This paper proposes a series of experimental determinations carried out with the aim of generating new conclusions regarding the ability of 3D-printed gears to be integrated into mechanisms without lubrication. The main factors that influence the appearance of wear in non-lubricated contact are sliding speed, material hardness, surface finish, surface geometry, and material microstructure. The tests considered the type of material from which they were made and the 3D printing technology type. For testing the gear wheels, a mechatronic experimental setup was made consisting of two shafts with adjustable axial distances, a wheel loading system gears, an electric motor, and a command-and-control system. In terms of materials, four types of materials were monitored: PA (polyamide), PLA (polylactic acid), ABS (acrylonitrile butadiene styrene) and PP (photopolymer). The evaluation of the gear wear was carried out by checking the gearing on two flanks (Frenco ZWP 06) and by scanning with the ATOS CORE 135 3D scanner. The PA and PP gears failed to meet the structural integrity standards after the tests. The PLA gears exhibited superior resistance to abrasive wear compared to the ABS gears, whereas the ABS gears generally demonstrated stronger structural integrity.

This paper presents an analysis of the abrasive wear influence on the tooth flank geometry of plastic gear wheels, emphasizing the contribution of tooth stiffness to the observed changes. The study examined gear wheels made from polylactic acid (PLA) with wall thicknesses of 0.6 mm, 1.0 mm and 2.4 mm, manufactured using FDM technology. A standard layer height of 0.2 mm was chosen as it offers a balance between good precision and reasonable printing times. The PLA gear wheels were tested for wear in a meshing configuration with a metallic reference gear. The results indicate that wear intensity increases as tooth stiffness decreases, suggesting an inverse proportionality between abrasive wear and tooth stiffness. In all tested cases, the tooth tip was more affected by abrasive wear compared to the rest of the profile. The analysis establishes that sliding velocity has the greatest influence on the abrasive wear characteristics of the evaluated gears. Based on experimental findings, a mathematical model was developed for simulating abrasive wear in plastic gears, with scalability across various manufacturing technologies. For PLA gears, both experimental and simulated data confirm that full tooth infill is essential for functional durability.

The compliant mechanism studied in this paper is used in the structure of an assembly necessary for the temporary mounting of visual markers on glasses frames. Proper correction of vision defects in patients is a field of study in healthcare that has grown in complexity, along with all aspects of technology, over the past decades. As such, along with better lenses and frames, including custom solutions, the devices used to determine the patient’s specific parameters need to be more complex and precise. However, this is only part of the problem: while many devices exist that take measurements such as interpupillary distance with great precision, these come at a very high cost and do not take into account aspects related to real-life usage of the lenses, such as the patient’s position, angle, etc. Given the considerations above, this paper approaches the design, simulation, realization and testing of a working model of a frame used to support markers used in the optometry process. The design proposed in this paper assumes that the system used can be used while the glasses are mounted on the patient’s face, without influencing in any way their position in front of the patient’s eyes. Furthermore, the system must allow assembly and disassembly with minimal effort, to allow the patient to perform some movements without changing the position of the frame, as well as the easy access to the markers mounted on the spectacle frame. The main scope of the paper is to design and choose the correct constructive solution of a compliant mechanism for this important clinical optometric application in terms of geometric parameters, material and technology used to obtain appropriate performances. The authors highlight how the parameters and manufacturing technology for the device were chosen, and a finite element analysis is used to simulate the mechanical behaviour of the mechanism and to choose the optimal variant in terms of the desired displacement between three proposed materials for the given application. After justifying the choice of the constructive solution, several physical models of optometric support markers were realised using Fused Deposition Modeling (FDM), and Polyethylene terephthalate glycol (PETG) or polylactic acid as materials. Furthermore, an electro-pneumatic experimental test stand was developed to simulate and test the functionality of the device and to validate the proposed model.