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CO2 reduction and increased load cycles in E-mobility: both are aims which are becoming achievable due to lightweight vehicles. This has been recognised for a long time in modern automobile engineering and it has been relying on lightweight materials instead of conventional steel for chassis design.
From high safety requirements, reliability of materials, simple repairs, easy replacement of bodywork components to recycling and the possibility of reuse - all are considerations which present challenges to the automotive industry. It necessitates a complete rethink, even in assembly: The choice of the correct joining technology is of decisive importance in lightweight construction. Flow drill screwdriving has established a place for itself within chassis design.

The specially formed tip of the so-called flow drill or flow form screw generates frictional heat under high pressure and at high speeds, effecting a flow process in metal sheeting which has not been pre-drilled. At the start of the process a ”crater” is formed in which the multiple thread is cut after the screw has penetrated and formed a funnel passage at reduced pressure. A machined thread is created which can accommodate a ”normal” screw if repairs are ever carried out. Once the flow hole has been shaped the speed is decreased, the next step is the pre-tightening of the screw until head contact is made and then final tightening of the fastener to the pre-set parameters of torque and angle.

The complete procedure usually takes less than two seconds. Additional securing parts such as nuts or bolts are not required because the assembly optimally penetrates and forms the thread for the screw so that the screw sits securely. There is no need for initial drilling or punching holes in the component.

This process does not only enable the connection of sheets of varying materials but it also offers clear advantages in relation to processing costs and time. But is this screwdriving process also suitable in applications with fluctuating tolerances and varied components?

In order to ensure high screwdriving quality despite component tolerances, such as deviating positions, sheet material thickness and screw length tolerances or structural differences, current solutions on the market are only able to offer screw assembly systems where settings for screwdriving parameters are time-consuming and have to be separately determined for each screw position. Usually the feed movement and force is provided by a compressed air cylinder with proportional valve.