Research and Application of Cost Reduction in Automobile Harness Design

This paper introduces automotive wiring harness, its cost structure and present situation. This paper introduces in detail six 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, one-to-many materials and localization, and VAVE cost reduction. These methods have been applied to the whole vehicle development project, and the cost reduction effect is remarkable.

Introduction

At present, the automobile industry is facing the "new four modernizations" of electrification, intelligence, networking and sharing. There are more and more electronic and electrical products in automobiles, and the automotive wiring harness, as the transmission of automobile signals and power to connect various electrical appliances, is becoming more and more complex. In order to produce high-quality and low-cost automobiles and improve the competitiveness of automobile products, automobile enterprises are constantly exploring ways to reduce costs. As a part of automotive wiring harness automobile, the cost reduction of wire harness is also the focus of attention. Nowadays, all enterprises pay great attention to the R&D design of products, because it is directly related to the benefits of enterprises. Studies have shown that 80% of the product cost is decided at the design stage, so many enterprises have invested a lot of energy to pay attention to this 80% established cost, and to explore further cost reduction methods before the R&D products enter mass production. Therefore, it is of great significance to study and apply cost reduction in the design stage of automotive wiring harness to further optimize the cost of wiring harness.

1 Introduction to Automotive Wiring Harness

Automotive wiring harness refers to all wiring harnesses of the whole vehicle, including the electrical box. It is composed of automotive wiring harness wires, connectors, terminals, sheaths, adhesive tapes, heat shrinkable tubes, fuses, relays, bellows, PVC tubes, fuse boxes and other accessories, and plays the role of automobile neural network, signal transmission and electric energy execution. The mainstream design of the vehicle harness adopts the "4+X" scheme, that is, the vehicle harness is divided into four main lines: engine harness, front cabin harness, instrument panel harness and body harness, with additional small lines such as trunk harness, ceiling harness, front and rear protection harness, four-door harness and grounding harness.

2 Automotive Wiring Harness Cost Composition and Current Situation

There are four kinds of processing technologies in automotive wiring harness, namely, thread opening, crimping, pre-assembly and final assembly. At present, only the opening and crimping parts have a high degree of automation. Because the wiring harness materials are numerous and miscellaneous and can't be positioned, the assembly and testing parts still need a lot of manpower. Although the automation of enterprises in automotive wiring harness has made great progress in recent years, the processing in automotive wiring harness is still a labor-intensive industry, with about 70% of the production processes being manual, and the proportion of labor cost to the total cost in automotive wiring harness is high. The cost of automotive wiring harness consists of material cost, processing fee, packaging and transportation fee and management fee, among which the packaging and transportation fee accounts for a very low proportion. Material cost of wire harness is mainly determined by the technical scheme of wire harness. Harness processing fee and management fee are mainly determined by the output of automotive wiring harness, the labor cost of harness suppliers, the profit of enterprises and the allocation of tooling. With the continuous improvement of vehicle configuration, the material cost of wire harness is increasing.

At present, the cost of labor and land use is rising, and the wiring harness processing fee and management fee are on the rise. The wiring harness material cost accounts for about 65% of the total wiring harness cost. In the design stage, the cost of wiring harness can be reduced mainly by optimizing the wiring harness design. In the later stage, the cost of wiring harness is mainly reduced by optimizing the manufacturing process and price comparison of wiring harness suppliers.

Research and Application of Harness Cost Reduction in Design Stage 3

3. 1 Platform and Standardized Design

In order to reduce the product cost and shorten the development cycle, platform design has become one of the important cost reduction measures for automobile enterprises. Through wiring harness connection, the platformization of wiring harness interface and hole position definition of electrical appliances can be promoted. Constantly promote the platformization of wiring harness materials and design schemes, the unification of wiring harness parts and the simplification of structure, improve the standardization of design, reduce the randomness of engineers' design, and try to share wiring harness secondary parts among different vehicle types. Establish the harness parts database, try to choose the existing platform parts, and avoid the development of special new parts. The unification of parts and components can concentrate the demand, which is conducive to the purchase of parts and components and improve bargaining chips. After continuous platform optimization design, the generalization rate of front cabin electrical box, instrument panel electrical box, harness connector and harness accessories has reached 100%. In terms of connectors, there are 312 types of components and 208 types of platformization, and the platformization rate has increased to 67%.

Before optimization, there are 5 types of PFB electrical box, including 4 types of tile and 1 type of side hanging. After optimization, there are only 3 types.

3. 2 Architecture Optimization and Controller Integration

Continuous optimization of automobile architecture can not only improve the performance of automobile, but also reduce the production cost. Promoting the optimization of electrical structure can effectively simplify the wiring harness structure. The more electrical appliances, the longer the wiring harness. Promoting the integration of electrical devices can reduce the number of connectors and harness branches. Taking an electric vehicle project as an example, the high-voltage electrical architecture is optimized, and the cost and quality of high-voltage wiring harness are greatly reduced. After the optimization of automobile architecture, the length of high-voltage wiring harness is reduced from 22 m to 9 m, the mass is reduced from 13.5 kg to 4.8 kg, and the cost of high-voltage wiring harness is greatly reduced by 41%.

