Design of Key Components of Crankshaft Machining Combination Machine Tool and Dynamic Balance Analysis

With the continuous improvement of performance indicators for medium-speed marine diesel engines, the manufacturing standards for crankshafts have become increasingly stringent, resulting in more complex machining processes. To address these challenges, this paper designs a specialized crankshaft fixture capable of meeting the machining requirements of both the connecting-rod journal and the crank arm. The fixture is applicable to multiple crankshaft models, offering good versatility, requiring only matched counterweights and indexing adjustments according to different crankshaft specifications.Existing non-circular polishing techniques fail to ensure the cylindricity of crankshaft journals and cannot provide ideal contact between the journal and bearing shell, which is unfavorable for the formation of a stable lubricating oil film. To solve issues such as insufficient contact area between the journal and abrasive belt during polishing, a dedicated polishing device is developed. The polishing process is divided into rough and finish stages, enabling complete circular polishing, and a corresponding detection method for journal contact area is proposed.In addition, the crankshaft assembly supported on elastic supports is simplified to an approximate two-degree-of-freedom vibration system, and its dynamic balance is analyzed. The unbalance of the crankshaft assembly is obtained, which provides a theoretical basis for mass reduction during balancing.