Conventional Mold Research Articles

Microstructure characterization and high-temperature wear behavior of plasma nitriding mold steel

Considering the cyclic variation of temperature and load in the glass molding, the mechanical properties and wear behavior of the nitriding mold steel at high temperatures are necessary to investigate. In this research, the microhardness variation of mold steel after plasma nitriding is elucidated and associated with the microstructure. The high-temperature nanoindentation experiments are conducted to clarify the impact of temperature on mechanical behavior of the nitriding steel. The hardness and elastic modulus of the nitriding steel are decreased by 40.9 % and 19.5 % when the temperature increased from room temperature to 400 °C. Correspondingly, due to the hardness dropping, the wear resistance of the nitriding mold steel decreases gradually with the temperature. However, the wear resistance of the nitriding mold steel under high temperatures is still superior to that of conventional mold steel. A wear schematic model is developed to elucidate the wear behavior evolution mechanism of the nitriding steel with temperatures. This work provides a comprehensive investigation of the mechanical and wear behavior of the nitriding mold steel under high temperatures which avoids mold wear failure in glass compressing molding.

Effect of twisted tapes and surface extensions in enhancing the condensation heat transfer of high-temperature saturated steam in a circumferential rectangular channel

This article numerically investigates the impact of twisted tapes and extended surfaces (fins) on enhancing high-temperature steam flow in a circumferential rectangular channel, akin to the external jacket cavity of a tyre cure press. The passive enhancement techniques for improving the mold warm-up time of the tyre curing process have received limited attention in previous studies, which have primarily focused on enhancing heat transfer in configurations and working conditions typical of heat exchanger applications. The objective of this article is to enhance the condensation heat and mass transfer rate by geometrically modifying the internal flow path of the circumferential rectangular channel, resembling an external jacket cavity of a tyre cure press, using twisted tapes and extended surfaces. Four configurations are simulated: i) conventional circumferential rectangular channel, ii) channel with twisted tapes, iii) channel with surface extension, and iv) channel with both twisted tapes and surface extension. The heat transfer performance of all the modified channel configurations derived from the simulation results is assessed in comparison to the conventional channel. The channel, featuring a design that includes five twisted tapes with a twist ratio of 8 and 54 extended surfaces, records a substantial 36.85% rise in heat flux along with a notable 24% increment in the condensation mass flux. The simulation results are validated using an in-house experimental study. The tyre cure press in the experimental setup is modified to align with the design proposed by the simulation results, and a warm-up study is conducted. The warm-up time for the modified mold to attain the desired temperature is reduced by 33%, with no accompanying increase in steam consumption, compared to the warm-up time for the conventional mold. This significant reduction in mold warm-up time holds immense potential in enhancing the productivity rate, an ongoing requirement of the automobile industry.

Cationic Gas-Permeable Mold Fabrication Using Sol-Gel Polymerization for Nano-Injection Molding.

Cationic gas-permeable molds fabricated via sol-gel polymerization undergo cationic polymerization using epoxide, resulting in gas permeability owing to their cross-linked structures. By applying this cationic gas-permeable mold to nano-injection molding, which is used for the mass production of resins, nano-protrusion structures with a height of approximately 300 nm and a pitch of approximately 400 nm were produced. The molding defects caused by gas entrapment in the air and cavities when using conventional gas-impermeable metal molds were improved, and the cationic gas-permeable mold could be continuously fabricated for 3000 shots under non-vacuum conditions. The results of the mechanical evaluations showed improved thermal stability and Martens hardness, which is expected to lead to the advanced production of resin nano-structures. Furthermore, the surface roughness of the nano-protrusion structures fabricated using injection molding improved the water contact angle by approximately 46°, contributing to the development of various hydrophobic materials in the future.

