μ-Scale CMM: A New Diagnostic Tool of Evolved Dimensional and Geometrical Deviations for Bus Diesel Engine Cylinder

μ-scale measurements of dimensional and geometrical features of components require an advanced precise and accurate device such as the CMM machine. Evolved changes in the dimensional and geometrical measurements as referred to benchmark values can be employed as a reliable diagnostic tool in monitoring the functional deterioration of mechanical parts that involve working surfaces during their operation. It is evident that excessive wear in a cylinder bore of an internal combustion engine can dramatically affect the quality of performance, the sealing function, the scheme of lubrication, and eventually the service life span of the piston rings and in turn of the engine as a whole. In this work, precise and accurate measurements of evolved deviations in the diameter, roundness, straightness, and concentricity in a cylinder bore of an air cooled Automotive Diesel Engine using a CMM machine have been carried out and analyzed. The results have been presented, discussed, and interpreted in order to demonstrate making use of them in monitoring the status of the engine during operation. Locations of severe wear occurrence in the cylinder bore are then detected and investigated. The measurements within relevant uncertainties would reflect the quality of engine performance, the suitability of the applied scheduled maintenance plan, and the adverse operating conditions which may have been probably encountered during service life. Thus, in the light of the findings, recommendations can be provided to the engine designer to improve his design regarding changes of material selection and/or surface treatments. Furthermore, an innovative constructional modification may be suggested to homogenize the wear occurrence in the cylinder bore during operation. For instance, a device can be added to the construction in order to cause continuous slow rotation of the cylinder about its geometrical axis while the engine is running, without having to dismantle the components. This may extend the operating life span of the cylinder and in turn reduce the maintenance expenses. In addition, power loss due to friction and wear in the engine may be favorably affected.