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Purpose: Three-dimensional (3D) casting means using additive manufacturing (AM) techniques to print the mould for casting the cast tool. The printed mould, however, should be checked for its dimensional accuracy. 3D scanning can be used for the same. The purpose of this study is to combine the different AM techniques for 3D casting with 3D scanning to produce parts with close tolerance for preparing electrical discharge machining (EDM) electrodes. Design/methodology/approach: The four processes, namely, stereolithography, selective laser sintering, fused deposition modelling and vacuum casting, are used to print the casting mould. The mould is designed in two halves, assembled to form a complete mould. The mould is 3D scanned in two stages: before and after using it as a casting mould. The mould's average and maximum dimensional deviations are calculated using 3D-scanned results. The eutectic Sn-Bi alloy is cast in the mould. The surface roughness of the mould and the cast tool are measured. Findings: The cast tool is selected from the four processes in terms of dimensional accuracy and surface finish. The same is electroplated with copper. The microstructure of the cast tool (low-melting-point alloy) and deposited copper is analysed using a scanning electron microscope. Energy dispersive spectroscopy and X-ray diffraction techniques are used to verify the composition of the cast and coated alloy. The electroplated tool is finally tested on the EDM setup. The material removal rate and tool wear are measured. The performance is compared with a solid copper tool. The free-form customised EDM mould is also prepared, and the profile is cast out. The same is tested on the EDM. Thus, the developed path can be successfully used for rapid tooling applications. Originality/value: The eutectic composition of Sn-Bi is cast in the 3D-printed mould using different AM techniques combined with 3D scanning quality to check its feasibility as an EDM electrode, which is a novel work and has not been done previously. [ABSTRACT FROM AUTHOR]

AlFeCoCrNiTi0.2 Ugh entropy alloy was prepared by vacuum casting and annealed at 600,800 and 1 100 C respectively. The microstructure and mechanical properties of the alloy with different heat treatment temperatures were studied by means of Scanning Electron Microscopy (SEM), energy dispersive analysis(EDS), X- ray diffractometer(XRD), Nano indentation instrument and universal mechanical testing machine. The results show that the as-cast and heat-treated AlFeCoCrNiTi0.2 High-entropy alloys are body-centered cubic structure. After heat treatment,BCC1 predicates BCC2 phase to form a biphasic structure (primary phase BCC1 + precipitated phase BCC2). At 600 C,the hardness of the alloy is 672 HV,the plastic modulus is 655. 7 Gatha pressing depth is 283. 4 nm, the compression plasticity is 28%,and the breaking strength is 1. 75 GA. The hardness of 800 C and 1 100 C alloy decreases, manly due to the decomposition of BCC phase to form a biphasic BCC (BCC1 +BCC2) sold solution structure, which reduces the strength of the alloy. [ABSTRACT FROM AUTHOR]

In order to study the accelerated electrochemical corrosion behavior under simulated acid rain, CoCrNiAl high entropy alloy (HEA) was prepared. The electrochemical performance of CoCrNiAl HEA and other typical metals (Q235 steel, AZ31 magnesium alloy, and 1060 aluminum alloy) in simulated acid rain solution with different pH (3.5, 4.0, 4.5, and 5.0) were studied. The results show that the microstructure of CoCrNiAl HEA is mainly composed of dendrites (DR). The alloy exhibits the diffraction patterns of the disordered A2-bcc phase with the ordered B2-bcc phase. Ni-Al is rich in dendrites, and Cr is rich in interdendritic (ID) regions that consist of the A2/B2. The CoCrNiAl HEA has excellent corrosion resistance in simulated acid rain solution with pH = 3.5, 4.0, 4.5, and 5.0. The self-corrosion current is reduced by 1-2 orders of magnitude compared with other typical metals. The self-corrosion potential is higher than for other typical metals except in a solution with pH = 5. The CoCrNiAl HEA has excellent pitting corrosion resistance. The corrosion resistance of CoCrNiAl HEA is related to the uniformity and compactness of the microstructure, passive surface film, and corrosion resistant elements in the alloy. The dense corrosion products on the surface also play a role in reducing the corrosion rate. The corrosion mechanism of the prepared CoCrNiAl alloy is intergranular corrosion when it comes into contact with a simulated acid rain solution, and then with the extension of time, the corrosion mechanism changes to uniform corrosion. [ABSTRACT FROM AUTHOR]

