Metal Finishing Guide Book


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better, start investigating new cleaning equipment while your current process is still functional. What if you don't have a production process? Some start-up companies put off even investigating manufacturing processes on the grounds that they might sell the company (or at least the idea for the product). Such companies may limp along using glass stirrers, lab wipes, and elbow grease provided by summer interns. Especially if the new product has very different characteristics from existing ones, part of what makes it sellable is a sense that the start-up company has considered the concept of manufacturability. Therefore, if you have a prototype process, it's a good idea to look at cleaning options and even to set up a prototype production line, whether or not the company ever actually produces the product. Six Questions Let's get started. Here are six questions to ask the rep (or you could Web search or look through the catalogues – sometimes it's more effective to ask); we summarize them in Table 1. They are not the only questions to ask; they will provide a starting point; and they may allow you to eliminate options that won't do the job for you. 1 - What kind of cleaning equipment is it? It's tempting to buy a system based on overall, outward appearance. All cleaning systems have features and limitations. Enthusiastic reps may honestly believe that their cleaning system will work for your process. Judge for yourself. An in-line conveyor belt cleaning system may be perfect for some applications. However, a spray cabinet might be better in situations where a few large parts are being cleaned at a time. Very small parts might have to be individually fixtured – this takes time. A vapor degreaser might be the best answer if you are considering only solvent cleaning; or if soils aren't being successfully removed with water. Keep the options open. An ultrasonic system could allow you to use aqueous (water-based) cleaners; ultrasonics may be needed with solvents as well. 2 - How does it work? Let's first review the basic concept of the cleaning process. Cleaning is removing soil, matter out of place, things that, if left on the part, will interfere with plating, other coating, or final assembly. A complete cleaning process includes washing, rinsing, and drying (Table 2). With some exceptions, effective cleaning involves the cleaning agent (chemistry), cleaning forces, temperature, and time. Washing is the first step. Washing removes the soil from the part and keeps it away from the part. Because the cleaning agent (the chemistry) can itself leave residue, a rinse step is often (but not always) needed. Rinsing can continue the washing action; however, the primary purpose, particularly in aqueous and semi-aqueous processes, is to remove the cleaning agent. The drying step can also continue the washing action; the primary purpose is to remove water or solvent. All of these steps have to be accomplished without damaging the parts or inadvertently recontaminating the parts. Is the process you are contemplating actually a cleaning process? Anodic or cathodic processes are often thought of as cleaning; and, in the sense that they remove unwanted material from the surface, there is a kind of cleaning function. However, electropolishing may not be a complete or sufficient cleaning process. If other soils are not removed first, there can be interference; it may be necessary to begin with a true wash/rinse/dry process. Be on the lookout for other processes, like passivation and heat treatment, that may not be true cleaning processes. 99

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