by Zhu Zhengde

China Shanghai VW Auto Co. Ltd, located in Anting Town, 30 kilometers northwest of Shanghai, is one of China's largest automobile manufacturers, and is ranked third among China's 18,000 state-owned large companies on a list of the top 10 economically successful enterprises in the country.

There are many reasons for the success of SVW, but one of the most significant is that the company has always considered product quality the "life" of the enterprise.

Flexibility is the operative term for the Brown & Sharpe-DEA DELTA measuring machine at Shanghai Volkswagen.

Using the FIVE flexible fixturing system, the DELTA can be quickly re-configured to measure a variety of thin-walled sheet metal assemblies.

In 1995, SVW celebrated its tenth anniversary and the production startup of the second stage of its project to develop the new generation "Santana 2000". The company's No. 2 plant adopted both advanced production technology and advanced testing/measuring technology at the same time to provide a technical guarantee of manufacturing quality, especially for automobile bodies.

Ten years ago when mass production of the Santana began, the first car body measuring lab was established in the body-in-white workshop of SVW's No. 2 plant. The inspection operation was carried out using manual coordinate measuring machines. However, with the rapid increase of output, and the introduction of advanced car body manufacturing technologies, the use of manual coordinate measuring machines became less suitable for the needs of SVW. The increase in automation and use of welding robots made the consideration of faster inspection techniques even more critical.

The Brown & Sharpe-DEA BRAVO dual-arm measuring robot at Shanghai Volkswagen is set up to inspect whole car bodies according to a pre-established sampling plan. The dimensional data gathered during the measuring operation is used to monitor the body assembly process.

To help meet these more sophisticated inspection requirements, SVW installed a Brown & Sharpe-DEA BRAVO 4306 measuring robot, and DELTA 3406 measuring machine equipped with the FIVE flexible support and clamping system.

Efficiency, Precision and Automation

Both BRAVO and DELTA boast a high level of efficiency, precision and automation. The BRAVO has two measuring arms and takes only 30 minutes to measure a complete body-in-white. The whole process is carried out automatically, except for lifting and moving the car body. One working team can measure up to 8-10 cars, with the norm being 6 cars. Both BRAVO and DELTA systems are computer controlled. Automatic measuring operations are carried out according to pre-programmed routines.

The BRAVO...takes only 30 minutes to measure a complete body-in-white.

The measuring operation has two roles at SVW. One is normal measuring, i.e. measuring several car bodies and assemblies according to a sampling rate. The other job involves process adjustment and quality analysis.

The BRAVO and the DELTA are designed for accurate measurements in a shop environment. The BRAVO has thermal sensors on all axes to correct for errors caused by thermal expansion, and the main carriage is completely protected by covers and bellows to eliminate errors caused by non-uniform temperature changes. The gantry structure of the DELTA quickly adapts to temperature changes and is designed to maintain dimensional stability.

The BRAVO measures not only the car body, but also the front assembly. The DELTA measures six different assemblies. Because special measuring programs for different tasks have been programmed into the computer, it is easy for the operator to select the correct program when changing tasks.

Car body and front end assemblies are supported in a fixed stand when measured in BRAVO, while different assemblies are measured on the DELTA with the help of the FIVE flexible fixture system. The FIVE system is an automatic flexible fixture system that replaces costly custom fixtures usually required to support and reference contoured workpieces. FIVE comes with a simple software program, LIZ, that lets users automatically generate programs necessary to configure the fixture for the physical support of the workpiece and give it its theoretical geometry during the inspection cycle. The coordinate measuring machine manipulates the modular fixture components to arrange them along X, Y, and Z axes. FIVE is particularly suited for body-in-white inspection, windshields, bumpers, dashboards, and stamped panels. The system is very flexible, and can be used for different parts, as well as for the same parts using different measuring requirements.

Another task under way is off-line programming of the coordinate measuring machines, using CATIA software, which will increase productivity and measuring machine utilization. The resulting measuring program is downloaded to computers to the measuring machines through communication interfaces.

Zhu Zhengde is the Vice Chairman of the China Auto Engineering Association Measuring Specialty Commission, and Senior Engineer at Shanghai VW.