Engineering Review: Multi-pass Welding MIG/MAG Welding Robot – Bengaluru, India

Field Report: Implementing Multi-pass Automation for Tool Steel Repair

Project Overview: Bengaluru Industrial Hub

This report details the commissioning and optimization of a high-precision MIG/MAG Welding Robot system at a Tier-1 tool and die facility in Bengaluru, India. The primary objective was to transition from manual GTAW (TIG) to an automated multi-pass MIG/MAG process for the reclamation of high-volume tool steel components. In the context of Bengaluru’s specific manufacturing climate—characterized by high ambient humidity during the monsoon and intermittent voltage fluctuations in the Peenya industrial grid—the deployment required a robust integration of hardware and software-driven Arc Welding Solutions.

The core challenge involved Tool Steel welding, specifically H13 and D2 grades, which are notorious for their sensitivity to thermal cycles. Achieving a metallurgical bond without compromising the base metal’s hardness or inducing cold cracking required a radical shift in how we approach heat input and bead sequencing.

The Technical Synergy: Robot and Arc Control

Defining the MIG/MAG Welding Robot Configuration

The cell utilizes a 6-axis industrial arm integrated with a 500A pulse-capable power source. While the robot provides the spatial precision (±0.05mm repeatability), the success of the operation hinges on the Arc Welding Solutions suite. These solutions include adaptive arc length control and through-arc seam tracking (TAST), which are critical for multi-pass applications where each successive layer alters the joint geometry.

In Bengaluru, where the technical skill gap for high-end robotic programming can be a bottleneck, we implemented a “Master Torch” calibration protocol. This ensured that the Tool Center Point (TCP) remained consistent across three shifts, regardless of minor collisions or nozzle changes. The MIG/MAG Welding Robot was programmed using a modular code structure, allowing operators to adjust the number of passes based on real-time groove measurements without rewriting the core logic.

Advanced Arc Welding Solutions for Tool Steel

Standard MIG welding is often too “hot” for sensitive tool steels. To combat this, we deployed Arc Welding Solutions featuring modified short-circuit transfer and high-frequency pulse regimes. This synergy allowed us to maintain a stable arc at lower mean currents, significantly reducing the Heat Affected Zone (HAZ). By using a specialized metal-cored wire rather than a solid wire, we achieved better wetting of the sidewalls, which is a common failure point in manual Tool Steel welding.

Metallurgical Challenges in Tool Steel Welding

Preheat and Interpass Temperature Management

Tool steel is unforgiving. During our first week in the Bengaluru facility, we observed longitudinal cracking in the center of the weld bead. The root cause was identified as insufficient interpass temperature maintenance. The MIG/MAG Welding Robot can weld much faster than a human, which paradoxically leads to rapid cooling if the sequence isn’t managed.

We integrated an infrared pyrometer into the Arc Welding Solutions feedback loop. The robot was programmed to “hold” or perform a low-amperage “simulated pass” to keep the die at 250°C if the temperature dropped below the martensite start (Ms) temperature. This level of thermal management is practically impossible to achieve manually over an 8-hour shift.

Multi-pass Bead Sequencing Strategy

For a 20mm deep groove in an H13 die, we utilized a “split-bead” technique rather than wide weaving. Weaving increases the time the arc dwells over a single spot, which destroys the grain structure of the tool steel.

Layer 1: The Buffer Layer

Using a 309L stainless steel or a high-nickel filler, we applied a buffer layer. The MIG/MAG Welding Robot was set to a spray-transfer mode with a travel speed of 450mm/min. This layer acts as a “shock absorber” to prevent carbon migration from the tool steel into the subsequent hard-facing layers.

Layers 2-10: The Build-up

Using an H13-compatible wire, we moved to a pulsed-MAG process. The Arc Welding Solutions software automatically adjusted the wire feed speed to compensate for the narrowing groove. Each pass overlapped the previous by 40-50%, ensuring a flat surface for the subsequent layer.

Field Observations and Lessons Learned

Environmental Factors in Bengaluru

One of the primary “lessons learned” during this deployment was the impact of the local environment on gas shielding. The Bengaluru workshop had large open shutters for ventilation. High cross-winds were disrupting the 80/20 Argon/CO2 shield gas, leading to porosity. We had to increase the flow rate to 22L/min and implement a localized “tenting” solution around the robotic cell.

Furthermore, the power quality in the industrial estate necessitated the installation of a dedicated servo-stabilizer for the Arc Welding Solutions controller. Even a 5% voltage drop caused the MIG/MAG Welding Robot to experience arc-outages, which, during a multi-pass run, creates a significant defect that requires manual grinding to fix.

Optimizing Wire Delivery

For Tool Steel welding, wire cleanliness is paramount. We found that the dust in the industrial area was accumulating on the wire spools, leading to liner friction and “bird-nesting” at the drive rolls. We switched to enclosed wire drums and felt-wiper attachments. This minor change reduced our downtime by 15% and ensured the constant voltage (CV) parameters remained stable.

Data-Driven Quality Control

Monitoring Heat Input

The integrated Arc Welding Solutions allowed us to log the heat input for every single pass. The formula used was:

Q = (V x I x 60) / (v x 1000) x Efficiency Factor

For the H13 tool steel, we capped the heat input at 1.2 kJ/mm. If the robot’s sensors detected a deviation—usually due to a worn contact tip increasing resistance—the system would trigger an alarm and pause the cycle. This level of granularity in data collection is what separates modern robotic integration from legacy automated systems.

Post-Weld Heat Treatment (PWHT)

In the Bengaluru site, we established a strict protocol where the welded dies were moved immediately from the robot platen to a tempering furnace. The MIG/MAG Welding Robot would signal the operator via a stack light the moment the final pass was completed. This minimized the time the tool steel spent in the brittle untempered martensite phase.

Conclusion: The Future of Automation in Indian Tool Rooms

The implementation of the MIG/MAG Welding Robot at this facility has reduced the repair cycle time for tool steel dies from 48 hours to just 12 hours. However, the hardware alone was not the solution. The synergy provided by advanced Arc Welding Solutions—specifically the ability to control the pulse shape and monitor thermal cycles—was the deciding factor in handling the complexities of Tool Steel welding.

For engineers looking to replicate this in other Indian industrial hubs, the focus must remain on the “boring” details: gas purity, stable power, and rigorous preheat protocols. Automation does not eliminate the need for welding metallurgy knowledge; it simply demands it be programmed into the system rather than applied by hand. The success in Bengaluru proves that with the right parameters, the MIG/MAG process can exceed the quality of TIG for even the most demanding tool-room applications.

End of Report.
Senior Welding Engineer, Bengaluru Site.