Friction Stir Welding Unit Has Monitoring Software

The Lowstir friction stir welding system includes a unit that attaches to most standard milling machines via an ISO taper, making it an affordable option for smaller enterprises. It is supplied with software to calibrate the system, monitor the welding process and log welding parameters for later analysis. However, standard milling machines lack the process monitoring capabilities required to ensure high-quality friction stir welded joints.

To ensure the forces from the welding process do not affect the electronics and gain the benefit of a wireless system, the sensor head has been modified to use a battery power supply and a Bluetooth connection to transmit machining data to a stationery receiver. This modification means that the sensitive electronics and rotating antenna for the telemetry transmission is no longer required, nor are the stationery receiver or the signal processing unit, power supply or associated trailing cables.

The Lowstir system now comprises one hardware and one software component, excluding the FSW tool, with the wireless link designed to support two-way communications for calibration and data collection. No consumerables are used and, as there is no arc drawn, there is no radiation, fume or spatter present. Additionally as it uses vastly less energy in the process, it is a very 'green' technique. The Bluetooth switch is a simple jack-plug arrangement; users pull out the plug and the Lowstir device will search for the laptop.

Once finished, simply replace the plug. The power supply is built in using a rechargeable battery. A weld-monitoring system has been developed to accurately measure the vertical and horizontal forces and torque on the tool. The sensor is machined from one piece of high-grade stainless steel, heat treated for maximum strength and stability. The sensor design allows for various taper sizes to be attached to accommodate the requirements of the user. The data gathered can be directly linked to the acceptance or otherwise of the weld.

The device has the capability to monitor two user-defined temperatures via thermocouples: one to be attached to the FSW tool, the second will serve as a safety cut out to protect the integral telemetry circuit, monitoring the temperature at the interface between the tool holder and the weld-monitoring system. The information gathered by the Lowstir device is displayed to the operator using a notebook PC running NI Labview. The instrument panel displays real-time numerical values of forces, torque, the temperature adjacent to the system electronics and (if desired) the tool temperature.

The system also has the capability to add real-time event markers to allow correlation between process conditions/stages and the recorded data. The main display screen has buttons to start and stop recording of data. Alternatively, an automatic trigger facility exists for initiating the recording of data. The display also shows the current captured data values for the weld in progress and indicates whether they are within the acceptable range for satisfactory welding. The display also has a multi-graph facility, where the user can select which sensor values are displayed.

Specifications: down force (Fz) to 50kN; lateral force (Fxy) to 25kN; torque (Mz) to 100Nm; temperature of the internal electronics (to warn of overheating); optionally, the temperature of any moving part; max rotational speed of 3,000rev/min; software logging rate selectable from 1 to 100Hz.


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