Mastering the Art of Cylinder Bore Honing

Abstract

Honing is a stock removal process intended to perfect bore geometry and size by removing a minimal metal layer while generating a finish pattern to provide optimum lubricant retention. The hone process produces extremely tight tolerances in straightness, roundness, size, and surface finish of cylindrical bores. The material removal is effected by abrasive stones of suitable grit and grade that are expanded against the work surface of the cylinder bore under controlled pressure while being rotated and reciprocated at the same time. Combining these motions produces a characteristic crosshatch pattern with a dedicated surface roughness profile essential for the piston/bore tribology, which in its turn affects the engine performance. Multistep honing processes that combine rough honing with peak or plateau honing are increasingly used to produce state-of-the-art surface finishes without compromising productivity. The outcome of the honing process - not only in terms of the GD&T but also the tribology of the finished component - depends on a great number of parameters including the machine type, working conditions, tools, process fluid, and most importantly the operator experience. As the piston/bore tribology is concerned, mechanochemical processes offers significant advantages over conventional mechanical processes. Thus, the mechanochemical finishing of cylinder bores using the Triboconditioning? process allows one to reduce friction mean effective pressure of the piston/bore system by 5 to 15% at the same time significantly reducing piston ring wear, blowby and oil consumption.