How to reduce the cost effectively in the initial design stage of automotive wiring harness?

Abstract: This paper introduces the automotive wiring harness and its cost structure and current situation. This paper introduces in detail 6 kinds of cost reduction methods in the design stage of wiring harness, including platform and standardized design, architecture optimization and controller integration, wiring harness layout optimization, wiring harness technology innovation, material one-to-many and localization, and VAVE cost reduction, and has been applied in vehicle development projects with remarkable cost reduction effect.

0 Introduction

At present, the automotive industry is facing the "new four modernizations" of electrification, intelligence, networking and sharing, and there are more and more electronic and electrical products on the car, and the car wiring harness connecting various electrical appliances as a car signal and power transmission is becoming more and more complex. In order to produce high-quality low-cost cars and improve the competitiveness of automobile products, automobile companies are also constantly exploring cost reduction. As a part of the car, the cost reduction of the wire harness is also the focus of attention. Nowadays, various enterprises are very concerned about the research and development of products, because it is directly related to the benefits of enterprises. Studies have shown that 80% of the product cost is decided in the design stage, so many companies have invested a lot of energy to pay attention to this 80% of the established cost, in the development of products into the pre-production link, to explore further cost reduction methods. Therefore, it is of great significance to carry on the research and application of cost reduction in the design stage of automotive wiring harness and further optimize the cost of wiring harness.

1 Introduction to automotive wiring harness

Automotive wiring harness refers to all the wiring harness of the vehicle, including the electrical box. Automotive wiring harness is composed of wire, connector, terminal, sheath, tape, heat shrink tube, fuse, relay, bellows, PVC pipe and fuse box and other accessories, which plays the role of automotive neural network, transmitting signal and executing electric energy. The mainstream design of vehicle wiring harness adopts the "4+X" scheme, that is, the vehicle wiring harness is divided into four main wires of engine wiring harness, front cabin wiring harness, instrument panel wiring harness and body wiring harness, with additional trunk wiring harness, ceiling wiring harness, front and rear wiring harness, four-door wiring harness and ground wiring harness.

2. Cost structure and current situation of automotive wiring harness

There are four kinds of manufacturing processes for automotive wiring harness, which are opening wire, crimping, pre-assembly and final assembly. At present, only the wiring and crimping part of the high degree of automation, because the wiring harness materials and more and more complex and can not be located, the assembly and testing part still need to rely on a large number of manual, although in recent years, automotive wiring harness enterprise automation has made great development, but the automotive wiring harness processing is still labor-intensive industry, about 70% of the production process for manual, manual The cost accounts for a higher proportion of the total cost of automotive wiring harness. The cost of automotive wiring harness is composed of material cost, processing fee, packaging and transportation fee and management fee, of which the proportion of packaging and transportation fee is very low. The material cost of wiring harness is mainly determined by the technical scheme of wiring harness. Wiring harness processing fees and management fees are mainly determined by the output of automotive wiring harnesses and the labor costs of wiring harness suppliers, corporate profits and tooling allocation. With the continuous increase of vehicle configuration, the wire harness material cost is increasing.

At present, with the increase of labor and land use costs, wiring harness processing fees and management fees are on the rise. Below are the low voltage wiring harness cost composition ratios (Figure 1) and wiring harness material cost composition ratios (Figure 2). The wiring harness material cost accounts for about 65% of the total wiring harness cost ratio. In the design stage, the cost of wiring harness can be reduced mainly by optimizing the design of wiring harness. In the later stage, the cost of wiring harness is mainly reduced by optimizing the manufacturing process of wiring harness suppliers and comparing prices.

