Multi-pass Welding Laser Welding Cobot – Warsaw, Poland

Field Report: Multi-Pass Laser Welding Cobot Integration – Warsaw Industrial Sector

1.0 Project Overview and Scope

This report documents the site deployment and technical validation of a 2kW Fiber Laser Welding Cobot system at a specialized aerospace and chemical processing facility in Warsaw, Poland. The primary objective was to transition a critical Titanium welding workflow from manual Gas Tungsten Arc Welding (GTAW) to an automated, multi-pass laser process.

The facility in Warsaw faced significant throughput bottlenecks due to the extreme skill requirements of manual Titanium welding. Titanium’s high reactivity with atmospheric gases at temperatures above 400°C demands meticulous shielding and heat input management. By integrating advanced Laser Technology via a collaborative robot (cobot) platform, we aimed to achieve the high energy density required for deep penetration while maintaining the surgical precision needed for multi-pass buildup on thick-walled (10mm+) Grade 5 Titanium (Ti-6Al-4V) components.

2.0 The Synergy of Laser Technology and Collaborative Robotics

The deployment in Warsaw marks a shift in how we approach “hard-to-weld” reactive metals. Traditional automation often lacks the flexibility for the high-mix, low-volume production typical of Polish aerospace contractors. The Laser Welding Cobot bridges this gap by combining the high-speed processing capabilities of fiber Laser Technology with the ease of “lead-through” programming.

In this specific application, the Laser Welding Cobot serves as the kinetic carrier for a high-intensity 1070nm wavelength beam. The synergy here is found in the cobot’s ability to maintain a constant Stand-Off Distance (SOD) and travel speed—variables that are notoriously difficult to stabilize manually when dealing with the high travel speeds required for laser processing. Because Laser Technology produces a much narrower Heat Affected Zone (HAZ) compared to plasma or TIG, the cobot’s repeatability ensures that the narrow fusion zone is precisely hit during subsequent passes in a multi-pass groove configuration.

3.0 Technical Specifications and Setup

3.1 Laser Source and Optics

The Warsaw workshop utilized a continuous wave (CW) fiber laser source. For Titanium welding, we employed a wobble-head attachment. This Laser Technology allows the beam to oscillate in various patterns (circular, figure-eight, or zig-zag), which is essential for multi-pass applications where the groove width exceeds the spot size of the laser.

• Power Output: 2000W (Adjusted to 1600W for root pass).
• Wobble Frequency: 150Hz.
• Wobble Width: 2.5mm for fill passes.
• Fiber Core: 50μm.

3.2 The Cobot Kinetic Profile

The Laser Welding Cobot was programmed with a 6-axis reach capable of covering the entire 1200mm diameter of the pressure vessel end-caps. We utilized a localized Warsaw-based software integration to synchronize the laser’s “Ramp-up” and “Ramp-down” sequences with the cobot’s acceleration/deceleration curves to prevent “crater cracks” at the stop points—a common failure in Titanium welding.

4.0 Multi-Pass Strategy for Titanium Welding

When welding thick Titanium sections, a single pass often results in excessive root sagging or lack of sidewall fusion. In Warsaw, we implemented a three-pass strategy: a root pass, a hot pass (fill), and a cap pass.

4.1 Root Pass Dynamics

The root pass utilized the Laser Technology in its most concentrated form. We used a “keyhole” welding mode to achieve full penetration. The Laser Welding Cobot was set to a travel speed of 1.2 meters per minute. The challenge here was the gas coverage. Unlike TIG, the laser moves so fast that standard shielding nozzles are insufficient.

4.2 Fill and Cap Passes

For the second and third passes, we introduced an automated cold-wire feeder integrated into the Laser Welding Cobot. Using Ti-6Al-4V ELI (Extra Low Interstitials) filler wire, we increased the wobble width to 3.0mm. This ensured that the laser energy was distributed across the bevel faces, preventing the “tunneling” defects common when Laser Technology is misapplied in deep grooves.

5.0 Atmospheric Management in the Warsaw Facility

Titanium welding in an industrial environment like Warsaw, which can experience significant humidity fluctuations, requires a strict “Argon Envelope.” We developed a custom trailing shield mounted directly to the Laser Welding Cobot head.

This shield provides a secondary and tertiary flow of high-purity (99.999%) Argon. While the Laser Technology provides the heat, the cobot ensures the shield remains perfectly oriented over the cooling weld bead. During the Warsaw trials, any deviation in the cobot’s angle of more than 5 degrees resulted in “straw-colored” oxidation, indicating a breakdown in the gas shield. We refined the cobot’s pathing to ensure the trailing shield remained perpendicular to the weld vector at all times.

6.0 Synergy Analysis: Why the Cobot + Laser Combo Works

In the Warsaw field test, the primary synergy observed was between the Laser Technology’s power density and the Laser Welding Cobot’s spatial accuracy.

1. Reduced Heat Input: Because the cobot can travel at 15-20mm/s (far faster than a manual welder), the total heat input into the Titanium is reduced by approximately 60%. This preserves the alpha-beta grain structure of the base metal.
2. Consistent Bead Profile: In multi-pass Titanium welding, the surface of the previous pass must be pristine. The Laser Welding Cobot produces a consistent, low-profile bead that requires zero grinding between passes, maintaining the integrity of the gas shield for the subsequent layer.
3. Real-time Parameter Modulation: The Laser Technology allows for high-frequency pulsing. By syncing this pulsing with the cobot’s movement, we achieved a “stirring” effect in the molten pool, which effectively floated out impurities and reduced porosity in the final NDT (Non-Destructive Testing) phase.

7.0 Lessons Learned and Engineering Recommendations

7.1 Thermal Accumulation

The most significant lesson learned in the Warsaw workshop was the impact of thermal accumulation during multi-pass Titanium welding. Even with the precision of a Laser Welding Cobot, the base material’s temperature rose steadily over three passes. We had to implement a “cooling trigger” in the cobot code, where an infrared sensor would prevent the second pass until the interpass temperature dropped below 150°C. Ignoring this leads to a widened HAZ and potential embrittlement.

7.2 Wire Feed Synchronization

The integration of the wire feeder with the Laser Technology is the most common failure point. If the wire enters the laser beam too high, it vaporizes; too low, and it “pokes” the weld pool. The Laser Welding Cobot must be calibrated daily to ensure the wire-to-TCP (Tool Center Point) relationship is within a 0.1mm tolerance. In Warsaw, we implemented a routine “Check-Point” station where the cobot runs a self-calibration script before every shift.

7.3 Optical Maintenance

Warsaw’s industrial grid can occasionally have voltage fluctuations. We found that the protective windows in the laser head were prone to “pitting” when the cooling system’s chiller fluctuated. Ensuring a stabilized power supply for the Laser Technology source is as critical as the welding parameters themselves. We installed a dedicated UPS for the laser source to prevent beam instability during the multi-pass cycles.

8.0 Conclusion

The transition to a Laser Welding Cobot for Titanium welding in the Warsaw sector has proven highly successful. We observed a 400% increase in productivity compared to manual GTAW, with a 98% first-pass yield under X-ray inspection. The success of this implementation lies not just in the hardware, but in the sophisticated application of Laser Technology—specifically using wobble parameters and precise atmospheric shielding carried by the cobot. For future multi-pass applications, the focus should remain on interpass temperature control and the rigid calibration of the wire-feed delivery system.

Report Compiled By:
Senior Welding Engineer
Field Operations – Warsaw Division