Contamination control techniques on surfaces

For many manufacturing processes, it is indispensable that component surfaces are clean in order to be able to manufacture high quality products. Due to current and acute problems in the automotive industry, the presence of particulate contamination on functionally-relevant automotive parts has become a focus of discussions associated with the subject of quality. The first step towards standardizing cleanliness analytics was taken when VDA Volume 19 was published in 2005 and ISO 16232 in 2007. These publications are mainly concerned with methods based on the extraction of particles using liquids. The methods are utilized to determine and monitor residual contamination levels (related to particles). However, this only Covers one aspect of cleanliness analytics relevant to the problems encountered in the automotive and subcontractor industries. A further area responsible for drastic losses in quality due to particulate contamination in manufacturing processes is the field of decorative coating and painting where appropriate cleanliness analytics are needed. Other cleanliness analysis methods are based on direct measurement procedures. These detect particles on component surfaces without the need for sample-taking or extraction and can be integrated into production lines for monitoring purposes. However, not only particles but also filmic contamination such as residues of lubricants or processing oils are responsible for deficits in quality. The presence of these types of residue can severely impair subsequent processes such as coatings or heat treatment. In some cases, though, greasing is actually desired, e.g. to protect against corrosion. A broad spectrum of analysis technology exists for detecting the presence of these filmic adherences, ranging from simple rapid diagnostic tests right up to complex laboratory procedures. This article focuses on production-related tests and on methods which can be automated and integrated into production lines for detecting the presence of particulate and filmic contamination. The aim of the paper is to give an overview of the state of the art of technology in this field as well as to evaluate the feasibility of integrating the methods discussed into machine equipment.