Products Finishing

OCT 2013

Products Finishing magazine is the No. 1 industrial finishing publication in the world. We keep our readers informed about the latest news and trends in plating, painting, powder coating, anodizing, electrocoating, parts cleaning, and pretreatment.

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Page 78 of 115

PARTS CLEANING When cleaning with solvents, oils and emulsions accumulate in the cleaning agent and react, distilling over time to form free acids. These not only reduce the cleaning quality and lifetime of the cleaning agent, but can also lead to corrosion of the cleaned parts or the system. Test sets are available for regular inspections for chlorinated hydrocarbons (CHC) and some modified alcohols. Inspecting And Documenting Inspecting particulate cleanliness of automotive industry parts has been governed since 2005 by VDA Vol. 19, Part 1 ("Inspection of technical cleanliness – Particulate contamination of functionally relevant automotive components") or the international equivalent, ISO 16232, Vol. 1 to 10 ("Road vehicles – Cleanliness of components of fluid circuits"). The purpose of the guideline is to objectively assess and compare the technical cleanliness of a component based on clear and precisely defined methods and procedures for extracting and analyzing particulate contaminants from manufacturing and the environment. This is the reason for the interest shown in this set of standards by other sectors such as medical and precision engineering, or the hydraulics industry. A key criterion with VDA 19 is that the required cleanliness level is always linked to an inspection specification containing unequivocal information about the cleanliness inspection parameters and particulate measurement techniques. It also stipulates that parameters for cleanliness inspection for the given component type shall be tested and optimized using a so-called extraction curve to achieve the most complete removal of particulates possible without damaging the component substance. Hindered By Geometry Because verification of particulates is hindered by geometry for most workpieces and cannot take place directly on the product surface, a cleaning step in which the particulates are transferred to a fluid medium is necessary. This extraction or removal of particulates from the component can be achieved through a variety of different fluid methods, including spraying, ultrasound, rinsing or shaking, however the extraction procedure is not predefined. This freedom continues to present one of the biggest problems for comparing the results of component cleanliness analyses. The revised VDA 19 that is currently being drafted should, therefore, include a decision matrix that enables users to select the appropriate extraction techniques for their inspection task. Different methods can be used to evaluate samples, with varying levels of validity: gravimetric microscopy, Editor's NotE: Products Finishing Editor tim Pennington will be attending the parts2clean international trade fair for industrial parts and surface cleaning oct. 22-24 in stuttgart, Germany, and reporting back on new developments in European cleaning technology and standards such as VdA 19. automated microscopy with image processing and scanning electron microscopy. The latter provides information about particulates' origin and potential for damage, and can examine even the smallest particulates. Even more precise information can be gained from microtomography, which can measure contaminant particulates in three dimensions. These are extremely precise, but also very tedious, expensive and time-consuming laboratory analyses. Another topic addressed in the revision to VDA 19 is the strict definition of cleanliness requirements, in terms of both their formulation and how to respond when they are not met. Thinking has evolved in this area. Rather than everemptier discussion around the "final micron," in the future processes and process chains will come into greater focus for understanding and inspecting cleanliness. This will require new, rapid and cost-effective particulate monitoring systems, and the necessary solutions are in part already available or under development. Detecting Film Residue Various inspection techniques are available to check cleaned components and surfaces for film residues such as grease and oil, fingerprints, or conservation agents that can detract from the quality of subsequent coating, painting, adhesive, hardening or welding processes. They range from test inks to mobile and inline-enabled testing methods that also permit documentation of the detected values. Once workpieces meet the required cleanliness specifications after manufacture, this cleanliness must be maintained through later steps such as transport, inspection, storage and packing. To prevent particulate contamination from the environment, these subsequent steps must be carried out in a location removed from the manufacturing area, and personnel must be equipped with the necessary clothing and gloves. Volatile Corrosion Inhibitor (VCI) packaging is available to protect cleaned components from corrosion. These packaging materials create a corrosion-proof atmosphere inside the packaging, as well as providing protection from outside contamination. Doris Schulz is with parts2clean, a trade show held every year in Germany. For more info, visit Ultrasonic Cleaning for Large Lots of Small Parts With ultrasonic cleaning, particulate and film-like soils can be removed not only reliably, but also very quickly and efficiently—even on parts with difficult-to-access hollow spaces such as blind holes, knurling and grooves. PRODUCTS FINISHING — 77

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