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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]

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]

Shortening the time-to-market is an important issue in the manufacturing industry. Indirect tooling technology was regarded as a promising approach of reducing time and cost to the market in a new product development phase. Silicone rubber mold was frequently employed in the indirect tooling. In this study, the service life of silicone rubber molds was investigated using both wax injection molding and vacuum casting. The experimental results revealed that the average roughness of the inner surface of silicone rubber mold were increased with increasing the number of test runs and saturated after 25 test runs. The degassing time needs to be increased with increasing the number of test runs in the vacuum casting process. The criteria for judging the service life of silicone rubber molds include surface quality of the parts fabricated, whitening regions in the inner wall surfaces of silicone rubber molds, and the overall elasticity of silicone rubber molds. [ABSTRACT FROM AUTHOR]

In the low cost application of vacuum casting in rapid prototyping, a mould cavity with high modulus is necessary for producing plastics parts in small quantity. In this work, a silicone matrix was reinforced with natural fibers to improve the modulus of composites to mould and to reduce the cost of silicone materials. Sisal fiber with different compositions was reinforced with silicone in a compression moulding process. Mechanical properties were studied. An increase in tensile strength, tear strength, and better hardness was observed in sisal fiber composites. The silane-treated fiber improved the adhesion between fiber and matrix and enhanced the mechanical properties of the composites. The swelling method was adopted to determine the crosslinking density of composites through the Flory-Rehner equation. The flexibility of silicone composites decreased for higher fiber loading and there was an increase in cross-linking of the fiber network to improve modulus of the composites. A morphological study was conducted using X-ray tomography and scanning electron microscopy (SEM) to predict the defects, orientation, debonding, fractography, and interfacial adhesion of fiber/matrix composites. [ABSTRACT FROM AUTHOR]

QAl9-4 aluminum bronze and 304 stainless steel composites were fabricated by vacuum smelting-casting at 1150 °C, in a vacuum of 4.0 × 10 −2 Pa. Microstructure and chemical composition were characterized by using transmission electron microscopy (TEM), X-ray diffraction (XRD), optical microscopy (OM) and scanning electron microscopy (SEM). Properties of interface were studied by shear tests and hardness measurement. Between the QAl9-4 aluminum bronze and 304 stainless steel, a transition zone that the width is about 133 μm and the maximum micro-hardness value is 467 HV was observed. It is much higher than that of QAl9-4 aluminum bronze and 304 stainless steel, the main reason is considered to the formation of the brittle intermetallic compounds such as AlCrFe 2 , Al 4 Cu 9 and AlNi 3 , but these intermetallic compounds are very easy to cause the interfacial fracture. The interfacial shape close to 304 stainless steel is flat, but to QAl9-4 aluminum bronze is zigzag. The shear strength of the composite is 278 MPa. Microstructure formation mechanism of interfacial layer can be mainly considered as Fe, Cr atoms of steel substrate are given a priority in molten copper liquid compared with impurity elements (Mn, Si), eventually forming a good metallurgical bonding state on both sides of the substrate through inter-diffusion of interfacial atoms. [ABSTRACT FROM AUTHOR]

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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]

This paper has described an indirect method of rapid tooling technique, using for made the mould to manufacturing a representative part with complex geometry shape, by injection. The different changes in the market requirements entail the necessity of a flexible and efficient manufacturing process. The flexible moulds are made of low - hardness materials, such as silicone rubber, epoxy resin, low - melting point alloys etc., using new techniques like Vacuum Casting and Metal Spraying. The metal spraying techniques is one of the most common procedures used in flexible tools manufacturing. The mould manufacturing by metal spraying was made in the laboratory of Innovative Technologies, at Technical University of Cluj-Napoca, as result of the theoretical and experimental research work of the author, in the framework of doctoral studies in the field of industrial engineering. [ABSTRACT FROM AUTHOR]

In this study, damping ratios of 3 samples made of aluminum foam material, which have different-density pores, were calculated, the effects pore density on damping were examined. Experimental modal analysis method was used for examining of the effects of the pore density on damping. In experimental modal analysis method, frequency charts were obtained by driving to the sample with a hammer. Through these frequency charts, damping ratios of each 3 samples were calculated with ME'scope VES program. It was observed in calculated damping ratios that pore density has influences on damping; thus, damping accordingly increases as the number of pores increases. It is seen that critical damping constant decreases as the material structure changes in terms of volume and density. [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]