As a device for processing bevel gears in the equipment manufacturing industry, bevel gear machine tools mainly consist of tool boxes, workpiece boxes
Composed of bed frame, electrical control cabinet, etc. Due to the direct impact of the assembly accuracy of spindle components in the tool box on the machining quality of bevel gears, this article mainly focuses on tolerance modeling, assembly error transmission laws, and tolerance optimization.
(1) According to the theory of small displacement spinor, the geometric element errors are decomposed into six degrees of freedom directions, targeting the plane
A geometric error model including dimensional tolerances and geometric tolerances was established for geometric errors such as surfaces, cylindrical surfaces, axes, and conical surfaces, and constraint inequalities and variation inequalities for spinor parameters in the error model were derived. The actual variation range of the error component was solved using Monte Carlo method, and compared and analyzed with the ideal variation range determined by the variation inequality. Use response surface methodology to establish the functional relationship between the actual range of variation and dimensional and geometric tolerances, and use complex correlation coefficients to test the fitting accuracy. Focusing on cone and cylindrical surfaces as examples, verify the machining economy based on the modeling method of small displacement spinor theory.
(2) Based on the geometric element error model, analyze common fitting forms such as plane, cylindrical surface, conical surface, etc Establish a model for error propagation in mating surfaces based on the accumulation and propagation laws of errors. Study the error transmission process of series and parallel coordination, analyze the error transmission form of parallel connection between flat and conical surfaces, and solve the model parameters. Establish an assembly error transfer model for the spindle component system of bevel gear machine tools based on the assembly surface as the error transfer node. Use software simulation to solve the assembly error of the tool head in the x, y, and z directions, and analyze the error sensitivity; Build a point cloud scanning experimental platform to verify the correctness of the assembly error transmission model and assembly error calculation results.
(3) Establish assembly accuracy reliability evaluation indicators based on mechanical reliability theory, using Monte Carlo simulation The fitting method is used to solve the reliability of assembly accuracy. Establish a tolerance optimization model for the tool spindle component system, with the minimum machining cost of tolerances as the optimization objective, assembly accuracy reliability and tolerance value principles as constraints, and dimensional and geometric tolerances as basic variables. And use particle swarm optimization algorithm to solve the tolerance optimization of the tool spindle component system.
As one of the more special types of CNC machine tools, bevel gear machine tools are used in industries such as aerospace, navigation, and vehicles Precision instrument processing is widely used in the industry. Cone gear machine tools require high assembly accuracy and assembly cycle for products Long and complex assembly process. Therefore, it is particularly important to conduct reliability assessment and analysis during the design phase of bevel gear machine tools. Taking the spindle component system of bevel gear machine tools as the research object, starting from tolerance modeling and assembly error transmission analysis, this study investigates the reliability evaluation and optimization methods of machine tool assembly accuracy. It has important theoretical and practical value for ensuring product quality and reducing economic costs in the design stage. The article considers the impact of dimensional and geometric tolerances on the error variation of geometric elements, and establishes a geometric element error model, which can significantly reduce the manufacturing cost of parts. Considering factors such as assembly process, mating surface type, and error transmission form, analyze the transmission mechanism of assembly errors to provide a theoretical basis for guiding the successful assembly of machine tools. Combining the theory of mechanical reliability with assembly accuracy, research the evaluation and optimization methods of assembly accuracy reliability, obtain tolerance optimization results, reduce product design changes and design time, lower manufacturing costs while ensuring the assembly accuracy of tool boxes, and improve the inherent reliability of machine tools.
Research contents
Taking the spindle component system of bevel gear machine tools as the research object, tolerance modeling is carried out on the geometric elements of plane, cylindrical surface, conical surface, and axis, and the functional relationship between tolerance and error component variation range is established. The transmission law of part errors in the assembly process is explored, and the assembly error transmission model of tool spindle components is established. The output of the assembly error transmission model is used as the response variable to study the method of tolerance optimization. The specific research content is as follows:
(1) Based on the theory of small displacement spinor, the part tolerance is decomposed into six degrees of freedom, and a plane is established The error variation model of geometric elements such as cylindrical surfaces, conical surfaces, and axes is solved using Monte Carlo method to determine the actual range of error components and compared with the ideal range, proving the rationality of this modeling method. Establish a functional relationship between the actual variation range of geometric elements and dimensional tolerances and geometric tolerances based on response surface methodology.
(2) Establish error transfer models for mating surfaces such as flat, cylindrical, and conical surfaces, and study serial mating The error transfer properties of parallel coordination were discussed, and the actual error transfer properties of the mating surface were investigated when considering positioning sequence and assembly interference. The parallel error of the tool spindle component plane and cone surface was solved. Establish an assembly error transfer model for the tool spindle system with the mating surface as the error transfer node, use software simulation to solve the assembly error of the tool head in three directions, and analyze the error sensitivity. By building a point cloud scanning experimental platform, verify the correctness of the assembly error transmission model and the calculation results of assembly errors.
(3) Establish reliability evaluation indicators based on mechanical reliability theory and solve them using Monte Carlo simulation method Assembly accuracy reliability. Establish a tolerance optimization model for the tool spindle component system with the goal of minimizing machining costs, various tolerances as basic variables, and assembly accuracy reliability and tolerance value principles as constraint conditions; Adopting an improved particle swarm optimization algorithm to achieve tolerance optimization of the assembly.
In the tool spindle component system, the cylindrical surface is controlled by the roundness of the surface circle and the parallelism of the element line to the axis
The various shape tolerances within the cross-section and axial cross-section of a cylindrical body have the same limiting effect as cylindricity. However, from a detection perspective, the difficulty of detecting cylindricity is greater than that of roundness and parallelism. Therefore, the annotation of cylindricity can be replaced by a combination of roundness and parallelism of cylindrical lines. The tolerance range of cylindricity variation and the tolerance range of radius dimension on the surface of a cylinder have isotropic variation characteristics, so the error variation of the cylindrical surface can be reflected by the error variation of the cylindrical surface contour line.
Cylindrical mating surfaces are commonly used in shaft hole bearings, consisting of the inner cylindrical surface of the hole and the outer cylindrical surface of the shaft. hole The machining error of the shaft and the clearance error of the mating contact surface constitute the error of the cylindrical joint surface, which can be considered as the error between the actual axis of the hole and the shaft. The error of the cylindrical joint surface is not only related to the machining error of the hole axis itself, which will cause the axis to shift from the ideal position to the actual position, but also to the fitting properties of the hole axis. The different fitting properties will also affect the actual installation position of the axis. Conical surface matching has high coaxiality and can transmit large torque, which has good application prospects in the engineering field, such as the connection of machine tool spindle taper holes, conical locating pins, and spindle cutterheads. The conical joint surface is composed of two conical surfaces, and its error formation mechanism is the same as that of a cylindrical surface. It can be regarded as the relative pose change of the ideal axis of the two conical surfaces., The composition of the error of the conical mating surface is the same as that of the cylindrical mating surface, and the error value of the conical mating surface is determined by the machining error of the hole axis conical surface and the properties of the conical mating surface.