Green Cars

Vehicle Assembly: Final Assembly

The final assembly process completes the assembly of various components, and installs parts and components into the interior and exterior of the vehicle.


Assembly Process Description
Many supplied parts and components require further assembly at the assembly facility before their installation into a vehicle body. From hoses, belts, and seats to fans, electrical motors, and gauges, this assembly is accomplished on a series of assembly lines. In the final assembly process, the engine, suspension, and transmission are added to the underbody of a vehicle using nuts and bolts. Interior component installation -- for example, electronics; the dashboard and instruments; seats; and carpeting -- are then installed, and the glass into and around the passenger space is set in place. A variety of adhesives, snap fits, nuts, and bolts are used in this assembly. Final interior and exterior trim and components are then added.

Primary Wastes: air releases, hazardous/solid waste

Likely TRI Chemicals: acetone, toluene

Likely AIRS Chemicals: VOCs


Final Assembly Pollution Prevention Options
Air emissions of volatile, often toxic, chemicals from adhesives have been the focus of pollution prevention initiatives within the final assembly process. During application and curing, adhesive solvents evaporate, contributing to the release of VOCs and toxic chemicals into the air. Alternatives to solvent-based adhesives that can reduce or eliminate the air releases from assembly processes include low-solvent and solvent-free formulations and two-part adhesives. Across the country, assembly facilities are slowly replacing solvent-based formulations with solvent-free alternatives, eliminating volatile and toxic air releases. When considering adhesive alternatives, the health and safety of workers also must be evaluated on a case-by-case basis. For example, solvent-based adhesives may harm the respiratory system, while solvent-free or two-part adhesive may harm the skin.

The use of adhesives in vehicle assembly, while causing the release of chemicals into the environment, also has implications in End-of-Life Vehicle Management. When used to bond dissimilar materials, adhesives minimize or eliminate the recycling potential of many vehicle parts. Plastics recycling, in particular, is limited if adhesives are used to bond dissimilar plastics. Few plastics can be recycled into high-end products if contaminated with dissimilar polymers; adhesion between bonded parts is so strong that complete separation is difficult to achieve. The use of adhesives, therefore, should be evaluated from both a vehicle assembly perspective (i.e., air emissions) and a life-cycle perspective (i.e., recyclability).

When using two-part adhesives, care must be taken to mix only the quantity needed for the job at hand in order to minimize adhesive waste. In assembly processes, this can be achieved with an adhesive application process that feeds the two components separately through the application gun, mixing them just prior to application on the vehicle.

Pollution Control
As part of an effective environmental management scheme, pollution control technologies, if used, must be efficiently operated. Although not the first choice within the waste hierarchy, control technologies can protect human health and the environment from potentially harmful materials. Industry must be held accountable for the efficient operation of these processes, while encouraged to implement pollution prevention options that may obviate such controls.

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