Simultaneously enhancing the flow properties and mechanical strength of polyphenylene sulfide via in‐mold ultrasonic‐assisted injection molding

AbstractInjection molding is widely used for making intricate plastic products due to its precision, cost efficiency, and fast production. Industries like consumer electronics, aerospace, and medical, demand high mechanical properties from these parts. However, high‐performance polymers face challenges in flowability. Ultrasonic‐assisted injection molding offers a solution, but its impact on flowability and mechanical properties is not fully understood. We propose a novel injection mold design with in‐mold ultrasonic vibration to address this. By applying high‐frequency shear forces to the melt, it alters polymer chain alignment, enhancing flow and microstructure. Employing polyphenylene sulfide (PPS) resin as the primary material, this study systematically explores the impact of varying ultrasonic vibration durations and stages on melt filling behavior and product performance. Compared with conventional molds, ultrasonic‐assisted molds reduce melt viscosity by 38% and improve mechanical properties by 10.21%, with a 17.1% increase in crystallinity. This technology shows promise for improving flowability and mechanical properties in injection molding, with potential for wide industrial application.

Treatment outcomes of digital nasoalveolar moulding in infants with cleft lip and palate: A systematic review with meta-analysis.

The aim of this systematic review was to compare the treatment outcomes of digital nasoalveolar moulding (dNAM) technique with conventional nasoalveolar moulding (cNAM) or non-presurgical intervention protocol in infants with unilateral (UCLP) or bilateral (BCLP) cleft lip and palate. A bibliometric search by MEDLINE (via Ovid), Embase, Cochrane Library, grey literature and manual method was conducted without language restriction until November 2023. Literature screening and data extraction were undertaken in Covidence. The risk of bias was evaluated using the Newcastle-Ottawa Scale and RoB-2. Pooled effect sizes were determined through random-effects statistical model using R-Software, and the certainty of evidence was assessed using the GRADE approach. Among 775 retrieved articles, nine studies were included for qualitative synthesis (6-UCLP, 3-BCLP), with only three eligible UCLP studies for meta-analysis. In the UCLP group, very low certainty of evidence indicated no difference in alveolar cleft width (SMD, 0.13 mm; 95% CI, -0.31 to 0.57; I2, 0%), soft tissue (lip) cleft gap, nasal width, nasal height, and columellar deviation angle changes between dNAM and cNAM. In the BCLP group, qualitative synthesis suggested similar changes in alveolar, lip, and nasal dimensions with dNAM and cNAM. In both cleft groups (UCLP, BCLP), reduced alveolar cleft width was observed in the dNAM group compared to the non-presurgical intervention protocol, along with fewer clinical visits and reduced chairside time for dNAM compared to cNAM. It can be concluded that the treatment outcomes with dNAM were comparable to cNAM in reducing malformation severity and were advantageous in terms of chairside time and clinical visit frequency. However, the overall quality of evidence is very low and standardization is needed for the virtual workflow regarding the alveolar movements and growth factor algorithms. Registration: PROSPERO-database (CRD42020186452).

Design and heat transfer numerical analysis of high-speed continuous casting mold water slot system

The water slot structure can reduce the temperature of the mold and increase the heat transfer between the mold and cooling water. It has significant impacts on high-speed continuous casting. Therefore, a three-dimensional model of heat transfer from mold to cooling water was used to analyze the influence of water slot size on the cooling capacity of a single water slot. Then, the fluid flow, heat transfer, and solidification three-dimensional models were used to analyze the temperature distribution and cooling effect of three kinds of water slot molds and non-water slot molds. Finally, the water slot mold was designed to achieve high-speed continuous casting. The results show that to make full use of the cooling water in the water slot, the width and height of a single water slot should be less than 8 mm. Compared with the conventional mold without the water slot structure, the temperature of the mold with the water slot structure significantly decreases. The final design of the mold water slot system is as follows: the water slot width and depth are 8 mm, and the number of water slots on one side of the mold is 9. The water slots have a symmetrical distribution, and the symmetrical plane is the middle plane of the mold. The high-speed continuous casting experiment was carried out, and the casting speed can reach 4–4.5 m/min. The water slot mold in this study can be applied in the high-speed continuous casting process.

