Optimum material flow between two levels

Gerhardi Alutechnik GmbH & Co. KG

When Gerhardi Alutechnik in Lüdenscheid, Westphalia, invested in a second extrusion line with 33 MN extrusion load, H+H Herrmann + Hieber was commissioned to supply the logistical automation system. The plant is set up in a new, two-storey building – a special feature which gives rise to particular demands as regards material flow.

The presses and run-outs are installed on the lower, ground-floor level, while heat treatment, packing and dispatch take place on the upper level. The extruded sections, sawn in layers, are stacked into racks on the lower level. For this two section-stacking machines are arranged one behind the other. With normal section lengths one of the two section-stackers is always in operation, whereas for excess-length sections the two section-stackers operate in synchronisation. Empty racks and the intermediate layers are brought in automatically.

Again automatically, the filled racks are taken up by an automatic crane and transported to the upper level. The automatic crane (process crane) is a three-axis design and, having regard to the range of operations to be performed, relatively high movement speeds were chosen. In relation to safe and trouble-free rack uptake the lifting height of 12 metres entails special requirements.

Since the existing racks for the original press cannot be used for the new, larger press, the load uptake process of the process crane had to be modified so that two different rack types can be transported in alternation, without refitting. This is achieved by a load uptake system which accommodates both rack types.

On the upper level the racks, when assigned to one of the two ageing furnaces, are deposited in stacks of four on the roller track ahead of the furnaces. The heat-treated material and the racks, which do not pass through the furnace, are transported by the automatic crane to an intermediate store. The automatic conveyor system also includes the transport of the intermediate layers, the scrap and the empty racks.

To manage the complex transport operations in the automated sequence, the section transport system has an operating system of its own which, for its part, has to be connected into the process control system of the extrusion plant as a whole. The process control system assigns tasks to the section transport system. The sequence of individual movements is organised fully autonomously by the controls of the operating system.

The plans also envisage a shared, largely automated section packing system for the two extrusion lines. At both packing stations the sections will be brought in individually ready for handling. For this an automatic section destacking machine and transport belts have been installed.