Automotive wiring harness production process and automotive wiring harness design principles

First: strip the wires.

The accuracy of wire stripping is directly related to the entire production progress. Once an error occurs, especially if the wire size is too short or too long, it will lead to rework of all work stations, which is time-consuming and labor-intensive and affects production efficiency. Therefore, when stripping wires, the opening size and stripping size of the wire must be reasonably determined according to the requirements of the drawing and the terminals to be punched.

Second: crimping process.

Determine the crimping parameters according to the terminal type required by the drawing, prepare crimping operation instructions, and indicate special requirements on the process documents and train operators. For example: some wires need to pass through the sheath before crimping, which requires pre-installing the wires and then returning from the pre-assembly station before crimping; there are also piercing crimping methods that use special crimping tools. This crimping method has good electrical contact performance. And be sure to test the pulling force value of the terminal. If the pulling force does not meet the requirements, you need to readjust the crimping mold.

Third: pre-installation.

First, we need to prepare operating instructions for the pre-assembly process. In order to improve the efficiency of the final assembly, pre-assembly stations must be set up for complex wire harnesses. The reasonableness of the pre-assembly process directly affects the efficiency of the final assembly and also reflects the technical level of a craftsman. If there are too few pre-assembled parts or the wire paths of the assembly are unreasonable, it will increase the workload of the general assembly personnel and slow down the speed of the assembly line, so the craftsmen must often stay on site for continuous review.

Fourth: Final assembly process.

Able to compile the assembly platen designed by the product development department, design tooling equipment, material box specifications and dimensions, and affix the numbers of all assembly sheaths and accessories on the material box to improve assembly efficiency. Prepare the assembly content and requirements for each station, and balance the entire assembly station to prevent excessive workload at one point and slow down the entire assembly line. To achieve work station balance, craftsmen must be familiar with each operation, measure working hours on site, and adjust the assembly process at any time.

Wire harness production is mainly divided into two processing methods: end pressing (crimping) and molding. There is no best method. It must be manufactured according to the functional characteristics of the wire harness. And be sure to fully inspect the product, test the conductivity, resistance, voltage, etc. of the wire to ensure the yield of the product and prevent defective products from entering the market.

Automotive wiring harness design principles

The automobile wiring harness is the network main body of the automobile circuit. Without the wiring harness, there would be no automobile circuit. At present, whether it is a high-end luxury car or an economical ordinary car, the form of wiring harness is basically the same, and it is composed of wires, connectors and wrapping tape.

Car wires are also called low-voltage wires, which are different from ordinary household wires. Ordinary household wires are copper single-core wires, which have a certain hardness. Car wires are all made of copper multi-core soft wires, some of which are as thin as hair. Several or even dozens of soft copper wires are wrapped in plastic insulating tubes (polyvinyl chloride), which are soft and not easy to break.

Commonly used specifications for wires in automobile wiring harnesses include wires with nominal cross-sectional areas of 0.5, 0.75, 1.0, 1.5, 2.0, 2.5, 4.0, 6.0 and other square millimeters. Each of them has an allowable load current value and is used for electrical equipment of different powers. of wires. Taking the vehicle wiring harness as an example, the 0.5 gauge wire is suitable for instrument lights, indicator lights, door lights, ceiling lights, etc.; the 0.75 gauge wire is suitable for license plate lights, front and rear small lights, brake lights, etc.; the 1.0 gauge wire is suitable for turn signals, fog lights, etc. Lights, etc.; 1.5 gauge wire is suitable for headlights, speakers, etc.; main power wires such as generator armature wires, ground wires, etc. require 2.5 to 4 square millimeter wires. This only refers to ordinary cars. The key depends on the maximum current value of the load. For example, the battery ground wire and positive power wire are special car wires used separately. Their wire diameters are relatively large, at least more than ten square millimeters. Above, these "big Mac" wires will not be integrated into the main wiring harness.

Before arranging the wiring harness, a wiring harness diagram must be drawn in advance. The wiring harness diagram is different from the circuit schematic diagram. A circuit schematic diagram is an image that expresses the relationship between various electrical parts. It does not reflect how the electrical components are connected to each other, and is not affected by the size and shape of each electrical component and the distance between them. The wiring harness diagram must take into account the size and shape of each electrical component and the distance between them, and also reflect how the electrical components are connected to each other.

After the technicians of the wiring harness factory make the wiring harness wiring board according to the wiring harness diagram, the workers cut and arrange the wires according to the regulations of the wiring board. The main wiring harness of the vehicle is generally divided into engine (ignition, EFI, power generation, starting), instrumentation, lighting, air conditioning, auxiliary electrical appliances, etc. There are main wiring harnesses and branch wiring harnesses. A vehicle main wiring harness has multiple branch wiring harnesses, just like tree poles and branches. The main wiring harness of the entire vehicle often takes the instrument panel as the core part and extends front and rear. Due to length or assembly convenience, the wiring harness of some cars is divided into the front wiring harness (including instrument, engine, front light assembly, air conditioner, battery), rear wiring harness (tail light assembly, license plate light, trunk light), roof Wiring harness (doors, ceiling lights, audio speakers), etc. Each end of the wire harness will be marked with numbers and letters to indicate the connection object of the wire. The operator can see the mark and correctly connect it to the corresponding wires and electrical devices, which is particularly useful when repairing or replacing the wire harness. At the same time, the colors of wires are divided into single-color wires and double-color wires, and the use of colors is also stipulated, usually according to the standards customized by the car manufacturer. Our country's industry standards only stipulate the main colors. For example, black is exclusively used for ground wires, and red is used for power cords. They cannot be confused.

The wire harness is wrapped with woven wire or plastic adhesive tape. For safety, processing and maintenance convenience, woven wire wrapping has been eliminated, and now it is wrapped with sticky plastic tape. The connection between wire harnesses and wire harnesses and between wire harnesses and electrical components uses connectors or wire lugs. The connector is made of plastic and is divided into plugs and sockets. Wire harnesses are connected with connectors, and wire harnesses and electrical components are connected with connectors or wire lugs.

With the increase in car functions and the widespread application of electronic control technology, there are more and more electrical components and wires, and the wiring harness has become thicker and heavier. Therefore, advanced automobiles have introduced CAN bus configuration and adopted multiple transmission systems. Compared with traditional wiring harnesses, multiplex transmission devices greatly reduce the number of wires and connectors, making wiring simpler.