Screw connections and assembly
Ensuring optimum preload force
Screws are components contained in technical machines. They are used to connect pieces together. In contrast to other methods of connection, such as rivets or welding, a connection created with screws is designed to be disconnected again at a later time.
Key to the screw connection achieved is the force with which the pieces are held together – the so-called preload force. This must not be too great, as otherwise the components get damaged. However, it must also not be too little, as otherwise the pieces do not get held together strongly enough and may move. Directly measuring the preload force of a screw connection is not possible / only possible by comparatively complex means, e.g. using sensors. Another important factor in the case of screw connections is the tightening torque, which compared to the preload force can be measured relatively easily using a torque wrench.
For the precise determination of the preload force and tightening torque and thus ultimately for producing a secure screw connection another elementary requirement is knowledge of the coefficients of friction. In this context the trueness to gauge and settling behaviour also play an important role.