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Cleaning Solutions for the Casting Industry.

Issued at 2012-07-29



Cleaning Casting Moulds Efficiently and Ecologically

Whether tooling, casting moulds, ingot moulds or core boxes are concerned – cleaning tasks in the casting industry are becoming more demanding and complex. Modern cleaning technologies allow for reliable, fast and gentle removal of contamination from the casting process – and thus, as a rule, more efficient and ecological cleaning.

Cleaning tasks in the casting industry involve above all the removal of casing residues, mould and release agents, sand and other contamination from tools and moulds. This is still done manually in many cases by means of abrasive scraping, scratching, brushing, grinding or sandblasting. These methods not only necessitate complete dismantling of the tooling and moulds in most cases, they also consume a great deal of time – usually somewhere between a few hours and several man-days. Beyond this, they also involve the danger of possible damage to the moulds, and thus impairment of the quality of the finished castings.

Fast, Gentle Cleaning with Sound Waves

Ultrasonic cleaning represents an effective, gentle and time-saving alternative to manual processes. Ultrasonic waves are produced by a generator which converts normal line frequencies into high frequency electrical signals. These signals are then transformed into mechanical vibration of the same frequency by means of sonic transducers or oscillators. So-called magnetostriction oscillators are usually used to this end for mould cleaning. They produce oscillations which are adequately powerful for cleaning even large moulds.

Ultrasonic waves develop their full cleaning effectiveness in a liquid bath based on the physical principal of cavitation: The great intensity of the alternating sound pressure levels causes alternating phases of underpressure and overpressure within the liquid. The liquid is broken up during the pulling phase of the oscillation cycle. This causes the formation of millions of microscopically small bubbles. During the subsequent pushing phase, these cavitation bubbles are rendered unstable and collapse (implode), and they generate hydraulic impacts with very high energy densities, thus causing micro-currents in the liquid. When these strike a surface, they blast off contamination which has been partially dissolved by a suitable cleaning agent and rinse the “dirt” away. Aqueous cleaning agents are used primarily, whose composition is matched to the respective types of contamination and materials to be cleaned.

When using ultrasound to clean die casting moulds, ingot moulds and core boxes, residues from production and deposits in the moulds including welded-on metals, release agents, facings, lubricants, oil, grease, lime and rust can be removed quickly and gently, but nevertheless thoroughly, without mechanical wear or impairment of surfaces and edges. Entire mould halves can be cleaned in the ultrasonic bath. The otherwise usual complete dismantling becomes unnecessary, because contamination can even be removed from difficult to access areas and complex geometries including, for example, vents, ejector guides, drill holes, scoring and hollow spaces thanks to the enormous cleaning effect of cavitation. As a rule, cleaning can be completed in roughly one hour – including rinsing and mould preservation.

The cleaning process is executed in systems which are laid out to fulfil actual requirements, usually with a sound frequency within a range of 18 to 25 kHz. In addition to sonic frequency, quantity and positioning of the sonic transducers also have a considerable influence on cleaning results. Power ratings of 10 to 30 W per litre are common for mould cleaning. The oscillating elements are usually distributed over several of the cleaning basin’s walls in order to assure that all surfaces are subjected to ultrasonic sound.

CO2 Cleaning – The Ice-Cold Alternative

Another process which has proven its worth for cleaning moulds, tooling and core boxes is dry ice blasting. As is also the case with other blasting processes, a medium is accelerated within a compressed-air jet and it removes contamination when it strikes the surface to be cleaned. Instead of hard blasting media, dry ice blasting uses carbon dioxide. The CO2 is not generated from fossil fuels, but rather occurs as a by-product, for example during manufacturing processes in the chemicals industry, and is therefore environmentally neutral. The blasting medium is produced by means of a separate process in the form of ice pellets, which are fed to the compressed-air jet generated by the blasting unit in a controlled quantity. Systems are also available which produce the pellets and execute the blasting process simultaneously.

Its cleaning effectiveness is based upon three different modes of action: The low temperature of the blasting medium, namely -78.5° Celsius, causes thermal stress due to the different coefficients of thermal expansion of the contamination and the substrate, resulting in embrittlement and separation of the contaminants. The separation process is accelerated when moulds are cleaned while hot. At the same time, the kinetic energy of the blasting medium results in mechanical separation. This is further promoted by the third mode of action, i.e. the pressure surge caused by sudden sublimation of the CO2 particles. As a result of sublimation of the blasting medium, only the removed contamination remains.

Cleaning by means of this dry processes is often possible without completely dismantling the mould or allowing it to fully cool down. At the same time, gentle cleaning is made possible as well, because dry ice is significantly less abrasive than conventional blasting media.

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parts2clean – Leading International Trade Fair for Industrial Parts and Surface Cleaning

Which processes allow for cleaning without dismantling? How can costs and personnel expenses be reduced for cleaning? How can cleaning of moulds, tooling and core boxes be optimised with regard to quality, environmental and work safety considerations. Answers to these and many other questions covering all aspects of parts and surface cleaning will be provided by parts2clean at the Stuttgart Exhibition Centre from the 23rd through the 25th of October, 2012. Thanks to its extensive offerings, the leading international trade fair provides comprehensive information on various system concepts, cleaning technologies, cleaning agents, alternative cleaning processes, washing racks and workpiece carriers, media treatment, cleanliness inspection, corrosion protection, preservation and packaging. In addition to this, the 3-day parts2clean expert forum offers know-how covering all aspects of cleaning. Further information, a preliminary exhibitor list and the agenda for the expert forum are available at www.parts2clean.de.


Source: pressetextschulz.de



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