Variable Shape Tooling for Composite Manufacturing: A Systematic Review

The choice of material, manufacturing process, and molding tool significantly affects the quality, environmental impact, and cost efficiency of composite components. Producing one-piece hollow profiles with smooth inner surfaces and undercuts presents major challenges for conventional mold concepts. There is yet no thorough review of shape-variable mandrels in composite manufacturing to be found in the literature. This paper provides an overview of research on shape memory polymers and other shape-variable materials used in tooling applications for composite manufacturing. This work covers shape memory, heat shrink, and other deformable tooling concepts that enable the production of one-piece Type V pressure vessels, air intake ducts, or curved struts and tubes. A systematic literature review in combination with a state-of-the-art open-source active learning tool ASReview is conducted. Fifteen relevant studies were identified. Research on shape-variable tooling is mainly conducted by three research groups in the USA and the PRC. The tooling is mostly made of unreinforced thermosets, especially styrene-based ones. Thermoplastic resins are less common, and reinforcements limit the usable elongation in the temporary shape. The shape variability is either a shape memory and/or a softening process, which, in all studies, is activated by heating. Release agents are widely used to ease demolding. No ecological or economical assessment of the manufacturing methods was conducted in the reviewed studies. Three fields for further research that could be identified are as follows: (1) thorough ecological end economical assessment of shape-variable mandrels in comparison with conventional tooling; (2) thermoplastic shape memory polymer mandrels; and (3) further investigation of simulation capabilities for shape memory mandrels.

Structural and thermoluminescence properties of lithium borate glass matrices under UV and beta radiation.

In the present work, glass samples in the (100 - x)B2O3-xLi2O binary system, with x varying from 30 to 50 mol%, were prepared using the conventional melting and moulding method, with the main objective of evaluating the thermoluminescence response when exposing these materials to ultraviolet (UV) radiation. Complementary analysis based on density, optical absorption on the UV-visible region (UV-vis absorbance), Fourier transform infrared spectroscopy on the medium region, X-ray diffraction, and differential thermal analysis measurements were performed. Thermoluminescence measurements of vitreous samples showed glow curves with at least one peak with a maximum temperature of ~170°C after exposure to UV radiation in the temperature range 50-250°C. Samples were also exposed to beta radiation in the temperature range 25-275°C, also showing single peaks with a maximum temperature of ~150°C.

Exploiting light-based 3D-printing for the fabrication of mechanically enhanced, patient-specific aortic grafts

Despite polyester vascular grafts being routinely used in life-saving aortic aneurysm surgeries, they are less compliant than the healthy, native human aorta. This mismatch in mechanical behaviour has been associated with disruption of haemodynamics contributing to several long-term cardiovascular complications. Moreover, current fabrication approaches mean that opportunities to personalise grafts to the individual anatomical features are limited. Various modifications to graft design have been investigated to overcome such limitations; yet optimal graft functionality remains to be achieved. This study reports on the development and characterisation of an alternative vascular graft material. An alginate:PEGDA (AL:PE) interpenetrating polymer network (IPN) hydrogel has been produced with uniaxial tensile tests revealing similar strength and stiffness (0.39 ± 0.05 MPa and 1.61 ± 0.19 MPa, respectively) to the human aorta. Moreover, AL:PE tubular conduits of similar geometrical dimensions to segments of the aorta were produced, either via conventional moulding methods or stereolithography (SLA) 3D-printing. While both fabrication methods successfully demonstrated AL:PE hydrogel production, SLA 3D-printing was more easily adaptable to the fabrication of complex structures without the need of specific moulds or further post-processing. Additionally, most 3D-printed AL:PE hydrogel tubular conduits sustained, without failure, compression up to 50% their outer diameter and returned to their original shape upon load removal, thereby exhibiting promising behaviour that could withstand pulsatile pressure in vivo. Overall, these results suggest that this AL:PE IPN hydrogel formulation in combination with 3D-printing, has great potential for accelerating progress towards personalised and mechanically-matched aortic grafts.

