Plastics are more and more frequently applied in the construction of hydraulic components and systems, and recently, in the building of microhydraulic assemblies. The basic unit of the microhydraulic systems is a micropump. It is an object which is quite difficult to design and manufacture, especially when using plastics. The paper is a presentation of challenges that must be met in the process of designing gear pumps, and, at the same time, of the theoretical grounds for the designing of those objects. The challenges include the geometry and the gears, the construction of the pump body, the hydraulics of the pump, and the material—the plastic of which the pump is made. The knowledge on those issues was applied to make and to successfully test a prototype of a micropump.

Gerotor technology is an important research area in the field of hydraulics which attracts the attention of both academic scientists and industry. Despite the numerous publications announced by academics, as well as a considerable number of projects made by industry, the subject has not been exhausted. This paper presents a new approach to gerotor technology which has been formed by gathering the authors’ knowledge of gerotors in a synthetic form. The following scientific and technical results have been obtained: (1) A uniform system of parameters and basic concepts regarding toothing and cycloidal gearing (z, m, λ, v, g) which is consistently used to describe the geometry, kinematics, hydraulics and manufacture of those elements; (2) description of the geometry and kinematics of the epicycloidal and hypocycloidal gears with the use of the adopted system of parameters. Additionally, the epicycloidal/hypocycloidal double gearing is presented, which is an original idea of the authors; (3) description of the hydraulics of the gerotor and orbital machines, and in particular: (i) determination of equations for delivery (capacity) q and irregularity of delivery (capacity) δ using the above-mentioned system of basic parameters; (ii) formulation of the principles of designing internal channels and clearances in the gerotor machines and presentation of the original disc distributor in the epicycloidal/hypocycloidal orbital motor; (iii) presentation of the methods of manufacturing the epicycloidal and hypocycloidal gearings with 12 examples of the systems implemented in practice; (4) presentation of the research methods applied for the examination of the gerotor machines, combining computer simulation and experimental research into a coherent and cohesive whole which results in the effect of research synergy. Such a synthesis of knowledge may serve the improvement, creation and investigation of gerotor and orbital machines carried out by academics and industry.

The article presents an author’s approach to the study of the behavior of plastic hydraulic cylinder structures under load. Plastics as design materials, due to their different properties, behave differently from metals. So far, there is little information about hydraulic cylinders made of plastics. They are a technical novelty, and there are no established standards or research methods for them. The tests were carried out on the example of two models of different internal diameter, the smaller one being Ø30 mm and the larger one Ø50 mm. Information was gathered by FEM simulation tests and tests of real models on a special test stand. The simulation section presents geometric models, discrete models and assumed boundary conditions, as well as the results of the performed simulations. For tests of real models, a description of the stand with the measuring equipment used is presented, e.g., laser displacement sensors, as well as the method of conducting the tests and the results. Then, the results are analyzed and compared. Deformations of the examined structures are discussed, e.g., tube swelling or deflection, which seem to be characteristic for plastic cylinders. Finally, the possibility of using selected plastics for the design material of hydraulic cylinders and the suitability of the research method used are assessed.

The paper concerns the innovative research area “Fluid power elements and systems made of plastics”. The aim of the work was to present original research on the topic of design, manufacturing and examination of plastic fluid power elements and systems, in a comprehensive way. It is presented in two stages. At the first stage, a set of prototype hydraulic components from plastics are presented. These are: gerotor pump, relief and on/off valves, and cylinder. A prototype hydraulic system from plastics was built from these components. At the second stage, the acquired knowledge and experience had been used for the development of advanced components and in experimental hydraulic axis. The results of the work include new knowledge in areas such as plastics selection, detailed design and manufacturing of components, experimental testing, and the formulation of special design rules arising from the use of plastics. In addition, a system of fluid power components made from plastics was developed, capable of operating at working pressures ranging from 3 to 6.3 MPa. The work also led to the creation of new hydraulic components, including a microgerotor pump with an electromagnetic drive and a hydraulic axis incorporating plastic elements. The directions of development of the research area “Fluid power elements and systems made of plastics” have been presented.

The article describes the course of the ultrasonic cavitation in a hydraulic tank and the hydrodynamic cavitation in a gear pump. The course of those phenomena was confirmed in experimental tests carried out with the use of a tank and a pump made of transparent plastics. It has been proved that the oscillator-cavitation system made according to the original project is useful to induce the phenomenon of ultrasonic cavitation. It has also been shown that the PIV visualization method, consisting in a special system of illuminating transparent objects and recording the flow through those objects with a fast camera, is useful for the studying of the cavitation phenomena. A visible interaction between the ultrasonic and the hydrodynamic cavitation was observed. The induction of ultrasonic cavitation in the tank causes degassing of the oil, and the degassed oil supplying the pump reduces the hydrodynamic cavitation in its internal channels and clearances. This is an example of beneficial effects of the ultrasonic cavitation on the operation of a pump and a hydraulic system. The presented work is an example of effective co-operation between the communities of Wroclaw University of Science and Technology and Igor Sikorsky Kiyv Politechnic Institute, National Technical University of Ukraine.