Method of individual selection of parts for selective assembly of electrohydraulic servo drives

A method for selecting parts and assembly units (hereinafter briefly referred to as parts) in sets for assembling a batch of electrohydraulic servo drives is presented, based on the measured (individual) mechanical and hydraulic characteristics of the parts. The preparatory stage is described: construction of a mathematical model of the product, determination of the parameters of parts and adjustments that have the greatest impact on the parameters of end products, formation of a system for assessing the quality of products in the batch, mathematical formulation of the task of selecting parts. The task of selecting parts is formulated as the assignment problem in the maximin formulation. A deterministic algorithm for solving the problem is presented, based on the branch and bound method and taking into account the fact that adjustments are made during the assembly of drives. A significant reduction in the number of steps (iterations) when searching for the optimal distribution of parts across assembly sets achieved due to the chosen mathematical formulation of the task, as well as due to the chosen strategy of selecting parts in the next assembly set. We suggest that an assembly set should include, first of all, the most troublesome parts the parameters of which do not allow obtaining a set, the projected quality indicator of which will be higher than the established value. At the same time, the negative impact of these parts on the product parameters is compensated by combining them with other parts in one assembly set. The results of mathematical modeling of assembling 992 drives with random formation of assembly sets and with individual selection of parts are presented. Modeling shows that as a result of implementing individual selection of parts in accordance with the described method, a significant reduction in the spread of parameters of end products within batches can be expected, as well as improvements in functional performance of the products. The presented method of individual selection of parts can be used in the assembly of various products.