3 Research and application of wire harness cost reduction in design stage

3.1 Platform and standardized design

In order to reduce product cost and shorten development cycle, platform design has become one of the important cost reduction measures for automobile enterprises. By wiring harness connection, the platform definition of wiring harness interface and hole position of electrical appliance can be promoted. The continuous promotion of wiring harness materials and design scheme platform, the unification of wiring harness components and structure simplification, improve the standardization of design, reduce the randomness of engineer design, different models as far as possible to share wiring harness secondary parts. Establish a wire harness parts database, try to use existing platform parts, avoid special new parts development. The unity of wiring harness parts can concentrate the demand, which is conducive to the procurement of parts and improve the bargaining chips. Through continuous platform optimization design, the universality rate of the front cabin electrical box, instrument panel electrical box, wire harness connector and wire harness accessories has reached 100%. In terms of parts connectors, there are 312 types of parts, 208 types of platform, and the platform rate has increased to 67%.

Before optimization, there are 5 types of PFB electrical boxes, of which 4 are tile type and 1 is side hanging type, and only 3 types are optimized. The following is a platform design optimization case of PFB electrical box for a platform project. The combination of three kinds of PFB electrical box is optimized into one kind of PFB electrical box, as shown in Figure 3.

3.2 Architecture optimization and controller integration

The continuous optimization of the vehicle architecture not only improves the performance of the vehicle, but also reduces the production cost. Promote electrical architecture optimization, can effectively simplify the wire harness structure. The greater the number of electrical components, the longer the harness. Advance appliance integration to reduce the number of connectors and harness branches. Taking an electric vehicle project as an example to optimize the high-voltage electrical architecture, the cost and quality of the high-voltage wiring harness are greatly reduced. After the optimization of the vehicle architecture, the length of the high-voltage wiring harness is reduced from 22 m to 9 m, and the mass is reduced from 13.5 kg to 4.8 kg, and the cost of the high-voltage wiring harness is significantly reduced by 41%, as shown in Figure 4 and Figure 5.

3. 3 Wiring harness layout optimization

Due to the application of a large number of electrical components and the small wiring space in the car, the difficulty of wiring harness layout is constantly increased. The wiring harness design and layout should be safe and stable, save materials, save space, and be easy to assemble and maintain. Further improving the uniformity of electrical appliance layout, reducing the types of fixed materials, reducing and simplifying the use of protective panels, avoiding heat sources, and reducing the application of thermal insulation materials can make the direction and layout of wiring harnesses more optimized. Optimizing the layout position of electrical components can shorten and simplify the wiring harness path. Figure 6 and Figure 7 are shown before and after optimizing the wiring harness layout of a certain project. A parts layout position remains unchanged, body rotation 180°. The antenna interface connector was changed from two 2PIN connectors to four 1PIN connectors, of which three 1PIN connectors were connected directly to part A and one was connected to the harness. The wiring harness reduces 3 small wire materials of 3 antenna loops connected with part A, the length is about 1m, the wiring harness feeders are shortened, and the total cost of this layout optimization is about 28 yuan.

3. 4 Harness technology innovation

Through the introduction of new technologies in wire harness material, design and process, light weight and cost reduction of wire harness can be achieved. For example, with the application of relay and fuse miniaturization technology, the total cost of the electrical box is reduced by about 29.5 yuan. For example, under the same impedance conditions, aluminum wires have less mass than copper wires (see Table 1). By choosing aluminum wire and thin wire diameter wire with smaller outer diameter and lighter weight, the weight of automobile wire harness can be reduced and the cost can be reduced. Wire cost accounts for a large proportion in the cost of automotive wiring harness, the promotion of 0.13mm2 alloy wire or even lower small square wire, the application of 0.13mm2 alloy wire is of great significance for the vehicle lightweight. Before optimization, 35 mm2 copper wire was used for a 48-V battery harness in a project, and after optimization, 50 mm2 aluminum wire was used to replace it. The length was about 4 m, the weight was reduced by 224 g/ m, and the total weight was reduced by 896 g, and the cost was reduced by about 30 yuan, as shown in Figure 8.

