Basic Composition and Production Process of Wire Harness

I. The basic components of the harness include wires, connectors, external materials and other components.

1.1. Wires
The purpose of the wire is to carry current to transmit signals and provide power. The wire itself contains internal copper wire and external insulation material. Each wire of different specifications has its current value of the allowable load, which is the basis of making a qualified harness. With the increase of automobile function and the general use of electronic control technology, more and more electrical parts and wires are used, and the wire harness becomes thicker and heavier. In the future, to reduce the utilization rate of wires, modern cars have introduced can bus configuration and adopted a multiplex transmission system. Compared with the traditional point-to-point wiring harness, can bus greatly reduces the number of wires and connectors, making the wiring harness lighter and easier.

1.2. Connector and terminal
The terminal and the wire shall be locked in the hole slot of military style electrical connectors after crimping according to the standard, and the male and female connectors shall be butt jointed to meet the connection between the harnesses and the circuit from the harness to the terminal. If they are arranged in the engine compartment with high humidity, according to the requirements of national regulations, waterproof bolts shall be added.

1.3. External parts and other parts
The external parts include corrugated pipe, polyethene pipe, polyethene cloth, sheath, sponge, adhesive tape, harness bracket, etc. to place the abrasion and fracture of wires. Meet the temperature and humidity requirements of different positions of the vehicle body. Generally, corrugated pipe, polyethene pipe, polyethene cloth, hard pipe and sheath are used to prevent the wire from wearing and breaking. Thin wall and thick wall adhesive tapes are used to wrap the wire, and clamps of different shapes are used to fix the wire harness in the proper position of the vehicle body. The purpose of the rubber ring is to prevent the wire harness from scratching when passing through the sheet metal hole.

II. The production process of wire harness

Because the harness contains many parts mentioned above, the manufacturing process is complex and almost all of them need human intervention. Of course, with the improvement of modern processing technology, more and more automatic devices are applied to the production of the wire harness.

2.1 Tangent line and end pressure
Cut the wire according to the opening size and stripping size required by the drawing, and then use the terminal crimper to crimp the terminal to the wire. Among them, the quality of the terminal crimping is very important. It can be roughly divided into the wrapping requirements of insulating skin and conductor. Only after necessary debugging of crimping machine can the qualified quality of terminal crimping be obtained.

2.2 Subassembly and general assembly
In the past, this process was all manual manufacturing. The wires with crimped terminals were run through pipes, waterproof bolts, military grade electrical connectors, sheaths, tapes and clips. Recently, the new generation of processing equipment can complete most of the above processes, greatly saving labor force and improving production efficiency. To prevent confusion, the manufacturer will provide the drawings shall be transformed according to their conditions, printed on the knotting board to guide the workers to carry out the general assembly, and reasonable process and material distribution shall be carried out to improve the production efficiency and quality.

2.3 Inspection and packaging
In order to ensure the quality of harness, each harness will be inspected for appearance, dimension, continuity and airtightness after manufacturing. Among them, the continuity check is particularly important. The instrument is a customized continuity table (composed of hardware modules and software programs). After connecting the harness connector to the continuity table, start the program to draw a judgment conclusion. Faults such as complete continuity or partial circuit break are easier to pack than other parts. Generally, cartons are used for transportation.

If the harness is a newly developed part, the part test and mainline test shall be carried out. The test of the whole line generally includes the following nine tests: temperature change resistance, high-temperature resistance, low-temperature resistance, damp heat cycle resistance, salt fog resistance, vibration resistance, industrial solvent resistance, voltage drop test and non-delayed combustion performance.

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