Search Results (86)

The quality of machined marine propellers plays a critical role in underwater propulsion performance. Precision casting is the predominant manufacturing technique; however, deformation of wax models and rough blanks during manufacturing frequently cause deviations in the dimensions of final products and, thus, affect propellers’ performance and service life. Current inspection methods primarily involve using coordinate measuring machines and sampling. This approach is time-consuming, has high labor costs, and cannot monitor manufacturing quality in real-time. This study developed a real-time online automated measurement system containing a high-resolution CITIZEN displacement sensor, a four-degree-of-freedom measurement platform, and programmable logic controller-based motion control technology to enable rapid, automated measurement of blade deformation across the wax model, rough blank, and final product processing stages. The measurement data are transmitted in real time to a cloud database. Tests conducted on a standardized platform and real propeller blades confirmed that the system consistently achieved measurement accuracy to the second decimal place under the continual measurement mode. The system also demonstrated excellent repeatability and stability. Furthermore, the continuous measurement mode outperformed the single-point measurement mode. Overall, the developed system effectively reduces labor requirements, shortens measurement times, and enables real-time monitoring of process variation. These capabilities underscore its strong potential for application in the smart manufacturing and quality control of marine propellers. Full article

This study aimed to improve the hydrophobicity of cellulose nanofibril (CNF) films using a natural wax coating. For this purpose, firstly, the selection, extraction and characterization of a natural wax and fatty acids were carried out. These compounds were extracted from the aerial part of the Halimium viscosum plant. The chromatogram resulting from the chemical analysis of the extract revealed the presence of 15 compounds, with nonacosane being the major compound present. For film production, two different chemical pulps gels (sulfite and sulfate) were first characterized in terms of solids content, rheology and Fourier transform infrared spectroscopy (FTIR). The CNF films were produced by the solvent casting method, coated on one side with the extracted wax and subsequently characterized by wettability, surface energy, differential scanning calorimetry (DSC), FTIR, structural properties and water vapor permeability. The results showed that the wax-coated films exhibited a significant increase in water resistance, with a water contact angle exceeding 100°, demonstrating improved hydrophobicity. Also, the water vapor transmission rate (WVTR) of the films was drastically reduced after wax coating. Furthermore, the coated films maintained good transparency, making them a viable alternative to synthetic plastic. This study highlights the potential of natural wax coatings to improve the moisture barrier properties of biodegradable CNF films, promoting their application in sustainable packaging solutions. Full article

The growing demand for sustainable energy solutions has intensified research on phase change materials (PCMs) due to their ability to efficiently store and release thermal energy. However, traditional PCMs are often made from petroleum-derived materials or rely on processes that pose environmental concerns. The aim of this work is therefore to explore the development and use of sustainable organic PCMs, in particular those based on bio-based or waste-derived materials. Bio-based PCMs, including fatty acids, natural waxes, and biopolymers, are in fact characterized by renewability and biodegradability. Waste-derived PCMs, such as those from the lost-wax casting industry and industrial by-products, offer an environmentally friendly approach to energy storage by reusing waste materials. This paper aims to analyze the thermal, mechanical, and in-service performance of these sustainable materials, highlighting their advantages and limitations compared to the most widely used commercial PCMs. Furthermore, recent progress in the integration of sustainable PCMs into building materials is illustrated to assess their practical implementation. Challenges and limitations, as well as possible solutions and future research directions, are also discussed. Full article

