Engineering Review: Double Pulse Cobot Welding Machine – Ontario, Canada

Field Evaluation: Implementation of Double Pulse Cobot Welding Systems in Ontario Heavy Fabrication

Executive Summary of On-Site Operations

This report details the technical deployment and performance metrics of Double Pulse Cobot Welding Machines within a high-output structural steel facility located in the Greater Toronto Area (GTA), Ontario. The primary objective was to evaluate the efficacy of Collaborative Robotics in executing multi-pass GMAW-P (Gas Metal Arc Welding – Pulsed) on Thick Plate Steel welding applications, specifically targeting 19mm to 25.4mm (3/4″ to 1″) Grade 350W structural sections.

In the current Ontario landscape, the scarcity of CWB (Canadian Welding Bureau) certified high-level pressure and structural welders has necessitated a shift toward automation. However, traditional industrial robotics often fail the cost-benefit analysis for high-mix, low-volume shops. The Cobot Welding Machine represents a middle ground, offering the precision of CNC control with the flexibility of manual intervention.

1. The Synergy of Collaborative Robotics and the Ontario Workforce

The integration of Collaborative Robotics into the shop floor environment differs fundamentally from legacy “caged” automation. In our Ontario field test, the cobot acted as a “force multiplier” for the lead welder. Unlike traditional systems that require complex PLC programming knowledge, the Cobot Welding Machine utilized lead-through programming (hand-guiding). This allowed our Senior Welders to “teach” the path by physically moving the torch to the start, intermediate, and end points of the thick plate joints.

The synergy is realized through the division of labor: the human welder handles the fit-up, tacking, and complex geometry transitions, while the cobot executes the grueling, high-heat multi-pass fills on long seams. This reduces welder fatigue—a critical factor in Ontario’s aging trade demographic—and ensures that the final “cap” pass meets the aesthetic and structural requirements of CSA W59 standards.

2. Technical Analysis: Thick Plate Steel Welding Challenges

Thick Plate Steel welding presents unique metallurgical challenges, primarily regarding heat input and interpass temperature control. On plates exceeding 12.7mm (1/2″), the risk of cold lap and lack of sidewall fusion increases significantly if travel speeds and arc parameters are inconsistent.

Double Pulse Waveform Advantage

The Cobot Welding Machine utilized in this study featured an advanced Double Pulse (Pulse-on-Pulse) waveform. By oscillating the wire feed speed and current between a high and low state, we achieved several critical outcomes:

• Controlled Heat Input: The “cooling” phase of the double pulse allows the puddle to freeze slightly, preventing the sagging often seen in large-diameter puddle management on thick sections.
• Grain Refinement: The thermal cycling inherent in double pulse technology helps in refining the grain structure within the Heat Affected Zone (HAZ), a vital metric for heavy machinery components used in Northern Ontario’s mining sector.
• Reduced Spatter: Operating in a pulsed spray transfer mode virtually eliminated spatter, reducing post-weld cleanup time by 85% compared to conventional CV (Constant Voltage) MIG.

3. Real-World Application: Multi-Pass Fillet on 25mm Plate

During the field trial, we focused on a T-joint configuration involving 25mm base plates. Standard manual procedures required five to seven passes to reach the specified leg size. Using the Cobot Welding Machine, we optimized the procedure as follows:

The Root Pass (Pass 1)

The root pass required deep penetration into the corner. We configured the Collaborative Robotics system for a high-frequency single pulse to ensure the arc stayed focused at the root. The cobot’s ability to maintain a consistent Contact Tip to Work Distance (CTWD) of 15mm resulted in a 100% success rate in ultrasonic testing (UT) for root fusion.

The Fill and Cap Passes (Passes 2-6)

For the fill passes, we switched to the Double Pulse mode. This created a “stacked-dime” appearance typically associated with TIG welding but at the deposition rates of high-speed GMAW. The Cobot Welding Machine was programmed with a slight weave pattern (2.5mm amplitude, 1.5Hz frequency). This mechanical consistency is impossible for a human welder to maintain over an 8-hour shift, particularly when dealing with the radiant heat emitted by Thick Plate Steel welding.

