Non-destructive materials testing and measuring equipment specialist, H.Rohloff, has developed the innovative Billet InspectIR, an automated, high-speed inspection system for use in the steel industry. The system utilises infrared thermography to detect open surface defects on round and square steel billets.
“In 2000 we were approached by Mittal Steel (then Iscor) to find an automated inspection method,” says Pieter de Lange, marketing director, H.Rohloff. “We accompanied them on a three week worldwide tour to search for an appropriate system but we were unsuccessful. H.Rohloff engineers started the development process in conjunction with Mittal.”
The steel producer required an automated, high-speed inspection system to replace the manual, visual inspection process that was being used. The existing method was time intensive and offered no traceability. The new solution needed to offer traceability and associated documentation for quality control purposes.
“After two years in development the system was ready for use and was installed and commissioned for Mittal. Our latest sale was to a German steel manufacturer that supplies mainly to the automotive industry. This solution is currently being commissioned,” says de Lange.
The system comprises a camera enclosure, signal processing system, operating control cabinet, induction heater, induction coils, water cooling system, conveyor and defect marking equipment.
Billets, bars or tubes are loaded onto the conveyors and fed through the camera box. Inside the camera box three different sized induction coils heat the surface of the material to a maximum of 20°C and defects show up as warmer than the rest of the area. Four infrared cameras capture the data generated by the warmed billet. This data is analysed by a sophisticated signal processing system to identify, quantify and display the defects. The marking station then uses water-based paint to mark the position of the defect or, if need be, mark the material as a reject.
The camera box is 5 m long, 1 m wide and 3 m high. It weighs 5 tons and is housed in an aluminium frame. It automatically adjusts its height according to the size of the material being inspected.
The design and manufacture of the camera box was done by Tectra Automation, the sole sub-Saharan African representative of Bosch Rexroth. Tectra used the Rexroth range of basic mechanical elements and aluminium profiles to build the structure, since H.Rohloff’s specification called for a system that was not only precise, but also aesthetically pleasing.
Tectra also provided the linear motion and drive system for the cameras, coils and vertical adjustment of the camera box and coils. Each camera is mounted on a sealed CKK15-110 compact linear module driven by Rexroth MSM type servo motors with EcoDrive Cs compact drives. The induction coils are positioned by an AGK type sealed ball screw drive unit and guided by standard Rexroth ball guide rails. In total there are seven Rexroth servo motors controlled via Profibus from the master PLC. To assist with installation and maintenance the motor power and encoder cables were made pluggable. In addition, the entire camera box is moved into a maintenance position by a Rexmover rodless cylinder whilst guidance is provided by Rexroth size 35 ball rail guides.
“We selected Tectra Automation because of its reputation in the industry and because of the depth and quality of its product range. Bosch Rexroth has an excellent reputation overseas and there is a good availability of spares. We also wanted a subcontractor that could supply as much of a turnkey solution as possible.”
De Lange notes that this technology can be applied to manufacturing of any sort from castings and forgings to motor components.
“This solution is unique – there is nothing like it on the market. The Billet InspectIR features traceable reporting and categorises the defects according to orientation, length and depth. This is especially important from a materials test point of view because it allows users to determine whether to scrap the item or rework it, removing the defect. It is also contact-less which ensures that there is no wear and tear and minimal maintenance needs due to the lack of working parts.”
For more information contact Kevin Lombard, Tectra Automation, +27 (0)11 971 9400, kevinl@tectra.co.za, www.tectra.co.za
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