Vacuum Casting Technology Research Articles

Comparison of the Torsional Strength of Material Samples Made Using Selected Rapid Prototyping Methods

In recent years, there has been a marked increase in the use of rapid prototyping techniques that support industrial processes. The analysis of studies on strength tests of parts manufactured using additive techniques from model materials and hybrid composites usually includes tests of material and strength parameters based on uniaxial tension, bending, and compression tests. For elements manufactured from polymeric materials using traditional methods (e.g. injection moulding), data obtained from these tests are sufficient to determine the strength of the material and to apply the results in the product design process. In the case of the layered extrusion method, due to the model construction process, strength data based on standard samples do not have a direct transposition on the strength of machine parts operating under various load ranges, especially torsional loads. The publication presents the results of tests on the torsional strength of cylindrical samples with splines produced by layered extrusion, vacuum casting technology, and hybrid technology, which combines both technologies. The test samples were made using a Prusa i3 MK3 3D printer and the plasticised plastic modelling (fused filament fabrication, FFF) method, while PolyJet technology was used to create a reference model. The findings indicate that hybrid technology, in which a thin-walled mould is filled with a chemically hardened polymer, achieves the desired strength for the manufactured parts while maintaining dimensional accuracy and shape. The research results show that producing rotating elements using the hybrid technology reduces the sample core’s ability to undergo plastic deformation due to the adhesion between the materials and the occurrence of notches resulting from the model production process using the layered extrusion method.

APPLICATION OF VACUUM SUCTION CASTING OF IRON-CARBON ALLOYS FOR THE PRODUCTION OF ENGINE PARTS

The use of vacuum suction casting technology for iron-carbon alloys for the production of internal combustion engine parts will improve their quality and wear resistance, preserve metal, and reduce emissions. The technology is widely used for non-ferrous alloys. At the same time, its implementation for iron-carbon alloys (including cast iron) in modern engine construction requires careful scientific and practical preparation. Problematic tasks arise when improving the pneumatic system of vacuum suction (large volumes of gas release), the stability of the metal pipeline (thermal overload in a high-temperature cast iron melt), and the stabilization of the casting microstructure (high-speed crystallization). The authors suggest using a specialized titanium alloy VT3-1 for the metal pipeline, for which the article calculates thermal loads during cyclic operation in the “Deep – take-out” mode for the use of cast irons of the SCH25 and VCH50-1.5 grades. For reliable operation of the metal pipeline and the absence of solidification of the melt on its inner surface, a thermal calculation method was develop, which allows determining the time of heat removal of overheating of the melt according to the diameter of the metal pipeline. The pneumatic system of the vacuum unit is supplement with a patented gas jet ejector, which, in combination with a powerful shop compressed air system, provides a full gas outlet. Applying the developed law of change in the discharge between atmospheric pressure and pressure in the mold cavity, the authors of the article regulate the rate of crystallization of castings, which makes it possible to form much smaller phases of perlite in the microstructure and reduce the presence of Ferrite. At the Enterprise "Pervomaiskdizelmash" using vacuum casting technology, blanks of guide bushings of engine valves 6CHN25/34 made of cast iron SCH25 and VCH50-1,5, as well as oils of piston rings made of cast iron VCH50-1,5 were obtained. The obtained parts showed an increased service life by 15-30%. Vacuum casting technology is recommend for iron-carbon alloys in the production of engine parts.

Casting technology with the formation of a uniform fine-grained metal structure

The paper is devoted to the development of vacuum casting technology, which ensures the formation of a casting with a uniform fine-grained metal structure. This effect is achieved by the slow filling of the cooled cavity of the mold with a cooling liquid due to the difference in the flow rate of the liquid at the inlet and outlet. At each moment of time, the cooling of metal is carried out in a thin layer of the casting, which ensures the uniformity and fine-grained structure of the casting material, the absence of shrinkage and internal stresses.

Verification of the Thermal Expansion Effect of Silicone Molds Intended for Production of the Prototype Components Using Vacuum Casting Technology

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.

