Research On Maintenance Strategy Of Machining Center Based On Reliability Analysis

CNC machine tool is a composite system integrated by several electromechanical devices,and as a strategic material of modern manufacturing industry concerning national defense and people’s livelihood,maintaining its smooth and reliable operation is an important work of manufacturing enterprises.Maintenance is the core content of machine tool operation and maintenance management,timely and effective maintenance has an important position and role in ensuring the service life,safety and reliability of equipment.Consequently,through the investigation of the failure regular pattern of machine tool components,proposing a practical and economical maintenance strategy is of great significance to the operation and maintenance management of CNC machine tools.For the maintenance of CNC machine tools cannot simultaneously take into account the law of equipment life,the risk of failure and maintenance costs,resulting in excessive maintenance or insufficient maintenance.This paper takes domestic machining center as the research object to explore the reasonable CNC machine tool maintenance strategy and improve the economy of CNC machine tool component maintenance.The main research contents are as follows:(1)Research on the failure pattern and failure risk factors of machining center subsystemsThe subsystem partitioning is based on structure-function mapping analysis.Considering the effect of truncation time,pre-processing of failure data,and the model parameters were estimated using modified maximum likelihood estimation and average rank order method respectively,the distribution hypothesis test is also performed on the proposed model,Finally,the error area ratio test is applied to the goodness-of-fit test to identify the optimal reliability model.The hierarchical analysis method is introduced to evaluate the failure risk factors of each subsystem by integrating the impact of failure on personal safety,the impact on system function and the difficulty of failure repair.(2)Research on preventive maintenance cycles of machining center subsystems under reliability constraintsBased on the comprehensive consideration of dynamic maintenance cost and reliability,a preventive maintenance replacement method with the optimization objective of maintenance cost rate per unit time is proposed.Based on the empirical determination of the failure rate increment factor and the service age decrement factor,a hybrid failure rate based non-equal cycle incomplete preventive maintenance model is established.A replacement maintenance cycle formula for the subsystem considering both maintenance cost and failure risk cost is given with reliability as a constraint,the optimal replacement threshold is given using the enumeration method.With the goal of minimizing the maintenance cost rate per unit of time,the optimal number of preventive maintenance,preventive maintenance cycles and replacement cycles are developed.(3)Research on the opportunity preventive maintenance model for machining center systemsBased on the single subsystem preventive maintenance,the maintenance tasks in the finite operation time domain of the machining center are combined based on the ideas of time relevance to construct the whole machining center opportunity preventive maintenance model under the maintenance cost and availability objectives.Introducing the idea of linear weighting to combine maintenance cost and availability objective functions to develop a dual-objective opportunity preventive maintenance model,and the model is solved using Matlab software to obtain the optimal opportunity maintenance threshold of the machining center and develop the maintenance strategy accordingly.The effectiveness of the multi-objective opportunistic repair model is verified by comparing it with a single-system preventive maintenance decision.