Figure 1/2 Folding machine: Connecting the outer and inner parts of doors
The use of hydraulics
In this case, the quality of folding is especially determined by the folding radius: The smaller the better. In order to achieve this, the Audi engineers proceed as follows: The outer part, whose flange is approximately 90 degrees open, is inserted into the folding system and positioned precisely. A robot adds the welded assembly which is to be joined as the inner part. Industrial hydraulic cylinders close the C-hoops with the folding jaws and position the preliminary folding jaws for the first folding step. A further cylinder moves the folding bed vertically upwards, and subsequently generates the necessary pressure in order to close the fold to an aperture angle of 45°. The preliminary folding jaws are now hydraulically withdrawn again. The folding bed moves against the final folding jaws and closes the fold with a correspondingly high pressure of 100 bar with 80 N/mm calculated along the length of the fold. The system therefore achieves the low bending radius which is required. Finally, the C-hoops are opened again, the folded part is removed from the folding system and further processed in the corresponding production process.
Third generation folding systems
The idea of actuating the preliminary folding jaws via a ram function has made the folding system considerably more compact and inexpensive. In the first generation, preliminary pressing was carried out in a 5-metre high press; final folding was carried out in a further, equally large, unit. In the second generation, the folding jaws were assembled above one another in two separate assemblies. The process was then completed in a 2.2-metre high system. The new systems of the third generation, with the C-hoops, have been in use since 1998, and are now only 1.6 metres high. The low folding time of 20 seconds is achieved as a result of this movement procedure optimisation.
Hydraulics - a significant basis for high precision in folding systems
High-quality hydraulic components create a considerable prerequisite for the fulfilment of customers' requirements for a folding system. These folding systems generate the necessary force and enable a high degree of movement and positioning precision; this is the experience of the Audi tooling division. "In Hänchen, we at Audi have a tried-and-tested partner. In this manner, we are able to achieve gap dimensions which satisfy the world's most stringent requirements with precise, extremely reliable cylinders in compact folding systems", Behringer is convinced.