Measuring Workpiece Temperature in Friction Stir Welding

There are certain knowledge gaps in manufacturing, details that elude the understanding of many machinists or fabricators. For example, how does the heat or stress of machining affect the workpiece or cutting tool? And how do those affects influence the results of their work?

In that example, the answers are available thanks to a recently introduced and patented technology. The TemperChip^® noncontact sensor offers machinists the means to track temperature variations between the machine and the work material during CNC cutting of composite materials or aluminum alloys, to provide reliable monitoring for tool life and efficiency.

There are similar unknown variables affecting welding operations – and TemperChip is stepping into that gap (or “joint”) too, to measure thermal variations precisely.

Friction stir welding (FSW) is a solid-state process invented in 1991 to join two pieces of metal without melting them. A rotating tool generates frictional heat that softens the material at the joint. Then the tool stirs and forges the softened pieces together, creating a strong weld with less distortion than standard welding methods.

It’s a process commonly used for aluminum and other metals in industries like aerospace and automotive manufacturing, to attain high-strength, durable joints.

Measuring temperature variation in FSW

While TemperChip^® was designed for machining, its principle can be effectively adapted for Friction Stir Welding applications, functioning in a way similar to in-tool temperature measurement systems like Stirweld’s Smart Tool Holder.

In FSW, temperature monitoring inside the rotating tool is critical because the process relies on frictional heat to soften the material without melting it. Unlike standard thermocouples that require drilling into workpieces, a chip-integrated sensor such as TemperChip^® can measure precise thermal data directly at the tool–workpiece interface, avoiding intrusive modifications.

TemperChip^® offers several specific advantages for FSW:

• Non-contact, wireless data acquisition: The embedded BLE (Bluetooth Low Energy) communication module transmits temperature data in real time, making it possible to have feedback control of spindle speed and plunge force without physical wires.
• Calibrated temperature thresholds: The system can be pre-calibrated for specific alloys (e.g., 7075 or 6061 aluminum) to alert operators—through smartphone or LED interface—when weld temperatures deviate from optimal FSW ranges (~375–450 °C, depending on material.)
• In-situ heat-zone tracking: Continuous measurements along the weld path help map temperature distribution, allowing process optimization and prevention of cold or overheated welds.

Implementation considerations

For FSW integration, TemperChip^® could be embedded near the shoulder or pin section of the tool, providing localized thermal data to refine process parameters, such as rotational speed, axial force, and traverse rate. The sensor’s calibration is crucial to ensure readings remain within frictional heat ranges of 350–450 °C, where most aluminum alloys achieve ideal plasticization without melting.

In summary, using TemperChip^® for temperature measurement in FSW enables non-intrusive, high-resolution, real-time thermal control, offering a smart alternative to wired thermocouple methods. When integrated into welding tool systems (like the Stirweld Smart Tool Holder or I-STIR™ technologies), it allows predictive temperature management and improved weld consistency across production batches.