Mannstaedt GmbH in Troisdorf near Cologne, a world-leading manufacturer of hot-rolled special steel sections, has successfully begun operating a plant supplied by H+H Herrmann + Hieber for the automatic sorting, stacking and packing of profile sections. Owing to the large variety of cross-sections processed and stacking patterns required, exceptional demands are made on the manipulation means and as regards precision
With this plant profile sections 500 to 5,100 millimetres long (maximum bundle weight 5 tonnes) can be processed in a fully automatic sequence, and in partially automated operation even up to 7,500 millimetres long. The sections are transported to the dispatch area stacked on squared joists and strapped to form packs. To ensure high stability of the section bundles, the layers within the pack of sections have individually designed stacking patterns nested in one another. The stacking time amounts to around 25 to 30 s per section.
The rolled section (up to 26 metres long) is weighed, its length measured, and it is then taken to the saw. In the conveyor stretch to the stacker its straightness is checked and some sections are rotated through 180 degrees with the help of a so-termed “Schmetterling” rotating device.
Owing to the large weights involved, tailor-made electromagnets had to be developed to carry the loads. To be able to pick up all the sections safely, magnetic fields in various orientations and of correctly matched field strengths have to be combined. The magnets used are made individually.
To form the stacks two roller conveyors are installed in parallel so that two stacks can be dealt with next to one another. This allows sections of different lengths to be processed at the same time.
Owing to the variety of tasks involved the structure of the control system is exceptionally complex. The most important strategies are:
- Flexible stack shapes in accordance with the customer’s wishes. As regards stacking, two basic alternatives are possible: in one case the entire stack with supporting squared joists can be strapped to form a single pack. However, the packed stack can also consist of individual, separately strapped section bundles which are then combined and strapped with their supporting joists to form packs.
- Minimisation of waste. To enable the initial rolled section to be used as completely as possible, different orders can be combined with one another so that the lengths of all the sections add up to a maximum. For this it is taken into account that the length of the initial section can vary. When stacking, the result of this is that two lengths in parallel have to be stacked in different packs.
- Different stack patterns and varying sequences. Differing section shapes make differentiated stacking necessary. The arrangement in the stack is determined for each individual profile cross-section and stored in the control system. Moreover, for each individual section it must be specified how it should be positioned under the stacking device to enable safe load uptake.
- Strapping and transport of packs with varying lengths. At the strapping station the squared joists needed in each case are positioned automatically and loaded. This is done taking into account the dimensions of the sections, the pack weight and the transport equipment to be used. The positions of the joists are specified from time to time by the computer.
The pack, supported by squared joists to which it is fixed by steel straps, is moved with the help of transporting forks to one of three available waiting positions or taken directly to the transfer point, where it can be taken over by a fork-lift truck.