Scientific paper ID 2092 : 2021/3

Creating a comprehensive reliability model of a complex technical object (CTO) is in principle a difficult task for objective reasons. The main difficulty lies in the need to cover the diversity of the whole range of mechanisms of occurrence of operational failures: in the mechanical, electrical and other parts of the WTO. And the task of building a comprehensive model of the reliable behavior of the CTO is important, because only through it can be revealed the relationships between the individual reliability processes in the site. The importance of this task is increasing due to the specific conditions under which the technological equipment works for the needs of the transport industry in Bulgaria. A considerable part of it is to a considerable extent morally and physically obsolete with all the problems arising from this circumstance regarding its operational reliability. A specific object of the present study is the component system of “feed drive along the z axis” of a metal-cutting machine (MM) with digital-program control (CNC). The construction of the model is based on the graph theory - it allows for the inclusion in one model of operational failures with a significant variety in the mechanisms of manifestation. The construction of the model takes place in several stages, and each subsequent stage is realized on the basis of the previous one.