Production Machining

SEP 2018

Production Machining - Your access to the precision machining industrial buyer.

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CONTRIBUTOR Barbara Kanegsberg and Ed Kanegsberg Ph.D., consultants with BFK Solutions, specialize in critical/precision and industrial product cleaning. For questions or to receive their newsletter, call 310-459-3614 or email info@ bsolutions.com. remove than large ones, in part because of the influence of non-polar (dispersive) forces. To understand the impor- tance of non-polar forces, consider the gecko. A gecko climbs walls and travels across ceilings not because its feet exude some sort of adhesive, but rather through the non-polar forces between the tiny cilia or hairs on its feet and the wall. Fine particles (of 5 microns and smaller), especially dried-on particles, behave like gecko feet and adhere to surfaces tenaciously through non-polar forces. Manufacturing processes often involve mixed soils of varying composition with particles embedded in thin film. e chemical nature of the soils and the size distribution of the particles may not be well characterized. e types of soil may vary for a given product, especially if a number of subcontractors/fabricators are involved. is adds to the challenge of particle removal, and it is why some manufac- turers choose to clean with both solvents and aqueous cleaners. e polarity of the surface itself is important, so some cleaning protocols involve alternating between cleaning with acids and bases to "wiggle" the particles off the surface. Proving that all (or almost all) particles have been removed is an even more vexing challenge. With any solvent, repeated extractions will continue to remove particles, although usually at a lower rate. Eventually (although sometimes right away), parts of the product may be extracted; that really muddies the waters (pun intended). Switching to another extraction solvent may result in an upswing in the number of particles removed, as a different solvent may have a different mix of forces and may be more effective at removing certain particles. For this reason, current Food and Drug Administration guidance for residue on medical devices includes extraction with multiple solvents (at least two) that differ in polarity. Choosing the right extraction solvents (including water) becomes a judgment call; that judgment call has to be based on logic and at least a modicum of testing. Ultrasonic cleaning, including cleaning at high frequencies (100+ kHz) are important for fine particle removal. Simple tests, such as graphite removal, are visual and subjective. COMING CLEAN productionmachining.com :: 53 ® Cl ean Parts . Tel. 716.763.4343 ■ www.miraclean.com ■ C lean Lines ■ Passivation Lines ■ Aqueous Chemistries ■ Data Management See Miraclean® at IMTS 2018 Booth 121015

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