Engineering Review: Double Pulse Laser Welding Cobot – Turin, Italy

Field Report: Implementation of Double Pulse Laser Welding Cobots in Turin Heavy Industry

This report details the technical deployment and operational validation of Double Pulse Laser Technology integrated with collaborative robotics at a Tier-1 structural steel facility in Turin, Italy. The objective was to transition from traditional Gas Metal Arc Welding (GMAW) to a high-efficiency Laser Welding Cobot system specifically optimized for Thick Plate Steel welding. As of the end of Q3, the system has logged 450 hours of active torch time, providing sufficient data to evaluate thermal dynamics, weld integrity, and the synergy between automated precision and human-collaborative flexibility.

The Evolution of Laser Technology in the Turin Workshop

Turin has long been the epicenter of Italian mechanical engineering. However, the local industry has historically faced a bottleneck: the high heat input required for thick-gauge structural components leads to significant plate distortion. By introducing advanced Laser Technology, we have shifted the paradigm from bulk heating to precision energy delivery. The core of this installation is a 6kW Ytterbium fiber laser source, modulated through a double-pulse frequency controller.

Synergy Between Laser Technology and Collaborative Systems

The integration of a Laser Welding Cobot represents a departure from the “black box” automation of the past. In the Turin facility, space is at a premium and the production mix is high-variety, low-volume. Traditional industrial robots require extensive floor space for safety light curtains and physical barriers. The cobot, equipped with high-sensitivity torque sensors and a Class 4 laser safety enclosure, allows our senior welders to work in close proximity to the setup phase, moving the arm via lead-through programming.

The synergy here is clear: Laser Technology provides the raw power and concentrated energy density, while the cobot provides the repeatable path accuracy (±0.03mm) that manual laser welding cannot achieve over long seams. This is particularly critical in Turin’s automotive and heavy machinery sectors, where aesthetic finish must meet structural rigidity.

Technical Deep Dive: Thick Plate Steel Welding Applications

The primary challenge in this field application was Thick Plate Steel welding, specifically S355JR grade plates ranging from 8mm to 12mm in thickness. Conventional single-pulse laser welding often results in a narrow “keyhole” that is prone to solidification cracking or lack of fusion at the root when dealing with these thicknesses.

The Double Pulse Modulation Strategy

To overcome the limitations of standard laser output, we implemented a Double Pulse regime. This involves modulating the laser power between a high-peak intensity (for deep keyhole penetration) and a lower-base intensity (to maintain the melt pool and allow for degassing).

• Peak Pulse: Focused on achieving the necessary depth in 10mm V-groove preparations.
• Base Pulse: Controls the cooling rate, effectively “stirring” the melt pool to refine grain structure and reduce porosity.

In our Turin test beds, this frequency modulation reduced the Heat Affected Zone (HAZ) by 40% compared to traditional spray-transfer GMAW. For Thick Plate Steel welding, this reduction in thermal energy is the difference between a flat workpiece and a warped plate requiring secondary hydraulic straightening.

Overcoming Fit-up Tolerances with Laser Technology

One of the “lessons learned” during the first month in Turin was the intolerance of Laser Technology to poor joint fit-up. Unlike arc welding, which can bridge 2-3mm gaps with ease, a standard laser beam will simply pass through a gap. We solved this by integrating a “wobble” head onto the Laser Welding Cobot. By oscillating the beam in a circular or “figure-8” pattern at 150Hz, we artificially widened the melt pool, allowing the system to bridge gaps up to 1.2mm in 12mm plates without sacrificing structural integrity.

Field Observations and Operational Lessons

The transition to a Laser Welding Cobot environment required a shift in the workshop’s technical culture. In Turin, the “master welder” is a respected figure. Initially, there was skepticism regarding whether a fiber laser could match the “depth” of a traditional arc.

Lesson 1: Shielding Gas Dynamics

Early runs on Thick Plate Steel welding showed intermittent oxidation. We discovered that at the higher travel speeds of the cobot (up to 1.5m/min), the trailing edge of the weld was losing its gas shield before it had cooled sufficiently. We redesigned the nozzle on the Laser Welding Cobot to include a “trailing shoe” gas manifold. Using a 70/30 Helium-Argon mix proved superior for penetration in thick sections, though we eventually settled on pure Argon for cost-efficiency once the double-pulse parameters were optimized.

Lesson 2: Wire Feed Synchronization

For plates over 6mm, autogenous welding (no filler) is rarely sufficient to meet ISO 5817 Level B requirements. We integrated a cold-wire feeder synchronized directly with the cobot’s controller. The logic ensures that wire feed speed (WFS) ramps up in a linear relationship with the laser’s power modulation. This ensures that the reinforcement height remains consistent even as the cobot rounds the corners of a complex structural frame.

Lesson 3: Thermal Loading of the Cobot Arm

While the Laser Technology itself is efficient, the reflected radiation from Thick Plate Steel welding is significant. We observed that the cobot’s wrist sensors were reaching thermal limits during continuous 20-minute runs. We implemented localized heat shielding and increased the air-cooling flow to the laser head mounting plate to maintain calibration accuracy over long shifts.

Quantitative Results from the Turin Implementation

After three months of continuous operation, the data yields the following improvements over the previous manual GMAW process:

1. Productivity Metrics

The Laser Welding Cobot has increased linear meter output by 300%. While a manual welder handles 10mm steel at roughly 0.3m/min, the laser system consistently hits 1.0m/min to 1.2m/min with full penetration. This has cleared a massive backlog in the Turin facility’s structural assembly line.

2. Consumable Reduction

Wire consumption has dropped by 60%. Because the laser focused energy creates a narrower joint preparation (30-degree included angle vs. the traditional 60-degree), significantly less filler metal is required to achieve the same structural rating.

3. Post-Weld Processing

The most significant cost saving has been the elimination of post-weld grinding. The Double Pulse Laser Technology produces a ripple profile that is aesthetically superior and requires only a light wire brush pass before painting/galvanizing.

Safety and Compliance in the Italian Industrial Context

In accordance with Italian health and safety regulations (DLgs 81/08), the installation of the Laser Welding Cobot required a dedicated “Laser Area.” Because we are performing Thick Plate Steel welding, the potential for high-energy diffuse reflections is high. We installed 4kW-rated laser-safe glass viewing windows and interlocked the cobot’s controller with the room’s entry points. The “collaborative” nature of the robot is utilized during setup and “dry-run” path programming, but the actual high-power firing occurs within a fully enclosed, interlocked environment.

Conclusion and Next Steps

The deployment of the Laser Welding Cobot in Turin has proven that Laser Technology is no longer restricted to thin-sheet electronics or automotive body-in-white applications. When combined with Double Pulse modulation, it is a formidable tool for Thick Plate Steel welding.

Our next phase will involve integrating “through-the-lens” seam tracking. Currently, the cobot relies on fixed jigging. By adding real-time optical tracking, we will enable the system to compensate for the slight thermal drift that occurs during the welding of 20-meter long structural beams. For now, the Turin facility stands as a benchmark for how traditional heavy industry can successfully adopt high-energy beam processes without losing the flexibility of human-centered manufacturing.

Report Authored By: Senior Welding Engineer, Turin Field Office
Technical Focus: Fiber Laser Modulation, Cobot Kinematics, Structural Steel Integrity