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Abstract

Contribution gives an overview of knowledge about the method of centrifugal casting with orientate on Tekcast system. Company Tekcast Industries has developed a device for centrifugal casting, extending the area of production of castings or prototyping of metal or plastic. Materials suitable for the centrifugal casting with flexible operating parameters may include non-ferrous metal alloy based on zinc or aluminum or non-metallic materials such as polyester resins, polyurethane resins, epoxy resins, waxes and the like. The casting process is particularly suitable for a wide range of commercial castings and decorative objects.
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Abstract

This article presents measurements of the thickness of alcohol-based coatings on sand foundry cores and moulds. These coatings were applied using two methods, the dipping method and the painting method. For the purposes of the study, a zircon alcohol-based coating was prepared with three different levels of nominal viscosity; very thin at 10s, average at 20s, and thick at 30s. The coating was applied to a core made of quartz sand and furan resin. The cores were made of sand with three different grain sizes; dL = 0.22 mm – fine sand, dL = 0.33 mm medium sand, and dL = 0.47 mm coarse sand. In the study, the thickness of the coating obtained to the core was measured immediately after application as well as after drying. Additionally, the extent of penetration into the intergranular spaces of the core matrix was measured. On the basis of this study, the impact of the grain size of the core matrix on the thickness of the coating and its penetration into the core was assessed. The thickness of coatings obtained using different application methods was also assessed.
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Abstract

The techniques of micro and nano structurization of surfaces of various materials are utilized in electronics and medicine. Such procedure as wet and dry etching allows to fabricate protruded or recessed micro and nanostructures on the surface. In the paper some examples of utilization of a surface structurization, known from literature, are described. Some structurization methods and experimental results for fabrication of the arrays of sharp microtips are presented. Wet and/or dry etching, and thermal oxidation process were used to form the arrays of sharp gated and non-gated, protruded or recessed silicon microtips on silicon wafer. For the first time, the arrays of silicon carbide (SiC) microtips on glass wafer have been produced by use of the transfer mold technique. Arrays of sharp microtips are used as field electron emission cathodes for vacuum microelectronics devices. Some electron emission measurements for these cathodes have been carried out. New application of silicon microtips array in biochemistry has been tested with satisfactory results.
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Abstract

In sand casting, Fused Deposition Modeling (FDM) printing by using Poly Lactic Acid (PLA) filament is one of the innovative foundry technologies being adopted to substitute traditional pattern making. Several literatures have reported the influence of process parameters such as raster angle and print speed on some mechanical properties of FDM-printed, PLA-prototypes used in other applications. This study investigated the effects of interior fill, top solid layer, and layer height on the compressive strength of rapid patterns for sand casting application. Different values of the process parameters were used to print the pre-defined samples of the PLA-specimens and a compression test was performed on them. The coupled effects of the process parameters on compressive strength were investigated and the optimum values were determined. Interior fill of 36%, layer height of 0.21 mm and top solid layer of 4 were found to produce a FDM-printed, PLApattern that sustained a compaction pressure of 0.61 MPa. A simulation analysis with ANSYS® to compare failure modes of both experiment and model shows a similarity of buckling failure that occurred close to the base of each specimen.
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Abstract

The paper presents a detailed description of one of the newest methods of vacuum saturation of reinforcing preforms in gypsum molds. As an appropriate selection of the infiltration time is a crucial problem during realization of this process, aim of the analysis shown in the paper is to present methods of selection of subatmospheric pressure application time, a sequence of lowering and increasing pressure, as well as examining influence of structure of reinforcing preforms on efficiency of this process. To realize the aim, studies on infiltration of reinforcing preforms made of a corundum sinter of various granulation of sintered particles with a model alloy were conducted. The infiltration process analysis was carried out in two stages. The first stage consisted in investigation of influence of lengthening of sucking off air from the reinforcing preforms on efficiency of this process. In the second stage, an analysis of influence of a two-staged infiltration process on saturation of the studied materials was conducted. Because the studied preforms were of similar porosity, the obtained differences of the saturation level of particular preforms have shown, that the saturation process is influenced mostly by size of pores present in the reinforcement. Because of these differences, each reinforcement type requires individual selection of time and sequence of the saturation process. For reinforcements of higher pore diameter, it is sufficient to simply increase air sucking off time to improve the saturation, while for reinforcement of smaller pore diameter, it is a better solution to apply the two-staged process of sucking off air. Application of the proposed analysis method allows not only obtaining composite castings of higher quality, but also economical optimization of the whole process.
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Abstract

The method of determining the accuracy of polymer molds in plaster forms has been discussed. Distortion of the surface of molds and plaster molds has been assessed. It has been found that the presence of monolithic and porous structure in the samples does not change the accuracy of the surfaces when forms are prepared for removing the material of the model. It has been found that in case of full-mold casting it is more expedient to form the mold cavity with cellular adjustable structures of molding prototypes.
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Abstract

Some metallographic studies performed on the basis of the massive forging steel static ingot, on its cross-section, allowed to reveal the following morphological zones: a/ columnar grains (treated as the austenite single crystals), b/ columnar into equiaxed grains transformation, c/ equiaxed grains at the ingot axis. These zones are reproduced theoretically by the numerical simulation. The simulation was based on the calculation of both temperature field in the solidifying large steel ingot and thermal gradient field obtained for the same boundary conditions. The detailed analysis of the velocity of the liquidus isotherm movement shows that the zone of columnar grains begins to disappear at the first point of inflection and the equiaxed grains are formed exclusively at the second point of inflection of the analyzed curve. In the case of the continuously cast brass ingots three different morphologies are revealed: a/ columnar structure, b/ columnar and equiaxed structure with the CET, and c/ columnar structure with the single crystal formation at the ingot axis. Some forecasts of the temperature field are proposed for these three revealed morphologies. An analysis / forecast of the behavior of the operating point in the mold is delivered for the continuously cast ingot. A characteristic delay between some points of breakage of the temperature profile recorded at the operating point and analogous phenomena in the solidifying alloy is postulated.
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Abstract

The paper presents the use of rapid prototyping technology of three dimensional printing (3DP) to make a prototype shell casting mold. In the first step, for identification purposes, a mold was prepared to enable different alloys to be cast. All molds being cast were designed in a universal CAD environment and printed with the zp151 composite material (Calcium sulfate hemihydrate) with a zb63 binder (2- pyrrolidone). It is designated to be used to prepare colourful models presenting prototypes or casting models and molds. The usefulness of 3DP technology for use with copper alloys, aluminum and zinc was analyzed. The strength of the mold during casting was assumed as a characteristic comparative feature in the material resistance to high temperature, the quality of the resulting casting and its surface roughness. Casting tests were carried out in vacuum – pressure casting. The casting programs applied, significantly increased the quality of castings and enabled precise mold submergence. Significant improvement was noted in the quality compared to the same castings obtained by gravity casting.
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