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Optimization of wire length of automobile wire harness
Time:2021-11-25 Read: 488

The wire is an important part of the car harness, and the optimization of the wire length is intuitive for the weight and cost of the car harness. The process part of wire length optimization in this paper is very clear and worth reading.


The automobile wire harness is mainly composed of four parts: wires, terminals, plastic parts and covers. Among them, the automobile wire is a very complex part in the process. Generally, a vehicle has about 1200 loops, and all the wires add up to about 1500 meters. So many wires are combined together, which requires us to design the wires of each loop into appropriate length, which puts forward high requirements for technicians. The usual method is to roughly calculate the wire length in the early stage of design to ensure that the length is sufficient, and then optimize the wire one by one in the mass production stage. The advantage of this method is that it can reduce a lot of work in the case of a short development time in the early stage, but the disadvantages are also clear. In fact, it wastes a lot of raw materials and also causes a lot of secondary work.

Today, let's talk about how to accurately calculate the length of a wire: the length of each wire should be composed of three parts: the length of the trunk, the length of the wire in the plastic parts, and the branch node compensation;

1、 Length of trunk

The length of the trunk refers to the total length L1 from one end of the plastic part to the other end. This dimension can be directly calculated from the drawing. For example, the size between AA and BB can be directly calculated from the marks on the drawing. It should be noted that our design drawings and tooling drawings may have deviations. The main reason is that the tooling drawings will appropriately relax the size on the basis of the design drawings. Therefore, when calculating the length of the trunk, we must use the dimensions on the tooling drawing.

2、 Length of wire in plastic parts

As part of the wire will be inserted into the harness, we need to measure the length between the plastic part surface and the terminal crimping wing. There are two methods to measure the length of the plastic part wire:

(1) Measuring method for common plastic parts: the length from the surface of the plastic parts to the terminal crimping wing is the length of the incoming line.

(2) Measuring method of special plastic parts: for this special plastic part, select side A of the plastic part as the measuring starting point, and calculate the length L2 of the wire from this point to the end of the wire (terminal crimping wing). Because the length of each hole location of plastic parts is different, we can measure the wire length of the farthest end and the wire length of the nearest section, and calculate the wire length of each hole location through the method of equal difference sequence.

3、 Branch node compensation

The length of the wire L2 of the plastic part of the trunk length L1 should be the shortest length L of a single wire, because many wires are mixed together during the assembly process, there will be stranded wires, and a part of the wire length will be lost. In addition, at branch nodes, due to the different thickness of the wire trunk, the turning radius of each wire is also different, so the required length is also different; In the case of stranded wire, we can compensate the length of trunk length * 1% (empirical value, for reference only), and the compensation of branch turning radius length can be divided according to the size of the line. If it is the length of the main branch of the instrument line, body line and engine line, each line can be compensated with a turning radius of 5-10mm. If it is a small line branch, we can compensate with a turning radius of 3-5 mm.

Finally, by adding these three lengths, we can get a relatively accurate wire length. The wire length calculated by the above method can ensure that most of our wires are in a reasonable length. Conductor optimization is very helpful for us to save material costs. I will use the following figures to illustrate that the average price of 0.5mm conductor on the market is 0.35CNY/m, and the 20% optimization space of a set of conductors at the initial stage of design is about 300m, and the price of a set of conductors is about 2000 yuan. That is to say, we can save 105 yuan through wire optimization, accounting for 5% of the total sales. If we do a good job of saving, it is all profits. If we do not do a good job, it is sunk costs. So the better the wire optimization in the early stage, the more conducive to saving material costs.

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