Deep cleaning with carbon dioxide

At the Fraunhofer Cleaning Technology Alliance booth, the Fraunhofer Institute for Manufacturing Engineering and Automation IPA is presenting a tool capable of completely removing processing residues from areas inside components that are difficult to clean, for example blind holes and boreholes. The tool was developed in the DeepClean collaborative project, where IPA researchers successfully combined different CO₂ cleaning techniques in a single cleaning step: degreasing with supercritical CO₂ and removing particles with CO₂ snow crystals. "At a pressure from 74 bar upward and a temperature of 31 degrees Celsius, carbon dioxide changes into a new state, becoming supercritical.

In this state, it absorbs foreign matter such as oils and greases," explains IPA engineer Dr. Markus Rochowicz. Fitting the tool over the borehole hermetically seals the inside of the component. Then it is rinsed and degreased with supercritical CO₂. When the cleaning tool is opened in the second stage of the process, CO₂ snow is produced, and this removes particles from the component. The force of the CO₂ snow crystals generated in the nozzle of the cleaning tool is so great that even the tiniest particles can be efficiently removed without damaging the cleaned surfaces. As the CO₂ changes back from a solid to a gaseous state immediately after the cleaning, i.e. the snow crystals evaporate, the cleaned component stays completely dry -- an advantage with moisture-sensitive materials.

Cleaning laboratory open to outsiders for carrying out tests

The compact size of the cleaning nozzles not only means that the tool is suitable for manually cleaning components, it can also be integrated into very tight spaces in fully-automated assembly procedures -- for example in the auto industry, where it can be used to remove residues from the hydraulic system, the ABS, or the distribution block during the production process. The innovative tool also has benefits for other sectors: in medical engineering, for instance, where it can be used to clean endoscopes, cannulae, and the bases of dental implants. "The exhibit should also interest manufacturers from the semiconductor, pharmaceutical, optical goods, and aerospace sectors," anticipates Rochowicz. After the trade fair, the system will be available to companies for industrial cleaning tests in the IPA's highly specialized CO₂ cleaning and analysis laboratories. The European Space Agency (ESA) has already used the laboratory infrastructure to look into ways of ensuring the absolute cleanliness of components for future missions to Mars.