Multi-pass Welding 6-Axis Collaborative Welder – London, UK

Field Evaluation: Multi-pass Deployment of 6-Axis Collaborative Welder in Structural Steel Fabrications

This report summarizes the technical deployment and performance metrics of a 6-Axis Collaborative Welder integrated into a high-capacity structural steel workshop in East London, UK. The primary objective was to transition high-volume, multi-pass heavy plate joints from manual processes to Automated Welding to address the dual challenges of local skilled labor shortages and the stringent quality requirements of London’s high-rise construction sector.

Project Overview and Site Constraints

The site environment presented typical London constraints: limited floor space and a high-density workflow. Traditional industrial robotics, requiring expansive safety cages and light curtains, were deemed unfeasible. The decision to implement a 6-Axis Collaborative Welder was driven by the need for a footprint-efficient solution that allows human operators to work alongside the machine. Our focus was on structural steel welding involving S355JR plate thicknesses ranging from 15mm to 40mm, requiring consistent multi-pass fillets and butt welds.

Synergy Between 6-Axis Collaborative Welder and Automated Welding Logic

The integration of a 6-axis system provides the necessary degrees of freedom to replicate the complex torch angles required for multi-pass structural steel welding. Unlike 3-axis or 4-axis gantry systems, the 6-axis articulation allows the cobot to manage torch orientation in 3D space, which is critical for maintaining consistent stick-out (CTWD) and work angles during the fill and cap passes of a deep groove weld.

Transitioning from Manual to Automated Multi-pass Sequences

In a manual environment, a welder adjusts for heat build-up and joint deviation intuitively. To achieve successful automated welding, we had to digitize this intuition. We utilized a “Lead-through-teach” method where the senior welder guides the 6-axis arm to define the root pass. The software then calculates the offsets for the subsequent hot pass, fill passes, and final capping passes.

Technical Parameter Calibration

• Process: GMAW (Gas Metal Arc Welding) utilizing a pulsed spray transfer mode.
• Consumables: 1.2mm G3Si1 wire with an M21 shielding gas (Argon/CO2 mix).
• Joint Configuration: 60-degree V-groove, 3mm root face.
• Travel Speed: Optimized at 350mm/min for fill passes to ensure adequate wetting and avoid cold-lap.

The London Workshop Context: Why Collaboration Matters

In many London-based fabrication shops, the workflow is erratic. We cannot afford the downtime associated with reprogramming a traditional robot for every new beam configuration. The 6-Axis Collaborative Welder thrives here because of its agility. An operator can tacks-weld a column, wheel the cobot into position, and initiate the automated welding sequence within minutes. The synergy lies in the cobot handling the high-arc-time heavy lifting while the human operator prepares the next assembly.

Lessons Learned: Structural Steel Welding Performance

1. Management of Interpass Temperatures

One of the primary ‘lessons learned’ during the London field test was the machine’s indifference to heat. While a manual welder might naturally slow down as the plate reaches 250°C, the automated welding system continues at a programmed pace. We found that without strict interpass temperature monitoring, the Heat Affected Zone (HAZ) in the S355 steel expanded beyond the limits of our Weld Procedure Specification (WPS). We implemented a “dwell timer” in the cobot’s logic, allowing the steel to cool to 200°C between passes, ensuring grain structure integrity.

2. The “Path Deviation” Challenge

Even in high-quality structural steel welding, plate distortion is inevitable. During a 12-pass weld, the plate moves. We found that a static program would eventually result in the wire hitting the sidewall. The solution was the integration of “Through-Arc Seam Tracking” (TAST). By monitoring the current fluctuations, the 6-Axis Collaborative Welder adjusts its path in real-time, compensating for the thermal expansion of the London-sourced heavy sections.

3. Consistency in the Capping Pass

The aesthetic and structural quality of the capping pass is a major KPI for UK structural inspectors. Manual welding often shows “starts and stops” which are potential failure points. The cobot’s ability to execute a continuous 2-meter cap pass with a consistent weave pattern resulted in a 98% first-time pass rate during Ultrasonic Testing (UT). This significantly reduced the “rework” overhead that often plagues manual London fabrication contracts.

Impact on Production Efficiency and Labor

The introduction of automated welding via cobots has shifted the role of our London-based welders from manual laborers to “Cell Technicians.” This is a critical evolution. A single technician can now oversee two 6-Axis Collaborative Welders, effectively tripling their arc-on time.

Comparative Metrics: Manual vs. Automated

Practical Rigging and Portability

A specific lesson from the East London workshop was the necessity of a “Mobile Base.” Given the size of structural beams (UB and UC sections), moving the workpiece to the robot is often impossible. Mounting the 6-Axis Collaborative Welder on a heavy-duty, locking-caster base allowed us to move the automated welding unit to the beam. This “man-to-goods” to “machine-to-goods” shift saved approximately 4 hours of crane time per week.

Final Technical Recommendations

For firms looking to integrate a 6-Axis Collaborative Welder into structural steel welding operations in the UK, the following technical prerequisites are recommended:

Standardize Joint Preparation

Automation is only as good as the fit-up. While the 6-axis system can track a seam, it cannot “fill a hole” caused by a poor plasma cut. We transitioned to CNC-cut bevels to ensure the automated welding parameters remained within their tolerance band.

Invest in Operator Upskilling

The “collaborative” nature of the welder requires the operator to understand both the metallurgy of structural steel welding and the basics of robotic coordinate systems. The learning curve is approximately two weeks, but the ROI is realized within three months through sheer volume of deposited metal.

Prioritize Power Supply Stability

In many older London industrial estates, power fluctuations are common. A 6-Axis Collaborative Welder is a sensitive electronic instrument. We recommend dedicated power conditioning to prevent “control-loop errors” during long-duration automated welding cycles.

Conclusion

The field deployment in London confirms that the 6-Axis Collaborative Welder is no longer a “light manufacturing” tool. In the realm of structural steel welding, it provides a high-fidelity, high-duty-cycle solution that fits within the tight spatial constraints of urban workshops. By leveraging automated welding for multi-pass joints, fabricators can achieve a level of consistency and throughput that manual processes simply cannot match in the current economic climate.