The choice of universal measuring instruments for monitoring the cylinder liners of the engine during selective assembly

Abstract

The issues of ensuring the quality of single and small-scale machine-building production, including machine repairs, are currently relevant due to a number of objective and subjective factors that are related to the culture of designing and manufacturing machines. The purpose of the research is to study the influence of the measurement error on the formation of the scattering of the cylinder liner sizes of the YaMZ engine during selective assembly, taking into account the number of incorrectly received and incorrectly rejected parts, as well as determining the probabilistic value of the output of the measured parameter for each tolerance limit for incorrectly accepted products. The choice of measuring instruments to ensure the necessary accuracy is a complex task and should be carried out in accordance with the requirements of GOST 8.051-81 and RD 50-98-86. To analyze the formation of the size distribution in the process of selective assembly of the cylinder liners of YaMZ engines, the indicator gauges were selected with a value of 0,001 mm, the first was adjusted for the end measures of class 1 (error of 6.5 micrometers), and the second was tuned to the mounting rings ). An analysis of the data obtained on the scattering of dimensions indicates that the process of processing the liner can be considered unsatisfactory, since there is a correctable defective products of 4 % and an unrecoverable defective products of 2 %, the scattering zone is shifted toward corrected defective products, which characterizes the good qualifications of the workers performing this operation. When using a caliper with an accuracy of 6,5 micrometers number incorrectly, or out-of band defective parts on more than 4,95 %, and the number of incorrectly received parts of 4,7 % more than when using a caliper with an accuracy of 4 micrometers. Thus, when choosing a measuring instrument to control the quality of the cylinder liners of YaMZ engines under the conditions of a single, small-scale and repair production, the most precise one should be used from the proposed nomenclature of universal measuring instruments of linear dimensions, with a sampling unit 0,001 mm in value for setting rings. This will lead to a significant decrease in the number of incorrectly accepted groups and incorrectly left from the group or rejected parts, which in turn will affect not only the quality of the subsequent assembly of the connection, but also the economy of the enterprise.