Body in white

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BIW stands for Body in White . All activities in the production of a Vehicle Body or Shell before it goes to the Paint shop are done in a weld shop and the end product of a Weld shop is referred to as BIW.

Two kinds of BIW Structures :

1. Monocoque : In this type of structure, all the members of the body are load carrying and they are integrated with each other. Here chassis is inbuilt with the BIW itself and there is no separate chassis. Wheels are directly mounted to the BIW with the help of suspension system. Used in all the passenger cars and to some extent in utility vehicles.

2. Body on frame : In this type of body construction, the body is placed on frame which is the major load carrying member. Body is mounted on a separate chassis/frame and the wheels are mounted on the chassis and not to the body. Used in utility vehicles, trucks, buses.

Major activities carried out in a Weld shop are: Spot welding, CO2/MIG welding, Sealing, Piercing, Clinching, Bolting, Hemming etc. to produce a shell and then this shell gets finished with Brazing and Grinding and Closures are screwed to the shell in a Finishing Line just before it goes to the Paint shop. Body in White or BIW refers to the stage in automobile manufacturing in which the car body sheet metal (including doors, hoods, and deck lids) has been assembled or designed but before the components (chassis, motor) and trim (windshields, seats, upholstery, electronics, etc.) have been added.

The name is derived from manufacturing practice before steel monocoque bodies, sometimes trademarked unibody. When most cars were made by firms as just a frame, with an engine, suspension, and fenders attached, the manufacturers built or purchased wooden bodies (with thin, non-structural metal sheets on the outside) to bolt onto the frame. The bodies really were painted white as a preliminary to being painted the customer's chosen color. During the Great Depression, firms had a large inventory of these bodies and took a long time to sell them off. Now that car bodies are made of steel, the phrase remains and has a folk etymology that it comes from the appearance of the car body after it is dipped into a white bath of primer (undercoat paint)—when actually the color is usually light gray.

In car design, the Body in White phase refers to the phase in which the final contours of the car body are worked out, in preparation for ordering of the expensive production stamping die. Extensive computer simulations of crash worthiness, manufacturability, and automotive aerodynamics are required before a clay model from the design studio can be converted into a Body in White ready for production.

Images and information on body-in-white, Cambridge University