Engineering Review: Double Pulse Cobot Welding Machine – Busan, South Korea

Field Engineering Report: Implementation of Double Pulse Cobot Welding Systems

Location: Busan, South Korea – Automotive Tier-1 Supplier Facility

1. Introduction and Site Context

This report outlines the technical deployment and operational validation of the 10kg-payload Cobot Welding Machine integrated into a high-volume production line in Busan. The facility, primarily focused on chassis component fabrication, had been struggling with consistency in Mild Steel welding using traditional manual Metal Inert Gas (MIG) processes. The primary objective was to leverage Collaborative Robotics to bridge the gap between manual dexterity and industrial automation, specifically focusing on the Double Pulse waveform to reduce post-weld cleanup.

Busan’s manufacturing sector is currently facing a dual challenge: an aging skilled workforce and a demand for higher aesthetic quality on structural components. The transition to a Cobot Welding Machine isn’t merely a hardware upgrade; it is a shift in the manufacturing philosophy of the workshop.

2. Technical Specifications of the Cobot Welding Machine

The unit deployed is a 6-axis collaborative arm integrated with a 500A power source capable of high-frequency pulsing. Unlike traditional industrial robots that require extensive safety interlocks and light curtains, the Collaborative Robotics framework allows this machine to operate alongside human technicians.

Key Specifications:

• Payload: 10kg (sufficient for water-cooled torches and wire-feed assemblies).
• Reach: 1300mm, covering the standard 1000mm x 800mm welding jigs used in this Busan facility.
• Interface: Lead-through teaching with a specialized “Welding App” UI for rapid parameter adjustment.
• Communication: EtherCAT protocol for real-time synchronization between the arm’s movement and the power source’s arc ignition.

3. The Synergy of Collaborative Robotics in the Busan Workshop

In the context of a Busan-based job shop, space is a premium. Traditional robotics require a significant footprint for safety enclosures. The implementation of Collaborative Robotics allowed us to install the Cobot Welding Machine within the existing manual welding booths with minimal structural modification.

The true synergy lies in the “Human-in-the-loop” workflow. The technician handles the fit-up and tacking of the Mild Steel welding assemblies, while the cobot executes the long-seam structural welds. This collaborative approach utilizes the human’s ability to compensate for part fit-up variations while exploiting the cobot’s ability to maintain a constant travel speed and torch angle—parameters that are often the first to degrade during a manual welder’s 8-hour shift.

4. Process Optimization for Mild Steel Welding

Mild Steel welding (primarily JIS G3131 SPHC and ASTM A36 equivalents at this site) typically presents challenges regarding spatter and heat distortion when using standard Short-Circuit Transfer. In this application, we utilized the Double Pulse (DP) function of the Cobot Welding Machine.

4.1 The Double Pulse Advantage

Double Pulse technology alternates between two distinct pulse frequencies. In the Busan facility, we set the primary pulse to handle penetration and the secondary pulse (lower frequency) to control the cooling of the weld pool. This creates a “shingled” bead appearance similar to TIG welding but at the speeds associated with MIG.

Technical Settings Used:

• Peak Current: 240A
• Base Current: 110A
• Pulse Frequency: 1.5 Hz to 3.5 Hz depending on material thickness.
• Wire: 1.2mm ER70S-6.
• Gas: 80% Ar / 20% CO2.

The result was a 75% reduction in spatter compared to the previous manual GMAW process. This is critical because post-weld grinding in Busan’s high-humidity coastal environment often leads to flash rusting on ground surfaces; by eliminating spatter, we preserved the mill scale integrity surrounding the HAZ (Heat Affected Zone).

5. Field Lessons: Programming and Torch Geometry

One of the major “lessons learned” during the first two weeks in Busan involved the Tool Center Point (TCP) calibration. Because Collaborative Robotics relies on lead-through teaching, operators initially tended to be “lazy” with torch angles, assuming the software would correct for drag or push angles.

5.1 Work Angle and Travel Angle Sensitivity

We discovered that on 4.0mm mild steel lap joints, a 15-degree push angle was optimal for the Double Pulse process. If the operator taught the path with a fluctuating angle, the arc length correction (Voltage Control) struggled to maintain a consistent plasma column, leading to undercut. We implemented a “Calibration Jig” at the start of every shift to ensure the Cobot Welding Machine TCP was accurate within 0.5mm.

5.2 Managing Heat Input

Mild steel is prone to warping if the heat input isn’t managed. We utilized the cobot’s ability to perform “stitch welding” with exact millisecond pauses between segments. This allowed the 10mm base plates to remain within the +/- 1.0mm flatness tolerance required for the subsequent assembly stage.

6. Operational Impact and ROI in Busan

Prior to the introduction of the Cobot Welding Machine, the defect rate (primarily porosity and over-welding) was hovering at 8.2%. After 30 days of Collaborative Robotics integration, the rate dropped to 1.4%.

Key Performance Indicators (KPIs):

• Arc-on Time: Increased from 35% (manual) to 65% (cobot).
• Consumable Savings: 12% reduction in wire waste due to optimized arc starts and ends.
• Training Time: A standard manual welder was able to program basic Mild Steel welding paths within 4 hours of instruction.

The “Busan Model” of deployment proved that Collaborative Robotics is most effective when the machine is treated as a high-precision tool for the welder, rather than a replacement for the welder. The welder’s knowledge of “puddle behavior” is essential for setting the initial DP parameters, while the cobot provides the mechanical consistency.

7. Technical Challenges Encountered

The implementation was not without hurdles. The Busan site is located near the Port of Busan, meaning the ambient air has high salinity and humidity.

Issue: We observed intermittent arc instability in the Cobot Welding Machine.
Root Cause: Moisture absorption in the wire conduit during weekend shutdowns.
Solution: We installed a pressurized wire delivery system and ceramic liners to minimize friction and environmental exposure. In Mild Steel welding, even minor surface contamination on the wire can disrupt the pulse frequency timing, leading to “stuttering” in the double pulse cycle.

8. Conclusion and Future Outlook

The deployment of Collaborative Robotics in the Busan facility has successfully demonstrated that high-tier Mild Steel welding can be automated without the complexity of traditional robotic cells. The Cobot Welding Machine has become a force multiplier for the engineering team.

The success of the Double Pulse application suggests that further expansion into aluminum and stainless steel components is viable using the same hardware platform. The focus for the next quarter will be the integration of “Seam Tracking” sensors to further enhance the cobot’s ability to handle non-linear fit-up variations in real-time.

Final Engineer’s Note: The synergy between the human operator’s intuition and the cobot’s precision is the definitive solution for mid-market manufacturing hubs like Busan. We have moved from “welding by feel” to “welding by data.”

End of Report.
Prepared by: Senior Welding Engineer, Site Operations – Busan.