Manufacturers need to react to the continuing boom in the sales of top-quality mobile homes because the customers are no longer prepared to accept excessively long delivery times.

Practically, however, the necessary rationalisation in the production of assemblies is relatively difficult and costly because, for example, the prefabricated side walls are large and heavy.

In addition, the surfaces of the prefabricated elements such as side walls and roofs are easily damaged during transport and handling, which means that great care must be taken during these steps. And last but not least, these elements are in some cases several metres long and correspondingly heavy, which means that they cannot be handled by a single person, even with suitable handling aids. Until now, the handling required two further persons, resulting in higher personnel costs.

Messrs. Bürstner in Kehl, a well-known manufacturer of caravans and mobile homes, was faced with this problem and asked Messrs. Haas Maschinenbau in Oberkirch  to design and build a device for turning their large and heavy caravan and mobile-home elements.

Bürstner produces a wide range of different caravans and mobile homes and there are thus many different assemblies with dimensions up to 2600 x 8000 x 40 mm (W X L X D) weighing up to 200 kg. The planned device was to be able to turn the various elements by 180° without interrupting the material flow, so that the workers can install the wiring and other fixtures without having to wait.

Furthermore, it was to be able to handle all of the various elements flexibly, without the need for conversion, and the handling should not damage the parts or present hazards to the health and safety of the users.

Vacuum components permit technically
convincing and economical solutions

No sooner said than done: the design engineers at Haas decided to construct a compact turning table which, with the assistance of vacuum, permits the flexible handling of the various elements by a single person.

For the vacuum components, Haas selected the powerful components from the vacuum specialist J. Schmalz GmbH in 72293 Glatten, which have already proved themselves in many years of industrial use.

When designing the table, the engineers had to take into account the fact that the side walls have surfaces made of aluminium and wood and, due to their design, are relatively thin and thus flexible. It was therefore necessary to provide a sufficient number of suction pads and cross-beams. In addition, possible changes to the sizes and shapes of the parts must be considered and provided for.

For the turning table, Schmalz supplied ten suction pads of the type SPU 210, ten spring plungers of the type FSTE ½"-25-HD (high-performance version with lower damping spring), ten check valves SVKG ½", five Schmalz MEGA Pump compact ejectors of the type SMP 20 NC ASVD with power function and increased blow-off power and various mounting and hose-connection elements.

The design of the cross-beams used for mounting the suction pads with their spring plungers permits rapid adjustment of the suction-pad positions for handling of differing versions of the parts to be handled (such as those for different vehicles and those with differing door and window positions).

In most cases, however, such adjustment is not necessary because any suction pads which are not in contact with the surface of the element are immediately disabled by their built-in check valves. 

Safe and flexible handling with vacuum

Since the caravan and mobile-home elements are first swung up from the horizontal position to the vertical position before being turned through a further 90° to the horizontal position again, the spring plungers and suction pads must be able to handle the resulting transverse forces. Most of these forces have to be handled by the spring plungers, which is why the HD (Heavy Duty) version was selected, since it is mechanically robust and rigid. The combination of the strong suction pads SPU and spring plungers FSTE-HD proved to be ideal for the applications at Bürstner.

Since the compact ejectors SMP ensure quick and secure gripping of the caravan and mobile-home elements and their integrated blow-off function ensures fast and precise release of the elements, the elements can be handled quickly, reliably and without damage.

When a side wall moves from the machining centre to the turning station, the brushes of the conveyor on which it is carried are retracted. The element is gripper, turned through 180° and placed on the conveyor system behind the turning station. This cycle is executed every 20 minutes.