Sensors for arc welding is a general term for devices that, as part of a fully mechanized welding equipment, receive information about the position and geometry of the proposed weld on the workpiece and provide data in the appropriate form to control the welding installation.
Content
Introduction
The quality of the weld depends on voltage , current , wire feed speed and welding speed, on the type of energy input and the filler materials used. The positioning of the welding arc has a direct effect on the consumption of material. The input heat for melting the seam and the constant heat flux are directly related to the arc torch and affect the quality of the weld.
In fully mechanized and automated installations, inaccuracies in the selection of shielding gases, roughness of a workpiece, processing, groove preparation, and thermal deformation reinforce changes in the position of the edge and its geometry. In fully mechanized welding, the information required for welding is detected using a sensor. Sensor sensors are used to monitor the position of any component of the weld (detection of the start of the weld and the end of the weld).
Deviations from the optimum position of the welding devices are measured using sensors. For example, electromagnetic sensors for changes in the parameters of the magnetic field provide information about the junction or surface of the product. Pneumatic inkjet sensors work by changing the pressure in the plasma nozzle when gas flows to the surface of the product: when the nozzle approaches the surface of the workpiece, the gas pressure increases. A large amount of welding information can be obtained using monochromatic laser radiation to illuminate the seam, and a lot of information can also be obtained.
Data on the welding process can be obtained using spectral analysis. In this case, the emission spectrum of the arc and the spectrum of the weld pool are compared with the specified reference values. Deviations in the spectra indicate a change in chemical composition or energy changes in the weld zone.
Sensors
The physical principles by which the sensors work are based on the generation by them in a different form of a signal when a parameter controlled by them changes.
Tactile Sensors
Contact sensors for tracking the position of the workpiece are a type of tactile sensor. The sensor is in electrical contact with the product by means of an electrically conductive part included in the measuring circuit of the sensor.
Mechanical contact sensors belong to the second category of tactile sensors.
Contact Sensors
Contact sensors work by contacting the workpiece with the sensor elements.
Thermal Sensors
In heat sensors, the heat flux is measured using two thermocouples located on the welding torch, the heat flux is used to control the height of the torch. The orientation of the welding torch to the side is determined by comparing the temperature of the sensors from both thermocouples. If the orientation of the torch is symmetrical, the difference in the radiated heat flux is zero. The lateral displacement of the thermocouple torch depends on external heat fluxes, deformation of the arc, and also on a change in the position of the weld pool.
Mechanical Sensors
Mechanical contact systems translate the spatial deviations of the sensor into an electrical signal. Such sensors include:
- micro switch;
- potentiometer;
- optical transformer (light barriers);
- inductive transformer.
Optical Sensors
Optical sensors belong to the group of non-contact measurements (Fig. 1). Semiconductor image sensors are used to detect radiation. They are divided into sensors with active and inactive lighting. The camera inspects the workpieces and extracts the necessary information from two-dimensional grayscale images. Active structured lighting means using a light source to illuminate certain areas of the part.
Mode of operation
To conduct optical measurements without active structured lighting, the camera is directed to the seam area, where it is monitored. This method is used, for example, for automatic submerged arc welding in order to provide the welder with a weld image on the monitor.
There are various types of construction of measuring sensors.
Literature
- Ulrich Dilthey: Schweißtechnische Fertigungsverfahren 1: Schweiß- und Schneidtechnologien , Band 1 von Schweißtechnische Fertigungsverfahren, Verlag Birkhäuser, 2006, ISBN 3540216731
- Werkstatt und Betrieb, Band 118 , 1985 [1]