Vacuum casting (VC) of reactive polymer resins in silicone molds is one of the oldest rapid tooling methods. It is widely used in the industry for prototype and small‐series production of thermoset plastic parts. Despite its widespread use, its scientific exploration is still scarce compared to other prototyping methods, such as three‐dimensional (3D) printing. Compared to conventional 3D printing methods, a wide range of excellent material properties can be achieved, making it well suited for the production of functional prototypes and even final products. The properties of the thermosets are comparable to those of injection molding in terms of viable shapes, mold fidelity, and material properties. However, due to the high cycle time and limited service life of the molds, VC is rarely utilized for mid‐ or large‐series production. Here, we provide a comprehensive overview of the state of the art and recent advances in the field. The review also provides a detailed technical introduction to the mold production, the process flow, and the materials used. A particular focus is on the key challenges facing industrial‐scale VC today—how to reduce cycle time, and how to increase mold service life? [ABSTRACT FROM AUTHOR]

Vacuum casting (VC) is a promising technique used for the production of functional plastic parts due to its fast production of high-quality prototypes. However, the mechanical properties of the fabricated products are affected by the composition of the molding materials. Additive manufacturing (AM) is also widely applied for low-volume prototyping applications. However, the mechanical properties of the fabricated products are affected by both build directions and printing angles. To investigate the difference in flexural strength of parts between vacuum casting and fused deposition modeling, glass fiber (GF) and carbon fiber (CF) are added to the matrix materials of polyurethane (PU) for improving the flexural strength of the molded products and three different printing angles and two build directions were applied in AM process. It was found that the flexure strength of the specimen fabricated by VC is generally greater than that of the specimen fabricated by AM. The highest flexure strength of the specimen fabricated by VC is 141 MPa, whereas the highest flexure strength of the specimen fabricated by FDM is only 102.7 MPa. The addition of short GF to the PU will increase the flexural strength. The flexural strength can be increased by about 41% when the PU is added with 4 wt.% short GF. The flexural strength can be increased by about 4.8% when the PU is added with 1 wt.% long GF. In contrast to above results, the flexural strength will be reduced when the PU is added with more than 2 wt.% long GF. On the contrary, the flexural strength can not be improved when the short CF or long CF is added to the PU. Finally, the flexural strength of the plastic prototype made by VC technology is superior to that of the plastic prototype made by FDM since the mechanical properties of the plastic prototype made by the FDM are affected by the build direction and printing angle. [ABSTRACT FROM AUTHOR]

Vacuum casting (VC) is a highly versatile manufacturing technique capable of producing parts in a wide range of polymers for end use plastic parts or prototypes. VC technology is ideally suited to low volume batch production compared with plastic injection molding since a silicone rubber mold (SRM) can be used to produce up to fifty to eighty parts. The main challenge of this method is that the both dimensional and form accuracies of the VC parts were affected by the fastening force of the SRM using tape due to the fastening force is inconsistent for different operators. In this study, an intelligent SRM clamping mechanism comprising a pressure sensor and Arduino pressure sensing module was developed for reducing the variations in both dimensional and form accuracies of the VC parts. It was found that the 14 kPa is the optimal clamping pressure. The angular deviation of the cuboid VC parts produced by the intelligent clamping mechanism falls within the range of one standard deviation (SD) to the average. The minimum zone circle deviation of the cylinder VC parts produced by the intelligent clamping mechanism falls within the range of − 1 to 2 SDs. In addition, the production cost of the SRM can further be reduced by about 23% using an intelligent clamping mechanism compared with that using the conventional method. [ABSTRACT FROM AUTHOR]

The article deals with vacuum casting technology and especially with the assessment of the influence of the tempering temperature of silicone molds on the dimensions of future castings. The aim was to evaluate the actual size of the castings, using different tempering temperatures of the molds and different casting materials. After examining the resulting dimensions of the individual castings, a procedure was established by which these effects could be minimized. In the end, a test of the proposed procedure is performed, which confirmed its correctness. [ABSTRACT FROM AUTHOR]

