Double Pulse Collaborative Arc Welding System – Chonburi, Thailand

Field Report: Optimization of Collaborative Arc Welding System for Carbon Steel Fabrication

Location: Eastern Economic Corridor (EEC) Workshop, Chonburi, Thailand

1. Executive Summary and Site Context

This report outlines the technical deployment and optimization of a Collaborative Arc Welding System integrated with a double-pulse power source for Carbon Steel welding. The site in Chonburi serves as a primary fabrication hub for heavy-duty automotive frames and structural components. Previously, the facility relied heavily on manual Gas Metal Arc Welding (GMAW) and traditional fixed-track Automated Welding. The transition to a collaborative framework was necessitated by the need for higher throughput and more consistent bead morphology on complex geometries that hard-automation could not economically address.

2. The Synergy of Collaborative Systems and Automated Welding

In the Chonburi workshop environment, the distinction between traditional Automated Welding and a Collaborative Arc Welding System is critical. Traditional automation requires extensive safety cage footprints and rigid jigging, which limits floor space in high-density industrial zones. By implementing a collaborative approach, we have bridged the gap between the dexterity of a human welder and the repeatability of a machine.

The synergy lies in the “lead-through” programming capability. During the field trials, our senior welders were able to manually guide the cobot arm along the complex fillet joints of the carbon steel chassis. This recorded pathing allows the Automated Welding process to commence within minutes of setup, rather than hours of G-code programming. In Chonburi’s fast-paced manufacturing climate, this reduced downtime is the primary driver for ROI.

3. Technical Deep-Dive: Double Pulse and Carbon Steel Welding

The core of this deployment involves Carbon Steel welding using a double-pulse waveform. Carbon steel, specifically S355JR grade used in this project, is prone to overheating and distortion if heat input is not strictly controlled.

3.1 Waveform Mechanics

The double-pulse process utilizes a high-frequency pulse superimposed on a lower-frequency pulse cycle. This creates a “pulse-on-pulse” effect that oscillates the weld pool. For our Chonburi application, we tuned the frequency to 1.5 Hz with a 30% duty cycle on the peak current. This oscillation effectively agitates the molten pool, helping to release trapped gases—a vital feature given the high ambient humidity in Thailand, which often leads to hydrogen-induced porosity in carbon steel.

3.2 Metallurgical Benefits

By utilizing the Collaborative Arc Welding System to maintain a constant torch angle and stand-off distance (15mm), the double pulse achieved a TIG-like aesthetic on 6mm carbon steel plates. We observed a significant reduction in the Heat Affected Zone (HAZ). Hardness testing across the weld cross-section showed a more uniform martensitic-ferritic grain structure compared to the standard spray-transfer Automated Welding we previously employed.

4. Practical Field Observations: The Chonburi Environment

Operating heavy-duty Automated Welding equipment in Chonburi presents specific environmental challenges that are rarely covered in European or North American manuals.

4.1 Humidity and Shielding Gas Integrity

During the monsoon transition, Chonburi’s relative humidity often exceeds 85%. For Carbon Steel welding, moisture is the enemy of the arc. We found that standard 80/20 Argon/CO2 mixes were susceptible to moisture contamination in the lines. Lessons learned: We implemented heated regulators and dual-stage filtration at the cobot’s gas inlet. The Collaborative Arc Welding System’s sensors were calibrated to abort the cycle if gas flow deviated by more than 2 L/min, preventing a batch of rejected frames.

4.2 Thermal Stability of the Arm

While the welding power source is industrial-grade, the collaborative arm’s joints are sensitive to the ambient 38°C (100°F) temperatures of an open-air Thai workshop. We observed a minor “drift” in the TCP (Tool Center Point) during 100% duty cycle shifts. To counter this, we integrated a thermal compensation routine into the Automated Welding software, re-zeroing the torch position against a fixed spike every 50 cycles.

5. Parameter Matrix for Carbon Steel (S355)

The following parameters were established as the “Golden Run” for the 10mm fillet welds on the Chonburi project:

• Wire: ER70S-6 (1.2mm diameter)
• Gas: 90% Ar / 10% CO2 (The higher Argon content improved pulse stability)
• Peak Current: 280A
• Base Current: 140A
• Pulse Frequency: 1.8 Hz
• Travel Speed: 35 cm/min
• Collaborative System Setting: 5N sensitivity (to prevent nuisance stops from minor cable drag)

6. Lessons Learned: Why “Collaborative” is Not “Hands-Off”

One of the major misconceptions we cleared up for the local team is that a Collaborative Arc Welding System does not replace the welder; it augments them.

6.1 Tack Welding Strategy

We learned that for Automated Welding of carbon steel frames, tacking must be incredibly precise. In manual welding, a technician compensates for a 2mm gap on the fly. The cobot is less forgiving. We revised the SOP to require 3mm bridge tacks every 150mm. This ensured the Collaborative Arc Welding System followed the root opening without burning through or losing penetration.

6.2 Spatter Management

Even with double pulse, Carbon Steel welding generates some spatter. In a collaborative environment, the torch is closer to the operator. We found that the standard air-cooled torches were overheating. We upgraded to water-cooled torches integrated into the cobot’s cable management. This increased the system’s uptime from 65% to 92% per shift.

7. Economic and Quality Impact

Post-implementation data from the Chonburi site shows a 40% reduction in grinding time. Because the double-pulse Automated Welding produces a rippled bead with almost zero spatter, the secondary finishing stage was nearly eliminated.

Furthermore, the Collaborative Arc Welding System allowed one operator to manage two cells simultaneously. In terms of Carbon Steel welding quality, our X-ray rejection rate dropped from 4.2% (manual) to 0.5% (collaborative automated).

8. Conclusion and Future Scaling

The Chonburi field trial confirms that for mid-to-high volume Carbon Steel welding, the synergy between Automated Welding precision and collaborative flexibility is the most viable path forward. The Collaborative Arc Welding System handles the “dirty, dull, and dangerous” aspects of the long seams, while the senior engineers focus on joint design and metallurgy.

Our next phase will involve integrating “Through-Arc Seam Tracking” (TAST) to further enhance the system’s ability to handle the slight thermal warping common in Thai fabrication shops. We are also looking into cloud-based monitoring to track the wire consumption and gas usage across the EEC sites from our central office.

End of Report.
Prepared by: Senior Welding Engineer, Site Deployment Division.