Background: Different methods have been used to fabricate and measure marginal gap in all-metal crowns, yet a systematic review on this topic has not been conducted. Objective: To review the existing literature regarding the measurement methods employed for the in vitro marginal gap measurement of pre-cemented all-metal single crowns and examine the influence of crown fabrication method on the marginal gap. Materials and Methods: A systematic search was performed from December 2024 backwards across EBSCO Host, Scopus, PubMed, and Web of Science databases following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines and predefined eligibility criteria. The quality of included articles was evaluated using the Joanna Briggs Critical Appraisal Checklist. Results: Ten studies, involving 180 crowns, assessed marginal gaps using computerised superimposition (102 µm), scanning electron microscopy (89 µm), profilometry (100 µm), photogrammetry (59 µm), impression replica techniques (124 µm), and direct view microscopy (35 µm). Marginal gaps varied across crowns constructed with cobalt–chromium (97 µm), titanium (56 µm), noble metals (127 µm), and base metal alloys (35 µm). No significant differences (t = 1.06, p = 0.315) were observed between CAD/CAM (103.21 ± 58.56 µm) and lost wax casting method (71.59 ± 43.94 µm) of crown fabrication when analysed using an independent t-test. Conclusions: Cobalt–chromium was the most used material for AMCs, while titanium alloys produced the lowest mean marginal gap per crown. No significant differences in reported marginal gaps were observed between crowns fabricated using lost wax casting and CAD/CAM techniques. However, the limited number of studies, variation in measurement methods, and inconsistency in methodological rigour restricted the generalisability of the findings. Full article

Structural research teams face significant challenges when conducting studies with explosives, including the costs and inherent risks associated with field detonation tests. This study presents a replicable method for loading spherical and bare TNT-based cast explosive charges, offering reduced costs and minimal risks. Over eighty TNT and Composition B charges (comprising 60% RDX, 39% TNT, and 1% wax) were prepared using spherical molds made of thin aluminum, which are low-cost, off-the-shelf solutions. The charges were bare, meaning they lacked any casing, as the molds were designed to be easily removed after casting. The resulting charges were safer due to their smaller dimensions and the absence of hazardous metallic debris. Composition B charges demonstrated promising results, with their performance characterized through blast and thermochemical experiments. Comprehensive data are provided for Composition B charges, including TNT equivalence, pressures, velocity of detonation, DSC/TGA curves at four different heating rates, activation energy, peak decomposition temperatures, X-ray analysis, and statistics on masses and densities. A comparison between detonation and deflagration processes, captured in high-speed footage, is also presented. This explosive characterization is crucial for structural teams to precisely understand the blast loads produced, ensuring a clear and accurate knowledge of the forces acting on structures. Full article

The investment casting process, also known as lost-wax casting, is widely used for producing ferrous and non-ferrous metal parts due to its excellent surface finish and dimensional accuracy. In recent years, the use of Co-Cr-Mo alloy has increased due to its high corrosion resistance, good biocompatibility, and relatively high wear resistance. Laser melting of materials has been demonstrated to refine the surface grain structure, reduce surface roughness, and improve both wear and corrosion resistance. The ability to fine-tune parameters such as laser power density and scanning speed facilitates the optimization of the treated layers’ thickness and homogeneity, thereby addressing many of the shortcomings inherent in conventional methods. This study investigates the microstructural, mechanical wear and bioactive behavior of investment-cast Co-Cr-Mo parts subjected to a Nd:YAG laser surface treatment. The effects of different processing parameters were analyzed quantitatively and comprehensively. The specimens were characterized using metallographic techniques, bioactivity evaluation, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), wear testing (Pin-on-Disk), and hardness testing. Our results demonstrate that Nd:YAG laser melting significantly enhances the surface properties and maintains the dimensional accuracy of complex Co-Cr-Mo biomedical components, through microstructural refinement, increased hardness, improved wear resistance, and preserved biocompatibility. The specific combination of investment casting with precisely controlled laser surface modification represents a significant advancement for improving the longevity and performance of biomedical implants. Full article