Hybrid moulds are an increasingly considered alternative for prototype series or short production runs. This type of tools resorts on the use of Rapid Prototyping and Tooling (RPT) to produce the moulding elements (blocks or other inserts). This study was developed using a hybrid injection mould with exchangeable moulding elements that were produced by additive manufacturing (AM), namely vacuum epoxy casting, stereolithography and ProMetal. A full steel tool was also used as a reference. The processing conditions for the polypropylene moulded parts using the hybrid mould were monitored for pressure, temperature and ejection force. The hybrid mould performance was assessed in terms of pressure and temperature evolution during the injection cycle and the AM moulding elements for physical integrity. The data from the polypropylene moulded parts and the moulding inserts are compared with structural and rheological simulations using ANSYS Workbench and MOLDEX 3D. The results show that the hybrid mould performance and the structural integrity of the moulding elements depend on the properties of the materials used. The moulding shrinkage, when resin cores are used, is also affected by the core deformation caused by the injection pressure. [ABSTRACT FROM AUTHOR]

Vacuum casting of polyurethane (PUR) in silicone molds is used industrially for the production of prototypes and small series as well as in various noncommercial research areas. This includes the reproduction of archeological findings, biological samples or electronic devices. In this study, the authors investigate the molding accuracy of different commercial silicones and PUR casting resins both on microscopic and macroscopic scales. For this, they used a variety of master models to generate silicone rubber casting molds. The resulting PUR castings are investigated by helium ion microscopy, confocal laser scanning microscopy, and optical 3D‐scanning. [ABSTRACT FROM AUTHOR]

Vacuum casting is one of the widely used methods for small-volume production of plastic parts. The main challenge of this method is to choose the optimal working parameters to manufacture plastic parts with better mechanical properties. The conventional vacuum casting (CVC) technology uses gravity to make the casing material to fill the mold cavity, resulting in the yield of the molded components with high tensile strength is relatively low. Vacuum differential pressure casting (VDPC) can overcome this disadvantage since the filling mechanism of the casting material is different from CVC process. In this study, integration of design of experiments approach and the VDPC technique was employed to enhance tensile strength of molded components. It was found that the most important control factor affecting the tensile strength of the fabricated component is the mold cavity temperature, followed by the material mixing time, the differential pressure time, and the mixing chamber inlet valve angle. The optimal process parameters for producing components with better tensile strength are the mold cavity temperature of 35 °C, the material mixing time of 40 s, the differential pressure time of 8 s, and the mixing chamber inlet valve angle of 60 °. [ABSTRACT FROM AUTHOR]

Vacuum casting of polyurethane in silicone molds is a widely used method for prototype replication and holds great potential for application in small batch production. Products produced in this way offer extremely good shape accuracy even in the nanometer range and high surface quality, as well as flexible material properties that are convenient for serial production. In this work, we present a new method for increasing the feasible output of silicone casting molds in vacuum casting processes. By supplementation of polyamide 12 powder, which is a waste product of the selective laser sintering process, to the silicone rubber the maximum output of the casting molds could be increased by up to 38.5% while the amount of new silicone used has been substituted by up to 20%. Both generic silicone samples and representative silicone molds have shown that with increasing polyamide content, aging characteristics decrease as the output increases. The improvement was quantified by comparative weight, hardness and thermogravimetric measurements. As surface energy and roughness measurements as well as extensive casting experiments have shown, the silicone surface and thus the product surface remains unimpaired. [ABSTRACT FROM AUTHOR]

Vacuum casting (VC) is the most economical production process for producing small numbers of prototype parts under vacuum conditions. The filling of the casting material in the conventional VC process only depends on the gravity. Thus, some defects of the cast part are observed. In this study, differential pressure (DP) VC was proposed to reduce the filling time and improve the quality of cast parts. In this study, the filling mechanisms in both horizontal and vertical directions were investigated theoretically and experimentally. The actual filling situations of the acrylonitrile butadiene styrene resin in both the horizontal and vertical directions are similar to the simulation results. The relationship of the filling time for DP time, sprue diameters, and mold cavity capacities was investigated. The filling time can be estimated in terms of DP time, sprue diameter, and mold cavity capacity. [ABSTRACT FROM AUTHOR]