Application of the vacuum casting technology in the production of small-size gas turbine engine blade machines

The application of casting technologies in the production of parts and assemblies of small-size gas turbine engines is justified in the paper. The technology of vacuum casting in gypsum molds was tested during the production of an experimental centrifugal compressor of a small-size gas turbine engine. On the basis of a 3D model of the designed centrifugal compressor, computational studies of vacuum casting were carried out and rational parameters of the technological process were determined. Prototypes of the developed centrifugal compressor of a small-size gas turbine engine were made. The results of calculations and the performed technological experiment confirmed the fill rate of the gating form and the absence of short pour. The distribution of shrinkage porosity and cavities corresponds to the design values and is concentrated in the central part of the casting that is subjected to subsequent machining. The area of the blades, disc and sleeve is formed without defects. The use of casting technologies in the production of parts and assemblies of small-size gas turbine engines assures the required quality with a comparatively low price of the finished product, making it possible to achieve the balance between the cost of the technology and the quality of the product made according to this technology.

Zastosowanie metody vacuum casting do wytwarzania prototypow badawczych polimerowych kol zebatych

Zastosowanie metody vacuum casting do wytwarzania prototypow badawczych polimerowych kol zebatych

Kompozyty handlowych nienasyconych zywic poliestrowych z dodatkiem nanonapelniaczy Nanobent. Cz. II. Nanokompozyty z udzialem krajowych nanonapelniaczy stosowane w technologii Vacuum Casting

The possibility of application of nanocomposites based on unsaturated polyester resin matrix (Polimal® 103 and Polimal® 109) and nanofillers Nanobent® (ZR1 and ZR2) in Vacuum Casting technology (VC) was investigated. The reactivity of the molding compositions (gel time and maximum curing temperature) as well as their thixotropic properties, which have an important impact on the technology process of prototyping gears in silicone matrices, were assessed. Using the optical measuring system ATOS II Triple Scan Blue Light (GOM) the dependence of geometric dimension accuracy of the gear wheel models on the type of nanofiller and its content in the composite was determined.

Using Simulation to Improve the Quality of the Metallic Industrial Components Made by Rapid Casting

Industrial parts with complex shapes are characterized by thin sections and complex geometries. Rapid vacuum casting is an ideal technology to manufacture complicated parts in small series production or prototypes. Contributions regarding simulation and analyzing of the parts made by rapid vacuum casting technology are presented in this study. Using dedicated software for simulating the casting process was analyzed and optimized the time of casting, the complete filling with material and also reducing the surface defects.

Study of the filling mechanism and parameter optimization method for vacuum casting

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.

The microstructure and mechanical properties of micro-scale Y2O3 strengthened 9Cr steel fabricated by vacuum casting

Casting process is not a common method in producing oxide dispersion strengthened (ODS) alloys due to its difficulty in distributing the oxides in matrix, especially for nano-scale oxide particles. In this paper, 9Cr steel strengthened by micro-scale 0.4 wt% Y2O3 was fabricated through vacuum casting technology containing electromagnetic stirring. Microstructural observation and energy dispersive spectrometry (EDS) analysis of the particles from tensile fracture dimples and extraction by dissolving metal elements, demonstrated that complicated oxides, several microns in diameter, containing elemental Y and O formed and evenly distributed in the steel matrix. The tensile strength was also improved after Y2O3 addition for the steels in both forged and heat treated states, the alloy matrix strengthened was due to the complicated oxides with Y element played a role as obstacles to dislocation gliding. The research confirmed that micro-scale Y2O3 was effectively added to the steel matrix during casting, which provided an alternative method for ODS alloy fabrication.

Hybrid composites with epoxy resin matrix manufactured with vacuum casting technology

The paper presents the methodology of the process of manufacturing of technical profile models on the example gear wheels made of epoxy composites cast in silicone molds using vacuum casting technology. Research on preparation of epoxy resin composites filled with hybrid modifiers has been carried out. Mechanical and processing properties of composites have been evaluated, particularly in terms of application in rapid prototyping of gear wheels. Considerable improvement of tensile strength (up to 44 %) and unnotched impact strength (up to 93 %) has been observed. Geometric accuracy of gear wheels prepared by casting of the analyzed hybrid composites has been determined using a coordinate measuring machine. Morphology of the brittle fracture of studied composites has been observed on brittle fractures using a scanning electron microscope (SEM).

