Prototype Castings Research Articles

The Concept of Using 3D Printing Technology in Ceramic Foundry Filter Manufacturing

AbstractThe article presents the concept of using 3D printing technology in ceramic foundry filter manufacturing. They are a crucial component for obtaining an acceptable quality of nickel superalloys by carrying out the process using the precision casting method. Commonly used filters of this type have a number of disadvantages. They are characterized by irregularity of the filtering structure, high brittleness, lack of resistance to mechanical shocks, and impacts of a stream of liquid metal. All these factors create a risk of introducing the material from the damaged filter into the casting mold, which translates into contamination of the casting alloy, and thus the occurrence of casting defects such as nonmetallic inclusions. The hope for a change in this state of affairs is the use of additive manufacturing technology in their production, which by assumption will allow to obtain a product with a repeatable shape, high mechanical resistance, and a specially designed structure regulating the flow of liquid metal into the mold during casting. The suitability of robocasting and binder jetting technology for producing filtration structures was initially assessed. The results have presented the selection of ceramic powder, as well as the development of the composition of the ceramic paste. The parameters of paste preparation and 3D printing individual processes were described. Moreover, the representative microstructures and basic mechanical properties of samples obtained by both of the compared technologies were presented. Furthermore, the final effect of prototype casting filters with a repeatable shape, manufactured with the use of both technologies, was presented, which were transferred for further technological research in a foundry producing critical aircraft engine parts. The possibilities of using each technology in various applications were also discussed.

INVESTIGATION OF MECHANICAL PROPERTIES OF SAND CASTING MOLDS PRODUCED BY BINDER JETTING 3D PRINTER

The use of the additive manufacturing method in the casting industry is increasing day by day. The production of reverse angled and complex shaped casting parts, which cannot be produced with the classical modeling technique, can also be produced very easily with this method. On the other hand, it is very fast, especially in terms of rapid production of prototype castings, which can be directly molded without the need for model production. In this study, a 3D Printer with binder jet was designed and produced firstly. 3D Printer; It consists of 3 parts, the main chassis, the sand spreader and the spraying part. In this printer, which was produced afterwards, sand molds were produced with different nozzle advance speeds, different catalyst ratios and sand grain sizes. The consumables used in the production of sand molds are silica sand, furan resin and catalyst. The mechanical properties of the produced samples were determined by performing compression and gas permeability tests. Afterwards, it was determined which of the produced samples were more suitable for a sand casting mold by comparing the results obtained from similar studies in the literature. In this study, a new printer was designed with direct spray technique without using cartridges and preliminary studies were carried out successfully.

Towards the Prediction of Tensile Properties in Automotive Cast Parts Manufactured by LPDC with the A356.2 Alloy

Aluminum-silicon-magnesium alloys are commonly used in the automotive industry to produce structural components. Among usual quality controls of produced castings, microstructure characterization and determination of mechanical properties are the most critical aspects. However, important problems can be found when measuring mechanical properties in those areas of castings with geometrical limitations. In this investigation, a set of A356 alloys have been prepared and then used to manufacture test castings and automotive castings in a laboratory and in industrial conditions, respectively, using Low Pressure Die Casting (LPDC) technology. Test castings were used to predict secondary dendritic arm spacing (SDAS) by using thermal parameters obtained from experimental cooling curves. The results have been then compared to the ones found in the literature and improved methods for estimating SDAS from cooling curves have been developed. In a subsequent step, these methodologies have been checked with different industrial castings by using simulated cooling curves and experimentally measured SDAS values. Finally, the calculated SDAS values together with the Mg contents present in A356 alloys and the temperature and aging time data have been used to develop new models so as to predict the tensile properties in different areas of a given casting prototype. These developed models allow casters and designers predicting tensile properties in selected areas of a given prototype casting even during design and simulation steps and considering the processing variables expected in a given foundry plant. The structures of these new models have been described and experimentally validated using different processing conditions.