Vacuum casting is a widely employed method for small batch production of plastic prototype parts by the use of silicone rubber mold. However, some undesired defects of the cast part such as micro-bubbles, voids, weld lines, shrink mark, sink marks, warpage, blister, or short shot are observed in the conventional vacuum casting process. Vacuum differential pressure casting (VDPC) can overcome these drawbacks because of the filling mechanism of the casting material is different from conventional vacuum casting process. In this study, the VDPC was proposed to enhance the quality of casting parts. The process parameters related to the VDPC are investigated theoretically. Fabrication of components with microstructures using VDPC was investigated experimentally. It was found that the quality of VC parts with microstructures can be improved significantly using the VDPC. The transcription rate of the depth of the Fresnel lens can be increased from 41.9 to 99%. [ABSTRACT FROM AUTHOR]

We present an in-depth investigation of the aging effects in silicone molds for vacuum casting processes. Their lifetime is limited to a few production cycles due to contamination with the diisocyanate component of polyurethane casting materials. Using thermogravimetric analysis measurements, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and helium-ion-microscopy the chemical and physical mechanisms of the aging process have been identified. It has been shown that a diffusion process of diisocyanate into the cavity surface leads to the formation of interpenetrating polymer networks of polyurea derivatives in silicone rubber. This has been proven by extracting and analyzing polyurea of low molecular weights from the silicone. [ABSTRACT FROM AUTHOR]

Highlights • Magnesium foam provides better physical properties. • The optimum parameter combination of casting process has been found. • Particle size can provide higher significant nature on nature of metallic foam. Abstract In the present study, an endeavour has been made to investigate the mechanical properties of hollow glass microspheres reinforced die cast magnesium alloy under vacuum die casting process. The particle size, mass fraction, stirring speed has been considered as input process parameters to analyze the mechanical properties such as hardness, compressive strength, porosity and density of the syntactic foams. Taguchi-Grey relational based multi response optimization has been utilized to compute the optimal process parameters and find the influence of those parameters on performance measures of casting process. From the experimental investigation, the optimal process parameters have been found as particle size (45 microns), mass fraction (20%) and stirring speed (600 rpm) among the chosen process parameters. The highest max–min indicates the particle size has higher influence on determining the mechanical properties of the syntactic foam owing to its importance on determining the porosity. It has been also observed that the density of syntactic foam decreases with increases in the mass percentage of hollow glass microspheres. [ABSTRACT FROM AUTHOR]

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In conditions of dynamic market environment there is an increasing requirement for rapid development and production of complex and functional parts from different materials. In this paper, we present the process of development and production of small batches of functional parts in the integrated system of additive and vacuum casting technology. All advantages of this integrated approach were used during the research. Data obtained from the manufacturer were used for the proper selection of materials and they relate to the value of mechanical characteristics. [ABSTRACT FROM AUTHOR]

Copyright of FME Transactions is the property of University of Belgrade, Faculty of Mechanical Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Warpage is the most common quality defect in parts produced by vacuum casting (VC). In this paper, the VC process and mold filling mechanism are analyzed, and a mathematical model of the filling process is constructed, incorporating fluid dynamical relationships. The filling process is simulated using a numerical simulation algorithm. A warpage optimization strategy combining response surface methodology (RSM) with the artificial fish-swarm algorithm (AFSA) is then proposed, in which the main function of the RSM is to fit the relationship between process parameters and warpage, while that of the ASFA is to obtain the optimized process parameters. Finally, the implementation of the optimization strategy is presented in detail, together with a specific example, and simulations and a real experiment are carried out. The experimental results verify the accuracy of the model and the reliability of the algorithm. In conclusion, the optimization method can reduce the warpage of VC parts and improve product quality, providing a reliable new low-cost method for optimizing the process parameters in VC technology. [ABSTRACT FROM AUTHOR]

Numerous facts have validated that sharkskin possesses the obvious drag reduction effect in certain turbulent flowing stations, and it has huge potential and important applications in the fields of agriculture, aerospace, industry, transportation, daily life and so on, which have attracted increased attention throughout the world. To meet the increasing requirements of practical applications, it has been progressively developing into an urgent problem to manufacture sharkskin surfaces with perfect forming quality and high drag-reducing effect. In this paper, the vacuum casting method is put forward to fabricate the drag-reducing surface with the real sharkskin morphology by eliminating the air bubbles from the bottom of sophisticated morphology in the pouring process. Meanwhile, a novel and facile 'marking key point' method is explored and adopted to search for the corresponding biological sharkskin and negative template, a more convincing way to evaluate the replicating precision is systematically illustrated and the hydrodynamic experiment is carried out in the water tunnel. The results indicate that wall resistance over sharkskin surface replicated by the vacuum casting method can be decreased by about 12.5% compared with the smooth skin. In addition, the drag reduction mechanism hypotheses of sharkskin are generalized from different respects. This paper will improve the comprehension of the sharkskin fabrication method and expand biomimetic sharkskin technology into more applications in the fluid engineering. [ABSTRACT FROM AUTHOR]

