Precleaning Prior to Ultrasonics

Q. Just purchased your book on industrial metal cleaning—very good. My question involves ultrasonic cleaning with aqueous detergent. We are cleaning deep-drawn parts that have significant amounts of heavy oil on them when received. Would you recommend some sort of gross oil removal first or just leave it to the ultrasonic cleaner? K.B.

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A. First, thank you for the feedback and kind words on the book. It is always rewarding to know people are reading it and finding it useful. That is a good question on essentially employing a gross soil removal step prior to the more precise, ultrasonic cleaning process step. In my experience, you can improve part quality and significantly improve line throughput and productivity by utilizing this type of scenario.

The precleaning step should be effective to remove the heaviest of the lubricant residues. This will allow the ultrasonic process to operate that much more efficiently in final contaminant removal. Another significant benefit can be improved process throughput. In one case, I was involved with the specification and installation of an aqueous cleaning system involving a wash, rinses and a rust inhibitor. As we finalized and validated the final cleaning process, it became apparent that the bottleneck or longest step in this multistage process was the time in the alkaline cleaning tank. This time was significantly reduced by the addition of a second cleaning step such that all parts went first through a preleaning and then a final cleaning process step. This enabled us to significantly reduce our throughput time and greatly increase the productivity from this process.

An additional benefit to the precleaning tank is to have a higher uptime on the entire line. If the line needs to go down for dumping of the cleaning tank, it will have to be done less frequently when you have a precleaning tank ahead of it to collect oil and lubricants, since they will be split between the two process tanks.