Single Crystal Casting with Fluidized Carbon Bed Cooling: A Process Innovation for Quality Improvement and Cost Reduction

Superalloy gas turbine blades are being produced by investment casting and directional solidification. A new process, Fluidized Carbon Bed Cooling (FCBC), has been developed and is now being optimized in a prototype casting unit with 10 kg pouring weight. In early test runs with still rather simple mold cluster geometries, a reduction of the primary dendrite arm spacing of around 40 pct compared to the standard radiation cooling process (HRS) could be demonstrated. The improvement is mainly attributed to higher temperature gradients driving solidification, made possible by a functioning Dynamic Baffle. Compared to earlier development efforts in the literature, contamination of the melt and damage to the equipment are avoided using carbon-based fluidized bed materials and the so-called “counter pressure concept.”

The Analysis of Prototype Cast Constructions and the Assessment of their Technological and Exploitation Properties

The article describes the application of various methods of rapid prototyping for manufacturing of prototype castings. This technology assumes that the properties of such a casting are similar to properties of a casting obtained in serial production involving die-casting technologies or high pressure die casting. However, other conditions of metal preparation, pouring, and the solidification process, related to the specificity of manufacturing of a single casting with the application of rapid prototyping, as compared to serial production generate different final properties. Numerical simulations of exploitation conditions, with the use of Ansys and Abaqus software, were conducted for selected constructions taking into account the final properties of a casting. MAGMASoft software was used for the analysis of the technological process for manufacturing of prototype castings, as well as in serial production. The article describes the consecutive stages for manufacturing of selected prototype castings - from the moment of designing to manufacturing of a ready-made element. The selected elements were produced with the use of rapid prototyping with a 3D Z-Corp printer and a FDM Titan machine, and then model sets were prepared for casting with the application of the lost wax casting technique.The conducted analysis was aimed at defining methodology for manufacturing prototype castings with the use of numerical simulation tools, especially the implementation of boundary conditions achieved as a result of solidification analysis and techniques of rapid prototyping. It was stated that final properties of a prototype casting and a serial casting may be different, which may impact the assessment of the construction under development. The use of numerical calculations for the assessment of a prototype and serial construction with exploitation parameters broadens the expertise with final properties of the analysed construction.

Effect of Technological Parameters on the Quality and Dimensional Accuracy of Castings Manufactured by Patternless Process Technology

Abstract Submitted article deals with the effect of selected technological parameters on the quality and dimensional accuracy of prototype castings made by Patternless process technology. During experiments were used two types of molding compounds (foamed gypsum and compound based on silica sand and resin). Experiments were focused on optimization of cutting parameters in terms of efficiency, accuracy and possibilities to minimize tool wear. Article deals also with the dimensional and shape accuracy of the castings made by Z-Cast technology. The main aim of the research is to optimize Patternless process technology to such an extent, that achieved dimensional and shape accuracy will be comparable to castings made by the Z-Cast technology.

Suitability of Molasses as a Core Binder Used in Non-Ferrous Sand Casting

The suitability of blackstrap molasses as a core binder used in non-ferrous sand casting has been investigated. Various core mixture samples were made with molasses varying from 1-5%, soybean oil 1-3%, and Chalawa Sand the balance. The foundry physical properties of the samples; Permeability, Green Compressive Strength, Dry Compressive Strength, Green Shear Strength, Dry Shear Strengths were determined via standard procedure. The sample of 2% molasses, 1% soybean oil, and the balance Chalawa Sand was chosen as the best core mixture based on the highest and optimum Baked Compressive Strength, Baked Shear Strength, and Permeability. Using the optimum mixture, a proto-type aluminium-silicon casting was made. The result revealed that the core has good collapsibility, and the surface finish of the internal cavity of the cast bushing is good.The research work has provided economically cheaper and environmentally friendly organic core binder from locally available raw material for industries as against poisonous and expensive resinous core binders.