The performed examinations concerning the process of filling the plaster ceramic moulds with aluminium alloys allowed to assess the influence of various methods of introducing the metal into the mould cavity on the macro- and microstructure of the obtained experimental castings. The comparison was performed for castings with graded wall thickness made either of EN AC-44000 alloy or of EN AC-46000 alloy, produced either by gravity casting, or by gravity casting with negative pressure generated around the mould (according to the Vacumetal technology), or by counter-gravity casting. It was found that the silicon crystals grow in size with an increase in wall thickness due to the slower cooling and solidification of castings [ABSTRACT FROM AUTHOR]

The work deals with the influence of change in the filling conditions of the ceramic moulds with plaster binder on the presence of gaseous porosity and the microstructure of the achieved test castings with graded wall thickness. Castings made of EN AC-44000 alloy, produced either by gravity casting, or by gravity casting with negative pressure generated around the mould (according to the Vacumetal technology), or by counter-gravity casting were compared. The results of examinations concerning the density of the produced castings indicate that no significant change in porosity was found. The increased size of silicon crystals was found for the increased wall thicknesses due to the slower cooling and solidification of castings. [ABSTRACT FROM AUTHOR]

the present paper presents the result of the theoretical and experimental research work of the author, in the framework of doctoral studies in the field of industrial engineering, with an emphasis on complex part manufacturing, using the new available manufacturing technologies also known as Rapid Prototyping and Rapid Tooling. This new group of technologies appeared worldwide in the early 1990. In 1995, it was the Technical University of Cluj-Napoca which founded in Romania first National Center of Rapid Prototyping. This is the place, where the author has acquired and improved the theoretical knowledge which was then put in to practice a series of research activities as the presented in the present paper. The paper present one of the Rapid Tooling technique, used for the manufacture a representative complex part, by vacuum casting process, carried out in two stages: one for forming of silicone rubber mould and the second for casting the part in the silicone rubber mould that has been obtained in the first stage. [ABSTRACT FROM AUTHOR]

This study presents a cost-effective approach for rapid fabricating modeling platforms utilized in fused deposition modeling three-dimensional printing system. A small-batch production of modeling platforms about 20 pieces can be obtained economically through silicone rubber mold using vacuum casting without applying the plastic injection molding. The air venting systems is crucial for fabricating modeling platform using vacuum casting. Modeling platforms fabricated can be used for building rapid prototyping model after sandblasting. This study offers industrial value because it has both time-effectiveness and cost-effectiveness. [ABSTRACT FROM AUTHOR]

Silicone rubber molding is a perfect solution to fill the gap between rapid prototyping and prototyping injection molding. Silicone molds reproduce the tiniest of details, so the quality of the pattern is critical; they are also a fast and affordable solution for functional prototypes and low volume production. The purpose of this work is to determine by experimental method the viscosity of SG95 polyurethane resin and the volume of the air bubbles in a resin parts casted in flexible molds. [ABSTRACT FROM AUTHOR]

To manufacture metal parts with complex shapes through Investment Casting (IC) process using wax models, it is necessary to have a complete control over the entire process. A very important aspect is to know the shrinkage value of the wax models. If the master model has a very small scratch or imperfection, this will appear also on the metal part surface. The structure and the mechanical properties of the metal part can be influenced by material porosity which can appear during the casting process. A given set of parameters such as preheating temperature, casting temperature, turbo pressure applied to finish the casting and also the wall thickness contributes to obtain a good surface quality and to material density which influences the part functionality. The objective of this research is to understand the utility of Vacuum Casting (VC) technology comparing with other casting technologies regarding the part surfaces quality. [ABSTRACT FROM AUTHOR]