Experimental evaluation on the mitigation performance of double-layered Kirigami corrugated cladding against impact load

The impact mitigation performance of novel single and double-layered kirigami corrugated (KC) claddings is investigated in this study via drop weight impact tests, as their significant improvements in energy absorption and crushing resistance were previously demonstrated over conventional corrugated structures. The feasibility of mass production on the proposed large-size KC core is also verified by applying conventional multi-stage mould pressing. A total of 15 different configurated single and double-layered KC cladding specimens are prepared and tested, where the effects of impacting speed, impacting mass, layer number, stacking configurations as well as graded design on the impact mitigation performance are considered. Impact force time histories, impact force-displacement curves, and transmitted force time histories at five different locations recorded using a custom-made measuring system are compared to evaluate the impact mitigating performance for the structure placed behind the proposed protective KC claddings. Transmitted force at centre is reduced by more than half as compared with the applied impact force for all double-layered KC claddings. Among the double-layered KC claddings, inverse symmetrically stacked KC cladding with no offset in the bottom layer, as well as the negatively graded KC claddings demonstrate a superior performance with a lower transmitted peak force at the centre and a more uniform force distribution transmitted to the support behind the claddings.

Comparative Studies of Microstructural, Mechanical and Tribological behaviour of A319 alloy cast in solid waste mold and conventional sand Mold

Abstract This study investigates the potential of utilizing industrial solid waste (blast furnace slag, ferrochrome slag, and red mud) as mold materials to improve the solidification rate and wear resistance of A319 alloy. Unlike conventional molds such as silica sand and olivine sand, industrial solid waste poses an eco-friendly alternative, contributing to waste valorization. The motivation for this research drives the need for sustainable and efficient waste management practices in the industrial sector. By exploring the utilization of industrial solid waste as a mold material, study aims to address the current challenges in disposal, reduce environmental impact, and enhance the overall performance of A319 alloy through improved solidification and wear resistance. The experimental phase involved multi-factor reciprocating sliding wear tests conducted on a sample using a linear reciprocating tribometer, employing a steel ball as a counter face. The investigation of reciprocating wear characteristics aimed to assess the correlations between solidification rate and wear properties of a specimen cast in an industrial solid waste mold as well as a sand mold. Notably, tribological test results revealed a low wear rate of 3.3 mg/Km for the blast furnace slag mold. The scanning electron microscopy (SEM) image of the wear surface showed adhesive wear mechanisms. This study contributes valuable insights into the potential environmental and performance advantages of repurposing industrial solid waste for foundry applications.

Experimental investigation of compressive behavior and vibration properties of layered hybrid foam formed by aluminum foam/EPS-filled syntactic foam

Hybrid foams are a type of composite material created by combining two foam materials. They are preferred in many applications due to their lightweight, high strength, and ability to absorb more energy. In this research, a new hybrid foam was designed for use in sandwich cores of structural materials. The hybrid foam was formed by combining closed-cell aluminum foam and expanded polystyrene (EPS)-filled syntactic foam. The EPS-filled syntactic foams were produced with the conventional mold casting technique. Uniaxial compressive behaviors (0.5 mm/min) of layered hybrid foams consisting of EPS-filled syntactic foam with three different densities and closed-cell aluminum foam were investigated experimentally and compared with conventional single-foamed materials. These results exhibited that in general, layered hybrid foams outperform conventional single-foamed materials in terms of compressive strength. Moreover, the natural frequency and damping ratio of the layered hybrid foams were investigated by vibration tests under clamped-free and free-free boundary conditions and compared to conventional single-foamed materials. It was established that the vibration damping capacity of the layered hybrid foams improved compared to the closed-cell aluminum foam. Additionally, the microstructure of the conventional single-foamed materials was examined by SEM. In the outcome of the research, the experimental results showed that layered hybrid foam provides an opportunity to design lightweight cellular materials with effective mechanical properties.

