Engineering Review: Single Pulse 6-Axis Collaborative Welder – Sao Paulo, Brazil

Field Evaluation Report: Single Pulse 6-Axis Collaborative Welder Integration

1. Project Scope and Environmental Context

This report details the field deployment and performance validation of the 6-Axis Collaborative Welder within a heavy-fabrication facility located in the industrial belt of Sao Paulo, Brazil. The primary objective was the transition from manual GMAW (Gas Metal Arc Welding) to Automated Welding for high-volume Structural Steel welding components, specifically ASTM A36 beam attachments and gusset plates.

The Sao Paulo environment presents specific variables that were factored into this deployment. High ambient humidity (often exceeding 75%) and occasional fluctuations in the local industrial power grid required robust secondary filtration for the shielding gas lines and the use of high-tier surge protection for the 6-axis controller. The facility’s goal was to mitigate a localized shortage of certified high-pressure welders by utilizing the collaborative system to augment the existing workforce.

2. Technical Specifications of the 6-Axis Collaborative Welder

The unit deployed is a medium-reach (1300mm) 6-axis arm integrated with a 400A inverter-based power source capable of high-speed pulsed GMAW. Unlike traditional industrial robots, this 6-Axis Collaborative Welder utilizes torque sensors in each joint, allowing for “lead-through” programming. This is critical in a Structural Steel welding context where part geometry can vary slightly due to upstream thermal cutting tolerances.

2.1. Single Pulse Waveform Modulation

We utilized a single pulse schedule to manage heat input on 12.7mm (1/2″) plate. The pulse parameters were tuned to 1.2mm (0.045″) ER70S-6 wire. By modulating the current to peak at 380A and dropping to a background current of 80A, we achieved a stable spray transfer at lower average heat inputs than traditional globular transfer. This reduced the Heat Affected Zone (HAZ) by approximately 15%, a vital metric for maintaining the structural integrity of the base NBR 6109 steel used in the Sao Paulo facility.

3. The Synergy Between Collaborative Hardware and Automated Welding

The primary friction point in Automated Welding has historically been the “setup-to-weld” ratio. In a job-shop environment like the one found in Sao Paulo, traditional automation fails because the programming time exceeds the manual welding time for small batches. The 6-Axis Collaborative Welder eliminates this bottleneck through its kinematic flexibility.

3.1. Kinematic Reach and Torch Orientation

The 6th axis is the differentiator here. When performing Structural Steel welding on complex I-beam assemblies, the ability to maintain a consistent 15-degree push angle while rotating around a vertical stiffener is impossible with 4- or 5-axis systems. During the field test, we observed that the 6-axis freedom allowed the torch to access tight “rat holes” in the structural skeletons that were previously only accessible by manual stick (SMAW) welders. This expands the scope of Automated Welding from simple longitudinal seams to complex, multi-plane joinery.

3.2. Lead-Through Programming in Practice

In the Sao Paulo workshop, we trained manual welders with 10+ years of experience to “teach” the cobot. By physically moving the arm to the start and end points of a fillet weld, the welder inputs the “craft” (torch angle, stand-off distance) into the Automated Welding routine. The synergy here is clear: the human provides the spatial intuition, and the 6-axis arm provides the mechanical consistency (travel speed variance < 0.5%).

4. Structural Steel Welding: Application Deep-Dive

The core of our testing involved 2F (Fillet) and 1G (Flat) positions on heavy structural members. For Structural Steel welding, penetration is non-negotiable. We faced an initial challenge with “cold start” lack of fusion, a common issue in automated cycles on thick plate.

4.1. Addressing Thermal Sink in Heavy Plate

Structural steel acts as a massive heat sink. In the Sao Paulo facility, the ambient temperature of the steel at 07:00 is significantly lower than at 14:00. To counter this, we programmed a “Hot Start” routine into the Automated Welding sequence. For the first 0.8 seconds of the arc, the power source increases wire feed speed and voltage by 15% to establish a fluid puddle immediately. This ensured that the root of the fillet met the AWS D1.1 structural code requirements for fusion.

4.2. Spatter Mitigation and Post-Weld Cleanup

Using a single pulse mode on the 6-Axis Collaborative Welder virtually eliminated spatter on the A36 base material. In manual operations, the shop was spending 20 man-hours per week on post-weld grinding. The automated pulse transition allows for a “one-drop-per-pulse” metal transfer, which keeps the surface clean. This is a significant “lesson learned”: the value of a cobot isn’t just the arc time; it’s the reduction of non-value-added activities like grinding and anti-spatter application.

5. Lessons Learned from the Sao Paulo Field Site

Fieldwork in Brazil provides unique data points that are often missed in laboratory settings. Below are the key engineering takeaways from this deployment.

5.1. Shielding Gas Consistency

We initially saw porosity in the Structural Steel welding beads. Investigation revealed that the high humidity in Sao Paulo was interacting with minor leaks in the gas delivery system, drawing moisture into the Ar/CO2 mix. We replaced standard rubber hoses with braided Teflon lines and moved the gas cylinders closer to the 6-Axis Collaborative Welder to minimize the pressure drop. Lesson: Automated Welding is more sensitive to gas quality than manual welding because the machine cannot “see” the puddle boiling and adjust its technique in real-time.

5.2. Tool Center Point (TCP) Calibration

In a collaborative environment, the arm is often bumped or moved manually. We learned that the TCP must be verified every shift. A 2mm deviation in the torch neck, caused by a minor collision or rough handling, can lead to a complete failure of the weld throat in Structural Steel welding. We implemented a simple “check block” on the welding table where the operator verifies the TCP before starting the morning production run.

5.3. Grounding and EMI

The inverter power sources used for pulsed Automated Welding generate high-frequency EMI. In the Sao Paulo facility, this interfered with the encoder signals of the 6-axis arm, causing “jitter” during long traverses. We solved this by implementing a dedicated common ground for the welding table and the cobot base, separate from the building’s main electrical ground. Engineering note: Never assume factory grounding is sufficient for high-speed pulse automation.

6. Performance Metrics and ROI Analysis

After 30 days of continuous operation, the data shows a marked improvement over manual baselines:

• Arc-On Time: Increased from 22% (manual) to 58% (automated).
• Wire Consumption: Reduced by 12% due to precise control over reinforcement levels (no over-welding).
• Rework Rate: Dropped from 4.5% to 0.8%, primarily due to the elimination of human fatigue on long longitudinal welds.

7. Final Assessment

The integration of the 6-Axis Collaborative Welder in the Sao Paulo structural steel sector is a success, provided the environmental variables (humidity, power stability) are managed. The synergy between Automated Welding and the collaborative “teach-by-hand” interface allows for a rapid deployment cycle that traditional automation cannot match. For Structural Steel welding, the single pulse capability is the optimal middle ground between high deposition rates and manageable heat input. Moving forward, we recommend scaling this solution to the sub-assembly lines, where the 6-axis flexibility can be fully exploited on multi-joint gusseting.

Engineer in Charge: [Senior Welding Engineer]

Location: Sao Paulo, Brazil Site B

Status: Production Ready