Con las piezas listas, ha llegado la hora de encajar las primeras fichas del puzle, es decir, ensamblar y soldar todas y cada una de las partes que darán forma a la carrocería. Al comienzo del primer apartado, decíamos que un coche se fabrica de fuera hacia dentro. Pues bien, habría que añadir que, además, se fabrica de abajo hacia arriba y en dos fases.


En la primera, se ensambla y suelda el piso del coche, la fábrica de Ford lo hace en 58”, y, posteriormente, se van instalando los pasos de rueda, salpicadero, laterales…hasta llegar al techo. En la segunda fase, ya con el “mascarón” hecho, se añaden las partes móviles de la carrocería (puertas, capó…) y las aletas...

https://www.autocasion.com/actualidad/reportajes/como-se-fab...

The term unibody or unit body is short for unitized body, or alternatively unitary construction design.

A type of body/frame construction in which the body of the vehicle, its floor plan and chassis form a single structure. Such a design is generally lighter and more rigid than a vehicle having a separate body and frame.

Traditional body-on-frame architecture has shifted to the lighter unitized body structure that is now used on most cars. The last UK mass-produced car with a separate chassis was the Triumph Herald, which was discontinued in 1971.

Integral frame and body construction requires more than simply welding an unstressed body to a conventional frame. In a fully integrated body structure, the entire car is a load-carrying unit that handles all the loads experienced by the vehicle—forces from driving as well as cargo loads. Integral-type bodies for wheeled vehicles are typically manufactured by welding preformed metal panels and other components together, by forming or casting whole sections as one piece, or by a combination of these techniques. Although this is sometimes also referred to as a monocoque structure, because the car's outer skin and panels are made load-bearing, there are still ribs, bulkheads and box sections to reinforce the body, making the description semi-monocoque more appropriate.

https://en.wikipedia.org/wiki/Vehicle_frame#Unibody

A single moulded unit forming both the bodywork and chassis of a vehicle.

as modifier ‘the car's unibody construction improves rigidity and reduces weight’

https://en.oxforddictionaries.com/definition/unibody

The difference between unibody and body-on-frame vehicles is fairly straight forward. Unibody vehicles have the chassis and body of the car together. A body on frame vehicle has a frame which the vehicle stresses pass through, and the body of the car rests on top of this. Unibodies are more rigid due to the forces spreading over the entire vehicle, and because of this can also use less material and are lighter. This means better fuel economy, handling, acceleration and deceleration. Body on frame vehicles allow for better NVH, as the body can be isolated separately from the frame. They are also modular, allowing for various bodies to use the same frame.

https://www.youtube.com/watch?v=IhbXPzPlzNI

For this I'll assume the most common methods and materials and that we're building a unibody vehicle.

1. underbody components, such as the floor pan and the motor component are built up as sub assemblies.

2. finished subassemblies are assembled and added to the floor pan and motor compartment.

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.

5. Roof time. A roof panel is placed on top of the sheet metal layer cake that you've created and welded into place.

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.

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.

Coming Soon:
II. Paint Shop
III. General Assembly
IV. Ship It!

https://www.quora.com/What-is-the-step-by-step-process-for-m...

https://forums.vwvortex.com/showthread.php?9031313-Unibody-m...