In the automotive wiring harness manufacturing process, bolt connections are a core element in ensuring the safety and reliability of the electrical system. Bolts of specifications M5, M6, and M8 are widely used in the central electrical box, front and rear compartment fuse boxes, and the positive and negative terminal connections of power wiring harnesses. These connection points bear the important functions of high-current transmission and circuit protection. Once loosening or poor contact occurs, it can lead to electrical failures at best, or even cause line overheating or vehicle self-ignition and other serious accidents at worst.

In automotive wiring harnesses, the clamped objects in bolted connections are mostly made of copper and zinc, which are considered soft connections. During the tightening process, care must be taken to prevent over-tightening that could cause terminal breakage. To ensure the reliability of the tightened bolts, it is necessary to adopt methods to increase friction when needed, such as using locknuts, adding spring washers, and threaded flange nuts, and applying appropriate tightening torque to ensure that the clamping force of the bolted connection meets product design requirements.

Pay close attention to the difference between static and dynamic torque to prevent torque decay due to thermal expansion and contraction: Simply put, dynamic torque is the torque setting value set by the tightening tool during the wiring harness bolt tightening operation, used to tighten the wiring harness fuse box or eyelet terminal; static torque is the torque verification value obtained by the quality inspector when inspecting the wiring harness bolt with a pointer or digital torque wrench. Dynamic torque is the tightening method recognized by General Motors. When re-checking bolts with a manual wrench, static torque is used, but static torque is not a tightening method recognized by General Motors. General Motors believes that dynamic torque is more accurate and has better repeatability than static torque.

Danikor's sensor-based smart electric screwdriver has a 6σ accuracy of ±5% across the full torque range and can provide a variety of tightening strategies. During the tightening process, it can record and monitor data such as slope, torque, angle, and steps in real time. The tightening curve is dynamically displayed, allowing for timely detection of issues such as floating screws or stripped threads. It also features data recording and storage functions, facilitating later traceability of the tightening status of each screw and providing strong data support for wiring harness assembly quality control.

Typically, the bolts of automotive wiring harness components are concentrated in the central electrical box and power distribution box, and the objects to be tightened are mostly large-diameter eyelet terminals and blade fuses. Therefore, if workshop space permits, an independent bolt tightening workstation should be designed, which can be separated from the main wiring harness assembly line.

After tightening the bolts of automotive wiring harness fuse boxes and components, static torque inspection or 100% secondary torque verification must be performed to ensure that the bolt tightening meets product design requirements. For torque inspection or secondary bolt tightening tool inspection, a digital torque wrench should be selected. First, set the inspection torque peak value on the digital torque wrench. When the inspected bolt torque reaches the set value, the digital torque wrench will emit a sound prompt or a green light indication.

The reliability of automotive wiring harness bolt tightening directly affects the quality and reliability of the wiring harness, and directly impacts and relates to the driving safety and reliability of the vehicle. Therefore, it is essential to pay attention to and ensure the correct tightening and reliability of bolts in automotive wiring harness components.