The rational design of ordered chromogenic supramolecular polymeric systems is critical for the advancement of next-generation stimuli-responsive, optical, and semiconducting materials. Previously, we reported the design of a stimuli-responsive, lamellar self-assembled platform composed of an imidazole-appended perylene diimide of varying methylene spacer length (n = 3, 4, and 6) and a commercially available diacid-functionalized diacetylene monomer, 10, 12 docosadiynedioic acid, in a 1:1 molar ratio. Herein, we expound on the importance of the composition of the imidazole-appended perylene diimide of varying methylene spacer length (n = 3, 4, and 6) and 10, 12 docosadiynedioic acid in the ratio of 2:1 to the supramolecular self-assembly, final morphology, and properties. Topochemical polymerization of the drop-cast films by UV radiation yielded blue-phase polydiacetylene formation, and subsequent thermal treatment of the films produced a thermoresponsive blue-to-red phase transformation. Differential scanning calorimetry (DSC) studies revealed a dual dependence of the methylene spacer length and stimuli treatment (UV and/or heat) on the thermal transitions of the films. Furthermore, small-angle X-ray scattering (SAXS) and wide-angle X-ray scattering (WAXS) showed well-defined hierarchical semiconducting nanostructures with interconnected “chessboard”-patterned lamellar stacking. Upon doping with an ionic liquid, the 2:1 platform showed higher ionic conductivity than the previous 1:1 one. The results presented here illustrate the importance of the composition and architecture to the ionic domain connectivity and ionic conductivity, which will have far-reaching implications for the rational design of semiconducting polymers for energy applications including fuel cells, batteries, ion-exchange membranes, and mixed ionic conductors. Full article

Background: The fit accuracy of removable partial dentures (RPDs) is essential for the functionality, patient comfort, and durability of RPDs. Traditional fabrication methods, like lost-wax casting, are reliable, but labor intensive, potentially affecting the fit accuracy of RPDs. Advances in digital fabrication techniques offer new avenues to improve RPD precision. This systematic review and meta-analysis will assess the impact of digital fabrication methods on the fit accuracy of RPDs compared to conventional techniques. Objective: To evaluate whether digital fabrication methods, specifically CAD/CAM and additive manufacturing, offer superior fit accuracy for RPD frameworks over conventional methods. Methods: The study protocol was registered with PROSPERO (registration number CRD42024586891). A comprehensive literature search was conducted across PubMed, the Cochrane Library, Scopus, and Ovid MEDLINE databases, covering publications published up to July 2024. The inclusion criteria comprised in vitro studies comparing the fit accuracy of digital versus conventional RPD fabrication techniques, with quantitative outcomes, such as the mean gap size or seating accuracy. The data were extracted and synthesized using a random-effects meta-analysis model. Results: Eleven studies met the inclusion criteria, with seven studies included in the meta-analysis. The mean gap size for digitally fabricated RPDs was 140 µm, compared to 164 µm for conventional methods, with a weighted mean difference (WMD) of 26.29 µm, favoring digital techniques. The subgroup analysis indicated variability in the fit across different digital techniques, with milling showing the best results, although the differences were not statistically significant. Limitations: The analysis included only in vitro studies, limiting the clinical generalizability of the findings. Additionally, heterogeneity in the study design and measurement methods persisted, which could have impacted the overall conclusions. Conclusions: Digital fabrication methods demonstrated a trend toward improved fit accuracy in comparison to conventional techniques, although the differences were modest. Future research should focus on standardizing digital workflows and conducting clinical trials to confirm these findings. Full article

