JAT developed an 8-axis manipulator for Salzgitter Mannesmann Forschung GmbH. The X-ray inspection at the Salzgitter site will be a stationary test in the laboratory. The tests include the inspection of welded pipes and the testing of samples as part of in-house training and the inspection of novel join connections.
As part of the changeover from conventional X-ray technology (RT) to digital radiography (DR), a flexible and automatable test system was to be developed that allows a wide variety of components or samples such as pipes, sheets and welded constructions with up to 60 kg to be recorded. A high level of repeatability of the sample position is also required for series examinations. The angular position of the components to be tested in relation to the beam axis must be just as easily variable as the distance between the radiation source and the component and between the component and the detector.
With this requirement profile, SZMF turned to Jenaer Antriebstechnik JAT. In the first step, various axle concepts and expansion stages were examined, compared and discussed in Jena. In the further course of the process, the final concept of a very flexible manipulator with five linear and three rotary axes was prepared together in a workshop: In the middle, an XY axis system takes up the rotary axis for the turntable. The samples with a mass of up to 60 kg are fixed to this. On a fixed Z-axis (Fig. 1, right) there is a swivel axis to which the X-ray tube is attached. An XZ axis system with an applied swivel axis is used to accommodate the detector. This arrangement allows the X-ray tube, sample and detector to be positioned at almost any distance from one another and at the same time to vary the angular position of the sample in relation to the beam direction, which is of great importance for locating and evaluating defects in the material.
The detector and X-ray source have relatively large masses of a good 60 kg, with the X-axes with a travel of around 800 mm adding the masses of the axes above. Roller bearing linear guides and ball screws ensure the necessary rigidity. JAT servomotors from the Ecostep® and Ecospeed® series with integrated brakes and encoders are used as drives. Low backlash planetary gears reduce the drive torques of the servomotors as well as the braking torques that are required to hold the positions.
The linear axes achieve a positioning accuracy of less than 100 µm and a repeat accuracy of less than 10 µm. Since the swivel axes for the X-ray tube and the detector are only adjusted by a maximum of + -25 ° and are always inclined to one side, the already small backlash of the planetary gears does not affect the positioning accuracy. On the other hand, the towing cable solutions for the eight nested axes turned out to be a constructive challenge. According to the specifications from Salzgitter, all cables of the manipulator were led to a central connection.
The control of the axes in the network as well as the development of the software and the visualization were implemented by technicians from SZMF. The axes can be moved with a joystick directly on the manipulator for optimal adjustment of the sample, X-ray tube and detector, outside of the X-ray room from a PC. A synchronous adjustment of the Z-axes is just as possible as an adjustment in the opposite direction. The latter is used to be able to irradiate a certain point in the sample at different angles. The software automatically adjusts the two swivel axes of the X-ray tube and detector when the radiation angle is changed. With the rotary drive on the turntable, image sequences can be automatically executed in defined angular increments. Mechanical engineering specialists from Salzgitter also implemented the entire safety technology for the manipulator and the X-ray room.
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