This study evaluated the vertical discrepancy of implant-fixed 3-unit structures. Frameworks were constructed with laser-sintered Co-Cr, and vacuum-cast Co-Cr, Ni-Cr-Ti, and Pd-Au. Samples of each alloy group were randomly luted in standard fashion using resin-modified glass-ionomer, self-adhesive, and acrylic/urethane-based cements ( n = 12 each). Discrepancies were SEM analyzed. Three-way ANOVA and Student-Newman-Keuls tests were run ( P < 0.05). Laser-sintered structures achieved the best fit per cement tested. Within each alloy group, resin-modified glass-ionomer and acrylic/urethane-based cements produced comparably lower discrepancies than the self-adhesive agent. The abutment position did not yield significant differences. All misfit values could be considered clinically acceptable. [ABSTRACT FROM AUTHOR]

The need to develop products with special characteristics and high mechanical properties led to the introduction of plastic deformation of semifinished materials. Special purpose products are produced from slabs, blooms, billets or from different size ingots. One of the critical conditions to meet quality expectations after plastic deformation is that the material must be as high quality as possible. For refining steels, a range of methods have been developed that can remove harmful elements from the physical and mechanical product properties. For these products, the chosen casting method is one of the most important factors that can ensure product quality because casting can easily remove the beneficial effects of the refining process conducted during the development of the steel melt by contamination with refractory material from the casting assembly, re-oxidation of the metal bath and others. Depending on the complexity of the casting product and to obtain a superior quality product, several methods of casting have been developed. The usual method of casting high quality large ingots is in vacuum, the advantage is that the steel stream is protected from the surrounding atmosphere, this paper aims to highlight the benefits of vacuum casting with wide stream on the improvement of ingot quality by increasing purity and decreasing gas content. [ABSTRACT FROM AUTHOR]

The paper presents the needs and importance to develop new software tools, in order to guide the engineers and assist them for a quick design of the gating system and to estimate the required quantities of materials, within the investment casting process. The existing software packages are discussed and new dedicated software called P-Cast was developed, in order to bring new important features, which are useful to sort out some tasks in rapid metal casting. Some important parameters which are automated calculated by the P-Cast software are: dimensions of the master model and wax parts, envelope size and materials quantities for SRP, was, plaster and metal, solidification time, etc. All these are depending onto the respective part, which is going to be made by vacuum casting. The structure of the new P-Cast software tool is presented and a case study application is presented, illustrated and discussed. [ABSTRACT FROM AUTHOR]

Some of the advantages inherent in the vacuum casting technique such as improved mechanical properties and elimination of shrinkage have been replicated in a low-cost design. Melting and vacuum requirements of the equipment were determined based on a furnace capacity of 15 kg of aluminium. Clay-based refractory and insulating bricks were used for furnace construction. The vacuum system was made from locally available materials and designed for efficiency required for vacuum casting. The equipment was used to melt and cast small-sized specimens using the lost-wax technique and compared with green sand and ceramic mould cast specimens. Tensile and shrinkage tests were carried out on all specimens. The results of the tensile tests were 123, 98 and 113 MPa for the vacuum cast, green sand cast and ceramic mould cast specimens, respectively. Furthermore, shrinkage defect which is common to both green sand and ceramic mould casting was eliminated in vacuum casting. The vacuum casting equipment cost an equivalent of about U.S $1000.00 (One thousand dollars) to construct and can be easily scaled-up for large-sized castings by increasing furnace capacity and the size of the moulding flask. [ABSTRACT FROM AUTHOR]

Hybrid moulds with mouldings blocks made with epoxy composites are being used in injection mouldings of precision parts. In the last decade developments were made in view of applying these production series of thermoplastics injection mouldings. This paper reviews some of the outcomes of research activity on specific issues of manufacturing and utilisation of these tools. Most of the results refer to moulding blocks produced in epoxy composites that were manufactured using the vacuum casting technique. Some references are also made to rapid tooling techniques based on laser sintering. [ABSTRACT FROM AUTHOR]

A rapid fabrication process was developed by combining stereolithography prototype, silicone rubber mould and vacuum casting process for zinc alloy moulds. Transfer coating mould was introduced as casting moulds reproduced from silicone rubber moulds. Vacuum casting process was applied to improve filling ability of complicated mould with fine pattern surface. Vacuum reduces the gas counterpressure in the casting mould cavity and then improves the filling ability. [ABSTRACT FROM AUTHOR]