The rapid investment casting (RIC) process requires a 3D-printed pattern to create a ceramic mold. Stereolithography (SLA) is a commonly used 3D printing method for pattern creation due to its ability to print complex shapes with smooth surfaces. The printing parameters can significantly affect the dimensional accuracy of the pattern. This study examines how different build orientations (0°, 45°, and 90°) affect the dimensional accuracy of parts produced using SLA. The specimens were printed using castable wax resin. They were measured to investigate the dimensional deviations using 3D scanning technology to understand the correlation between orientation and accuracy better. It was found that the orientation of the print affects the overall accuracy significantly. Parts printed at a 45° angle generally showed the smallest deviations from their nominal dimensions, except for certain features. For instance, cylindrical features showed deviations improving from −7.28% at 0° to −4.81% at 90°, while spherical features had deviations decreasing from −5.01% at 0° to −2.46% at 90°. Simple features, such as holes, exhibited minimal deviation across orientations, with the smallest error observed at 45° (1.98%). These results demonstrate different features and build orientations can affect the accuracy of the printed part differently. To ensure better accuracy, parts printed in different build orientations will require varying amounts of compensation during the design stage. By managing build orientations and controlling the inherent limitations of SLA, users can improve the print’s accuracy and meet quality standards more effectively. Research results can help industries optimize print settings and reduce dimensional errors. Full article

Traditionally, precious metals are processed by either lost-wax casting or the casting of semi-finished products followed by cold or hot working, machining, and surface finishing. Long process chains usually conclude in a high material input factor and a significant amount of new scrap to be refined. The maturing of Additive Manufacturing (AM) technologies is advantageous with regard to resources among other criteria by opening up new processing techniques like laser-based powder bed fusion (LPBF) for the production of near net shape metal products. This paper gives an insight into major advantages of the powder-based manufacturing of precious metal components over conventional methods focusing on product carbon footprints (PCF). Material Flow Cost Accounting (MFCA) for selected applications show energy and mass flows and inefficient recoverable losses in detail. An extended MFCA approach also shows the greenhouse gas (GHG) savings from avoiding recoverable material losses and provides PCF for the products. The PCF of the precious metals used is based on a detailed Life Cycle Assessment (LCA) of the refining process of end-of-use precious metals. In the best case, the refining of platinum from end-of-life recycling, for example, causes 60 kg CO_2e per kg of platinum. This study reveals recommended actions for improvements in efficiency and gives guidance for a more sustainable production of luxury or technical goods made from precious metals. This exemplary study on the basis of an industrial application shows that the use of AM leads to a carbon footprint of 2.23 kg CO_2e per piece in comparison with 3.17 kg CO_2e by conventional manufacturing, which means about a 30 percent reduction in GHG emissions and also in energy, respectively. Full article

3D printing technology can easily and quickly produce small batch models and full-size parts, which has obvious and important benefits in shortening development time. Since metals exhibit excellent mechanical strength and high wear resistance, metal additive manufacturing (MAM) is a popular technology for making metal parts. However, metal powders and 3D-printing machines are costly, which increases the difficulty of achieving mass production through MAM. In this study, the 3D wax printing and investment casting (WPIC) approach was developed to manufacture high-quality metal optical lenses with high efficiency and low cost. The manufactured lenses had a diameter of 38.1 mm, two radii of curvature (15 and 90 mm), and a cooling channel. These lenses were manufactured through 3D printing by using wax patterns produced through investment casting. The manufacturing efficiency and machining accuracy of the lenses produced using the proposed method were compared with those of lenses produced through MAM and investment casting. The results indicated that the total costs of manufacturing an optical lens through MAM and investment casting were nine and eight times greater, respectively than that of manufacturing an optical lens through WPIC. In addition, the surface roughness of metal lenses manufactured through WPIC was 45% lower than that of lenses manufactured through MAM. Finally, the time required to manufacture 50 metal lenses was only 15 days when WPIC was used; the corresponding time was 25 days and 6 months when MAM and investment casting were used, respectively. According to the above-mentioned results, the WPIC process has excellent advantages in product manufacturing cost and developing schedule over MAM and traditional methods of investment casting. Full article

