What is automotive wiring harness

Automotive wiring harness is the main network component of automotive circuits, and without wiring harness, there would be no automotive circuits. A wire harness refers to a component that is made of copper material punched into contact terminals (connectors) and crimped with wires and cables, and then covered with plastic insulation or an external metal shell to form a connected circuit. The wiring harness industry chain includes wires and cables, connectors, processing equipment, wiring harness manufacturing, and downstream application industries. Wiring harnesses are widely used and can be used in automobiles, household appliances, computers and communication equipment, various electronic instruments and meters, etc. The body wiring harness connects the entire body of the vehicle and has a general H-shaped shape.

Main specifications and performance requirements for automotive wiring harnesses

1. Cross sectional area of the wire
Select the cross-sectional area of the wire according to the load current of the electrical equipment. Generally, for electrical equipment that works for a long time, a wire with an actual current carrying capacity of 60% can be used, and for electrical equipment that works for a short time, a wire with an actual current carrying capacity between 60% and 100% can be used; At the same time, voltage drop and wire heating in the circuit should also be considered to avoid affecting the electrical performance of electrical equipment and the allowable temperature of wires; To ensure a certain mechanical strength, the cross-sectional area of low-voltage wires is generally not less than 1.0mm ².
2. Color of the wire
There are color and numbering features on the car circuit. With the increase of automotive electrical equipment, the number of wires is also constantly increasing. In order to facilitate identification and maintenance of automotive electrical equipment, low-voltage wires in automotive circuits are usually composed of different colors and marked with color letter codes on automotive electrical circuit diagrams.
On car circuit diagrams, the color codes of wires are usually marked (represented by one or two letters). The colors of wires on cars are generally different, and there are two commonly used selection principles: monochrome and two-color. For example: red (R), black (B), white (W), green (G), yellow (Y), black and white (BW), red and yellow (RY). The former is the main color and the latter is the auxiliary color in the two-color line.
3. Physical properties of wires
(1) Winding performance: The wires between the car door and the vehicle body should be composed of wires with good winding performance.
(2) High temperature resistance performance: Wires used in high-temperature areas are generally coated with vinyl chloride and polyethylene, which have good insulation and heat resistance.
(3) Shielding performance, in recent years, the use of electromagnetic shielding wires in weak signal circuits has also been increasing.
4. Binding of wiring harness
(1) The cable half stack wrapping method involves applying insulation paint and drying to increase the strength and insulation performance of the cable.
(2) A new type of wiring harness, partially wrapped in plastic and placed inside a plastic corrugated tube with a side cut, enhances its strength, improves its protective performance, and makes it easier to locate circuit faults.

Production process of wire harness

The first workstation in wire harness production is the wire opening process. The accuracy of the opening process is directly related to the entire production schedule. Once errors occur, especially when the opening size is too short, it will result in rework at all workstations, which is time-consuming and labor-intensive, affecting production efficiency. So when preparing the wire cutting process, it is necessary to reasonably determine the wire cutting size and stripping size according to the requirements of the drawings.
The second workstation after opening the line is the crimping process. The crimping parameters are determined according to the terminal type required by the drawing, and a crimping operation manual is made. For those with special requirements, they need to be noted in the process documents and trained for operators. For example, some wires need to pass through the sheath before crimping, and they need to be pre installed before returning from the pre installation station for crimping; There is also a special crimping tool used for piercing crimping, which has good electrical contact performance.
Next is the pre assembly process. Firstly, a pre assembly process operation manual needs to be prepared. In order to improve the overall assembly efficiency, complex wire harnesses need to be equipped with pre assembly workstations. The rationality of the pre assembly process directly affects the overall assembly efficiency and reflects the technical level of a process personnel. If there are too few pre assembled parts or the wiring path is unreasonable, it will increase the workload of the overall assembly personnel and slow down the speed of the assembly line. Therefore, the process personnel need to stay on site frequently to constantly summarize.
The final step is the assembly process. Capable of designing tooling equipment, material box specifications and dimensions based on the assembly platform designed by the product development department, and attaching all assembly sleeves and accessory numbers to the material box to improve assembly efficiency. Develop assembly content and requirements for each workstation, balance the entire assembly station to prevent excessive workload and slow down the entire assembly line.

Composition of wiring harness

The car wiring harness consists of wires, terminals, coverings, connectors, and other parts.
1. Wires
Wires are the main components of a wiring harness, commonly referred to as wires, and are the main body of the harness. Their function is mainly to carry the current required by the load. The important parameter of a wire is its current carrying capacity, which is influenced by the wire diameter (cross-sectional area of the wire conductor), wire length, electrical resistivity of the conductor, and ambient temperature.
2. Connectors
A connector is also called a connector, CONNECTOR, or plug. Connectors are essential components for connecting wire harnesses to other electrical equipment, and are divided into wire harness end connectors and electrical appliance end connectors.
We often hear about male connectors (referred to as male terminals) and female connectors (referred to as female terminals), where the connector where the male terminal is located is called a male connector, and the connector where the female terminal is located is called a female connector. Our wire harness end is usually a female connector.
Connectors can be divided into two categories: waterproof and non waterproof. At the beginning of the design, different widths of PIN pins were selected based on the current carrying capacity of each pin, and then chambers were formed on the connector to accommodate different PIN pins, thus forming a housing that can accommodate multiple PINs.
(1) CPA Plastic Shell Secondary Locking Mechanism ConnectorPositionAssurance:
Its function is to ensure that the locking mechanism of the plastic shell and electrical interface will not easily retract after assembly. Due to its special function, CPA must ensure the operability and recognizability of workers during design. This requires CPA to be an independent mechanism on the plastic shell and must have special color markings.
(2) Waterproof sealing ring:
There are two types of waterproof sealing mechanisms, one for sealing between plastic shells and the other for sealing terminal leads.
(3) TPA Terminal Position Assurance: Terminal Secondary Locking Structure
Not all terminals require a secondary locking structure. VW requires that TPA should be used for terminals with a width of 2.8mm or less (including 2.8). To ensure ease of installation for wiring harness factory workers, the color of TPA should also be recognizable, and there should be a clear hand feel during assembly. To ensure that the plastic shell does not automatically enter the locking position during transportation to the wiring harness factory, a mechanism for anti locking is necessary on TPA.
3. Wiring harness wrapping material
The main function of wire harness wrapping is to protect the wire harness. Depending on the material of the wrapping, the types of wrapping mainly include corrugated pipe, PVC tape, cloth tape, velvet tape, sponge tape, and aluminum foil tape.
Due to different materials, the material characteristics of different wrapping materials are also inconsistent. Correspondingly, their application conditions and methods on the wire harness assembly are also inconsistent. The specific selection should be based on the specific usage environment of the wire harness and its wear resistance and heat resistance.

4. Wiring harness fixing device
Unlike other components on other cars, wire harnesses are flexible parts that cannot be sampled according to a predetermined shape. Therefore, in order to constrain the layout path of the wire harness on the entire vehicle, additional parts need to be added to fix the wire harness. These additional parts are wire harness fasteners, which play a role in fixing and constraining the layout path of the wire harness.
Wire harness fasteners include zip ties, buckles, rubber sleeves, wire harness brackets, etc. Depending on the installation environment of the wire harness, such as the installation space, temperature requirements, and waterproof requirements, the form and material of each wire harness fastener are not consistent. Even so, wire harness fasteners also show a trend towards standardization and are one of the components that are relatively easy to achieve in the selection of wire harness platforms.
5. Wiring harness accessories
Wire harness accessories refer to other smaller products on the wire harness assembly, such as product labels, fuses, clips, etc. on the wire harness assembly.