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General Motors Janesville Assembly Plant - The General's Assembly

Building fullsize GM SUVs in Janesville, Wisconsin

Photography by Ken Brubaker

If you want to experience a true engineering marvel, visit a modern automobile assembly line. We did, and we'll say without reservation that you'll be astonished at the vast amount of technology, quality, and precise planning that goes into assembling a vehicle.

We recently toured the General Motors Janesville Assembly Plant in Janesville, Wisconsin. Janesville is one of the final assembly plants that produce all trim levels of the new, hot-selling Chevy Tahoe, Chevy Suburban, and the GMC Yukon and Yukon XL. The GM team granted us unrestricted access to the entire assembly line from start to finish so we could give you a virtual tour of how these exceptional SUVs are assembled.

It's important to remember that long before the complicated procedure of assembling (or "marrying," as they call it) the many components, GM invested a mind-boggling amount of time and money into an infrastructure that includes creative design engineers, quality suppliers, a just-in-time parts delivery system, cutting-edge robotics, and of course, a vast number of highly skilled employees.

After all that, one may think that the actual assembly process of these SUVs would be the easy part, but that is not true. The GMT900 SUVs are renowned for their tight and reliable build quality. To accomplish this, a vast amount of technology and quality control are integrated into the assembly process. As a matter of fact, we were left speechless after witnessing the attention to detail and tight quality control exhibited by the team at the Janesville plant. Add to this their focused priority on safety and the never-ending requirement of controlling costs, and it becomes apparent that these folks have their ducks (OK, trucks) in a row.

We'd love to show you how every component in the finely choreographed assembly procedure comes together because almost every step is fascinating and notable in its own right, but that would take hundreds of pages. Instead, follow along as we spotlight some of the highlights of this captivating and awe-inspiring procedure.

  • 1. We began our tour with Body Shop Area Manager Craig Colby at the end of the floorpan process. The floorpan you see here contains about 50 welded parts and is the foundation for the body structure.
    1. We began our tour with Body Shop Area Manager Craig Colby at the end of the floorpan pr
  • 2. Conveyers carry the floorpan through a number of different "zones." In this photo you can see that the dash and the "inner quarters" have been "married" to the floorpan.
    2. Conveyers carry the floorpan through a number of different "zones." In this photo you c
  • 3. Pictured are a few of the 650 robots that work in the body shop. These robots have the ability to precisely place body components to strict dimensional positioning quickly and repeatedly. Here you can see the body beginning to take shape. The rear outer panels are positioned by the robots and then a different set of robots swing into position and tack-weld the panels in place.
    3. Pictured are a few of the 650 robots that work in the body shop. These robots have the
  • 4. This fascinating zone is where the roof is married to the body. In the foreground you can see a body assembly moments before a robot positions a sunroof-equipped roof (seen poised for installation on the right side of the photo) into position and tack-welds it in place. If you look close you can see black beads of sealer that have been robotically added to the body assembly and roof bows. This sealer is one of the reasons the roof doesn't "flutter" when a door is slammed or a window is opened at speed.
    4. This fascinating zone is where the roof is married to the body. In the foreground you c
  • 5. Up until this point in the process, the body has been mostly tack-welded together. These re-spot robots add hundreds of finish welds to the body to deliver the structural integrity engineered into the design. The whole process is monitored intensely to ensure that they are getting the best quality weld. As a matter of fact, during each shift a body is randomly removed from the line and chiseled apart to ensure that the welds are perfect. Interesting fact: When completed, there are over 4,000 welds on each body.
    5. Up until this point in the process, the body has been mostly tack-welded together. Thes
  • 6. Doors, fenders, hoods, and liftgates are all manufactured in-house. Here you can see a door during the manufacturing process. The inner and outer door panels are married to exacting specifications by a machine called a "hemmer." Like everything else in the process, there's more here than meets the eye. What clamps fire first and which welds are added first were carefully analyzed by the engineers to guarantee the dimensional integrity and best seal margins of the doors. After assembly, the components go through a high-tech station where their parameters are checked with cameras to ensure they meet the exacting specifications set forth by the engineering team.
    6. Doors, fenders, hoods, and liftgates are all manufactured in-house. Here you can see a
  • 7. At this point, the "closure panels" are added to the vehicle. The doors are installed on the body using bolt-on hinges as opposed to weld-on hinges. These hinges are more expensive, but give the installers the ability to easily fine-tune door fitment to exacting specifications. After the closure panels are added, the body is inspected to make sure it is in perfect condition before it goes to paint.
    7. At this point, the "closure panels" are added to the vehicle. The doors are installed o
  • 8. Paint Area Manager and 25-year veteran of GM, Paul Durant, walked us through the processes of the paint area. This amazing area takes the raw metal truck and applies the many coatings that give it the right appearance and corrosion protection. The major processes include clean and prep (phosphate), electro-deposition (ELPO), sealer, prime and bake, liquid applied sound deadener (LASD), main color, clearcoat, and finesse (inspection, polishing, and so on). Here you can see a body being rinsed after it has exited the first tank of ELPO.
    8. Paint Area Manager and 25-year veteran of GM, Paul Durant, walked us through the proces
  • 9. Here, a body travels through a part of the line that completes the sealing process as well as a few other miscellaneous operations. When the body leaves here it will be ready for primer.
    9. Here, a body travels through a part of the line that completes the sealing process as w
  • 10. After the body is primed, robots apply the LASD. Here you can clearly see the sound deadener (black material) after it has been added to the floor and dash area. Tim Herrick, Assistant Chief Engineer, explained that this noise-abatement material is applied to very specific areas to significantly eliminate sound generation from under the vehicle; be it from the road or powertrain. This material is one of the reasons why the cabin area of the GMT900 SUV is so quiet.
    10. After the body is primed, robots apply the LASD. Here you can clearly see the sound de
  • 11. Before the body is painted it is meticulously cleaned with tack rags and this ostrich-feather duster. This process is electrostatic so the feathers collect even the tiniest particles of dirt.
    11. Before the body is painted it is meticulously cleaned with tack rags and this ostrich-
  • 12. All interior and exterior body painting is done via robotics, and most of the time it's done with the lights off. After all, the robots don't need light to see what they're doing, and eliminating them helps reduce GM's energy bills. Here you can see a body entering the main color booth. The GM team turned the lights on for us so we could get a photo. One of the main benefits of robots in painting is that they apply the paint the same way to every vehicle, thus the finish is impeccable and consistent. From here, the bodies travel through a few more processes including baking and clearcoat.
    12. All interior and exterior body painting is done via robotics, and most of the time it'