This article presents the results of testing the suitability of X-ray computed tomography for the quality control of the casting moulds used for producing turbine blades. The research was focused on the analysis of cross-sectional images, spatial models and the porosity of moulds using a Phoenix L 450 microtomograph. The research material consisted of samples from three mixtures of ceramic materials and binders intended for producing casting moulds using the lost wax method. Various configurations of filling materials (Molochite and quartz flours) and binder (Remasol, Ludox PX 30 and hydrolysed ethyl silicate) mixtures were considered. X-ray computed tomography enabled the detection of a number of defects in the ceramic mass related to the distribution of mass components, porosity concentration and defects resulting from the specificity of the mould production. It was found that casting mould quality control on cross-sectional tomographic images is faster and as accurate as the analysis of three-dimensional models and allows for the detection of a whole range of ceramic defects, but the usefulness of the images is greatest only when the cross-sections are taken at an appropriate angle relative to the object being examined. Full article

This paper presents the authentication analysis of a bronze bust of Napoleon I, attributed to the Italian artist Renzo Colombo (1856–1885) based on his signature and other casting and molding inscriptions. The bust was made using the lost wax technique and artificially patinated in the Pinédo variant workshop. This study combined historiographical research (using the specialized literature) with data from auction catalogs. These were compared with photographs of the entire bust and close-up images of key areas, including anthropomorphic features, clothing, inscriptions, and structural and ornamental details. The condition of the bust and its historical and chemical characteristics were assessed through direct analysis with magnifying tools and indirect analysis using scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDX). Full article

Meat is known for its high perishability and short shelf life if not properly packaged or stored. Packaging materials play a crucial role in preserving food quality, and there is a growing demand from consumers, industry professionals, and researchers for natural packaging materials that incorporate health-beneficial extracts. Additionally, there is an increasing emphasis on avoiding non-biodegradable plastics in order to reduce environmental pollution. Currently used polymers in food packaging typically feature properties such as oxygen barriers, moisture resistance, and oxidation inhibition, helping to prevent undesirable aromas, flavors, and colors in food. Packaging not only serves as a container for transportation but also prevents physical damage, maintains quality, and ensures food safety. In the pursuit of more sustainable solutions, various compounds are being explored for food packaging, including those derived from proteins, lipids, waxes, and polysaccharides. These materials can be combined with bioactive compounds, such as natural plant extracts, which provide antioxidant, antimicrobial, anti-inflammatory, and anticancer benefits. Different techniques, such as electrohydrodynamic processes and casting methods, are employed in the preparation of these packaging materials. This review highlights the applications and properties of polymers used in meat packaging and promotes the use of biodegradable materials as a viable solution to reduce environmental pollution. Full article

Investment casting is a widely utilized casting technique that offers superior dimensional accuracy and surface quality. In this method, the wax patterns are employed in the layer-by-layer formation of a shell mold. As is customary, the patterns were created through the injection of molten or semi-solid wax into the die. The quality of the final casting is affected by the quality of the wax pattern. Furthermore, the filling of the die with wax can be associated with die-filling challenges, such as the formation of weld lines and misruns. In this study, the injection filling of the fluidity probe die with RG20, S1235, and S1135 pattern waxes was simulated using ProCast software. The thermal properties of the waxes, including thermal conductivity, heat capacity, and density across a wide temperature range, were determined with the assistance of a laser flash analyzer, a differential scanning calorimeter, and a dynamic mechanical analyzer. A favorable comparison of the acquired properties with those reported in the literature was observed. The Carreau model, which corresponds to non-Newtonian flow, was employed, and the parameters in the Carreau viscosity equation were determined as functions of temperature. Utilizing the thermal data associated with the wax patterns and the simulation outcomes, the interfacial heat transfer coefficients between the wax and the die were ascertained, yielding a value of 275–475 W/m²K. A strong correlation was observed between the experimental and simulated filling percentages of the fluidity probe across a wide range of injection temperatures and pressures. The analysis of the simulated temperature, fraction solid, viscosity, and shear rate in the wax pattern revealed that viscosity is a crucial factor influencing the wax fluidity. It was demonstrated that waxes with an initial high viscosity exhibit a low shear rate, which subsequently increases the viscosity, thereby hindering the wax flow. Full article