Engineering Review: Precision CMT Cobot Welding Machine – Sao Paulo, Brazil

Field Engineering Report: Implementation of Precision CMT Cobot Welding Machine

Site Location: São Bernardo do Campo, Sao Paulo, Brazil

Date: October 24, 2023

Subject: Integration of Collaborative Robotics in Tool Steel Repair and Fabrication

This report summarizes the field deployment and performance validation of the Precision Cold Metal Transfer (CMT) **Cobot Welding Machine** within a high-output die and mold facility in the industrial hub of Sao Paulo. The objective was to replace traditional manual GTAW (Gas Tungsten Arc Welding) processes with **collaborative robotics** to address consistency issues in **tool steel welding**, specifically targeting H13 and P20 grades used in automotive injection molding.

1. Infrastructure Context: The Sao Paulo Industrial Environment

The facility in São Bernardo do Campo presents specific environmental challenges typical of the region. High ambient humidity (often exceeding 80%) and fluctuating power grid stability required the implementation of dedicated line conditioners and advanced gas drying systems. Unlike traditional industrial robots that require extensive safety cell footprints, the **Cobot Welding Machine** was selected for its compact footprint, allowing it to be integrated directly into the existing workflow alongside manual bench-work stations.

The local labor market in Sao Paulo is currently seeing a shortage of Grade-A manual welders capable of the sustained concentration required for complex tool steel overlays. By leveraging **collaborative robotics**, we aimed to bridge this skills gap, allowing semi-skilled operators to manage the programming interface while the machine handles the precision execution of the weld path.

2. Technical Specifications of the Cobot Welding Machine

The unit deployed is a 6-axis collaborative arm integrated with a specialized CMT power source. CMT technology is critical here because it utilizes a mechanized wire retraction system that physically pulls the wire back when a short circuit is detected. This results in:

• Minimal heat input, crucial for maintaining the metallurgical integrity of tool steels.
• Virtually spatter-free deposits, reducing post-weld machining time.
• High gap-bridging capability, essential for worn die repairs where geometry is inconsistent.

In this specific application, the synergy between the power source and the **collaborative robotics** controller allowed for real-time adjustments to wire feed speed (WFS) and travel speed based on the thermal feedback from the workpiece.

3. The Role of Collaborative Robotics in Tool Steel Welding

**Tool steel welding** is notoriously difficult due to the high carbon and alloy content of the base metals. These materials are prone to hydrogen-induced cracking (HIC) and the formation of brittle martensite in the Heat Affected Zone (HAZ).

The use of **collaborative robotics** changes the paradigm of tool repair. In a manual setup, the welder struggles to maintain a consistent torch angle and arc length over a 4-hour shift, especially when preheating the die to 300°C. The **Cobot Welding Machine** does not suffer from thermal fatigue. During the Sao Paulo trials, we observed that the cobot could maintain a constant 1.5mm arc length across a complex curvature, which is nearly impossible for a manual operator wearing heavy thermal PPE.

Furthermore, the “collaborative” aspect allows for “lead-through programming.” An engineer can physically move the cobot arm to define the weld path on a damaged die. This is far more efficient than traditional offline programming for one-off repair jobs.

4. Process Deep-Dive: Executing H13 Tool Steel Overlays

The primary task during this field visit was the restoration of an H13 hot-work tool steel die. The following parameters were established as the baseline for the **Cobot Welding Machine**:

4.1 Thermal Management and Preheating

We implemented a strict preheating protocol of 350°C using induction heating blankets. The **collaborative robotics** system was calibrated to operate within this high-temperature zone. Lessons learned from previous deployments in colder climates were adapted for the Sao Paulo humidity; we increased the flow of the Argon/CO2 shielding gas mix by 15% to ensure the arc column remained stable despite the high moisture content in the ambient air.

4.2 Bead Morphology and Interpass Temperature

The **tool steel welding** process required a multi-layer stringer bead approach. Using the **Cobot Welding Machine**, we programmed a 50% overlap between passes. The integrated sensors monitored the interpass temperature, pausing the cycle automatically if the temperature exceeded 450°C. This level of precision prevents the over-tempering of the base material, preserving the bulk hardness of the die.

5. Synergy Between Human Operators and Collaborative Systems

In the Sao Paulo workshop, the “Collaborative” nature of the robotics was tested through the interaction between the machine and the senior toolmakers. The **Cobot Welding Machine** was not isolated by light curtains. Instead, it used built-in torque sensors to detect any physical obstruction.

This allowed the toolmakers to inspect the weld bead after every two passes without de-energizing the entire system. This “man-and-machine” approach reduced the total repair cycle time by 40% compared to traditional robotic cells. The ability to quickly pivot the cobot arm away to measure the bead height with a micrometer, then return to the exact coordinates, is the hallmark of effective **collaborative robotics**.

6. Lessons Learned and Engineering Observations

Several critical technical insights were gained during the 14-day commissioning period:

• Wire Stick-Out Consistency: In **tool steel welding**, even a 2mm variation in stick-out can alter the heat input enough to cause localized hardness spikes. The cobot’s ability to maintain a tolerance of ±0.1mm is the primary driver of the improved metallurgical results we saw in the hardness testing phase (achieving a consistent 52-54 HRC post-weld).
• Software Offsets for Thermal Expansion: Large tool steel blocks expand significantly at 350°C. We learned that the programmed path must account for a 0.3% dimensional expansion. Future iterations of the **Cobot Welding Machine** software in this plant will include a thermal expansion calculator based on the base metal’s Coefficient of Thermal Expansion (CTE).
• Shielding Gas Purity: We encountered porosity issues on Day 3. Investigation revealed that the local gas cylinders had inconsistent purity. We integrated a point-of-use gas purifier, which is now a mandatory spec for all **collaborative robotics** setups in high-humidity regions like Sao Paulo.

7. Conclusion

The deployment of the Precision CMT **Cobot Welding Machine** in Sao Paulo confirms that **collaborative robotics** is no longer a niche laboratory tool but a robust solution for heavy industrial applications like **tool steel welding**. The combination of CMT’s low heat input and the cobot’s spatial precision provides a significant advantage in die repair, reducing scrap rates and extending the service life of critical manufacturing assets.

For future installations, the focus should remain on environmental controls (gas purity and power stability) and the continued training of manual welders to transition into “robotics supervisors.” The success in the São Bernardo do Campo facility serves as a benchmark for the rest of the South American automotive supply chain.

Report Compiled By:
Senior Welding Engineer, Global Field Operations