Reliability Allocation Method Of Car Crankshaft Production Line Based On Comprehensive Fuzzy Evaluation

Production line is a complex system composed of serialized or parallel connectedCNC machining equipment, manipulators, test platforms and material handlingequipment, making it less reliable and stable compared to the conventional machiningsystems. The reliability allocation technology for a crankshaft production line whichis in the design stage is studied in this paper. Using the fuzzy comprehensiveevaluation method and based on the maintenance data of similar crankshaftproduction systems and experience of relevant experts, the various kinds of thereliability factors and weights of the crankshaft production system are determinedtogether with the reliability index of each device engaged in the system, assuming thatthe maintenance level does not change in this process. With the allocation results ofthis study, the company will, to some extent, be better at choosing machiningequipment and the reliability of the entire production line will be ensured.This research is supported by the National Science and Technology MajorProjects—"Car Crank Automatic Production Line (2014ZX04001020)".The specific contents of this article are as follows:1. Based on the characteristics of the target production line, we have chosenseveral similar production lines to make on-site research according to the followingrequirements:（1）The chosen production lines must contain similar machining equipment tothe target production line under design.（2）The chosen production lines must undertake similar producing processes tothe target production line under design.（3）The chosen production lines must have similar maintenance level to thetarget production line under design.Considering the characteristics of the chosen production lines, some relevantnorms have been formulated in this research. In the period of on-site tracing process,research fellows was required to follow the norms mentioned above, handle thecollected data canonically and calculate the MTBF, MTTR, availability of the similarproduction lines.2. In this research, the starting rate and availability of the similar chosenproduction line have been transmitted to the availability of the target production line.Based on the collected maintenance data, the distribution of the maintenance time isbuilt under the parameter estimation process and Kolmogorov test of goodness of fit. determine the final distribution function, Substituting the distributed parameters intomodel, obtaining the MTTR of the similar production line. The machine model,connections and process of the similar production line is very similar with the targetproduction line. Company technical configured substantially the same level of servicepersonnel. Therefore, the research determine that the MTTR of the similar productionline is same with the target production line. And then it get the MTBF of the targetproduction line. The MTTR and MTBF of the target production line are obtained.3. Using the fuzzy comprehensive evaluation method, the reliability allocationfor the target car crankshaft production line is conducted. In the first place, the variousinfluence factors of production system reliability are determined and ranked based onthe experience of relevant experts and engineers. Then, using the rank of theequipment engaged in the target production line and fuzzy operator of averageweighted factors, evaluation matrix is established according to the weights of theequipment. Finally, the MTBF of each equipment is determined.4. EM-Plant is used to simulate the working process of the target in real time inthis project. The allocated reliability indexes and processing parameters are put intothe virtual models of the production elements. Correctness of the reliability allocationresult will be valued with the comparison of the simulation results and the reliabilityindexes obtained above.5. Reliability indexes of the chosen similar production lines and the targetproduction line are compared in this research. If some of the equipment contained inthe target production line cannot fulfill the reliability requirement, then redundancydesign shall be considered to make the target production line more reliable in giventime and cost.