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Cleaning with CO 2 Introduced in the 1980s for cleaning precision surfaces in highly controlled environments, carbon dioxide (CO₂) cleaning installations are achieving cleaning performance results in open-cell automotive assembly plants at a fraction of the cost and floor space of traditional aqueous cleaning and drying lines. Nelson Sorbo, PhD, who heads R&D; at Cool Clean Technologies ( coolclean. com ), says the patented process starts with liquid CO₂ being injected into a capillary condenser where it is transformed into solid CO₂ particles of variable size and density. These are then mixed with a heated and pressure-regulated inert propellant gas. The resulting CO₂ spray can be adapted to deliver particle impact pres- sures as high as approaching 10,000 psi without damaging part surfaces. Delivered under pressure, the solid CO₂ "sublimes," or turns into gas on contact with the part surface, which provides the cleaning energy and allows for a total "dry cleaning" process. "This cleaning spray can be CO₂ only or can be combined with an integrated additive injection to modify the chemistry, and can further be combined with atmospheric plasma and ionized air de-stat systems to provide additional surface-treatment capability," Sorbo says. "Because the cleaning spray generated is designed to clean without condensation, no special compo- nent heating or cleaning zone segregation is required." Sorbo's company recently installed an integrated CO₂ spray cleaning system at the paint line of a North American supplier that produces various ABS plastic parts. It is configured as a dual robot system in the cleaning room just upstream of the entrance to the paint booth. • 3-D cleaning of both sides required • Cleaning system must accommodate existing fixture on racks on 40 x 60 in. BY RAY CHALMERS, Contributing Editor A dual-robot CO 2 cleaning station can meet automotive specifications at a fraction of operating costs and floor space of traditional aqueous systems. • Required cleaning time: 45 seconds per rack • Surface must be clean and dry after cleaning • Surface must be free of all release agent and remains after cleaning • Must have no negative impact to visual appearance or function of parts after they are painted • Contaminants of concern: • hand sweat • dirt and dust • mold release agents • tool oils The cleaning system selected includes two CO₂ spray modules with four nozzles each; custom-designed nozzle assembly; and two 6-axis robots designed to actuate the nozzle assembly for cleaning both sides of the parts. The system Process offers performance at significant cost, time, and space reductions. 34