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Understanding technical cleanliness: importance, assessment, maintenance

Development of the automotive industry, including so-called downsizing and rightsizing, entails the need to ensure, and hence to verify, the stringent cleanliness levels of an increasing number of car components. The presence of foreign particles is especially crucial in case of any flow system in vehicle, pressurized or not, and with extreme importance in all injections systems. Particles such as sand, metals, machining chips or abrasive residues may have negative impact on proper component or assembly functioning. The function of the component determines the level of permissible particle types and sizes. The assurance of proper cleanliness level requires knowledge of the entire production process and precise information on the contaminants that will allow to identify their sources. Avoiding product contamination requires awareness of all operations that influence the product’s cleanliness level. This leads to stringent productions regimes, including assembly operations to be performed in clean areas, separated from production lines, or even in clean-rooms. However, the requirements are based on engineering needs and technical premises, the product should be as good (in this case - clean) as required, and not necessarily better because every change and every new operation carries additional costs. In order to get knowledge about cleanliness level of component, laboratory tests in special clean-rooms are required. Obtaining reliable information requires establishing of many different factors, i. a. selection of proper contamination extraction and collection technique (i.e. pressure rinsing, ultrasound-assisted extraction, flushing, and others), proper parameters of extraction, validation of extraction procedure (declining performance), methods of particles analysis. Analytical techniques which are implemented include gravimetric (total amount of all particles collected from component), optical microscopy (determination of sizes and types of particles, including division to metallic, non-metallic and fibrous particles), and advanced techniques like scanning electron microscopy (SEM, allowing determination of elemental composition and hardness of particles). The aim of present work is to present actual state of knowledge regarding technical cleanliness of components, required analytical techniques to perform cleanliness test in laboratory in order to check the compliance with specific customer’s requirements. Important aspects of QA&QC in technical cleanliness assessment will also be discussed.
Topic: Other
Author: Joanna Faber
Co-authors: Krzysztof Brodzik, Marta Nycz