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Considering the precision required for every component in a Mercedes Benz engine, carmaker Daimler AG, Stuttgart, Germany, needed to quickly and repeatedly clean large numbers of parts, such as the cast pistons, engine cylinder heads and blocks. To meet strict dimensional tolerances, it was imperative the components were not altered during cleaning.

 

Using abrasive sand blasting or blasting with glass beads can slightly damage the surfaces of the cleaned objects, while producing secondary blasting media waste that then must be disposed. Rather than opt for a complex manual cleaning system or the use of a solvent, Daimler turned to Asco Carbon Dioxide Ltd., Romanshorn, Switzerland, a company that specializes in dry ice blasting technology. The cleaning units use compressed air to accelerate solid carbon dioxide pellets to a speed of approximately 1,000 ft. per second. The dry ice hits the object causing unwanted material to freeze, contract and fall off. The CO2 then sublimates into a gas and re-enters the atmosphere without leaving any residual moisture.

 

The AscoJet dry ice blasting units clean Daimler’s engine components in a timely manner and without damage, improving process planning and overall efficiency. Even so, the piston’s narrow ring grooves presented an additional challenge for Asco, one where an alteration to the dry ice blasting equipment helped clean the narrow channels. Asco added a special light on the end of the dry ice unit’s gun, and the grooves were cleaned with dry ice before the remaining contaminant was removed in an ultrasonic bath.