Engineering Review: Multi-pass Welding Cobot Welding Machine – Michigan, USA

Field Evaluation Report: Multi-pass Implementation of Collaborative Robotics in Michigan Heavy Fabrication

1.0 Executive Summary of Field Operations

This report details the technical deployment and performance analysis of a high-payload Cobot Welding Machine within a Tier-1 automotive and aerospace supplier facility located in Grand Rapids, Michigan. The primary objective was to transition a series of thick-gauge Aluminum Alloy welding applications from manual Gas Metal Arc Welding (GMAW-P) to an automated framework utilizing Collaborative Robotics.

The Michigan manufacturing landscape is currently facing a dual challenge: a critical shortage of Level 3 certified welders and an increasing demand for structural aluminum components that require stringent multi-pass bead profiles. Unlike fixed industrial automation, the synergy between the operator and the collaborative system allowed for rapid “teach-by-touch” programming, which proved essential for the variable tolerances found in heavy-plate aluminum weldments.

2.0 The Synergy of Collaborative Robotics and the Cobot Welding Machine

In the context of a Michigan workshop, the term “Collaborative Robotics” is often misunderstood as simply a “safe” robot. In practice, the synergy is found in the distribution of labor. The Cobot Welding Machine handles the high-frequency oscillation and constant travel speeds required for consistent penetration, while the human welder manages the environmental variables—such as cleaning the oxide layer and adjusting for part fit-up discrepancies.

2.1 Integration with Existing Workflow

Traditional robotic cells require extensive floor space and light curtains. In our Michigan field site, floor space was at a premium. By utilizing a Cobot Welding Machine, we eliminated the need for bulky physical guarding. This allowed the lead welder to stand adjacent to the arc (with proper PPE) to monitor the puddle in real-time. This proximity is vital when dealing with Aluminum Alloy welding, where the narrow window between proper fusion and burn-through requires immediate intervention.

3.0 Technical Challenges in Multi-pass Aluminum Alloy Welding

Aluminum presents a unique set of variables: high thermal conductivity, a low melting point, and a tenacious surface oxide (Al2O3). When performing multi-pass welds on 12.7mm (1/2 inch) 6061-T6 plates, heat management is the primary hurdle.

3.1 Heat Input and Interpass Temperature

For the Michigan field trial, we established a strict interpass temperature limit of 250°F (121°C). Excess heat in 6061-series Aluminum Alloy welding leads to a significant reduction in the Heat Affected Zone (HAZ) strength. The Cobot Welding Machine was programmed with a “cool-down” dwell timer between the root, fill, and cap passes. Because we were using Collaborative Robotics, the operator could use a digital pyrometer to verify temperatures and then simply tap the cobot’s wrist to resume the next pass, rather than returning to a remote HMI (Human Machine Interface).

3.2 Wire Feeding and Torch Geometry

We utilized 4043 filler wire (1.2mm diameter). Aluminum wire is notoriously soft, leading to “bird-nesting” in standard feeders. The Cobot Welding Machine was outfitted with a push-pull torch system specifically calibrated for the cobot’s payload capacity. A major lesson learned: the lead-lag angle of the torch must be adjusted by 5 degrees between the root and the cap pass to ensure adequate gas coverage and to prevent porosity, which is a common failure point in Michigan’s humid summer months.

4.0 Programming for Multi-pass Geometry

The complexity of multi-pass Aluminum Alloy welding lies in the bead sequencing. We utilized a three-pass strategy for the 1F and 2F fillet positions:

1. The Root Pass: Focused on 100% penetration at the vertex. The cobot used a spray-transfer mode with a slight weave (1.5mm amplitude).
2. The Fill Pass: Offset by 2.0mm vertically and horizontally. This pass required a faster travel speed to prevent overheating the root.
3. The Cap Pass: A wider weave (3.0mm) to ensure a smooth transition to the base metal, minimizing stress risers.

The advantage of Collaborative Robotics here was the “Through-Arc Seam Tracking” (TAST). While the cobot followed the programmed path, the software made micro-adjustments based on voltage fluctuations to compensate for the thermal expansion of the aluminum plate during the welding process.

5.0 Performance Metrics and Michigan Case Study Results

Over a 30-day period, the Cobot Welding Machine was pitted against manual production. The results were quantifiable:

• Arc-on Time: Manual welders averaged 22% arc-on time due to fatigue and heat exposure. The cobot maintained a 65% arc-on time.
• Defect Rate: Porosity and undercut were reduced by 85%. The consistency of the Collaborative Robotics motion eliminated the human “tremor” that often causes inconsistencies in long-path Aluminum Alloy welding.
• Gas Consumption: While the flow rate remained 35 CFH (Argon), total gas waste was reduced because the cobot’s pre-flow and post-flow were timed to the millisecond, unlike manual triggers.

6.0 Lessons Learned: The “Michigan” Specifics

Field engineering in the Midwest requires acknowledging environmental impacts on Collaborative Robotics. During the trial, we identified three critical areas for improvement:

6.1 Humidity and Hydrogen Porosity

Michigan’s high humidity levels in July led to moisture condensation on the aluminum plates stored in the unconditioned warehouse. This moisture dissociates into hydrogen in the arc, causing porosity.

Lesson: We implemented a mandatory pre-heat of 150°F using an induction heater before the Cobot Welding Machine commenced the root pass. This “drove off” the moisture and improved bead wetting.

6.2 Grounding and High-Frequency Interference

The electronic sensors within the Collaborative Robotics arm are sensitive to electromagnetic interference (EMI). In several instances, the high-frequency start of an adjacent TIG station caused the cobot to trigger an emergency stop.

Lesson: Dedicated grounding blocks were installed for the Cobot Welding Machine, and shielded cabling was utilized for all peripheral sensors to isolate the collaborative logic from the shop floor “noise.”

6.3 Wire Shaving and Liner Clogging

The tight radius of the cobot’s cable management system during multi-axis maneuvers caused the aluminum wire to shave against the liner.

Lesson: We switched to a graphite-infused Teflon liner and replaced the standard drive rolls with U-groove polished rolls. This is a non-negotiable requirement for Aluminum Alloy welding in an automated environment.

7.0 Conclusion

The implementation of the Cobot Welding Machine at our Michigan site has proven that Collaborative Robotics is no longer a “future” technology—it is a current necessity for high-quality Aluminum Alloy welding. By allowing the machine to handle the repetitive, high-heat multi-pass sequences, we have empowered our senior welders to focus on weld procedure development and quality assurance. The ROI for this system, based on the reduction in rework alone, is estimated at 14 months. Moving forward, we recommend the standardization of cobot-integrated push-pull systems across all Michigan-based aluminum fabrication lines.

Report End.