Clarification of the Amount of Machining Error Resulting from the Cutting Force and Thermal Expansion during the Cylinder Liner Boring Process

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It is well known that the total machining errors of the engine cylinder liner are mainly dominated by the elastic deformation caused by the cutting force and the thermal expansion caused by the temperature rise during the boring process. Clarification of the amount of machining errors resulting from the cutting force and thermal expansion is useful for determining whether thermal expansion or the cutting force has a larger influence on machining errors during the boring process. This would provide a clear approach to the optimization of cutting conditions or to product improvement, leading to a higher degree of machining accuracy. In this paper, in order to clarify the amount of machining errors, the machining error caused by the thermal expansion apart from the elastic deformation of a cylinder liner caused by the cutting force was first determined. For this purpose, an experimental method is suggested in this paper. The temperature rise that causes the thermal expansion of the cylinder liner was simulated by a YAG laser heating process instead of by an actual boring process. During this heating process, the machining errors caused by the thermal expansion could be solely investigated. First, an actual cylinder boring process was performed (cutting speed: 900 m/min, feed rate: 0.2 mm/rev, depth of cut: 0.3 mm, dry cutting). The total machining errors caused by the cutting force and thermal expansion were measured. Then, the YAG laser heating experiment was also carried out. Comparing the results between the two experiments, it was clarified that the thermal expansion of the cylinder liner caused by the cutting energy is dominant and the deflection caused by the cutting force is small.