13. Here, the author and Durant check out a painted GMT 900 body. This area, called the strip bank, is a holding area of sorts. This area is used to store the painted bodies overnight when the line is not operating. We're wearing a variety of mandatory protective clothing designed to ensure that the paint area remains dirt- and dust-free.



14. This is the finesse area. Here the body is given an inspection to ensure that no dust or dirt has adhered to the body. If foreign material is found, it can be sanded and polished out. From this point the body continues on to the Hard Trim area. This is where things get even more complicated. Once the body is released from the body shop, a sequencing procedure is placed in motion behind the scenes that ensures that the various components of the vehicle are ordered and delivered to correspond exactly with the final assembly of that specific vehicle. In other words, there are several assembly lines working at the same time, and they all must be timed to deliver their product to final assembly at the correct moment. For instance, dashboards are being built, seats are being ordered and the frame, suspension, and powertrain are being built (we'll get to chassis assembly in a minute).

15. General Assembly Area Manager Gary West, a 27-year veteran of GM, took us through the rest of the process. This is the Hard Trim area, and this is where the doors and liftgate are removed from the vehicle so they can be sent to another line to be "built." Items installed in the Hard Trim area include the sunroof, roof rail, airbags, interior moldings, third seat, and instrument panel (which come from an in-house instrument panel assembly line). Here you can see a worker guiding a sunroof assembly through the windshield opening of a body. Interesting fact: There are hundreds of fasteners installed in the final assembly process. Computers monitor the torque pressure of each fastener as it's installed to ensure it is tightened to spec. If a fastener isn't correctly torqued, the assembly line stops until the proper torque is achieved. This guarantees a 100 percent perfect torque rate of all fasteners.

