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The Birth of a Z4 Roadster
by Sarah Reiff
A Z4 in the showroom
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Wouldn't it be interesting to see a baby grow from a fetus to a full-grown human being in about an hour? At the BMW plant in Spartanburg, South Carolina that is about how long it took Mr. Jim Utterback's E-Business Strategies class to see all the steps it takes to turn an engine, frame, seats, steering wheel, some paint, and some steel into a fine, fully developed Z4 Beamer two seater. The plant also makes the X5 SUV.
There are three parts of the BMW plant - the Body Shop, the Paint Shop, and Assembly. We got to walk through the Body Shop but we had walk single file in between two lines that were about 2 feet apart because forklifts were driving by all the time. In the Body Shop, we were warned not to look into the blue flame of the welder's blowtorch because it was very harmful to your eyes.
The Body Shop: Six stages. Walk single file between the lines because forklifts drive by all the time, and don't look into the blue flame of the welder's torch, because it will harm your eyes.
Major Sub-Assemblies - An extensive robotic system welds smaller parts together to form the three main components of the underbody: the motor compartment, the floor pan, and the rear compartment.
Underbody - A geometric pallet is used so that the body can be lifted and rotated. This helps workers consistently make identical body frames.
Sides/Framing - This is where the pre-assembled sides come together with the underbody, and the body side inner and the body side outer are assembled.
Welding, Grinding, and Brazing - Here the workers weld and braze the body for added strength and to prevent water leaks.
Metal Finish Fit - This is where the hinges for the doors, hood, and trunk are mounted. Then the "skin" or the "hang-ons" (which means the hood, doors, fenders, and trunk) are attached.
Final Body Inspection - Workers check the car carefully for pluses (raised areas) and minuses (indentions) to make sure the body is smooth before it goes to the paint shop. The gaps between the hood, trunk, and doors are also measured so that they are identical all the way around. If a car passes the final inspection it goes on to the paint shop.
The Paint Shop - Tours can't actually go into the Paint Shop because it is a very controlled environment. Workers put on special suits and go through a room where wind blows off all the dust. However, we got to walk by the entire line of the eight stages involved in taking a BMW from "body-in-white" to the color each customer has requested:
Phosphate and E-coat - Each BMW passes through fit hooks, brush wash, and degreasing where it is dipped and fully submerged into liquid solvent . It then moves to the Phosphate station where a crystalline structure of zinc, manganese, and nickel provide the body with corrosion protection and adhesion for the E-coat. The E-coat is paint electrodeposited onto the body for added corrosion protection.
Sealer - After the E-coat stage is baked dry in the oven, the car is sent to the Sealer Deck where there are five lanes with three to four workers per lane. They go through and spray all body areas that have the potential to leak water or let noise in.
Underbody Sealer Area - Each car has polyvinyl carbonate sprayed onto the entire underbody and side sills of the car for further protection. The car is then baked in another oven to dry and then on to the E-Finishing and the Inspection deck.
Inspection - At this stage workers look for and fix any defects in the E-coat, seam seals, and the underbody spray. They use orbital sanders on flat surfaces and hand held pads on contours to smooth and polish the entire car. They also install "sound deadener pads" to add further quietness.
Primer Spray Booth - Here, the workers again wear special suits and they have to enter through an air booth that blows off dust and lint. The body is wiped off and feather dusted.. Then robots apply the primer and the body is moved to another oven.
Inspection and Clear Coat - At this stage the body is transferred to a sanding and inspection deck where all the defects are corrected. Orbital sanders remove any particles from the body and sanding residue is wiped clean. The body is then sent back to the Primer Booth for the basecoat.
Clearcoat - The body travels through a quick oven to get to the Clearcoat Booth where the Clearcoat is applied and the car gets that shiny look. Then it moves through the largest oven to the Final Inspection.
Cavity Wax - In the Cavity Wax stage, the body is covered in a paraffin wax and it is tilted back and forth to ensure that the entire body is covered. Then the body takes its last ride on the overhead conveyor where it is transferred to the Stacker. The Stacker is basically a huge steel shelf that holds many cars at one time. Only bodies that have been painted the same color stay on the Stacker at one time because it makes it easier. From the Stacker the bodies are ready to be transferred to Assembly where they will become a complete car.
Assembly - Seven stages
Trim 1A - At this first stage, the body is tilted on its side by a tilt conveyor and is put on an Automated Assembly Build Vehicle so that the workers can raise and lower it. It is pushed down the assembly line by an electric monorail. The doors are removed and transferred to the door assembly line so that the handles, glass, and side air bags can be installed.
Trim 1B - The majority of the car's interior parts are assembled here. The cockpit, which is assembled separately, is installed. The car is moving slowly down the assembly line while everything is being installed. The BMW side marker is attached here and the doors are put back on.
Power Train - In this stage, everything comes together - the engine, the transmission, the axles, and the brakes, the engine harness, belts, transmission and oil lines, radiator hoses and manifold.
Trim 2 - Workers put the power train assembly and the engine in the body, and it starts to look like a car. Bumpers and exhaust are attached. The AC lines are filled with air, and the wheels are mounted. When the wheels are in place, the automobile is transferred to a slat conveyor and it touches the ground for the first time.
Final Inspection 1 - In the first stage of inspection, all electronics such as window and locks are tested. The car is filled with fluids - window washer fluid and antifreeze and then driven over a hole in the slat conveyor where a worker is underneath to make sure the car isn't leaking. Headlight and wheel alignment are checked.
Final Inspection 2 - The car is driven into an enclosed room, locked in by pads, and driven up to 85 miles per hour. During all of this, a computer checks for bumps and vibrations. At the end the car is inspected under intense lighting.
Final Inspection 3 - In the last stage of inspection, workers take the finished BMW to the test track and inspect steering and handling. The car is put to an 8-minute water test to check for leaks. We didn't get to see this stage but almost everyone agreed that if we worked there, we would want that job.
On the tour, someone asked "Do these workers do the same job all day long?" The answer is NO. Worker switch every few hours so that their job doesn't get too monotonous. However, workers do stay in their department - a welder from the Body Shop wouldn't switch places with a painter from the Paint Shop.
Throughout the tour of the Body Shop, not only the human workers but also the humanlike robots impressed the group.. These were not ordinary robots. If you watched them long enough they actually looked like a human arm. They could do things such as open and close doors, paint the body, attach windows, windshields and doors, weld the car together, and also inspect it with lasers sensors. While we were watching, one stopped putting a windshield into the body of a car because it had a little piece of tape hanging off of it. The robot refused to keep working or to let go of the windshield until workers fixed it.
Before I went to the BMW Factory, I paid no attention to cars at all. I barely looked at them, and I could definitely not tell individual makes and models. However, now that I have experienced what it takes to make a BMW, I notice them EVERYWHERE. I can spot BMW's from streets away. I haven't changed much with other cars, but I definitely notice every Beamer that passes, and I could probably tell you what model it is too.
To learn more about BMWs and the BMW Factory in Spartanburg, South Carolina, visit http://www.bmwzentrum.com/. The information in this article can be found at http://www.bmwzentrum.com/exhibits/virtual_plant_tour.asp.
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