Process Analysis And Deformation Control On Automobile Engine Cylinder Block Machining

Engine is the heart of the car, and its manufacturing quality directly impacts on car performance. Engine cylinder block is the basic assembly component of all mechanisms and systems, and its manufacturing precision has an important effect on the overall performance of the engine. To improve engine performance, the machining precision and manufacturing quality of engine critical parts must be controlled.In this thesis, the SGMW automobile B11/B12-type engine cylinder block is studied. The influence law of the machining deformation caused by clamping force and milling force is analyzed through processing analysis and finite element simulation. Then, the relationship of machining error and machining internal stress release caused by the clamping state changes is researched. Therefore, the effective control plans of machining precision are presented to achieve optimization and improvement of cylinder block machining processes in production line. This research work mainly includes the following three aspects:Firstly, the clamping process scheme of cylinder block during machining is analyzed, and the clamping deformation of cylinder block is simulated by finite element. Based on the inline 4 cylinder block structural features and the 5-axis CNC milling process system characteristics, this chapter analyzes the clamping state from location mode and the spatial relationships of clamping force and supportive force by analyzing clamping device. Through analysis and calculation of the hydraulic loading system, the value of the clamping load of the engine block is determined. Based on the 3D software CATIA, a numerical model of the cylinder is established and is meshed by software HyperMesh. By taking advantage of software ABAQUS, the clamping deformation of cylinder block finite element model is simulated to obtain the clamping deformation cloud charts of rare face and pan face and the clamping deformation situation under different clamping force. The simulation results show: the deformation on the rear face upper position and the position of pan face near the site of the fixture chuck is significantly large; the overall deformation of pan face is larger than the overall deformation of rear face; the changes of clamping force have insignificantly effected on the overall deformation of rear face and pan face.Secondly, the cylinder block milling force model during machining is established,and the milling deformation simulation of cylinder block finite element model is carrying out. The milling orthogonal experiment of cylinder block material HT250 is conducted to make sure that the cylinder block milling force model is established and the cutting force is calculated to carry out the milling deformation simulation. Through cylinder block finite element simulation, the coupling effects of clamping deformation and milling deformation is analyzed. The simulation results show: milling deformation is significantly larger than clamping deformation; rough deformation is larger than semi deformation; milling deformation becomes larger with the increase of milling force.Finally, the prediction model of perpendicularity error about machining workpiece numbers is established,and precision control plans during cylinder block machining are put forward. Based on multiple linear regression analysis and equidistant stratified sampling datum, the quantitative relationship formula of perpendicularity error about machining workpiece numbers is established to determine workpiece numbers and predict tool change cycle. Through analysis of process and simulation of machining deformation about cylinder block, precision control plans during cylinder block machining are presented. The control plans include: the rough milling and semi milling process separation program, and the B-axis angle compensation program. The feasibilities and effectiveness of two programs are verified by the corresponding experiments, which is the basis of machining process optimization and improvement.In summary, the digital simulation model of engine block machining deformation is established. And the effect laws of the machining deformation caused by clamping force and milling force are obtained. Thus, the precision control plans during cylinder block machining are put forward. The researches of this article provide the appropriate theoretical basis and technical reference to the production of automobile engine cylinder block.