Resistance spot welding is the most important joining process in the production of car bodies. Currently, the spot welds are mainly inspected manually and with ultrasound. VOGT Ultrasonics is a ” pacesetter ” of digitalization also in the inspection sector, for example with the intelligent applications of the modern PHAsis inspection system. After successful tests, a well-known automobile manufacturer is transferring this testing solution to series production and expects savings in the millions.
Manual ultrasonic inspection will be replaced in the future by automated, robot-controlled ultrasonic inspection in many areas. Imaging ultrasonic inspection devices will be used for this purpose. A high-end representative of these devices is the PHAsis. In addition to the imaging display of spot welds when used for conventional manual inspection, it offers the interface requirements for automated spot weld inspection and evaluation by robot.
Specialist for spot weld inspection
The ultrasonic device was developed for precise inspection of resistance welded spots. It is particularly suitable for inspection of welded steel or aluminium sheets with individual sheet thicknesses of 0.7 mm to 5 mm. Equipped with the phased array technology, the device enables the physical resolution of the welding lens diameter to be more precise than 0.35 mm. The simultaneous recording of more than 700 measuring points over the inspection area of the spot weld results in the exact welding lens diameter. In combination with the mathematical processing of the measured data, this results in an exact diameter determination based on the reflected ultrasound. The imaging representation guarantees a reliable evaluation of the inspection results. The generated cross-section of the spot weld with colour depth display of the welded areas shows defects such as pores or a welding lens that is too small.
Ready for industry 4.0
PHAsis communicates with the robot or welding control via standardized REST interfaces and transfers test data in real time to an IT system. In this way, quality deviations are detected immediately. At the same time, the use of robot technology optimizes the comparability of the measurement results. A robot positions the probe exactly and reproducibly. This results in a considerable reduction of the inspection time. The inspection time is reduced by up to six times compared to manual inspection. The robots are usually supported by a camera during positioning. As soon as the spot weld is within the inspection area of the probe, PHAsis offers an additional automated positioning assistance. With this assistance, the probe can be positioned vertically even if the spot weld is at an angle, thus ensuring measurement safety and reliability.
PHAsis allows simultaneous scanning of a larger inspection area as well as the evaluation of a spot weld in the image; this shortens inspection times even more compared to conventional ultrasonic testing.
Application example – ABB fully integrated ultrasonic system robot with the PHAsis technology for spot weld inspection (factory picture ABB)
Couplant simply sprayed on, quickly evaporated
PHAsis offers even more for robot applications. By coupling via a water delay path with a flexible plastic membrane, the probe can be precisely positioned on the spot weld, which is important in the case of compressed spot welds. A big advantage is the minimal moistening for coupling, which is sufficient when using the VOGT membrane. When using water, the advantage is that the sprayed on water evaporates quickly. This eliminates the need to remove the coupling agent, as is still required today by conventional rexolite delay path. In addition, the inspection results are more reproducible.
For round-the-clock operation
A typical test island designed for 24/7 operation often looks like this: The robot scans the component number and feeds the component to the fixed inspection unit. Alternatively, a robot moves the probe as the materials inspector does by hand and moves it from spot weld to spot weld on a positioned component. In this case, the probe is mounted on the robot arm along with the coupling agent spraying unit and the camera.
The robot follows an inspection plan, so that individual spot weld dependent setup and evaluation parameters are automatically loaded. The inspection results are synchronized with host systems and/or the PHAsis database. In addition, the system offers a data manager and a post-processor for subsequent optimization or special evaluations. VOGT Ultrasonics supports producers, integrators and welding robot manufacturers on the basis of many years of experience with the implementation of the task- and company-specific ultrasonic testing (see factory picture ABB). With the aid of automated testing solutions, very considerable savings potentials can be realized with best reproducibility of the inspection results. Inspection systems combining PHAsis and robot technology contribute to future-oriented quality assurance as well as to the detailed documentation of the inspection results.
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