Soldering is a method of joining parts with molten auxiliary material, the so-called solder with the melting point lower than the components to be joined. It is customary to distinguish the so-called soft and hard soldering, depending on the melting point of the solder. Solders with the melting point of up to ca. 450°C are referred to as soft, above the temperature, as hard. Soldering methods may be distinguished mainly by the method of heating the soldered parts and solder. In the larger extent, we heat soldered objects and solder with hot gas flow or flame. Hard soldering ensures greater weld strength; it is used, for instance, for soldering aluminium or copper pipes. For soft soldering, a natural gas flame with air is sufficient; the hard soldering requires warmer oxygen-acetylene or oxygen-hydrogen flame.
Setting of the Assignment
The company Xxxxx, one of the leading companies in the automotive industry, is involved in the production of automotive air conditioning and its components. In this case, the temperature course needed to be monitored during aluminium torch soldering to reach the desired temperature and therefore to ensure the proper soldering operation and a quality joint of the two air conditioning distribution pipes. The second assignment should ascertain the weld temperature after cooling with water to avoid burning the operator that takes the component.
Solution of the Assignment
To address the application, the ThermoInspector thermal imaging system was used, which is primarily intended for the applications monitoring production processes, monitoring temperature stability and homogeneity during processes, input – output temperature monitoring, etc., and where up to 4 WIC thermal imaging cameras may be connected simultaneously.
However, in this particular case, only one thermal imaging camera connected to the ThermoInspector control computer via the Ethernet cable was sufficient. The thermal imaging camera was placed on a static holder to be as perpendicular as possible to the soldered area, but at the sufficient distance from the flame to prevent damage and influence the camera’s accuracy by flame. The system has been configured to the Start/Stop Measurement Mode, which means that the camera monitors the respective areas in the image (ROI) during the active incoming trigger signal, the measurement starts on the leading edge and ends on the trailing edge. The trigger signal was brought to the ThermoInspector system from the control PLC and it is activated when the flame starts to solder and deactivated when the soldering is terminated The second trigger signal comes when the soldered area gets colder with water. Here only a short signal from the PLC is sufficient. If the temperature limit on any of the ROI is not met, an alarm is displayed on the screen that informs the operator and saves the appropriate record to the control computer for each particular soldering. The system has also digital outputs that inform the control PLC of the wrong soldering course or high temperatures of the second measurement.
Optionally adjustable ROI were used to check the welds, in which the camera evaluates the measured data in real time. Polygons, precisely copying the soldered area, were chosen as the optimal ROI. In these areas, the maximum measured value/temperature is monitored in real time and compared with the set limits, lower limit of reaching the optimal temperature for soldering. On the other hand, during the second monitoring, the temperature is compared with the upper limit to make sure that a person is not burned when handling the component. Visualisation of the entire process for operators was displayed on the ThermoInspector.
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