Forged from special hard steel and equipped with a robust M42 thread at their ends, the tie rods represent a soft screw case for Arburg. Soft because after the so-called head support of the screwdriving case, around 720 degrees of angle still need to be tightened to achieve the final torque. "The torque-correct assembly of the eight to twelve tie rods, depending on the model, is one of the most important screw connections on our machines," emphasizes Martin Widmaier, Group Manager Equipment Design at Arburg: "Precise screwing of these rods creates the prerequisite for optimum force distribution in the clamping unit."

The Allrounders shape molded parts with clamping forces of up to 6,500 kilonewtons. Together with the tool supplier Technik Center Tuningen, Arburg adapted a Tensor electric screwdriving system from Atlas Copco to this special joining task.

The Tensor Revo screwdriver, which is housed in a maneuverable tool trolley, can be conveniently moved to its place of use in the assembly hall and receives all data on the required torques and tightening angles via a WLAN module. The system can also be connected to the electronic machine file, which accompanies every Allrounder throughout production. The digitally controlled high-torque screwdriver is programmed for two-stage tightening in order to reliably prevent any distortion of the cast plates at a target torque of 3,400 newton meters.

Operation is intuitive and simple: in the first step, the Tensor Revo initially transfers 1,800 newton meters into the screwdriving case, in the second stage the tool then tightens to the final torque of 3,400 newton meters. Compared to the previously used high-torque pneumatic screwdriver, the Atlas Copco tool turns 30 times faster and reaches the required 3,400 Newton meters in less than ten seconds.

Arburg was able to reduce the time required to screw the tie rods together to just ten to twelve minutes. "The new screwdriving technology has made us around six times more productive - and even more reliable - in this assembly area," says Martin Widmaier. as