Choosing an Appropriate Cleaning Solution

When I look at all the industries that have implemented stringent cleanliness specifications for many of their workpieces—no matter if they manufacture them in-house or receive them from suppliers—it was surprising to learn at this year’s parts2clean show that there are part manufacturers not using parts cleaning equipment. In several discussions with exhibitors, I heard there were a lot of visitors, mostly from machining and metalforming shops, gathering information on part cleaning solutions because they are faced with cleanliness specifications for the first time. As I looked deeper into this situation, it became clear that the customers of these companies have been cleaning the parts themselves after delivery. But now they want to transfer the cleaning process to their suppliers in order to reduce cost. 
Attempting to decrease cleaning costs per unit was a hot topic of conversation. Discussion about whether an aqueous or solvent-based cleaning solution would be the right one is becoming more application-oriented and less emotional. 

Going back a few years, for many companies, cleaning with solvents was seen as an absolute no-go. This attitude was based on the bad reputation solvents had received after the ban of fluorinated hydrocarbons for cleaning purposes in Germany in 1993 and the toxic properties of chlorinated hydrocarbons such as perchloroethylene and trichloroethylene. Thus, for a long time, many companies decided in favor of an aqueous cleaning solution, regardless of the cleaning task in question. The selection process was not based on the contaminants that had to be removed, but rather on “gut feeling.” 

Alternative solvents such as hydrocarbons and modified alcohols were available as well as fully closed solvent cleaning machines with an integrated distillation unit, working under vacuum conditions and enabling a virtually emission-free vapor degreasing and cleaning process without any contact of the machine operator with the solvent. Use of an inappropriate cleaning solution would typically result in additional time and cost. Selection of the cleaning solution should be based on objective aspects, such as contaminations and part material, the degree of cleanliness needed to achieve, cycle times, energy efficiency and cleaning machine flexibility. 

I have also gotten the impression that automation will become an important topic in industrial parts cleaning for exploiting savings potential, even for smaller companies. One reason might be that automation solutions with robots or handling systems have become less expensive, so payback time will shorten. The integration of the cleaning process and equipment into Industry 4.0 technology was also the buzz. The status of almost all relevant machine components, such as pumps and ultrasound frequency, and process parameters, must be able to be automatically monitored, controlled and recorded. 

An increasing use of alternative technologies, such as carbon dioxide snow jet, plasma and laser beam cleaning that enable dry cleaning processes, is another trend. These methods allow for cleaning functional surfaces and component areas selectively, for example, before welding, bonding and assembly processes. This offers savings potential. Functional areas usually require a higher cleanliness degree than the rest of the part. In classical aqueous or solvent processes, the entire part must needlessly be cleaned to this high cleanliness standard, which is not only time consuming, but also often requires a more sophisticated and thus more expensive cleaning machine. 

The alternative cleaning systems are more or less space-saving and can easily be integrated into automated manufacturing, bonding, assembly or packaging lines. This has an additional advantage: having the respective surface cleaned right before the bonding, welding or packaging process, the required cleanliness can be provided “just-in-time,” therefore eliminating any measures and costs to keep parts clean after cleaning and during transport.

Since an increasing number of parts are joined by (laser) welding or bonding, or they are coated, film-like residues on cleaned parts’ surfaces are becoming more of a problem for part manufacturers and their customers. As a result, two mutually complementary projects have been started to support users of industrial cleaning technologies in this area.