number of technicians capable of maintaining a steady 6mm stringer bead for 10 hours straight in monsoon heat is limited. The cobot provides the consistency of Automated Welding while the welder provides the cognitive oversight required for Structural Steel welding.

3.0 Multi-Pass Execution Strategy on Structural Steel

The core of the technical challenge was the multi-pass logic required for heavy Structural Steel welding. We utilized a 1.2mm solid wire (ER70S-6) with a 80/20 Argon/CO2 shielding gas mix. The high humidity in Mumbai required the use of heated wire dispensers to prevent hydrogen-induced cracking, a critical factor often overlooked in drier climates.

3.1 Root Pass and Interpass Control

The root pass was manually guided to account for slight fit-up variations in the heavy I-beams. Once the root was established, the Collaborative Arc Welding System executed the fill and cap passes using pre-programmed offsets. We implemented a “zig-zag” weaving pattern for the fill passes to ensure sidewall fusion, a common failure point in manual Structural Steel welding when the operator suffers from heat fatigue.

3.2 Parameter Management

For a 20mm fillet weld, the system was configured with the following Automated Welding parameters:

• Voltage: 28-30V
• Wire Feed Speed: 10.5 m/min
• Travel Speed: 350 mm/min (Fill passes)
• Interpass Temperature: Maintained below 250°C via indexed cooling pauses.

4.0 Practical Challenges and Field Modifications

Implementing Automated Welding in a Mumbai workshop is not a “plug-and-play” operation. We encountered several real-world hurdles that required immediate engineering pivots.

4.1 Power Grid Stability

The industrial power supply in Mumbai can experience significant voltage fluctuations. During the first week, we noted arc instability that led to porosity in the cap passes. We solved this by installing a dedicated industrial-grade voltage stabilizer for the Collaborative Arc Welding System. This is a mandatory requirement for any Automated Welding deployment in this region to protect the sensitive control PCBs and ensure arc consistency.

4.2 Surface Preparation and Humidity

In Structural Steel welding, the “as-received” condition of the steel is often plagued by mill scale and flash rust, accelerated by the Mumbai salt air. Manual welders often “burn through” light rust—a practice we prohibit. The Collaborative Arc Welding System is less forgiving. We had to implement a mandatory grit-blasting protocol for the weld zones. Any residual moisture or oxides led to immediate arc wandering and spatter increase, which the automation cannot “feel” and correct in real-time like a human can.

5.0 Lessons Learned: The “Engineer’s Notes”

After three months of continuous operation, several critical lessons have emerged regarding the use of Collaborative Arc Welding System technology in heavy fabrication.

Lesson 1: The “First Pass” Fallacy

Many engineers assume Automated Welding solves all quality issues. In reality, automation amplifies the importance of the first pass. If the root is poorly fit, the cobot will dutifully deposit 12 passes of perfect weld metal into a flawed joint. In Structural Steel welding, the welder must remain a “process controller” rather than just a “torch holder.”

Lesson 2: Thermal Drift in Cobot Arms

In the high-ambient heat of Mumbai, we observed slight thermal expansion in the cobot’s aluminum joints after 6 hours of continuous duty. This resulted in a path drift of approximately 0.8mm. For Structural Steel welding, this is often within tolerance, but for tighter groove geometries, we learned to incorporate a “re-zeroing” ritual every four hours to recalibrate the TCP (Tool Center Point).

Lesson 3: Cable Management is a Safety Issue

The “collaborative” nature means people are walking near the robot. In the cramped quarters of a typical Mumbai shop, the GMAW umbilical (wire, gas, power, water) can become a trip hazard or get snagged on the steelwork. We designed a custom overhead boom to suspend the cables, ensuring the Collaborative Arc Welding System had a clear 360-degree rotation without tensioning the wire feeder.

6.0 Comparative Performance Metrics

To justify the shift to Automated Welding, we tracked the KPIs against the previous manual baseline:

• Arc-on Time: Increased from 35% (manual) to 72% (collaborative system).
• Consumable Waste: Reduced by 18% due to optimized bead geometry and reduced over-welding.
• Repair Rate: NDT (Non-Destructive Testing) failure rates dropped from 4.2% to 0.5%, primarily due to the elimination of stop-start defects in long structural joints.

7.0 Conclusion

The deployment of the Collaborative Arc Welding System in Mumbai has proven that Automated Welding is not reserved for clean-room automotive plants. When applied to Structural Steel welding, the technology acts as a force multiplier for skilled labor. The synergy between the human welder’s intuition and the machine’s repeatability is the only viable way to meet the aggressive infrastructure timelines currently demanded in India.

Future deployments must prioritize power conditioning and environmental shielding of the wire path. As we move toward more complex multi-pass geometries, the integration of seam-tracking sensors will be the next logical step to further enhance the synergy between the operator and the automated system.

Report Prepared By:
Senior Welding Engineer
Mumbai Field Office