Metal Finishing Guide Book

2013

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Consider what sorts of cleaning forces are needed. Applying force can move the soil away from the surface. Will ultrasonic cleaning help the process? Even solvent-based cleaning can benefit from ultrasonics. There are many variables and, therefore, many choices in ultrasonics (1). Don't assume ultrasonics cleaning is a magic bullet. Test ultrasonics in your process for effectiveness and for the potential for product deformation and surface damage. The same holds true for other sorts of cleaning action, like spray and turbulation. Styles in cleaning change; and the assertion that "everyone buys this great cleaning system" doesn't mean that it's right for you. Does the equipment being offered have rinsing and drying capabilities? Are those capabilities adequate for your current and near-future product line? If you need rinsing, resist the temptation to purchase an inexpensive washing system where the rep tells you that you can "always add a rinse tank." It probably won't happen. Some newer cleaning agents have high boiling temperatures; and, if they are not rinsed, can leave a residue that does not readily evaporate and interferes with coating. Often, a single wash tank needs to be followed by at least two rinse tanks. A reverse cascade pattern, where water moves from the final rinse to the first rinse, can provide for more effective, efficient water usage. We see too many instances where the rinse tanks are static dip tanks that rapidly fill with cleaning chemistry. They wind up functioning as wash tanks; rinsing is not taking place. Then, there is drying – the orphan step in the cleaning process. This is the step where the budget runs out; and too many people buy into the delusion that drying equipment is not really necessary. Then, they find that it is necessary; parts become recontaminated or they corrode. It is possible to add drying equipment later on. However, first comes the battle with the bean counters. Also, achieving a seamless, effective cleaning process will be more difficult. Consider recycling. Recycling, reuse, and closed-loop systems have traditionally been thought of as politically correct concepts – activities that would be nice to do, if only we had the money. However, consider the quality and economic implications of recycling and closed-loop systems. Water treatment and disposal costs are high. Cleaning chemicals cost money. It is often cost-effective to restore and reuse the cleaning agent and rinsing fluids. In addition to saving money in disposal costs, on-board recycling can result in more consistent chemical quality and can contribute to higher yield. 3 – What cleaning chemicals can I use? This is rather a loaded question; particularly because we are considering the cleaning equipment. We could write a totally separate article about questions to ask the cleaning agent vendor. Choosing the right cleaning chemistry is a crucial part of selecting the cleaning process (2,3). Consider the choice of cleaning agent in parallel with the choice of cleaning equipment. Linear thinking takes too long and costs too much money. There are many types of cleaning agents, broadly categorized as aqueous, semi-aqueous, co-solvent, and solvent. Even so-called solvent free processes use chemicals like steam, CO2, and the numerous chemicals species generated in plasma systems. Understanding cleaning agents is a separate topic, with specific questions for cleaning agent vendors. Some factors include how well the cleaning agent performs, the potential to damage the product, initial costs, process costs, whether or not it can be filtered or distilled, how long it lasts, waste management costs, and safety and/or environmental regulatory constraints. Just as there is no universal cleaning agent or universal solvent, there is no universal cleaning system. Some systems are more flexible than others; and you 100

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