Electrical laboratory

Screw Joint Analysis
he various DEPRAG screwdriving tools which are used for the laboratory tests are equipped with appropriate electronic measuring equipment and are thus capable of graphically depicting the screwdriving process on a display. By means of the recorded graph, the screwdriving specialist can precisely analyze the screw joint. The test is now repeated ten or twenty times - always with original components. At the end of this test series, after careful analysis, the results are made available for the manufacturer to see which screwdriving parameters and type of screwdriving tool are most suitable for this particular screw assembly task.

What is the difficulty with screw joints? In the technical world, the screw process is the only reversible process with respect to the connection of assembled components. After screw assembly, they can be used as if they were a single part, meeting the highest requirements. The purpose of the screw in this process is to clamp the components tightly together so that they cannot be shifted by external forces. The achieved force is called pre-tension. The screw assembly has to remain within the range of defined tolerance limits: On the one hand, the achieved pre-tension must be sufficient to keep the component together, while on the other hand the screw and component should not be damaged by over tightening.

However, direct methods for the measuring of the achieved pre-tension are not suitable for serial production. Therefore, the industry has to draw on indirect measuring means in screw assembly. Thus, the torque counts as the determining process value in the screwdriving process, as it behaves proportionally to the pre-tension. The angle of screw rotation is also used in the determination of the actual achieved pre-tension