3. 3 Optimization of Wiring Harness Layout

Due to the application of a large number of electrical devices and the small wiring space in the car, the difficulty of wiring harness layout has been continuously improved. In the design and layout of automotive wiring harness, the wiring harness should be safe and stable, saving materials and space, and 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 plates, avoiding heat sources and reducing the application of thermal insulation materials can make the wiring harness route and layout more optimized. Optimizing the layout position of electrical components can shorten and simplify the wiring harness path. The A arrangement position of parts remains unchanged, and the body rotates by 180. The antenna connector is changed from two 2PIN connectors to four 1PIN connectors, of which three 1PIN connectors are directly connected to the A component and the other one is connected to the wiring harness. The wire harness is reduced by three small wires of antenna loop connected with Part A, the length of which is about 1m, and the feeder of the wire harness is shortened. The total cost of this layout optimization is about 28 yuan.

3. 4 Technological Innovation of Wiring Harness

By introducing new technologies in harness materials, design and technology, the lightweight and cost reduction of harness can be realized. For example, by applying the miniaturization technology of relays and fuses, the total cost of the electrical box is about 29.5 yuan. For example, under the same impedance condition, the quality of aluminum wire is smaller than that of copper wire. By selecting aluminum wire and thin wire with smaller outer diameter and lighter weight, the weight of automotive wiring harness can be reduced as well as the cost. The cost of conductor accounts for a large proportion in the cost of automotive wiring harness, so it is of great significance to popularize the 0.13mm² alloy conductor or even lower small square conductor and apply the 0.13mm² alloy conductor to reduce the weight of the whole vehicle. 48V battery harness in a project was replaced by a 35mm² copper wire before optimization, and a 50mm² aluminum wire after optimization, with a length of about 4m and a weight loss of 224g/ m, with a total weight loss of 896g and a cost reduction of about 30 yuan.

3. 5 One-to-Many Materials and Localization

In the past, the technical scheme changed from one kind of second-and third-grade materials to one-to-many mode of using the same material, providing a "selection resource library" to first-grade suppliers. Foreign-funded wiring harness factories and local wiring harness factories selected low-cost materials according to their own procurement system, which enhanced the bargaining power of wiring harness suppliers and improved the stability of supply chain. One-to-many schemes such as grounding terminals, heat shrinkable tubes, insurance sheets, corrugated pipes and common wires have been implemented. Taking the cloth-based sleeves of a project as an example, the cloth-based sleeves of the same diameter can be exchanged by three different brands. Improving the localization rate of second-and third-grade materials and reducing the cost of materials have become the main measures to reduce the cost of many parts. With the continuous improvement of the intelligence of domestic connectors, the quality of domestic connectors is getting better and better through the continuous innovation of technology by domestic connector manufacturers. Because imported connectors are generally expensive and have a long supply cycle, domestic connector brands have received more attention. While ensuring the quality, domestic connectors are being used to replace some foreign connectors for wiring harnesses of many vehicle models, which reduces the material cost of wiring harnesses and improves the supply stability of supply chain. Some connectors and accessories in a project are replaced.

3. 6 VAVE to Reduce Costs

At present, the awareness of VAVE cost reduction in automobile enterprises is getting stronger and stronger. VAVE cost reduction activities can effectively reduce the cost of wiring harness and improve the cost-performance advantage of products. Because it is more difficult and expensive to promote the implementation of VAVE after mass production, more attention is 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 involved in VAVE activities, so that the relevant engineers of each department are clear about the specific measures and contents of the VAVE scheme, and actively cooperate with the promotion and implementation of the effective proposal of wiring harness. The proposal and implementation of VAVE for wire harness can not be separated from the active participation and cooperation of wire harness suppliers. The wire harness design department regularly holds regular project meetings with wire harness suppliers to exchange VAVE schemes and follow up the progress, which effectively promotes the implementation of VAVE schemes.

The wiring harness design department has formulated the VAVE record form to ensure the plane development of VAVE scheme. For each project, the VAVE check list of the project itself is compiled according to the VAVE record table, and the drawings of each valve are reviewed according to the VAVE check list. There are 12 types of optimization types in the VAVE table. Taking a vehicle as an example, through continuous optimization of VAVE in the design stage, the cost reduction ratio of the whole vehicle wiring harness materials is about 11%. Taking the combination of the body harness and the roof harness of this vehicle as an example, the original harness scheme before VAVE optimization is that the roof harness is separated from the body harness, and two pairs of harnesses are connected inline to form two independent harnesses. The parts are managed separately and assembled separately, which is not the optimal design scheme from the perspective of cost and quality. Under the existing layout conditions, after VAVE analysis and comprehensive consideration of all aspects, the roof harness can be integrated into the body harness. After integration, there are no roof harness parts, which can save one part and reduce tooling costs. After VAVE, the ceiling harness is merged into the body harness, and there is no ceiling harness. Through VAVE optimization, the cost is reduced by 16 yuan/set, and the quality is reduced by 0. 1kg/ set. After the combination of tooling, the tooling cost is reduced by about 30,000 yuan.

4 Concluding Remarks

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