What is the step-by-step process for making a car in a factory?
2 Answers
Chris Kaschner, Here's my start, I'll update as I add more:
Steps to making a car from my experience working on 6 different vehicles production lines as a Control Engineer as well as visiting a number of additional factories:
Automotive factories are typically broken into 3 main departments. In consecutive order they are Body Shop, Paint Shop, and General Assembly. There are some variations depending on the type of vehicle your producing, the materials it is made out of, the volume of vehicles being produced.
For this I'll assume the most common methods and materials and that we're building a unibody vehicle.
I. Body Shop
Start with: unpainted individual formed sheet metal components
Finish with: an assembled car body, also called a @Body in white
1. underbody components, such as the floor pan and the motor component are built up as sub assemblies. This is accomplished by taking individual sheet metal components of varying sizes, fixturing them into a precise location and then RSW (resistance spot welding) them into their final location. Here's the starting point:
2. finished subassemblies are assembled and added to the floor pan and motor compartment. At the beginning a vehicle body starts flat, additional assembles add some length, but also all the components that give a vehicle body height, things like the firewall separating the motor from the passenger compartment and the waterfall section between the backseat and the trunk.
3. at this point you have the rough shape of a car, but still lack the external body panels that make it look like the final product, lack a roof, and have none of the swing metal parts: doors, hood, deck lid (what you call a trunk/ boot in an automotive factory)
4. In one of the more complex operations in the body shop the body sides are placed onto the vehicle. This is typically the largest single piece of sheet metal used in a vehicle. Here's an example of one:
It runs from the headlights to the taillights and gives the external shape to a vehicle. In the factories I worked at the left and right body sides were placed in the same station at the same time on a vehicle. While being held in position a number of robots will weld them into location. If I were to take you on a tour of the Body Shop, this would be a required stop since there's up to 6 robots working in concert to locate, fixture, and weld components at a single time. Also, there's sparks that fly when you spot weld, and visitors absolutely *love* to see the sparks. Like this
5. Roof time. A roof panel is placed on top of the sheet metal layer cake that you've created and welded into place. Depending on which company you work for, this is one of the defining features of a vehicle since many of the previous steps are common between manufacturers. Whether your car has a "ditch molding" on the roof or simply a smooth continuous roof is an easy way to tell the difference between cars. The ditch molding is a simpler method where a panel is placed on top of your vehicle and has an offset surface that allows RSW. The more complex methods have either brazing or laser welding to produce a continuous flat surface over the entirety of your roof. An example of roof fixturing:
6. Swing metal time. Doors were built up in separate sub-assembly lines and are placed on a conveyor to be mounted onto the rest of the body. Doors are lifted via a specially designed piece of tooling to lift them and locate them accurately to the car body. Bolts are torqued, and verified, to a specific value to mount the doors. This (along with deck-lids and hoods) are typically the the only threaded fastener in the entire Body Shop everything else is welded into location.
7. Hoods and deck-lids are placed in a similar manner to doors.
8. At this point the BIW looks like a car without wheels, a chassis, a motor, or an interior. But it's the right shape. Before moving on there's a final section of the production line called "body finishing". Imagine a tunnel of fluorescent light fixtures with cars running down its center and people on both side of the assembly line at 20' intervals. The purpose is to identify and fix any problems or defects that would show up once painted. Workers sand and smooth the body panels to ensure no problems occur once painted. It's far easier to fix things at this point then to remove paint.
9. Transfer to paint shop. Depending on the size of the factory this takes a few forms, usually your BIW gets to ride on some form of conveyor or AGV (automatic guided vehicle), ride up an elevator or hoist of some sort, and ride another conveyor before arriving in the paint shop.
***Things ignored***
* rework stations- placed at the end of each main area or sub-assembly, so the entire motor compartment line may have one rework station. Any defects or issues, such as a bad weld, would be repaired at that station.
* automated inspection stations - laser/ camera combo's are used to verify the exact location of panels and gaps. They record those locations and allow quality engineers to track the process over time. If dimensions move outside of permissible limits, then changes will be made in the previous processes to make sure you're always making "good" parts.
0 comments :