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Mechanisms of machines completing a repeating operation have many applications in the processing industry. During the working cycle, the output link of the mechanism has one or more periods of dwell, while the input link moves continuously. The paper presents the graphical synthesis of 6-bar linkage mechanism with high class structure groups. The procedure is based on the synthesis at the extreme positions of the mechanism, simplifying the task to a problem with a finite number of precise positions. At the core of this procedure are simple, easily visible and understandable geometric constructions that are then used to form equations suitable for further analysis and optimization. Motion of the mechanism resulting from the synthesis has some inaccuracy - the output link moves during the dwell phase, completing an angle of ±0.5°, which is considered accurate enough for a wide range of practical applications.

The use of 3D models of the human bone system has great utility in the biomechanical study, due to the fact that these structures cannot be analyzed or tested in vivo. Within this paper, taking into consideration its real bone structure, the human femur CAD modelling is established. Firstly, a preliminary anatomical study is done, in order to highlight the fact that the thigh bone is a heterogeneous structure, consisting of several entities with different mechanical characteristics. The modelling starts from a homogenous 3D model of the femur, from which, every single separate entity is designed and finally they are assembled within a single product assembly. Therefore, the final result ensures a complex CAD structure, able to get assigned different material properties, specific for each entity this modelling furtherly allows the characteristic pathological structures studies of the referred entity or to simulate specific surgical interventions.

By analysing and comparing the existing solutions of universal gear reducers with helical gears of the leading manufacturers, it can be noticed the effort to increase the load capacity of the gear reducer within the same axis height. In this way, the manufacturers can offer smaller (cheaper) gear reducers, as well as to simultaneously increase the values of the largest gear ratios. This concept enables the offer of lower-stage (cheaper) gear reducers with higher gear ratios in certain segments of gear ratios. By these efforts, it is reached the maximum, but the further increase is possible only by changing the current concept of universal gear drives. Within this paper, it is given an overview and analysis of one of the possible new conceptual solutions of modern universal motor gear reducer.

Today, for almost all products, the appearance is very important. Thus, for example, the appearance of universal gear reducers was not given so much attention, but today there are many very interesting solutions of shape, colour and graphic design. It should have in mind that universal gear reducers have much complex construction comparing them with special gear reducers. In the same time, they have to provide different positions and way of mounting and different speeds with different powers (torques) at the output shaft. Particularly, it should be noticed, that within all universal gear reducers single-stage gear units are nowadays increasingly used because their gear ratio values are increased (values of gear ratio can go up to 15) so that these reducers largely cover most of the two-stage gear reducers with their gear ratio values, so thereby their exploitation is significantly increased. Single-stage gear reducers are very simple products, and today there is a large number of manufacturers of such product. However, their mounting dimensions and way of mounting are not defined by a standard, so there is a variety of units with different dimensions and way of mounting. Although, most manufacturers look up to dimensions of leading manufacturers (usually SEW) in order to ensure greater exchangeability of their gear units. It is interesting to note, that most manufacturers tend to adopt the design of housing that will be substantially different from competing solutions. The reason is probably to avoid the possibility of being accused of copying someone else’s solution. However, there are manufacturers that retain almost identical housing design as a competing solution (probably they bought the licence or the solution is copied without permission). This paper considers only the design solutions of single-stage gear reducer in order to indicate the expected directions of their further development.

High contact ratio (HCR) gearing is a special kind of the basic involute profile gearing with higher contact ratio, since there are always at least two pairs of teeth in contact. Compared to standard gearings, HCR gearings have greater load capacity, higher resistance and a lower relative noise level. Their main drawbacks are more complicated design than standard involute profiles, greater predisposition for interference, pointed tip thickness and undercut of teeth during production. There is also a larger possibility of some interference or pointed tooth tip occurring. All these issues represent serious design constraints which need to be resolved in the design phase. In this paper, a new method for HCR gearing design is proposed, which uses Generalized Particle Swarm Optimization Algorithm (GPSO) for gearing parameters optimization. This recently introduced global optimization method enables finding of global optimal solution(s), ensuring that all relevant design and function constraints are satisfied.

The operating principle of rolling bearings generates vibrations that come from the periodic change in the stiffness of the bearing. The vibration level of the bearing depends on a large number of factors such as waviness, surface roughness of the raceways, deviation of the raceway radius, exploitation conditions, amount of lubrication in the bearing and other. This paper presents the influence of the roughness of the raceways and the amount of lubrication on the level of vibrations of the ball bearing, designation 6006. The determination of the influence of these parameters was done experimentally. The experiment was performed according conditions prescribed by ISO 15242-2, and the analysis of the measured signals was performed according to the guidelines given by the standard ISO 15242-1.

Possible concept solutions of chain drives are analysed in this paper in order to point out the benefits of chain drive application and, in particular, the possibility of application of multi-level chain drive. The paper also analyses the possibility of replacing the gear drives with chain drives, which, in the case of short-term drive and using the same direction of rotation, enables a slightly simpler drive solution. The paper doesn’t consider difference between the roller and gear chains application because these two types of chains can be used very successfully. Also, the possibility of using timing belt drive is not considered, but it can be also used very successfully in this type of drive, but only as a transmission of motion.