Effect of magnetic field on growth of intermetallic compound layers in Fe-Fe50wt.%Si diffusion couple

In this paper, Fe-Fe50 wt.%Si diffusion couples are subjected to 1200℃ heat treatment in static magnetic field. Fe-Fe50 wt.% Si diffusion couples were prepared by vacuum casting technology and later sectioned and polished for scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) studies before heat treated. Microstructures of the treated samples which were polished first were analyzed by SEM and EDS; results show that the phase components of the interfacial intermetallic compound layers are FeSi phase layer and Fe-Si solid solution layer whether the samples were treated with or without magnetic field, and the layer widths in the samples treated with magnetic field are smaller than those without magnetic field. According to the parabolic law, the interdiffusion coefficients of the interfacial intermetallic compound layers were calculated and the interdiffusion coefficients of FeSi phase and Fe-Si solution under a field of 0.8 T are reduced by 26.7% and 34.1%. The Gibbs energy due to applied field was calculated, data analysis shows that the reduction of interfacial intermetallic compound layer coefficients is attributed to the decrease of frequency factor, not the activation energy. Decrease in layer thickness decrease is suggested to be related to the retardation of atomic diffusion resulting from the magnetic field, and a possible theory based on Larmor precession is given to explain this effect.

Micro-spike EEG electrode and the vacuum-casting technology for mass production

An innovative dry electroencephalography (EEG) electrode has been successfully designed and tested, in which multiple micro-spike electrodes, each of them consisting of a micro-pillar with a micro-tip on top of it, were designed to pass through the hairs and establish electrical conduction at the skin-electrode interface by penetrate into the stratum corneum of the skin. For hygiene reasons, such electrodes should be made disposable, at the same time, should be cost effective. Therefore, a mass production technology, including the processing methods, such as casting, has to be designed and developed. In this project, the micro-spike dry electrodes were fabricated by a vacuum casting method using a master pattern piece made by CNC micro-machining, in which silicone rubber moulds are created and then used to vacuum cast polyurethane (PU), epoxy or epoxy-carbon micro-spike electrodes. In order to obtain a harder polymeric material, varying amount of carbon fillers were added to the epoxy resin, and the hardness of the resulting material were measured and compared. It was found that a higher concentration of added carbon fillers resulted in a harder cast polymer composite. Further to the vacuum casting, to create an electrically conductive layer on the vacuum-casted electrode, an Ag/AgCl electroless deposition method has been developed. The sputtering of the conductive layer was also carried out for comparison. The developed micro-spike electrodes showed better performance in terms of the impedance level and stability as well as a much higher efficiency in EEG measurement.

Composites of unsaturated polyester resins applied in vacuum casting technology

The paper deals with hydrophobization of bentonites (layered aluminosilicates) with quaternary ammonium salts (QAS) and potential application of the products obtained as fillers for preaccelerated unsaturated polyester resins (UPs) to be applied in vacuum casting. Natural purified bentonites of "Special" and "SN" type, enriched with montmorillonite and modified with QAS according to the earlier patented method were used. An addition of modified bentonites (1.5 or 3.0phr) to commercial preaccelerated UPs, caused a considerable improvement in mechanical properties (tensile strength, Brinell hardness and Charpy impact strength). Also, a clear effect of nanofiller concentration in resin on the quality of cast products was observed.

Micro-mould fabrication for a micro-gear via vacuum casting

A micro-mould fabrication method based on vacuum casting was developed and its functionality and reproducibility were demonstrated. The micro-components used in this study were SU-8 photoresist micro-gears fabricated by UV photolithography. These micro-gears served as the master patterns from which silicone rubber micro-mould cavities were fabricated with the use of the vacuum casting technology. The process parameters that had an influence on the quality of the micro-mould cavities were identified and optimised. Using the optimised process parameters resulted in high fidelity silicone rubber micro-mould cavities at high resolutions. Dimensional analysis was carried out using white light interferometry. It was found that all the micro-gear cavities in the micro-moulds were dimensionally accurate and consistent to the master gear, with a dimension deviation less than 3% of the respective dimensions. Micro-casting was also carried out using the silicone rubber moulds. Micro-gears were successfully transferred from the silicone rubber moulds into PU resin and wax pieces under vacuum conditions, thereby demonstrating that the micro-mould fabricated was capable of producing functional micro-parts that were able to replicate micro-features.