4. Lessons Learned: Environmental and Technical Constraints

Operating in an Ontario workshop environment revealed several practical “lessons learned” that are often omitted from manufacturer data sheets.

Lesson A: Ambient Temperature and Gas Flow

During the winter months, Ontario shops can experience significant temperature fluctuations. We noted that the shielding gas (90% Argon / 10% CO2) required a heated regulator to prevent “icing” during the high duty cycles the Cobot Welding Machine is capable of. Without consistent gas flow, the double pulse arc stability degraded, leading to porosity in the thick plate starts.

Lesson B: Fixturing Rigidity

While Collaborative Robotics are marketed as flexible, Thick Plate Steel welding induces massive thermal stresses. We found that standard “soft” fixturing was insufficient. The plates would move 1-2mm due to contraction, throwing the cobot’s pre-programmed path off-center. We had to implement “Smart Sensing” or “Touch Sensing” routines where the cobot uses the wire to find the plate location before every weld cycle. This added 10 seconds to the cycle time but eliminated rework.

Lesson C: The “Collaborative” Misconception

A major takeaway is that “collaborative” does not mean “unsupervised.” While the Cobot Welding Machine handles the arc, the technician must monitor the interpass temperature using infrared pyrometers. For our Grade 350W steel, exceeding 250°C interpass temperature led to a drop in yield strength. The cobot doesn’t know the plate is too hot; the human collaborator does.

5. Impact on CWB Certification and Quality Control

In Ontario, adherence to CWB W47.1 is mandatory for structural work. One of the primary advantages of implementing the Cobot Welding Machine was the ease of qualifying the Weld Procedure Specifications (WPS). Because the cobot logs every parameter (voltage, current, travel speed, gas flow) to a digital cloud, the Quality Assurance (QA) department had a complete “birth certificate” for every weld.

This digital traceability is becoming a requirement for Tier 1 infrastructure projects in Toronto and Ottawa. The Collaborative Robotics platform allows for a level of data logging that manual welding simply cannot provide, making the audit process significantly smoother.

6. Economic and Labor Implications for the Ontario Market

The ROI (Return on Investment) for the Cobot Welding Machine in this field test was calculated at 14 months. This was driven by:

1. Arc-on Time: Increase from 25% (manual) to 75% (cobot).
2. Consumable Efficiency: 15% reduction in wire waste due to optimized starts and stops.
3. Labor Allocation: One CWB-certified welder was able to oversee two cobot stations while simultaneously performing fit-up on a third jig.

In the context of the Ontario “Skills Gap,” this technology does not replace the welder; it elevates the welder to a Robot Technician. This shift has proven to increase employee retention, as the physical toll of Thick Plate Steel welding is significantly mitigated.

7. Final Recommendations

For Ontario firms looking to adopt Collaborative Robotics for heavy fabrication, I recommend the following:

• Prioritize Power Source: Ensure the Cobot Welding Machine is paired with a high-duty cycle (100% at 400A) power source capable of sustained double pulse output.
• Invest in Training: Spend the time to train shop-floor welders on the “logic” of the robot, rather than just the “buttons.”
• Focus on Prep: Automated systems are less forgiving of poor fit-up. Precision plasma or laser cutting of thick plates is recommended to maximize the cobot’s efficiency.

Conclusion

The field application of Double Pulse Cobot Welding Machines on Thick Plate Steel welding is no longer a theoretical exercise. In our Ontario-based trial, the technology demonstrated that it could meet the rigorous demands of CWB-regulated structural welding while providing a scalable solution to the skilled labor shortage. The key to success lies not in the machine alone, but in the strategic integration of Collaborative Robotics into a well-managed, human-centric production workflow.

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Report Compiled By:
Senior Welding Engineer, Ontario Field Division
Specializing in Automated Systems & Metallurgical Integrity