1. ASSEMBLY PROCESS FOR BODY STRUCTURES
Typically, the automobile body assembly process comprises numerous steps, utilizing 300–500 compliant sheet metal parts, 50–120 assembly stations and 3000–6000 spot welds.
An automotive body assembly system is a multi-leveled hierarchical system, in which sheet metal parts are joined together to form subassemblies, which in turn becomes the component to the next level of assembly.
A simplified process is shown in the diagram. At Level 2, the body is framed by assembling the major subassemblies, such as the underbody, side frames, roof, shelves etc. At Level 3, the major subassemblies are formed. For example, the side frame is assembled by welding together the door ring, quarter panel, and motor rail. At Level 4, parts are welded together to form the components for the level 3 assembly, e.g., door ring inner and door ring outer are assembled to form the door ring. (S. J. Hu, 1997)
Source: MOHD NAJMI BIN MOHAMAD, BODY ASSEMBLY PROCESS IMPROVEMENT FOR AUTOMOTIVE INDUSTRY, Thesis, UMP, 2008

2. ASSEMBLY PROCESS FOR BODY STRUCTURES
In the Body in White assembly process, a hierarchy of assembly stations can be established, as shown in the following chart.
Source: MOHD NAJMI BIN MOHAMAD, BODY ASSEMBLY PROCESS IMPROVEMENT FOR AUTOMOTIVE INDUSTRY, Thesis, UMP, 2008

3. Assembly Sub-System Details ASSEMBLY PROCESS FOR BODY STRUCTURES
Step 1
Underbody
Cross-members are welded to the rails. Floor pan is welded to the grid. Rocker inner is welded to the floor.
Step 2
Front End
Radiator support, inner fender, shotgun, shock tower, cowl side and inner hinge pillar are welded together.
Step 3
Front End, Underbody, cross-car beam and cowl
Front end is welded to the underbody, cowl and cross-car beam. Cross-car beam is used for alignment
Step 4
Dash Panel and Strainer
Dash panel and strainer is welded to the floor and the cowl
Step 5
Body Side
Body sides are welded on each side
Step 6
Pillars
A, B, C, and D pillar inners are welded
Step 7
Roof
Roof rail inners, headers and bows are assembled. Roof panel is attached.
Step 8
Paint, Trim and Closures
Body, closures, fenders are painted. Trim is assembled and then closures/fenders are hung.