Leak-tightness and technical cleanliness in screw fasteningsEngineering360 News Desk | October 27, 2022
Clean and tight — this essential technical relationship is the basis for leak-tight fastening solutions such as are required in the electric vehicle (EV) sector. Arnold Umformtechnik investigates the fundamentals required to guarantee leak-tightness and cleanliness, specifies applications, and analyzes the factors that influence the system. Arnold Umformtechnik has been active in technical cleanliness for many years and the fastening solutions manufacturer, based in Forchtenberg, Germany, believes that it is important to create an awareness that a certain requirement for leak-tightness also requires a defined degree of cleanliness.
Technical cleanliness requirements
The requirements for technical cleanliness were first set by the automotive industry. Today, general regulations establish a standardized framework to achieve technical cleanliness. These include VDA19.1 for testing technical cleanliness, VDA 19.2 for technical cleanliness in assembly; then there is ISO 184.108.40.206, as well as a guide to technical cleanliness for the electronics industry published by the ZVEI (German Association of Electrical and Digital Industries).
Arnold Umformtechnik has a comprehensive range of instrumentation to analyze leak-tightness and technical cleanliness. The company boasts two leak-tightness test benches that use test gas to measure leaks, a mass spectrometer that uses helium as its test medium, and a differential pressure method using air as its test medium. Added to the above another leak test bench uses water as its test medium and can additionally produce an IPX7 certificate.
For the cleanliness analysis it is important to determine the specific particle load present. At Arnold, contaminating particles are detached and gathered up inside an extraction cabinet. There are several different ways of making the necessary analysis that follows. For example, the part can be analyzed under an optical microscope to determine the length and width of any contaminating particles, and these can be categorized as metallic bright or non-metallic bright. Laboratory scales can provide information on particle mass. Arnold has recently acquired a scanning electron microscope to determine the chemical elements that make up a contaminating particle and to draw conclusions about the source of error. The company also has a residual magnetism test stand.
Solutions for individual customer applications
The “clean and tight” theme plays an important role for many fasteners. Here the focus is on leak-tight applications such as battery cases, final assembly and installation. It is also very important for the electronics industry, for example when conductor tracks are set close to one another. Clean fasteners are absolutely essential when used in any oil-conducting systems as well as for the sensor technology in autonomous vehicles. Complex multi-functional and multi-stage components — such as those produced by Arnold’s Conform Next process — can also be included into these cleanliness analyses.
The aim of the clean and tight analyses at Arnold Umformtechnik is to guarantee a reliable evaluation of the leak-tightness of the fasteners within the context of the customer’s application. As well as ascertaining how leak-proof a component is, the analysis should also include long-term effects such as corrosion or environmental influence. From all these analyses it is possible to derive a result as to which fastening solutions will meet what leak-tightness requirements.