Engineering Review: Multi-pass Welding 6-Axis Collaborative Welder – Lyon, France

Field Technical Report: Multi-pass Integration of 6-Axis Collaborative Welder

Site Location: Lyon, France – Heavy Industrial Fabrication Zone

1. Introduction and Project Objective

The objective of this field deployment in Lyon was to transition a critical line of heavy-gauge copper components from manual TIG (Tungsten Inert Gas) to a semi-autonomous GMAW (Gas Metal Arc Welding) process. Specifically, we focused on the integration of a 6-Axis Collaborative Welder to handle multi-pass requirements on high-purity copper busbars and heat exchange plates.

The challenge with Copper Components welding is the material’s extreme thermal conductivity (approx. 400 W/m·K). In a manual environment, the heat dissipation requires such high amperage that operator fatigue and inconsistent penetration are inevitable. By implementing Automated Welding through a collaborative platform, we aimed to standardize heat input and maintain travel speeds that a human operator cannot consistently achieve over a 10-hour shift.

2. Hardware Configuration and Synergy

The system deployed consists of a high-torque 6-Axis Collaborative Welder integrated with a 450A pulsed power source. In the Lyon workshop, space is a premium. Unlike traditional industrial robots that require extensive safety cell fencing, the collaborative nature of this 6-axis arm allowed us to integrate the unit directly into the existing workflow.

The synergy between the 6-Axis Collaborative Welder and Automated Welding logic is realized through the “Lead-Through” programming. For Copper Components welding, the 6th axis is vital for maintaining the torch’s Work Angle and Travel Angle during complex circular interpolations around heat-sink fins. In Lyon, we utilized the 6-axis freedom to maintain a consistent 15-degree push angle, which is essential for managing the molten copper puddle and ensuring proper gas coverage.

3. Technical Deep-Dive: Multi-pass Strategy for Copper

Copper requires a specific multi-pass approach due to the risk of “cold start” defects. Our procedure in Lyon involved three distinct phases:

Root Pass: We utilized a Helium-Argon (70/30) mix. The 6-Axis Collaborative Welder was programmed for a high-travel-speed root pass to prevent burn-through while ensuring full penetration into the root face.
Fill Passes: This is where Automated Welding excels. We programmed a weave pattern (oscillation) with a 2.5mm amplitude. For thick Copper Components welding, the filler metal must be deposited rapidly to stay ahead of the heat sink effect. The 6-axis arm maintained a precise 2.0mm contact-tip-to-work distance (CTWD), which is nearly impossible for a manual welder to maintain at the 350°C preheat temperatures required.
Cap Pass: The final pass focused on aesthetics and minimizing the Heat Affected Zone (HAZ). We reduced the pulse frequency and increased travel speed via the cobot interface.

4. Practical Application in the Lyon Workshop

During the three-week implementation, we observed that the 6-Axis Collaborative Welder reduced our cycle time by 45%. The primary bottleneck in Lyon had been the cooling time between manual passes. With Automated Welding, the thermal profile of the part remained more consistent.

Because we were dealing with Copper Components welding, we had to integrate an external induction preheating system. The collaborative welder’s sensors were calibrated to ignore the electromagnetic interference from the induction coils—a common “field fix” we had to implement on-site. The 6-axis flexibility allowed the torch to navigate around the induction blankets without tripping collision sensors, a task that 4-axis or 5-axis systems struggle with on non-linear joints.

5. Lessons Learned: Thermal Management and Grounding

One of the most significant lessons learned in the Lyon deployment involves the expansion of copper during the weld cycle.
* Lesson 1: Dynamic Offsetting. Copper expands significantly more than steel. We found that a pre-programmed path for Automated Welding would be off by 1.2mm by the third pass due to thermal expansion. We had to implement a “Touch-Sensing” routine before each fill pass. The 6-Axis Collaborative Welder uses the wire tip to find the updated joint position, adjusting the coordinate system in real-time.
* Lesson 2: Grounding Strategy. Copper’s conductivity means that “stray arc” is a constant risk. We had to establish a dual-grounding point on the fixture to ensure the 6-Axis Collaborative Welder control electronics were protected from high-frequency noise generated during the pulsed-spray transfer.

6. Synergy of Automation and Human Skill

The term Automated Welding often implies “operator-less,” but in the context of our Lyon project, the 6-Axis Collaborative Welder acted as a “force multiplier.” The senior welders on site transitioned from holding a torch in a 350°C environment to managing the parameters of the weld. This is critical for Copper Components welding because the operator must still monitor the fluid puddle—copper is notorious for sudden “runaway” if the interpass temperature exceeds 450°C.

The collaborative interface allowed the Lyon team to “teach” the robot the path for a new busbar geometry in under 15 minutes. This flexibility is the core advantage of using a 6-axis cobot over fixed automation; it allows the Lyon plant to handle small-batch, high-complexity copper parts without the overhead of complex PLC programming.

7. Shielding Gas and Porosity Control

In the Lyon field test, porosity was an initial concern. Copper is highly susceptible to hydrogen embrittlement and oxygen contamination.
* Automated Welding allowed us to maintain a consistent gas shroud that manual welding couldn’t match.
* The 6-Axis Collaborative Welder was programmed with a “post-flow” dwell time. After each pass, the arm remains stationary over the crater for 5 seconds, ensuring the copper solidifies under a protective curtain of Argon.
* This precision in Copper Components welding resulted in an X-ray failure rate of less than 1%, down from 12% in the manual baseline.

8. Conclusion and Future Scalability

The implementation of the 6-Axis Collaborative Welder in Lyon has proven that Automated Welding is not just for high-volume automotive steel. For specialized tasks like Copper Components welding, the precision, thermal management, and 6-axis dexterity provide a massive leap in quality and safety.

Future iterations at this site will include integrating a laser profile sensor onto the 6th axis to automate the “fill-to-level” logic in real-time, further reducing the need for manual intervention in multi-pass heavy plate work. The Lyon workshop is now the blueprint for our other European facilities tackling high-conductivity alloy fabrication.

End of Report
Senior Welding Engineer, Field Operations.