3. 5 One-to-many materials and localization

From the past technical solution corresponding to a kind of second and third level materials to the use of the same kind of material one-to-many mode, to provide first-level suppliers with "selection resource library", foreign wire harness factories and local wire harness factories according to their own procurement system, choose low-cost materials, enhance the bargaining power of wire harness suppliers, improve the stability of the supply chain. A one-to-many scheme such as ground terminal, heat shrink tube, safety piece, bellows and ordinary wire has been implemented. Taking the cloth base sleeve of a project as an example, the cloth base sleeve of the same pipe diameter can be exchanged with three different brands of products, as shown in Table 2. Improving the localization rate of secondary and tertiary materials and reducing material costs have become the main measures for many parts to reduce costs. With the continuous improvement of the intelligence of domestic connectors, domestic connector manufacturers through continuous innovation technology, the quality of domestic connectors is getting better and better. Because the imported connectors are generally expensive and the supply cycle is long, the domestic connector brand has received more attention, while ensuring the quality, the wiring harness of many model projects is replacing some foreign-funded connectors with domestic connectors, reducing the cost of wiring harness materials and improving the supply chain stability. Some connectors and accessories in a project are replaced by domestic brands such as Hulian and Aohai, as shown in Table 3.

3. 6VAVE reduces costs

At present, the awareness of VAVE cost reduction in automobile enterprises is becoming stronger and stronger. VAVE cost reduction activities can effectively reduce the cost of wiring harness and improve the cost performance advantage of products. Since it is more difficult and costly to push forward the implementation of VAVE after mass production, more attention is now paid to the application of VAVE in the design stage. At present, the mechanism of the regular meeting of the project team is fully utilized, and all relevant departments are fully involved in the VAVE activities, so that the relevant engineers of each department are clear about the specific measures and contents of the VAVE program, and actively cooperate with the promotion and implementation of the effective proposal of the wiring harness. The proposal and implementation of wiring harness VAVE are also inseparable from the active participation and cooperation of wiring harness suppliers. The wiring harness design department regularly holds project meetings with wiring harness suppliers to exchange VAVE plans and follow up progress, which effectively promotes the implementation of VAVE plans.

The wiring harness design department developed a VAVE record table to ensure that the VAVE plan is unfolded. For each project, the VAVEcheck list was compiled according to the VAVE record table. The drawings of each valve were reviewed according to the VAVEcheck list. There were 12 types of optimization types in the VAVE table. Taking a certain model as an example, through the continuous optimization of VAVE in the design stage, the cost reduction ratio of vehicle wiring harness materials is about 11%. For example, the car body wiring harness and ceiling wiring harness are combined into one. Before VAVE optimization, the original wiring harness scheme was separated from the body wiring harness, and two pairs of wiring harnesses were inline docking to form two independent wiring harnesses, with parts managed separately and assembled separately, which was not the optimal design scheme from the perspective of cost and quality. Under the existing layout conditions, through VAVE analysis and comprehensive consideration, the ceiling harness can be integrated into the body harness, and there is no ceiling harness parts after integration, which can reduce the management of one part and reduce the tooling cost. After the roof harness is merged into the body harness after VAVE, there is no roof harness as shown in Figure 9 and Figure 10. Through VAVE optimization, the cost is reduced by 16 yuan/set, the quality is reduced by 0.1 kg/ set, and the tooling cost is reduced by about 30,000 yuan after the tooling merger.

4 Closing remarks

Nowadays, the competition in the automobile industry is fierce, and various automobile companies are paying attention to cost optimization. In the stage of automotive wiring harness design, we make full use of platform design, wiring harness layout optimization and VAVE to optimize the wiring harness design, and the cost reduction effect is remarkable. Cost reduction is a long way to go. In the future, we will further strengthen the cost reduction optimization work in the wiring harness design stage, explore the extension of the wiring harness design upstream, and promote the streamlining of the wiring harness design. Effectively reduce costs and increase efficiency to provide more competitive products