Engineering Review: Double Pulse 6-Axis Collaborative Welder – Quebec, Canada

Field Report: Deployment of Double Pulse 6-Axis Collaborative Welder in Quebec Heavy Fabrication

1.0 Introduction and Site Context

This report details the technical deployment and operational assessment of a 6-Axis Collaborative Welder integrated into a medium-to-heavy fabrication facility located in the Chaudière-Appalaches region of Quebec. The facility primarily handles CSA G40.21 44W carbon steel welding for structural components and heavy industrial racking.

The objective of this deployment was to transition from manual GMAW (Gas Metal Arc Welding) to a semi-contained Automated Welding workflow. Given the current labor scarcity in rural Quebec, the focus was not on replacing personnel but on augmenting the existing workforce by delegating high-volume, repetitive fillet and groove welds to the collaborative system. This report evaluates the synergy between the 6-axis kinematics and the double pulse power source, specifically under the environmental conditions of a Canadian winter workshop where ambient temperature and humidity fluctuations often impact gas shielding performance.

2.0 Hardware Configuration: The 6-Axis Collaborative Welder

The core of the system is a 10kg-payload 6-Axis Collaborative Welder mounted on a mobile, high-rigidity weld table. Unlike traditional industrial robots, this 6-axis cobot utilizes force-torque sensors at each joint, allowing for “lead-through” programming. This is critical for carbon steel welding in a job-shop environment where part geometry changes weekly.

2.1 Kinematic Advantages in Complex Geometry

The 6-axis configuration is non-negotiable for the types of structural nodes processed at this site. We encountered several “wrap-around” weldments where a 4 or 5-axis system would have hit a singularity or suffered from cable interference. The sixth axis allows for the maintenance of a consistent torch angle (15-degree lead) even when navigating circular tubular intersections on the carbon steel frames. During the commissioning phase, we calibrated the Tool Center Point (TCP) to within 0.05mm, ensuring that even as the robot articulated through its full reach, the wire stayed centered in the root of the joint.

3.0 Transitioning to Automated Welding in a Manual Environment

The leap to automated welding in this Quebec facility required more than just hardware; it required a shift in upstream tolerances. Manual welders are adept at compensating for poor fit-up. A robot, even a collaborative one, is only as good as the gap it is fed.

3.1 Synergic Integration

We implemented a synergic communication protocol between the 6-axis controller and the double pulse power source. In this automated welding setup, the robot’s travel speed is dynamically linked to the wire feed speed. In the Quebec shop, we observed that by automating the travel speed at a consistent 350mm/min on 1/4″ plate, we reduced the Heat Affected Zone (HAZ) by 22% compared to manual operators who tended to “weave” excessively, over-depositing metal and risking burn-through.

3.2 The Human-Machine Interface (HMI)

The “collaborative” aspect was tested by allowing senior welders to refine the paths. We found that the most successful automated welding sequences were those programmed by the welders themselves, using the cobot’s hand-guiding feature. This bypassed the need for complex G-code knowledge and allowed the shop to remain agile.

4.0 Carbon Steel Welding: Double Pulse Performance

The primary material processed was CSA G40.21 44W (Carbon Steel). Historically, carbon steel welding with standard MIG results in significant spatter, requiring hours of post-weld grinding. By utilizing a Double Pulse waveform on the 6-Axis Collaborative Welder, we achieved a “TIG-like” aesthetic with MIG productivity.

4.1 Metallurgical Benefits of Double Pulse

The Double Pulse process alternates between high and low energy states. This serves two purposes in carbon steel welding:

• Grain Refinement: The pulsing action agitates the weld pool, breaking up dendrite growth and leading to a finer grain structure in the solidified weld metal.
• Spatter Mitigation: By precisely controlling the droplet detachment, we virtually eliminated spatter. In the Quebec facility, this reduced “non-value-added” time (grinding) by 40 minutes per frame.

4.2 Gap Bridging and Heat Control

One of the “lessons learned” during the January field test involved heat dissipation. In the colder shop environment, the carbon steel acts as a massive heat sink. The 6-Axis Collaborative Welder was programmed to use a higher background current for the first 20mm of the weld to ensure proper penetration (hot start), before settling into the double pulse rhythm. This eliminated the “cold start” defects commonly found in automated welding on heavy plate.

5.0 The Quebec Factor: Environmental and Standard Compliance

Operating in Quebec introduces specific variables, notably compliance with CSA W59 (Welded Steel Construction). The automated welding procedures were qualified to these standards.

5.1 Humidity and Gas Shielding

Large temperature swings in Quebec shops can lead to condensation on gas lines. We integrated a secondary gas dryer to the 90/10 Argon/CO2 mix used for the carbon steel welding. The 6-Axis Collaborative Welder was fitted with an oversized gas shroud to maintain laminar flow, as the shop’s HVAC system created significant drafts that previously caused porosity in manual welds.

6.0 Lessons Learned and Technical Observations

After 500 hours of arc-on time, several technical realities emerged that differ from the marketing literature:

6.1 Cable Management is the Seventh Axis

While the robot has 6 axes, the torch lead behaves like a seventh, unpredictable axis. We learned that the “collaborative” nature of the robot means it is often moved around the shop. If the cable dress pack is not tensioned correctly, the 6-Axis Collaborative Welder will experience torque spikes and “collision” errors. We switched to a spring-loaded overhead balancer to keep the leads clear of the cobot’s joints.

6.2 The “Fit-Up” Paradox

The biggest hurdle to automated welding wasn’t the robot; it was the saw. We found that the carbon steel welding plates were being cut with a tolerance of +/- 2mm. While a human can bridge a 2mm gap, the cobot requires +/- 0.5mm for consistent root pass penetration. We had to upgrade the shop’s cutting station to match the robot’s precision. Automation is a chain; the robot is just one link.

6.3 Pulse Frequency Tuning

We initially set the double pulse frequency too high (4Hz). This resulted in a very narrow bead profile that was susceptible to undercut on the vertical member. Dropping the secondary pulse to 1.8Hz widened the puddle, allowing better wetting of the toes on the carbon steel. This “sweet spot” was critical for meeting CWB (Canadian Welding Bureau) visual inspection criteria.

7.0 Conclusion: Synergy in the Workshop

The integration of the 6-Axis Collaborative Welder into the Quebec facility has successfully proven that automated welding is viable for small-to-medium enterprises. The synergy lies in the cobot’s ability to handle the “dirty, dull, and dangerous” aspects of carbon steel welding, while the human operator focuses on fit-up and quality control.

The Double Pulse technology effectively bridged the gap between speed and quality, producing welds that required zero post-weld cleanup. For future deployments in similar Canadian environments, emphasis must be placed on upstream part precision and climate-controlled gas delivery systems. The 6-axis cobot is no longer a futuristic luxury; in the context of the current labor market, it is a structural necessity for Quebec’s manufacturing resilience.

Report Prepared By:
Senior Welding Engineer, Heavy Fab Division
Date: October 2023