Prototyping Development of Cross Car Beam
Brief introduction of "Cross Car Beam"
The Cross Car Beam (CCB) is a component located in the front of the vehicle under the instrument panel (IP). It is normally designed to support the steering column, airbags, and instrument panel, but can also support other systems depending on the complexity of the car. Aside from its support role, this component is instrumental in the absorption of impact energy, minimization of steering wheel displacement in case of a collision, reduction of overall cockpit vibration, and in providing a greater strength and control of the steering wheel.
1. Project Background
The client is a well-known automotive company. RPWORLD specializes in interior and exterior projects; from prototype stage to low-volume production stage. Mass production problems caused a delay of mold production of the Cross Car Beam (CCB) during R&D process, but assembly of the prototype vehicle had to begin within one month. The good news, however, was that the CCB problem was the only one; other parts, including body-in-white and other interior and exterior parts, could be completed on time. The CCB is normally required at the early stages of the vehicle assembly process, therefore its delay would prevent vehicle assembly work. A major challenge, however, was that the R&D budget meant that manpower and material resources were limited. As a long-term strategic partner, we were asked to help the client. After professional analysis, we proposed rapid tooling solution to the client as it could meet both time and budgetary requirements. We used to offer interior and exterior production services only during pilot production stages, however, meaning automotive sheet metal parts were unfamiliar to us. Even though we had the confidence to meet all requirements, the client still had some concerns.
2. Project Evaluation
We prepared a detailed project plan and strategy that considered all potential risks. After communication with the client, we learned that the primary objective was to verify the installation points between beam and body-in-white, the assembly of beam, instrument panel and other parts and to simulate the strength of material performance. Considering the demand of engineering and assembly verification and the importance of the CCB, we decided to focus on the precision of various holders and the complete welded body. To ensure the success of the project, we established the following process plan: optimize technological processes, set reasonable project schedule, perform thorough analysis of data, set precision and tolerance standards, mold design , welding jig design, CMM measurement, assembly welding, initial sample checking with CMM, issue feedback and adjustment, pilot production, safe shipment, on-spot feedback, project summary and risk control. The client ultimately approved our strategy.
3. Preparation of the Project
It is impossible to successfully complete a large project without significant project preparation work. Before project implementation of the 47 sets of CCB, we did our best to confirm key points as below:
3.1. Process Optimization
Firstly, we need to confirm all processes that would be involved in the project and plan a reasonable work flow for all activities (i.e. Gantt chart). Secondly, due to tight time constraints, we needed to optimize the development of each part to save on overall production time.
3.2. Setting a Reasonable Project Plan
The client required 5 initial CCB sample sets within 30 days. Normally, however, this requires 6 to 10 months for preparation and implementation. Within such a limited time frame it was necessary to establish a reasonable project strategy in order to make high quality products on time.
3.3. Verifying Accuracy of Initial Data
A CCB project normally requires the production and assembly work of several sheet metal parts. The main assembly is achieved by welding and threaded connections. After analyzing the client’s 3D data, bonding wire, welding spot, weld nut’s quantity and type and support structure opening, we identified some design issues that required adjustment. We immediately summarized all issues and submitted a report to the client. Through close communication, we helped them to finalize and modify these issues. Good finished product may only be achieved if the accuracy of the initial data is first verified.
3.4. Fully Understanding the Required Precision and Tolerance
A single CCB must be welded to several other parts, therefore the precision and tolerance of the parts themselves and the overall CCB (especially the mounting holes) requires an extremely high standard. It is very important to fully understand the precision and tolerance required.
4. Production Implementation
Because the CCB assembly is very complicated, neither prototype nor mass production can be performed integrally by stamping. After stamping all individual parts, welding assembly is necessary. Because the shape of CCB assembly is irregular, and each holder has different directions and angles, even minor deviations would lead to failure. The use of a welding jig is the key.
CCB’s assembly project may be divided into: mold production of parts, design and production of a welding jig, stamping of parts, assembly welding, CCM measurement, mounting and fixing.
4.1. Manufacturing the Mold for CCB Parts
Due to the small quantity of CCB’s required, we decided to use standard tool steel for production. It represented a good way to ensure the accuracy of production for 47 sets of low-volume production and to save a lot of money.
4.2. Design and Production of Welding Jig
Due to time constraints, we had to start the design and production of the welding jig while the molds for CCB parts were still being developed. During design, we had to develop a welding jig to ensure proper operation of the finishing welding assembly and checking fixture. After client confirmation, we started producing the welding jig. A CCM was used to measure these after each step.
4.3. Production of CCB Parts
Stamping is the primary process for producing CCB parts. Mass production stamping process requires many molds for various processes, such as drawing, trimming, punching, flanging and shaping. But due to the small quantity required, we produced a much simpler tool to save money and time for the client; punching, flanging and shaping were all replaced by manual work.
4.4. Assembly Welding Work
A proper sequence must be followed to weld various parts. We widely use CO2 shielded welding which is a cost-effective process that provides less deformations in part due to the visibility of the electric arc, which ensures the weld position. Especially in a semi-automatic welding, short and curve welding work can easily be performed and therefore it can produce welding lines that are accurate and of high cosmetic appearance.
4.5. Measurement by CCM
CCM was used for final measurement and data modification in case of deformation.
4.6. Mounting and Fixing
After quality control and validation, we needed to devise a shipment plan. Considering the irregular shape of CCB’s assembly, robust packaging/bracing was required. Any damage during shipment would render the entire project a failure. We designed and produced a specialized support to fix the CCB assembly and guarantee transportation without any problems.
5. After-sales Service
After-sales service mainly included on-spot assistance to engineers with feedback, analysis, modifications and processing.
During final assembly, some unexpected issues arose from parts were produced by other suppliers. We recorded all issues and worked with engineers from these other companies to make the required adjustments in order to keep the entire trial project successful.
6. Final Result
The CCB project done by RPWORLD helped the client save 50% of the working time in the project cycle. 47 sets of CCB were produced in less than 2 months. Rapid sheet-metal processes saved 95% of cost compared with mass production.
After 6 months, the client told me that what we did produced using rapid sheet-metal process resulted in better accuracy than the samples from mass production factories.
The high level of success of the CCB project, is mainly a result of our teamwork and deep understanding of project. In my mind, not only do we supply high-quality products and outstanding services, but also we deliver even beyond stated commitment to clients; as per one of our core values: Under promise over deliver.
Sam Dong (Project Engineer)