The failure of functioning feeders and assembling mechanisms can result in major productivity losses of machines. Predicting of reliability of an automatic machines work has become an important part of precision engineering and involves mathematical approaches and calculation. The reliability of work of automated high-speed assembly mechanisms depends from the accuracy and tolerances of linear and angular sizes of parts and their dispositions relatively to elements of devices. This paper presents mathematical modeling for calculation of tolerances of assembled parts and feeder elements geometry, which results on reliability of the assembling and feeding processes in automatic machines. It also discusses about the computing of the optimal geometrical parameters of the feeding and assembling units that allows for mechanism to work in proper mode. Various mathematical dependencies derived for calculation of the limited size of the feeder’s components, tolerances of parts and tolerances of linear and angular orientation for assembled parts that allow avoid the part sticking into feeders or brakes of assembling processes. Besides, a case study has undertaken to calculate the value of tolerances of feeder elements geometry and assembled parts for reliable assembly processes.

Key words: Assembling Process, Feeders, Reliability,Tolerances