Sensors & transducers
HIGH PRECISION SENSORS FOR AUTOMATION AND QUALITY CONTROL OF WELDING PROCESSES
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Maximum productivity and consistent quality are critical in automated welding processes. This requires robust, high precision sensors that perform path planning, distance control and quality inspections, says Glenn Wedgbrow, business development manager at Micro-Epsilon UK.
n automated welding processes such as spot welding, additive manufacturing procedures and robot welding, all process steps are clocked and carried out with the highest precision. This increases the need for sensors that perform path planning, welding head distance control, and quality checks. Micro-Epsilon offers a wide portfolio of robust sensors for welding automation which impress in harsh environments and with high precision. Their high precision and high measuring rates enable the sensors to increase the performance of various welding processes.
PATH PLANNING
3D scan of components before laser cladding
With laser cladding, the component surface is melted by a laser beam and joined to form a new, pore-free layer by the addition of a powdered filler material. Prior to laser processing, the components are scanned with a scanCONTROL laser scanner from several directions. The core task of the scanners is the detection of free forms as well as the recognition of form deviations. Regardless of the reflection properties of the material, the scanners provide stable measurement values. The raw data is transferred directly to the user’s software, assembled into a 3D model and used for the path planning of the laser welding head. The welding nozzle is then placed at the correct distance from the surface and guided along the calculated path.
Fully automatic 3D repair welding scanCONTROL laser scanners are also used for repair welding of large parts in order to determine the welding track and the robot path. First, the surface of the defective area is scanned by a laser scanner, which is guided over the surface by a robot. The 3D data of the worn area together
with the position data of the robot are generated. The measuring points determined are inserted into the CAD target model of the component. Therefore, the difference in volume between the high resolution measurement values and the target contour is obtained. Based on this difference, the required welding track is calculated and then transmitted to the robot control.
Calculation of welded paths on gas valves The position of the welding head relative to the welded seam is a decisive factor in the quality of automated welding processes. Even minor deviations can affect the welding result and lead to manual rework or rejection of the component. scanCONTROL laser profile sensors are used for profile measurements and provide precise profile information of the seam, even on difficult surfaces. The calculated paths eliminate deviations from the component tolerance in such a way that the welding head is positioned over the desired seam at all times.
WELDING HEAD CONTROL Distance control with fully automatic laser welding
In fully automatic welding units, welding head positioning is crucial for the quality of the welded joint. In order to position the welding head at the correct distance, optoNCDT 1900 laser sensors are used. These measure the distance from the steel plates with high accuracy and dynamics. As they offer the highest insensitivity to ambient light in their class, the laser sensors are ideal for the distance control of welding heads.
Focal point control in additive manufacturing
With additive manufacturing methods such as selective metal melting, the focal point control of the laser is crucial for the process speed and the
quality. In order to determine the distance between the print head and the powder surface and to control the laser focal point, optoNCDT 1900 laser sensors are used. Their high measuring rate and repeatability enable fast and reliable distance measurements regardless of the respective alloy.
Displacement measurement of electrodes in resistance welding
In resistance welding processes, various parameters must be monitored. In automatic welding machines, eddy current sensors from Micro-Epsilon ensure high quality welded joints while measuring the travel of the electrodes. The non-contact displacement sensors detect the axial displacement which is influenced by thermal and mechanical factors. These robust sensors are insensitive to welding currents, vibrations and fluctuating temperatures, which means they operate reliably in harsh environmental conditions. High resolution and frequency response allow for the electrode position to be dynamically controlled while enabling repeatable quality of the welding joints.
QUALITY ASSURANCE
3D Inspection of weld seams using laser scanners
Laser scanners from Micro-Epsilon are used for quality assurance and the documentation of weld seams. Their high resolution enables the scanners to detect three-dimensional shapes and extremely fine details and structures. The 3D View software from
February 2025 Instrumentation Monthly
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