OPTIMAL PLANNING OF TECHNOLOGICAL MODES OF MECHANICAL WORK AT A LIMITED TERM REPAIRS FREIGHT WAGONS

Abstract

Purpose. The purpose of this work is to develop optimization algorithms for determining the optimal group schedule and optimal cutting speeds during the repair work of freight wagon. Methodology. To solve the problem of optimal planning of machining regimes, the group planning model for the current multi-site production is given and analyzed with limited production time periods for the restored parts of freight cars. In addition, the batch processing model includes interchangeable processing times and costs, which depend on the processing conditions. The proposed optimal group planning schemes were developed primarily to minimize the number of parts with an increase in artificial operational time. To calculate the lower limit of the total time of the technological process, the following theorem is used, which represents the extension of the Johnson theorem for two-stage planning to the group planning method. Results. The article discusses two criteria for group planning. The main criterion is the number of parts with increased artificial operating time, which must be minimized. The second criterion is the total time of the technological process (processing cycle), the total time of the technological process being the time that lasts from the beginning of processing the first part of the first group to the end of processing the last part of the last group; it should also be minimized. When determining the optimal cutting speeds, after the optimal group planning scheme has been established, cutting speeds can be changed to reduce production costs, if the planning scheme provides for inter-operation delay (tracking) of parts in individual operations. Based on the results of the preliminary analysis, the following optimization algorithms have been developed to determine the optimal group graph and optimal cutting speeds. Scientific novelty. The proposed group planning model, based on the group technology method, was developed for the conditions for carrying out restoration and restoration works on parts and assemblies of freight cars for mass-production production at car-repair enterprises. In group planning, when parts are classified into several groups, the optimal should be obtained as a sequence of groups and details in each group. Practical significance. In this study, a group planning method based on the group technology method was proposed. It was developed for streaming multi-site repair production with variable processing times and costs that depend on the cutting conditions of the metal.