Micromoulds are generally produced by lithography methods that often use glass and silicon wafer as substrates, with the exception of the Lithographie Galvanoformung Abformung (LIGA) method, which uses metal substrate. These fabricated moulds are then integrated into the injection moulding machine for mass production. This paper presents the use of vacuum casting methods to produce micromoulds instead of lithography. Silicone rubber is used as the mould material, which is capable of achieving nanometre surface finish. The master pattern of 1-mm diameter microgear of 60-μm teeth width and 38-μm thickness was created by standard ultraviolet (UV) lithography using SU8 photoresist. Using the vacuum casting method, ten polyurethane microgear specimens of 1-mm diameter and 38-μm thickness using the silicone rubber micromoulds have been successfully cast under vacuum conditions as a demonstration. Measurement from white-light interferometry (WLI) showed that all of the microgear cavities in the micromoulds were dimensionally accurate and consistent to the master microgear, proving that its repeatability is possible. [ABSTRACT FROM AUTHOR]

Utilisation of functional prototypes during the upstream design stage is able to shorten the product development cycle of a medical device and quicken the transfer process to mass manufacturing. Innovative synergy of conventional manufacturing techniques and rapid prototyping techniques is thus needed to fabricate functional prototypes successfully. This case study reports on the development of an automatically activated safety needle using different prototyping approaches for the fabrication of functional prototypes. The approaches include rapid prototyping, computer numerical control (CNC) machining and vacuum casting. The challenges of each technique are discussed and solutions are presented. A hybrid technique involving CNC machining and vacuum casting is adopted to fabricate the prototypes. This hybrid prototyping approach was able to expand the choices for materials to fabricate the prototypes and thus enabling the validation of the design mechanism in a shorter time. [ABSTRACT FROM AUTHOR]

The elastic modulus and density of (2024+LiX) alloys are investigated. To the alloy of 2024, the weight percentages of lithium added are 2,3, and 4. Melting is carried out in an induction furnace under argon gas protection; casting is done under vacuum. To obtain the maximum strength and hardness, the specimens are solution heat treated under 495 C and quenched in water at room temperature. Then, they are aged naturally and artificially. For the purposes of comparing, some of the specimens are melted under argon gas, but casting is done without vacuum. All the specimens are subjected to tension tests. As a result of this work, the alloys of aluminum that are difficult to manufacture by the known methods are manufactured safely by the vacuum casting method. For 1% of lithium added to the alloy, an increase of 6% in the elastic modulus and 3% decrease in the density are obtained. The specific elastic modulus, E/ρ, ratio increases by about 10% for each 1% addition of lithium. [ABSTRACT FROM AUTHOR]

Connectors are developed to satisfy the needs of advanced technology in telecommunication switching systems and companies have several products designed to fulfil the needs of the many switching networks available. The “Four-wall-header” is one such product from one company. The traditional manufacturing line relies heavily on hard tooling which is both expensive and time-consuming. This paper presents an alternative method of integrating rapid prototyping technologies, in particular, stereolithography apparatus (SLA), with a vacuum casting system to produce a wide range of polyurethane parts. Altogether, three approaches are analysed and evaluated for making the moulds: rapid pattern, rapid tooling and a hybrid approach. [ABSTRACT FROM AUTHOR]

Porous materials are widely employed in a wide variety of industrial applications due to their advanced functional performance. Porous aluminum is among the most attractive metallic materials. It can be produced using repeatable methods involving a replicated Al foam that also provides porosity control. In this work, a highly porous replicated Al foam was fabricated. First, the model of multifunctional packing density was used and corrected to select the appropriate space holders. Then, Al foam was produced using a double-granular sodium chloride space holder. The obtained results showed a maximum porosity of 65% that was achieved using a mix of coarse, irregular granules with spherical granules of intermediate size. [ABSTRACT FROM AUTHOR]

Sample preparation is an important step when testing the mechanical properties of materials. Especially, when carbon nanotubes (CNT) are added to epoxy resin, the increase in viscosity complicates the casting of testing specimens. We present a vacuum casting approach for different geometries in order to produce specimens from functional nanocomposites that consist of epoxy matrix and oxidized multi-walled carbon nanotubes (MWCNTs). The nanocomposites were characterized with various mechanical tests that showed improved fracture toughness, bending and tensile properties performance by addition of oxidized MWCNTs. Strengthening mechanisms were analyzed by SEM images of fracture surfaces and in-situ imaging by digital image correlation (DIC). [ABSTRACT FROM AUTHOR]