Effect of hot rolling on superplasticity of a SiC/6061 aluminum alloy composite made by a vortex method

The chapter deals with vacuum casting, a process that refers to the casting and solidification of alloys within low pressure atmospheres which are often purged with inert gas. Pressures set at 0.1 Pa and below are commonly used with vacuum casting technology. This technology is employed where high cleanliness and purity are required during liquid metal processing. Vacuum casting helps to avoid contamination from reaction of the liquid metal with either the environment gases or crucible and mold container materials. In addition, recent advances in the high pressure die casting process, a process where a hydraulically powered plunger injects liquid metal alloys at high speed into a reusable steel mold are described for die castings produced from aluminum alloys, magnesium alloys, and zinc alloys. A review follows of the fabrication of composites by casting techniques, a promising route for manufacturing near net shape parts at relatively low cost and looks at several liquid fabrication techniques available to manufacture composite materials, classified according to the type of reinforcement. Fabrication techniques can vary considerably and include stir casting, liquid metal infiltration, squeeze casting, spray co-deposition, and compocasting. The chapter concludes with a review of both single roller and twin roller roll casting, processes that can cast strip directly from the melt in a one step, promising savings in effort and energy.

Industrial casting of superalloys

The current status of precision vacuum casting technology is reviewed in outline and the historical background of the subject is briefly covered. Particular reference is made to its application to the manufacture in nickel-base superalloys of aerofoil and associated components for gas turbine engines, and possible directions for further development of the process and ancillary technology are examined. The current state of progress in both alloy technology and casting process development is reviewed. In connection with the latter, both the scope of currently available product geometries, from small solid equiaxed components through complex hollow shapes to integrally cast multi-aerofoil components, and the extension of the technology to include large, integrally cast, near-net-shape structural components, are discussed. Specific brief reference is made to the main contributory changes and developments which have taken place in each sector of the process from pattern technology to post-casting processing. The more recently adopted and now increasing utilization of multi- and monocrystalline directionally solidified aerofoils in gas turbine engines is addressed with reference to its impact on alloy chemistry and to the conflicting opinions on the relative merits of the diverse process technology. Also addressed are the increasingly important favourable effects on product quality and casting design flexibility of post-casting coating processes, thermal and thermomechanical treatments, advances in non-destructive testing, and the steady trend of progressively improving product quality assurance technology. Finally, consideration is given to the degree to which the casting of superalloys has reached maturity, and what, if any, prospective further improvements may be developed from which gas turbine engines could derive benefits in performance, weight, or operating efficiency in the future.MST/243

Industrial casting of superalloys

The current status of precision vacuum casting technology is reviewed in outline and the historical background of the subject is briefly covered. Particular reference is made to its application to the manufacture in nickel-base superalloys of aerofoil and associated components for gas turbine engines, and possible directions for further development of the process and ancillary technology are examined. The current state of progress in both alloy technology and casting process development is reviewed. In connection with the latter, both the scope of currently available product geometries, from small solid equiaxed components through complex hollow shapes to integrally cast multi-aerofoil components, and the extension of the technology to include large, integrally cast, near-net-shape structural components, are discussed. Specific brief reference is made to the main contributory changes and developments which have taken place in each sector of the process from pattern technology to post-casting processing. The more recently adopted and now increasing utilization of multi- and monocrystalline directionally solidified aerofoils in gas turbine engines is addressed with reference to its impact on alloy chemistry and to the conflicting opinions on the relative merits of the diverse process technology. Also addressed are the increasingly important favourable effects on product quality and casting design flexibility of post-casting coating processes, thermal and thermomechanical treatments, advances in non-destructive testing, and the steady trend of progressively improving product quality assurance technology. Finally, consideration is given to the degree to which the casting of superalloys has reached maturity, and what, if any, prospective further improvements may be developed from which gas turbine engines could derive benefits in performance, weight, or operating efficiency in the future.MST/243