Research On Assembly Tolerance Analysis And Kinematic Accuracy Analysis Of Mechanical Equipment

Kinematic accuracy is an important performance index for evaluating the quality of mechanical equipment.High kinematic accuracy is a necessary guarantee for mechanical equipment to complete the specified operational tasks.The assembly tolerance quality of the whole equipment is the premise to ensure the kinematic accuracy,and the assembly quality of a mechanical product will directly affect the running quality of the product.Therefore,the design quality of mechanical equipment can be evaluated progressively from two aspects: static assembly tolerance quality and dynamic kinematic accuracy quality.This dissertation firstly analyzes the tolerance analysis method from the static perspective of the assembly from the influence of tolerance on the assembly during the mechanical design process.In view of the general uncertainty in the actual assembly process of mechanical equipment,a new C-NPS(Convex and Non-probabilistic Set)tolerance analysis method is proposed by using non-probabilistic analysis technology methods to analyze the limited tolerance data information.The non-probabilistic set(NPS)can be used to construct the tolerance model,and the convex method is applied to analyze and evaluate the requirements of assembly quality.Compared to the traditional tolerance analysis method,this method expands the quantitative analysis approach of uncertainty under limited sample data conditions.Applying this method at the mechanical product design stage can timely evaluate possible assembly quality problems and optimize the effective structures and tolerances to avoid unassemblability due to ignoring the part processing deviations.This dissertation illustrates the application of this method by the assembly of a one-way clutch.Secondly,it is difficult to analyze the kinematic accuracy of mechanical equipment because the precision of the mechanical equipment assembled is affected by complex conditions.A new analysis method of kinematic accuracy of mechanical products based on DP-SDT(Deviation Propagation and Small Displacement Torsor)theory is proposed in this dissertation,and the method of tolerance optimization is used to improve the motional precision of the product.The causes of the error in the dynamic process of the mechanical product(such as the assembly gap,the force of the parts in the product and so on)and the mechanism of the error propagation is analyzed in detail.On this basis,the analysis model of the error propagation of the parts based on the DP-SDT theory is proposed.The model includes:(1)we propose a semantic-based exploration algorithm to solve the influence of force direction and vibration on parts deviation.According to this algorithm,the solving process of DP-SDT kinematic accuracy analysis method is introduced in detail,which can be used to predict the quality of mechanical products under different quality requirements and actual operating conditions;(2)a displacement transformation algorithm is proposed to comprehensively describe the deviation caused by motional displacement.Finally,the comprehensive evaluation of the operation quality of the mechanical products is achieved by considering the product design information and the actual complex conditions(such as complex geometric structure,assembly mode,tolerance,force direction and vibration)at the design stage.This dissertation takes the saddle assembly of CK8011 lathe of a heavy duty machine tool factory as an example to illustrate the applicability of the proposed method in practical engineering.Based on the above two theories,a computer-aided prototype system is designed and developed.This system considers and analyzes the kinematic accuracy of the mechanical products,and conducts the studies of the influence of tolerance on the assembly process,and carries out a background algorithm for the modeling of error generation,accumulation and propagation.The prototype system realizes the information interaction with the three-dimensional CAD simulation system.A three-dimensional real-time kinematic accuracy control system for mechanical products is designed in this dissertation.This prototype system makes use of Visual Studio to develop a three-dimensional simulation platform after the secondary development of Solid Works software to predict the kinematic accuracy of mechanical products at the design stage,which can achieve a full range of working conditions for mechanical products kinematic accuracy calculation.At the end,the dissertation uses the assembly of “marine high-pressure swash plate type axial piston pump” in engineering practice as an example to verify the effectiveness of this system.