Effects of hollow sand mold on the microstructure and mechanical properties of a low pressure aluminum alloy casting

The hollow mold revolutionizes conventional dense mold design as it can optimize the solidification and cooling processes of casting and offer potential to improve performance of castings. In this paper, the effect of hollow mold structures on the microstructure and mechanical properties of a low pressure thin-walled aluminum alloy conical cabin casting was investigated. A hollow mold combined by four sectors with different shell thicknesses was tactfully designed. The hollow mold structures delayed the cooling and solidification of casting. They significantly reduced the pore defect from 0.4 % to 0.03 % at the lower, from 0.68 % to 0.04 % at the middle and from 0.3 % to 0.03 % at the top, compared to dense mold. In the lower and middle areas of casting, improvements of 1.0 % and 1.1 % in mechanical properties were respectively achieved when applying 50 mm-thick-shell hollow sand molds compared with using dense sand mold, while an improvement of 1.1 % was achieved in the upper area of casting with 70 mm-thick-shell. This allows designers to create hollow molds with different shell thicknesses depending on the position in the casting to meet specific needs. For example, thin shell for the bottom to achieve high fluid flow and feeding while thick shell for the top for improved cooling. For castings with wall thickness of 10 mm–20 mm, the most effective shell thickness for the hollow mold is 50 mm–70 mm. The hollow mold provides the feasibility to differentiated semi-quantitatively control the solidification and cooling processes of castings, which can be applied in production of high-end castings in the future.

THE LUXURY WATCH INVESTMENT MARKET

The luxury watch investment market offers a distinctive blend of history, craftsmanship, and exclusivity. While it may not fit the conventional mold of traditional investments, the allure of owning a piece of horological art has attracted a growing number of collectors and investors. As with any investment, thorough research, an understanding of market trends, and a passion for horology are essential for success in this unique niche. In a world driven by technology and rapid change, luxury watches stand as timeless symbols of elegance and a testament to the enduring appeal of meticulous craftsmanship.

Prospects for manufacturing of complex 3D-shaped all-cellulose composites

All-cellulose composites (ACC) have been investigated as a high-strength bio-based alternative to commodity plastics. However, plastic products frequently demand complex 3D geometries as part of their functionality. Hence, a critical factor in the broader application of ACCs is the production of dimensionally-accurate 3D forms. Interestingly, there have been no attempts in the literature to produce 3D geometries based on all-cellulose composites. In the present work, the production of ACCs with 3D geometries is explored for the first time using conventional vacuum and compression moulding procedures. The level of 3D complexity possible in ACCs was examined using a closed mould design that incorporated a range of geometric shapes and angles of varying intricacy. The dimensional accuracy of the final 3D forms was analysed via 3D laser scanning of the surfaces of the as-moulded ACCs. The choice of coagulant type was found to strongly influence the dimensional accuracy of the as-moulded ACCs.

Conventional Border Molding versus Digital Impression on Complete Denture Impression: A Review

Background: Definitive working impression of a complete denture requires proper border molding as part of impression techniques to capture the essential details of anatomical landmarks and the functional sulcus. In the era of digital dentistry, the digital impression using optical scanners may be an alternative to conventional techniques. Objective: This paper discusses the differences between conventional methods and digital impression in a complete denture covering its procedures, importance and relevance of border molding in both methods for a good working impression. Methods: The study reviewed papers from 2000 to 2022 in Medline and PubMed on border molding and complete denture working impression. Both methods were revised and contrasted to discuss the relevance and advantages of both approaches. Results: It is still controversial to conclude that digital impression is superior to the conventional method. Both methods have the strength to improve the quality of the impression taking procedure and complete denture quality of retention and stability. Digital impression gives more comfort and less post insertion adjustment. The conventional method still has good clinical outcomes in terms of retention and stability. Border molding should not be disregarded as part of the working impression procedure. Conclusion: The paper concludes that border molding and the conventional working impression technique are still relevant due to their comparable outcome compared to digital impression, as less cost and high skills are involved.

