Design Of Maintenance Time For CNC Modular Machine Tool Based On Reliability Analysis

CNC modular machine Tool is widely used in China’s automobile manufacturing process for its design and manufacturing cycle is short and high production efficiency. The planned preventive maintenance system of the combination of regular maintenance and maintenance is used by the most of the enterprises in our country, and their maintenance planning is derived from the maintenance cycle of machine tool equipment manufacturers. Due to the status of the equipment is different from the production environment of its own design considerations, in the specific maintenance and production is reflected in the lack of repair and maintenance surplus. Therefore, it is very necessary to study and formulate scientific and reasonable maintenance plan, ensure the machine’s production does not stop, the utilization of the machine to maximize the maintenance cost minimization, reasonable arrangements for the maintenance time, improve the efficiency in the use of machine tools.This paper is based on this background, and the main contents are as follows:(1) Failure correlation analysis of CNC modular machine Tool. Firstly, according to the overall structure and working principle of the machine tool, and the machine tool is divided into subsystem according to the modular method; then, the acquisition scheme of reliability data is proposed, and the data of fault information required in this paper are collected; then combined with the subsystem failure correlation data of CNC modular machine Tool, the correlation order of the subsystem and the hierarchical relationship model of the subsystem are found out based on DEMATEL/ISM, and the structure of the related fault subsystem is realized.(2) Reliability modeling of CNC modular machine Tool. Establishing the reliability model of all levels subsystems of CNC modular machine Tool based on time between failures, and the MLE method is used for parameter estimation, taking into account the subsystem failure data of small sample using the unbiased estimation of the parameter value is modified, which is considered the subsystem of the remaining subsystems and the impact of the cut-off test censored data for the first time, and using the method of Johnson to correct the fault order and makes the results more reliable. Then using the Copula theory, all levels of subsystems connected by Copula function considering fault correlation and transitivity, and considering the correlation of the CNC modular machine Tool overall reliability function curve and the correlation coefficient of the relevant subsystem, which provide the basis for the design of maintenance time by considering the correlation between the subsystems.(3) The design of CNC modular machine Tool maintenance time. Firstly, we derive the integrated fault rate of each level subsystem of CNC modular machine Tool considering the correlation and transmission of subsystem; and then analysis maintainability modeling for each level subsystem of CNC modular machine Tool, considering the characteristics of the various subsystems of small samples, using a normal distribution of small sample data processing methods are calculated respectively. The estimated value of the model parameters using PSO algorithm on system maintainability evaluation; then CNC modular machine Tool of various levels of system considering failure rate weighted combination of each subsystem design the whole machine maintenance time maintenance time; finally, derived the best preventive maintenance intervals time of two aspects under the specific common maintenance strategy based on minimum maintenance cost and maximum availability, for providing this type of modular machine tool with reference resources of making maintenance plan in the whole life cycle time.