The paper presents the results of testing gearboxes in coal open pit mine which have been damaged by various mechanisms. Gearboxes, as constituents of belt conveyors, bucket-wheel excavators and bucket chain excavators and spreaders, are the most loaded segments of drive units the functionality of which affects the operation of complete coal and overburden systems. Therefore, special attention has to be paid to their condition so that the analysis of relevant condition indicators could lead to correct conclusions as to their functionality, as well as point to the factors causing their fault. Tests were carried out on 95 gearboxes throughout 2017, during general repairs at Drmno mine workshop. After examination, all identified failures were illustrated with an appropriate photo, classified according to the appropriate standard, and described in the form of manifestation and cause. The research has shown that the most dominant were faults of bearings and lubrication, whether seals and cuffs or a thin hermetic layer between the housing and covers. In addition, some of the faults happened on gears and toothed and stepped shafts. Major irregularities in operation, resulting from damage to gearbox elements, are show by fault tree analysis (FTA).
There is intensive rolling and sliding between the meshing elements of a cycloidal reducer, whereby a significant amount of mechanical energy is converted into heat and absorbed by the lubricant. In order to stabilize the temperature of the lubricant, it is necessary to achieve thermal equilibrium, i.e. the amount of heat dissipated should equal the amount of heat generated. A complex task of determining the equilibrium temperature of a lubricant generally involves theoretical analysis, numerical calculation, computational simulations and experimental testing. The aim of this paper is to develop a model to predict the amount of heat dissipated from the outer surface of the housing as well as the equilibrium temperature of the lubricant. The model is based on the basic laws of thermodynamics, while the computational simulation is performed for an actual cycloidal reducer in the Matlab software package. The simulation results show changes in the equilibrium temperature in relation to: the coefficient of heat transfer from the lubricant to the inner wall of the housing, ambient air velocity, wall thickness and housing material.
U okviru ovog rada izvršena je analiza naponsko-deformacionog stanja vratila karakterističnih pogonskih bubnjeva na trakastim transporterima površinskog kopa Drmno. Oblik i mere vratila definisane su na osnovu originalne tehničke dokumentacije, a provera naponskog stanja izvršena je primenom metode konačnih elemenata u softverskom paketu Catia. Opterećenja su simulirana za realne radne uslove u eksploataciji. Rezultati analize su pokazali da najbolju raspodelu opterećenja imaju vratila sa konusom između steznog prstena i ležaja, i da glavčine oblika" T " najpovoljnije prenose opterećenja na vratilo. Takođe, analize su pokazale da vrednosti napona nastalih u vratilima na mestu otkaza nisu dovoljno velike da bi dovele do oštećenja vratila preopterećenjem i da uzrok otkaza treba tražitiu zamoru, zatim u plastičnm deformacijama, zaostalim naponima posle reparacije vratila i neuravnoteženosti mase bubnja.
The robotics industry has experienced a rapid expansion in the last decade. As a result, the market of speed reducers with high gear ratios, high precision and a compact design is growing rapidly. In addition to these characteristics, it is very important for gear trains to have high efficiency. Because of their compact design, cycloidal speed reducers are not exposed to axial forces, which is their important characteristic. This means that radial bearings can be used in their supports. The bearing type has significant effects not only on the design and dimensions of the cycloid speed reducer but also on its efficiency. In this paper, an analysis of power losses for different types of rolling bearings of a cycloid disc has been performed. At the end of the paper, concrete conclusions are presented as well as directions for future research.
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