16. Here you can see a worker installing an overhead DVD system in the Soft Trim area. Items installed in the Soft Trim area include glass (the windshield and quarter glass are installed robotically), center console, carpet, and seats. This is also the area where the assembled doors and liftgate are reinstalled. Because many of these installation procedures are repetitive, yet done by hand, GM has worked hard to devise ways to make each job easier and safer. For instance, this worker glides into the moving vehicle while seated on a trick device that eliminates the need to physically climb into each vehicle and install the product. Further, a substantial amount of work was incorporated into the design of the vehicle in an effort to aid in its assembly.

  • 17. Here is a completed body that is ready to be married to a chassis.
  • 18. At the same time the body is being built, its corresponding chassis is also being built. Here you can see the chassis assemblies as they arrive at the plant from an outside supplier.
    18. At the same time the body is being built, its corresponding chassis is also being buil
  • 19. The chassis travels down the assembly line inverted. As it moves along, components like the suspension, axles, driveshafts, rack-and-pinion steering, fuel tank, brakes, and hoses are all installed. The chassis is then turned right-side-up by machinery for the installation of the engine, transmission, transfer case, radiator, wheels, and tires. Interesting fact: The assembly line that mounts, balances, and adds the tire-pressure monitoring sensors to the wheels and tires produces a complete ready-to-roll unit every 12.5 seconds.
    19. The chassis travels down the assembly line inverted. As it moves along, components lik
  • 20. The engines arrive from various GM engine plants completely assembled and ready to be married to the transmissions, which are also built outside the plant.
    20. The engines arrive from various GM engine plants completely assembled and ready to be
  • 21. Assistant Chief Engineer Tim Herrick shows us an engine/transmission/transfer-case assembly that is ready to be installed in a chassis.
    21. Assistant Chief Engineer Tim Herrick shows us an engine/transmission/transfer-case ass
  • 22. The engine set is installed next. The radiator set and the wheels and tires are the last things to get bolted on before the chassis is ready to be married to the body.
    22. The engine set is installed next. The radiator set and the wheels and tires are the la
  • 23. It's a spectacular sight to see an assembled body and a rolling chassis coming down the line moments before they are married together.
    23. It's a spectacular sight to see an assembled body and a rolling chassis coming down th
  • 24. GM says that it only takes 55 seconds to marry the body and chassis. After the two are conjoined, the running boards and fluids are installed.
    24. GM says that it only takes 55 seconds to marry the body and chassis. After the two are
  • 25. The front fenders, rear fascia, hood, headlamps, front fascia, and bodyside moldings are some of the next items to be installed. As the vehicle progresses toward the end of the line, lasers even measure gaps and "fits" (fitment) of the vehicle panels to ensure they are true to the tight tolerances set forth by the engineering department.
    25. The front fenders, rear fascia, hood, headlamps, front fascia, and bodyside moldings a

26. This is the proverbial end of the line as far as assembly goes. From here, each vehicle undergoes a significant number of quality checks. Included is a Dynamic Vehicle Test (DVT) that powers the vehicle and tests all of its running systems including engine, transmission, brakes, and so on. There's also a squeak/rattle test and a water test among other things. Once the vehicle passes these tests it's staged for shipment to the dealer.



The Janesville assembly plant, located 105 miles northwest of Chicago, has a long and storied history. It was originally founded in 1919 by GM to produce Samson tractors, but by April of 1929, the plant had produced more than 500,000 cars. During World War II, the plant ceased vehicle production and was used to produce over 16 million 105mm Howitzer and other shells, among other things. Production of cars and trucks resumed in 1946. Over the years, Janesville assembled the "B-body" Caprice/Impala, the "J-body" Cavalier/Skyhawk, medium-duty trucks as well as motorhome and school-bus chassis. In 1991, the plant began producing the GMT400 SUV vehicles. In 1992, the Chevy Blazer won Four Wheeler's Four Wheeler of the Year award and even though GM was suffering through a recession period, Janesville employees worked 5-6 day workweeks to meet demand.

Today the plant encompasses 137 acres and boasts more than 4.8 million square feet. It is home to 2,800 hourly employees and 220 salaried employees. This translates to a stunning payroll of 1 million dollars per day. Currently, 50 GMT900 SUVs roll off the end of the assembly line every hour.

If you would like a free tour of the facility (and we'd highly recommend it), make your reservations by calling the Tour Hotline at 608/756-7681. Each tour is led by a knowledgeable retired employee. Tours begin at 9:15 a.m., 10:45 a.m., and 1 p.m. Monday through Thursday.

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