Axial deformation of early-age concrete-filled steel tubular columns under multi-stage loading

The continuous construction scheme for concrete-filled steel tubular structures in practice is time-saving and cost-effective in comparison to the conventional moulding construction methods, whilst this also results in complex stress conditions and working mechanisms in the early-age concrete-filled steel tubes (CFSTs) during construction. This investigation aims to explore the influence of continuous construction process on the axial compressive behaviour of early-age CFSTs as subject to multi-stage loading schemes. Eight short square early-age CFST columns are designed and tested. The axial deformation evolutions of CFSTs are analyzed for different load parameters including the initial stress of steel tube, loading time interval and load magnitude. The test results show that the deformation of early-age CFSTs varies significantly with various load parameters. Excessive deformation can be observed during the multi-stage loadings due to the local buckling of the steel tube. Based on the shrinkage and creep model of concrete, a theoretical algorithm for calculating the relationship between the deformation of early-age CFST and the age of concrete is developed. Furthermore, a simplified calculation method for the deformation of early-age CFST under multi-stage loading is proposed that can realistically describe the deformation of early-age CFSTs under continuous construction process. The research findings lay a foundation for the deformation control and safety assessment of CFST under continuous construction scheme.

Black liquor-based epoxy resin: Thermosets from untreated kraft lignin

The production of thermosetting resins from lignin is a promising route to upcycle this biomaterial, currently overwhelmingly used as fuel. Raw kraft black liquor with no prior purification or treatment was derivatised using epichlorohydrin and an aniline catalyst to yield a black liquor-based epoxy resin (BLER). BLER is a liquid resin, which can be processed using conventional moulding techniques prior to curing into black liquor-based thermosets using maleic anhydride as hardener. We report the production of liquid lignin-based thermosets containing a biocarbon content of ∼ 16%. These thermosets possess Young’s moduli and tensile strengths exceeding 1 GPa and 40 MPa, respectively. The chemical composition of the starting material and BLER were characterised, and the mechanisms of cure as well as the mechanical properties of lignin-based thermosets were determined.

Development of a Rapid Tool for Metal Injection Molding Using Aluminum-Filled Epoxy Resins.

Metal injection molding (MIM) is a near net-shape manufacturing process combining conventional plastic injection molding and powder metallurgy. Two kinds of injections molds for MIM were developed using conventional mold steel and aluminum (Al)-filled epoxy resins in this study. The characteristics of the mold made by rapid tooling technology (RTT) were evaluated and compared with that of the fabricated conventional machining method through the MIM process. It was found that the service life of the injection mold fabricated by Al-filled epoxy resin is about 1300 molding cycles with the average surface roughness of 158 nm. The mold service life of the injection mold fabricated by Al-filled epoxy resin is about 1.3% that of the conventional mold steel. The reduction in manufacturing cost of an injection mold made by Al-filled epoxy resin is about 30.4% compared with that of the fabricated conventional mold steel. The saving in manufacturing time of an injection mold made by RTT is about 30.3% compared with that of the fabricated conventional machining method.

Characterisation of microneedle replication and flow behaviour in ultrasonic micro-injection moulding through design of experiments

This research investigates the impact of process parameters on ultrasonic micro-injection moulding (u-μIM) by studying microneedle replication efficiency, temperature evolution during moulding, melt flow consistency and sonication behaviour. The experimentation comprises of a full-factorial design of experiments using three process variables: sonication time, mould temperature and injection force. The current study presents that; (i) mould temperature was found to be the most influential parameter to tune and optimise micro-feature replication, (ii) consistent ultrasonic micromoulding flows can be achieved using higher mould temperatures, (iii) injection force is a key parameter influencing sonication frequency, a critical aspect of the ultrasonic method to obtain a repeatable manufacturing process. These outcomes will be a datum during development of the manufacturing processes for specific products using the ultrasonic method. The research presented here takes a unique approach to characterise the ultrasonic method for the development of this novel technique, particularly for microneedle patch and medical device production. With this increased level of understanding of u-μIM process characteristics, the method can become an energy efficient and cost-effective alternative to conventional micro-injection moulding processes for delivering high-quality, miniature components.