3-D Measurement And Visual CharacterisationOf Cylinder Liner Bore Polishing

Abstract

Wear in engine cylinder liners has long been a problem which has attracted considerable attention over the past 50 years. The surface of the liner is usually generated by a combination of base and plateau honing. The honed surface serves a dual function of providing good bearing capability as well as the ability to retain lubricant. Excessive wear can lead to the removal of the honing grooves and the formation of polished regions. These areas, known as bore polish, are detrimental to the overall performance of the engine and can lead to gas blow-by and scuffing. The engine testing industry, as part of their criteria for determining the performance of a lubricant, will inspect an engine liner for the size and frequency of these polished regions. The inspection of bore polish is a long and tedious process carried out by an inspector peering over the liner block with a torch and tracing the outline of polish regions onto an acetate sheet. There are numerous sources of errors and problems associated with this technique. In order to provide to provide a better insight into bore polishing the School of Manufacturing and Mechanical Engineering, in collaboration with an independent engine testing laboratory, investigated this phenomenon. This paper will describe the current inspection technique and introduce a method of visually characterising the degree of bore polish. In an attempt to quantify the polish categories recently-developed 3-D surface characterisation techniques were employed.