When you're building a different kind of vehicle, the only way to do it is differently.
That was BMW's philosophy when it decided to build the X5, the model BMW dubbed a 'sports activity vehicle.' The goal was to take the X5 from concept to production in just 35 months - slightly more than half the time the company previously allotted for turning around a new vehicle.
But building a new vehicle at the Spartanburg, S.C., plant also meant creating a new factory environment, even though the X5 would go into the plant BMW had launched just five years earlier to produce 3-series and Z3 roadsters. As a result, the launch of the X5, which went on sale in the United States in December 1999, has led BMW down a new manufacturing path.
To meet its goal of reducing vehicle development time, BMW began with computer-based 3D programs that carried the project through development and testing. Computer-aided design models identified potential tooling problems and found solutions. The models also performed design tests and structural evaluations that offered highly reliable results.
At the same time BMW was designing the vehicle, suppliers were busy designing the tooling to build it.
'The whole process chain used CATIA as the main system,' says Manfred Moser, body shop manager at the BMW Manufacturing complex in Spartanburg. CATIA is the 3D modeling system developed by Dassault Systemes S.A. of France. 'All the data we used for product design and for fixture design came from the same database. You don't lose any data if you use the same base.
'The whole shop is designed in CATIA 3D, so we had the chance to test the facility in a very early phase and to eliminate the mistakes before it got to the shop floor, before we even had hardware.'
Like the Z3 roadster, the X5 is built exclusively in Spartanburg. But the production of both is so vastly different it's like having two plants under one roof.
The Z3 has about 3,000 parts, and BMW employees handle most of them. By contrast, the X5 has three times as many parts, but suppliers deliver them in modules rather than as separate pieces.
How the lines differ
The major difference between the Z3 and X5 lines is in body assembly. While employees are building roadster bodies, robots are putting together X5s. Building a Z3 requires about 80 percent perspiration and 20 percent automation, while the figures are reversed on the X5 line.
'If you look at the difference of the products, you have an explanation of why the manufacturing process is so different,' Moser says. 'The roadster is smaller, has fewer parts and the design is more accessible to a manual process.
'The X5 is much more difficult to access. It is much higher than the roadster, so you have to consider the access for an operator, for both the lower part of the body and the upper part. You would basically work on your knees and then go up and work on the roof. That is why we have a much higher degree of automation in that shop.'
Employees still do the X5 welding in a subassembly area, where the parts are easier to lift and access. But for the larger and inaccessible pieces - such as the motor compartment or the rear compartment - the robots take over.
'The X5 has about 6,400 weld spots, and the size of the vehicle makes it impossible to do it all manually,' points out Ed Slaton, a process planner who started in the Z3 body shop and moved to the X5 line. 'You have to have more automation.'
Working in a series of chain-link cages, the robots perform two operations: welding and transportation. The robots, designed by the German tooling supplier Nothefler, apply the appropriate welds and then pass the part to the next station.
'Theoretically, we knew this would be a very accurate method to build bodies, but now we have the proof,' Moser says. 'I guess that's the important part of it.'
Each robot is equipped with a spare welding gun. If one gun breaks down or there is a problem, the second gun is quickly loaded onto the robot.
'We are very fast in fixing problems if something breaks down,' Moser said.
To ensure that it is within specifications, BMW installed three stations with robot-mounted Perceptron cameras on the X5 line - an innovation for the auto assembly industry, Moser said. The robots sit on an axis and travel the length of the car scanning for problems.
In the good old days - which, for the Spartanburg plant, means 1995 - employees took one car a day, tore it down and inspected it. But with the Perceptron cameras, every X5 is inspected.
The first station on the underbody line measures the motor compartment, floor pan and rear compartment. The second takes readings after the framing, when the shell of the car is completed. The third is used when the body is completed.
'What we accomplish with this is to measure every body that is produced in that line,' Moser says. 'So we get the repeatability analysis of that line, which leads to a capability study. As soon as we deviate in our process, we have the capability to go back and correct the process.
'We have data about the last 4,000 cars. We can look at how we deviated from the first car to the 4,000th car, if we did. It is a very fast method to go back and correct processes or parts coming in from suppliers.'
The Z3 line has one Perceptron station, which the company installed about two years ago. Perceptron now is marketing the idea to other automotive companies and the BMW South Carolina plant is visited frequently by officials from factories looking at installing it, according to the company.
Engineers began designing the X5 line in November 1997, and the company began installing equipment in the Spartanburg plant in October 1998. But before it reached Spartanburg, the production line was tested in Germany.
'The whole shop was set up at the supplier facility before it came over,' Moser says. 'We tested everything in their facility. It was in automatic mode before we tore it down and shipped it. We designed everything in modular components so that we could put it in containers and bring it over.
'In some of the critical stations, we used a camera measurement system to check the position at the suppliers' facility, and then used the same camera system here to make sure it was in the same place when we rebuilt it,' he says.
Suppliers also faced a rigid test. Before any of the 9,000 vehicle components could be introduced to the shop floor, they first had to fit an X5 aluminum prototype set up at the Spartanburg plant. Every few hours, suppliers came in to work on the prototype. While it often took several tries to get the perfect fit, the practice run eliminated many problems once production began, Moser says. The concept was first used to make the new 3-series sedan.
1 old-fashioned idea
Laying out the new X5 line followed an old-fashioned concept: common sense. Processes that use a lot of material were set up near the loading docks. 'You don't want to transport (material) to the other end of the facility,' Moser says. 'So jobs that are not so material intensive are over there.'
Similarly, jobs that might be outsourced someday because of increased volume also are concentrated in one area. That way, the company could clear an area should it need additional floor space.
BMW engineers in South Carolina and Germany earned two patents in developing the manufacturing of the X5.
One was for a flexible underbody marriage station. The assembly technique makes the underbody more accessible and ergonomic for employees who apply weld bolts.
The other patent was for a door-mounting process that gave BMW improved quality around its hinges. It produced BMW's lowest door gap tolerance.
'We have the advantage that this is new,' says BMW spokeswoman Bunny Richardson. 'It gives you an opportunity to test some new technologies. One of the things that we have found here at the Spartanburg plant is that we try things. We are a catalyst for change.'
That does not necessarily mean BMW will embrace its innovations at other plants. For now, the process will remain unique to Spartanburg, Moser says.
'You have to look at the setup of your plant,' he says. 'If you start something brand new, you could put it in. If you modify an existing line it could be very costly to implement.'
Robert W. Dalton is city editor of the Herald-Journal in Spartanburg, S.C.