The problem of defining the load (nominal torque on the output shaft - T2N) of universal gear drives depending on the size of the gear ratio is analysed in this paper. It is logical that the load capacity of gear drive depends on the weakest gear component. Since the gears are the most expensive components of gear unit, it tends to maximize their performance. However, for low gear ratio, i.e. for high speeds, the bearings often limit their load capacity since the same bearings are used in all transmission ratios because it is not practiced to oversize the bearings at low speeds. Nowadays, when high values of gear ratio are used, it is interesting to consider the dependence of the nominal torque at the output regarding to gear ratio and operating life of the unit.

In this paper we present a design method for a modular device used in different types of HIGH TIBIAL OSTEOTOMY surgical procedures. The requirements, necessities and functions of this modular device are presented in the first part of the article. An important aspect is the fact that the device must be designed in a manner which permit to use it for all types of HIGH TIBIAL OSTEOTOMY: opening wedge osteotomies, closing wedge osteotomies, medial osteotomies, lateral osteotomies, uniplanar osteotomies or biplanar osteotomies. This fact is possible using modular elements for the main parts of the devices. The researches could be the starting point for others researches regarding the appropriate materials and the possibility to execution customized several parts of the modular device using Additive Manufacturing facilities.

Gear transmissions are relatively simple mechanisms whose quality, price, delivery time and design appearance are almost equal. This is the common reason why it is very difficult for all gear manufacturers to ensure the successful placement of their products on the market. However, regardless of their simplicity, gear transmissions may have different design and technical solutions, and due to different limitations of individual components, the calculation of load capacity and other technical characteristics can be quite complicated. In accordance with the basic settings of Industry 4.0, smart transmissions are being developed that will be able to provide a certain advantage over the competition and thus, for sure, ensure the successful business of these innovative companies. This paper describes the basic principles of construction using new technologies, primarily using the Internet of Things and digital twins. The paper includes an analysis of approaches to the creation of Digital Twins. Describe why Industry 4.0 is so different and specific, define what is Cyber-physical systems and the Internet of Things, and what is predictive monitoring with using different sensors. [ABSTRACT FROM AUTHOR]

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 so-called intermediate sizes of gear reducer are not used.

The paper presents the development of neck mechanism for humanoid robots. The research was conducted within the project which is developing a humanoid robot Marko that represents assistive apparatus in the physical therapy for children with cerebral palsy.There are two basic ways for the neck realization of the robots. The first is based on low backlash mechanisms that have high stiffness and the second one based on the viscoelastic elements having variable flexibility. We suggest low backlash differential gear mechanism that requires small actuators. Based on the kinematic-dynamic requirements a dynamic model of the robots upper body is formed. Dynamic simulation for several positions of the robot was performed and the driving torques of neck mechanism are determined.Realized neck has 2 DOFs and enables movements in the direction of flexion-extension 100°, rotation ±90° and the combination of these two movements. It consists of a differential mechanism with three spiral bevel gears of which the two are driving and are identical, and the third one which is driven gear to which the robot head is attached. Power transmission and motion from the actuators to the input links of the differential mechanism is realized with two parallel placed gear mechanisms that are identical.Neck mechanism has high carrying capacity and reliability, high efficiency, low backlash that provide high positioning accuracy and repeatability of movements, compact design and small mass and dimensions.

Within the universal motor helical gear reducer, single row deep groove ball bearings are usually used, but for larger driver dimensions and heavily loaded shafts, spherical roller bearings are used. In order to achieve the maximum load capacity of the gearbox, within the same axis height, relatively large single-row ball bearings are necessary. In some cases, due to dimensions constraints, they cannot be installed in the gearbox, so many manufacturers, in certain cases, use somewhat smaller and more expensive single-row cylindrical roller bearings. Though these bearings are not specifically designed to transmit axial forces, they can bear axial loads. The idea of this paper is to point out this problem and the benefits that come from the use of cylindrical roller bearings. [ABSTRACT FROM AUTHOR]

Within this paper is described an analytical model for the analysis of quasistatic load distribution in four contact ball bearings. The quasistatic model was developed on the basis of the static model, applying Hertz's theory of contact and John-Harris's load distribution on ball. In this paper, the model is extended by introducing parameters such as positive/negative clearances into static equilibrium equations. Behavior analysis of the four point contact ball bearing (FKL LSQFR 308) was performed for different operating conditions. Within certain analyzes, the analysis of the influence of conceptual parameters (positive/negative clearances) on the operational characteristics of bearings was performed. The change in external load also varied. Verification of the static behavior of the ball bearing LSQFR 308 was performed by comparing the results obtained by quasistatic modeling and the results obtained using the finite element method. [ABSTRACT FROM AUTHOR]