Today, a rational flow of materials plays a very important role in the industrial machining of metal sheets. Although this is obvious, it is still not implemented everywhere. The material flow is so important because the running times of the machines can be fully utilised for productive purposes only if they are continuously supplied with raw materials and the finished parts and waste materials are removed equally quickly. If, however, one takes a look at the operations around metal-cutting machines, the conditions could almost be called anachronistic: the high-performance machine is loaded and unloaded manually by several persons, which means that it cannot produce anything during the loading and unloading times. Even machines with so-called dual tables cannot do much to rectify this situation cutting times are shorter than the loading and unloading times or if one person has to operate several machines.

Loading with vacuum lifting devices
saves time and increases productivity

The only correct solution was selected by the responsible persons at Messrs. Schwenk GmbH in 72290 Loßburg, an innovative service provider for sheet-metal working and for the manufacture of complete sheet-metal assemblies. This company uses a laser-cutting machine and a high-pressure water-jet cutting machine for cutting various metal sheets into parts of various sizes. Whereas the laser-cutting machine was equipped from the very beginning with a vacuum lifting device for rational loading by only one person, the situation for the water-jet cutting machine is very different. Here, the sheets are loaded manually and up to four persons are required for this at times.
But let us look separately at the two machines. The laser-cutting machine is loaded by one man with the aid of a vacuum lifting device of the type VacuMaster Vario 500-8, whose eight large vacuum plates can easily lift metal sheets weighing up to 450 kg and with dimensions of up to 1.5 x 3.0 metres. Operation by one man is possible because the extended operator handle of the VacuMaster Vario permits the safe lifting, guidance and positioning of the metal sheets, which have to be taken from a stack and placed on the machine table. For this, the vacuum lifting device, which includes its own vacuum pump, is suspended from a monorail overhead crane running on a rail with a length of 2.3 metres, permitting a suitably large working area without interfering with other operations on and around the machine. After the sheet has been cut, the operator removes the finished parts manually and returns them to the material flow for further machining.

Flexible and independent handling
with self-powered vacuum lifting devices

The loading of the high-pressure water-jet cutting machine is carried out in a different manner, because it is used to cut very thick sheets of stainless steel, plastics and stones and this generally takes more time. However, in order to improve the economics of the cutting process, by measures such as reducing the number of persons needed, the company recently purchased a further vacuum lifting device for this purpose. The company selected is a vacuum lifting device of the type VacuMaster Eco, which operates without external power supplies of any kind, since it is self-powered. The vacuum is generated from the weight of the workpiece as the crane pulls a piston out of a cylinder on the lifting device. Depending on the weight of the load, the lifting motion generates a vacuum in the cylinder and this grips the workpiece securely. Messrs. Schwenk use a VacuMaster Eco 500/1 with a large vacuum pad, which is capable of handling loads weighing up to 500 kg. The lifting device is suspended on a chain hoist mounted on one arm of a fork-lift truck, which means that it can be used very flexibly, especially as it needs no external power supply. Thanks to the vacuum lifting device VacuMaster Eco 500/1, the high-pressure water-jet cutting machine can now be loaded and unloaded by a single person, instead of the four who were previously needed.