Additive manufacturing (AM) technology refers to the process of producing 3D objects by adding material in successive layers. Fused deposition modeling (FDM) is one of the AM technologies where objects are built by adding layers of melted thermoplastic filament onto the printing surface. Mechanical properties of FDM printed part depend on many influencing factors such as material composition, extruding temperature, printing parameters and environment temperature. The aim of this study was to investigate consistency of mechanical properties of elements produced by FDM additive manufacturing technology. To do so, mechanical tensile and compression tests were conducted on ten samples using polylactic acid (PLA) and ten samples using acrylonitrile butadiene styrene (ABS) thermoplastic material. Tensile tests were conducted using Shimadzu Compact Tabletop Testing Machine EZ-LX and the compression tests were done using VEB ZDM 5/91 testing machine. The ultimate tensile strength, strain, Young modulus and compression yield strength values were analyzed. The ABS thermoplastic material showed greater consistency in mechanical properties during tensile tests. Tensile strength values for PLA material varied between samples thus showing greater inconsistency in repeatability of mechanical properties. Compression tests, on the other hand, showed that PLA samples had greater consistency in mechanical properties compared to ABS samples.

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Abstract. Universal gear reducers are quite simple products, so today there are many manufacturers around the world that produce this kind of reducers. Their connecting dimensions and shape are not defined by the standard, so there is a large number of solutions. The most of manufacturers produce gear reducers with connecting dimensions and axis height, usually the same like the biggest manufacturers do (mainly company SEW), because they want to provide interchangeability of their gear reducers. It is interesting to note that most manufacturers are trying to adopt such a form of reducer that will be different from competing solutions in order to avoid an accusation of coping with someone else's solution, although manufacturers have almost identical shape and competing (copied) solutions. The paper presents, due to the volume of matter, only the analisys of forms of the housing of modern single-stage universal gear reducers in order to point out the expected directions of their further development.

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Abstract:The purpose of this paper is to point out the usual methods of determining the service factor, which is the most influential parameter. In order to provide the proper selection of the size of the worm gear reducer, manufacturers are trying to take detailed look at all the factors which influence the work gear and to provide customers with the best possible solution. The greatest impact on their defining has a safety factor which is used to calculate the gear unit and the effect of an ambient temperature i.e. cooling method.

A special kind of the basic involute profile of non-standard gearing is called high contact ratio (HCR) gearing, where the contact ratio is higher, there are always at least two pairs of teeth in contact and the unit addendum height is not equal to one like for standard gearing. Thus, the tooth height is increased. When HCR gearing is used, it is not necessary to achieve a greater gear load capacity, but nevertheless there is a greater risk of interference due to the greater tooth height. The advantages of HCR gearing is higher resistance (load is distributed on more pairs of teeth at the same time) and a lower relative noise level of gearing, which can be significantly reduced by using an integer HCR factor. HCR profiles are more complicated than standard involute profiles, they have a greater predisposition for interference, pointed tip thickness and undercut of teeth during production (primary production interference). Due to increased addendum height, there is a larger possibility of some interference or pointed tooth tip occurring. Therefore, these issues need to be prevented in the design phase, and ensured that all relevant equations and constraints are satisfied. The described method of finding optimal gear parameter values uses a Generalized Particle Swarm (GPS) optimization algorithm and MATLAB. The GPS optimization is shown to be a very fast and reliable method.

Abstract. In the area of universal gear reducers, standard does not prescribe relations between load capacity, gear ratios and axis heights. Therefore, larger load capacity of some gear reducers manufacturers has advantage for lower gear ratio and, vice versa, smaller load capacity of the gearbox achieves higher values of gear ratio. However, there are some manufacturers who produce gear reducers with smaller or larger load capacity for higher or lower gear ratio, within the same axis height. This paper deals with analysis of justification of applying two gear sets, especially in the case when socalled intermediate sizes of gear reducer are not used.

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