Senior boss Hans Hager from Möttingen points to his special machines. With the huge portal handling systems, the special machine manufacturer has made the assembly line production of car bodies more flexible. The linear axes of the machines are now being retrofitted and equipped with a monitoring solution from Schaeffler. "No more flying blind," says Hager.

In 2012, the Mötting-based family business became known far beyond the Bavarian-Swabian border as a winner of the "Central Innovation Program for SMEs". The project, funded by the German Federal Ministry of Economics and Technology, involved the development of a clamping frame changing system for precise fixing devices for car body parts. The conventional changing systems used to date severely restricted the number of body shapes that could be produced on an assembly line and took up too much space.

Bodyframing in car body production

How does the production of passenger compartments actually work today? It is important to know that a rigid body is only created by welding the floor assembly to the side panels and the roof. The individual sheet metal parts are relatively flexible and must therefore be precisely positioned and fixed before welding. For this purpose, the two side panels are initially placed loosely on the floor assembly and fed to the welding station - also known as precision steel construction, PSB. Large clamping frames weighing over two tons then approach the side parts from both sides. Once the clamping frames have been locked into position, the side panels are clamped precisely onto the clamping frames. The robots then weld the floor assembly to the side panels. The clamping elements are then released and the clamping frames are moved apart into their initial position to release the body for transportation.

The catch is that a special pair of clamping frames is required for each body shape. The tenter frames therefore have to be replaced every time the body is changed. They are kept in a magazine called a stenter frame storage system. The challenge now is to be able to replace the stenter frames automatically within a few seconds. In the past, this was done at ground level using slide systems. Hans Hager, developer of the KFG3 Framer, on the task: "We very quickly realized that the ground-level feeding of the change frames in the very cramped precision steel construction was the Achilles' heel of the production system. However, thanks to our many years of experience with large gantry handling systems for flat glass, we were able to implement a vertical transport solution for the clamping change frames."

The dimensions of the gantries are enormous: they enclose the entire production line and even have to provide space for two supply lines. This adds up to 20 m or more for the Y-axis alone, while the Z-axes offer a travel distance of around 2.6 m. For each body, the Y-axis has to move the clamping frames apart by around 0.7 m and back together again. Each time the bodywork is changed, the appropriate stenter frames are retrieved from the storage area, moved over the PSB and the stenter frames are replaced with the aid of the Z-axes. This innovative solution from Hager can now be found in automotive industry plants all over the world. Maintenance, general overhaul and assembly of the portal handling systems are also carried out by Hager's 150 or so employees.

Avoid standstill

To ensure high availability of the production line, system-critical parts are replaced at fixed intervals in the automotive industry. This also applies to the profile rail guides in the linear axes of the "Framer" - as Hager calls its gantry handling systems. If they were to fail, the entire production line would come to a standstill. This led to interest in a retrofittable monitoring solution for the linear axes. Michael Martinkovich from the Schaeffler engineering office in Munich suggested Schaeffler DuraSense as a monitoring solution for the linear axes. The system consists of carriages with a sensor system specially developed for this task and a pre-processing unit for up to seven sensors.