Present state of 3D printing from glass

This paper deals with the issue of additive technologies using glass. At the beginning, our research dealt with a review of the current state and specification of potentially interesting methods and solutions. At present, this technology is being actively developed and studied in glass research. However, as the project started at the Department of Glass Producing Machines and Robotics, the following text will be more focused on the existing 3D printing machinery and basic technological approaches. Although “additive manufacturing” in the sense of adding materials has been used in glass manufacturing since the beginning of the production of glass by humans, the term additive manufacturing nowadays refers to 3D printing. Currently, there are several approaches to 3D printing of glass that have various outstanding advantages, but also several serious limitations. The resulting products very often have a high degree of shrinkage and rounding (after sintering), and specific shape structures (after the application in layers), but they generally have a large number of defects (especially bubbles or crystallization issues). Some technologies do not lead to the production of transparent glass and, therefore, its optical properties are significantly restricted. So far, the additive manufacturing of glass do not produce goods that are price competitive to goods produced by conventional glass-making technologies. If 3D glass printing is to be successful as an industrial and/or highly aesthetically valuable method, then it must bring new and otherwise unachievable features and properties, as with 3D printing of plastic, metal, or ceramics. Nowadays, these technologies promise to be such a tool and are beginning to attract more and more interest.

Interface Formation and Bonding Mechanisms of Laser Welding of PMMA Plastic and 304 Austenitic Stainless Steel

Laser welding experiments involving amorphous thermoplastic polymer (PMMA) and 304 austenitic stainless steel plates were conducted to explore the influence of laser welding process parameters on plastic–metal joints. A high-speed camera was applied to record the dynamics of the molten pool and the formation of bubbles to reveal the bonding mechanisms of the hybrid joints. The influence of process parameters on the joints was analyzed using temperature measurements performed with thermocouples. The microstructure morphology of joints was observed using SEM. The mechanical characterization of the hybrid joints was carried out to understand the effect of the welding conditions on the weld morphology, flaws and shear stress. Different interface temperatures resulted in two types of bubbles and led to different weld morphology characteristics. A stable hybrid joint with the best shear stress was produced with a laser line energy of 20.16 J/mm2, a temperature of 305 °C and small bubbles. The shear stress of the effective joint under the maximum mechanical resistance was 4.17 MPa. The chemical bonds (M-O, M-C) and mechanical anchoring that formed on the steel’s surface contributed to the joint bonding. Range analysis provided guidance for identifying the impact of individual factors in the shear stress for the laser welding of plastic–metal.

Effectiveness of Plasma-Treated Hydrogen Peroxide Mist Disinfection in Various Hospital Environments

Hospital environments are associated with a high risk of infection. As plasma-treated hydrogen peroxide mist disinfection has a higher disinfection efficacy, we tested the efficacy of plasma-treated hydrogen peroxide mist disinfection on several surfaces in various hospital environments. Disinfection was performed in 23 rooms across different hospital environments, including hospital wards, outpatient departments (OPDs), and emergency rooms. A total of 459 surfaces were swabbed before/after disinfection. Surfaces were also divided into plastic, metal, wood, leather, ceramic, silicone, and glass for further analyses. Only gram-positive bacteria were statistically analyzed because the number of gram-negative bacteria and mold was insufficient. Most colony-forming units (CFUs) of gram-positive bacteria were observed in OPDs and on leather materials before disinfection. The proportion of surfaces that showed a percentage decrease in CFU values of more than 90% after disinfection were as follows: OPDs (85%), hospital wards (99%), and emergency rooms (100%); plastic (97%), metal (83%), wood (84%), leather (81%), and others (87%). Plasma-treated hydrogen peroxide mist disinfection resulted in a significant decrease in the CFU values of gram-positive bacteria in various environments. Plasma-treated hydrogen peroxide mist disinfection is an effective and efficient method of disinfecting various hospital environments.

Model-Based Estimation of the Strength of Laser-Based Plastic-Metal Joints Using Finite Element Microstructure Models and Regression Models

Plastic-metal joints with a laser-structured metal surface have a high potential to reduce cost and weight compared to conventional joining technologies. However, their application is currently inhibited due to the absence of simulation methods and models for mechanical design. Thus, this paper presents a model-based approach for the strength estimation of laser-based plastic-metal joints. The approach aims to provide a methodology for the efficient creation of surrogate models, which can capture the influence of the microstructure parameters on the joint strength. A parametrization rule for the shape of the microstructure is developed using microsection analysis. Then, a parameterized finite element (FE) model of the joining zone on micro level is developed. Different statistical plans and model fits are tested, and the predicted strength of the FE model and the surrogate models are compared against experiments for different microstructure geometries. The joint strength is predicted by the FE model with a 3.7% error. Surrogate modelling using half-factorial experimental design and linear regression shows the best accuracy (6.2% error). This surrogate model can be efficiently created as only 16 samples are required. Furthermore, the surrogate model is provided as an equation, offering the designer a convenient tool to estimate parameter sensitivities.

Influence of the structure and thermomechanical properties of oriented carbon plastics on their tribotechnical characteristics

It has been established that carbon plastics are increasingly used in various industries as structural materials. By the set of their properties, carbon plastics outperform steel, cast iron, alloys of non-ferrous metals. However, the application of these materials for parts of machine friction units is still limited due to the difficult operating conditions of modern tribosystems. This work aims to conduct a comprehensive experimental study of the tribological properties of materials in the tribosystem "carbon plastic-metal" taking into consideration their structure, as well as the mechanical-thermal characteristics. Comparative tests of the dependence of the friction coefficient on load for metal and polymeric anti-friction materials have shown a decrease in the friction coefficient for plastics by 3...4 times (textolite, carbotextolite, and carbon-fiber plastics). The influence of the filler orientation relative to the slip plane on the anti-friction properties of carbon-fiber plastics was investigated; it was found that the direction of fiber reinforcement in parallel to the friction area ensures less carbon-fiber plastic wear. A linear dependence of the wear intensity of carbon-fiber plastics, reinforced with graphite fibers, on the heat capacity and energy intensity of the mated steel surface has been established. Based on the microstructural analysis, a layered mechanism of the surface destruction of carbon-fiber plastics was established caused by the rupture of bonds between the fiber parts, taking into consideration the direction of the fibers' location to the friction surface. The results reported here could provide practical recommendations in order to select the composition and structure of materials for the tribosystem "carbon-fiber plastic-metal" to be used in machine friction units based on the criterion of improved wear resistance

A Study on the Bond Strength of Plastic–Metal Direct Bonds Using Friction Press Joining

Friction press joining (FPJ) is an innovative joining process for bonding plastic components and metal sheets without additives in an overlap configuration. This paper focuses on the resulting bond strength. Tensile tests showed that the direct bonds produced by FPJ have either an equivalent or a higher bond strength compared to adhesive bonds. For the material combination of HD-PE and EN AW-6082-T6, an equivalent bond strength was achieved. In contrast, for the material combinations PA6-GF30 with EN AW-6082-T6 and PPS-CF with EN AW-2024-T3, higher tensile shear strengths were achieved via the FPJ technology. In addition to the technical considerations, this paper presents an evaluation of the technological maturity of FPJ. It was found that the basics of the technology are already well developed, and prototypes for showing the applicability have already been manufactured. The last part of this paper deals with the classification of FPJ into the standard for manufacturing processes, according to DIN 8593. The authors suggest a categorization into Activation bonding (item 4.8.1.3). These investigations show the high technical potential of FPJ for joining plastic components with metals.