Positioning Error Analysis On Engine Cylinder Block Machining

Over the past decade, The rapid development of China’s automobile industry, theautomotive R&D and manufacturing have made tremendous achievements. The total carsales has emerged as the world’s first, but the key automotive engine parts processingequipment and technology still needs to be imported from the United States, Germany,Japan and other countries. Seriously hampered the development of the automotive industry.The key core components of automobile engine is a cylinder. The quality and accuracy of thecylinder direct impact on the engine’s performance and life, thus improving engine blockmachining accuracy and quality to enhance the overall competitiveness of China’sautomobile industry has significance. In the engine block machining process,the fixturepositioning error is the main factor affecting the cylinder block machining accuracy.In thisthesis. The fixture positioning errors of engine block machining process based on errormapping model are analyzed and calculated to estimate the positioning element size error (aplane and two pins positioning). Specifically the related works done in this thesis are asfollows:(1) Introduce the positioning principle and concepts of workpiece, then describe thecontent related with engine block machining, based on the traditional method of positioningerror analysis and calculation in engine block machining process, and point out the drawbackof the methods.(2) Establish a common error mapping model, based on the model analyzing the errorof―a plane and two pins positioning‖which is the most common positioning in engine blockmachining process. Fully consider the impact of the underside and the positioning errorbetween the two positioning pins and the positioning hole to the cylinder positioning error,and use the model to analyze and calculate the of the four-cylinder engine block’s positioningerror.(3) Describe the precision evaluation in engine block machining process, using theerror mapping model for estimating the error of fixture positioning element whose position points are known. Determine the largest gap between the two pairs of locating pins andlocating holes. Provide a reference for the design and distribution of positioning element’sdimensional tolerances.