Verification of Modification Effect on Prototype Castings from GJV Using Ultrasound Checking

Abstract Reason for and risks of using of cast iron with vermicular graphite for typical construction parts. Ultrasound checking of graphite shape. Factors influencing plausibility of result. Difference between laboratory and operation application. Roughness, parallelism, stability and size dimension of walls. Conditions, proposals for simplification and productivity enhancement of castings checking. Recommendation.

Applying RP-FDM Technology to Produce Prototype Castings Using the Investment Casting Method

Abstract The research focused on the production of prototype castings, which is mapped out starting from the drawing documentation up to the production of the casting itself. The FDM method was applied for the production of the 3D pattern. Its main objective was to find out what dimensional changes happened during individual production stages, starting from the 3D pattern printing through a silicon mould production, wax patterns casting, making shells, melting out wax from shells and drying, up to the production of the final casting itself. Five measurements of determined dimensions were made during the production, which were processed and evaluated mathematically. A determination of shrinkage and a proposal of measures to maintain the dimensional stability of the final casting so as to meet requirements specified by a customer were the results.

Numerical modelling of tilt casting process for γ-TiAl alloys

The tilt casting method is used to achieve tranquil filling of γ-TiAl turbine blades up to 400 mm long. The reactive titanium alloy is induction melted in a cold crucible, and the crucible with the attached mould is then rotated through 180° to transfer the metal into the mould. In the cold crucible, heat losses to the water cooled copper walls and base limit the superheat available, increasing the risk of premature freezing during mould filling. A compromise is required between fast and slow rotations to minimise the casting defects, such as misruns or gas entrainment. Simulations are presented using the authors’ Computational Fluid Dynamics code with several novel developments in front tracking, heat transfer algorithms and turbulence model adaptation, which accounts for an advancing solid front. The computational results are validated against prototype castings produced at the University of Birmingham, and the model is then used to optimise the tilt casting process.

Low-Cycle Fatigue Behavior of Die-Cast Mg Alloys AZ91 and AM60

The influence of microstructure and artificial aging response (T6) on the low-cycle fatigue behavior of super vacuum die-cast (SVDC) AZ91 and AM60 has been investigated. Fatigue lifetimes were determined from the total strain-controlled fatigue tests for strain amplitudes of 0.2 pct, 0.4 pct, 0.6 pct, 0.8 pct, and 1.0 pct under fully reversed loading at a frequency of 5 Hz. Cyclic stress–strain behavior was determined using an incremental step test (IST) and compared with the more traditional constant amplitude test. Two locations in a prototype casting were investigated to examine the role of microstructure and porosity on fatigue behavior. At all total strain amplitudes microstructure refinement had a negligible impact on fatigue life because of significant levels of porosity. AM60 showed an improvement in fatigue life at higher strain amplitudes when compared with AZ91 because of higher ductility. T6 heat treatment had no impact on fatigue life. Cyclic stress–strain behavior obtained via the incremental step test varied from constant amplitude test results due to load history effects. The constant amplitude test is believed to be the more accurate test method. In general, larger initiation pores led to shorter fatigue life. The fatigue life of AZ91 was more sensitive to initiation pore size and pore location than AM60 at the lowest tested strain amplitude of 0.2 pct. Fatigue crack paths did not favor any specific phase, interdentritic structure or eutectic structure. A multistage fatigue (MSF) model showed good correlation to the experimental strain-life results. The MSF model reinforced the dominant role of inclusion (pore) size on the scatter in fatigue life.

PDMS Microfluidic Device with an Integrated Optical Sensor for Determination of Zinc (II) in Pharmaceuticals: Toward the Production of Miniaturized Green Chemistry Analytical Systems

ABSTRACT A simple miniaturized system was fabricated in general laboratory from polydimethylsiloxane (PDMS) according to a prototype casting and molding process permitting the construction of three-dimensional (3D) microchannel (100 µm i.d.) with T-type network, together with an integrated optical sensor for on chip detection. The fabricated device has been successfully applied as a green chemistry-compatible miniaturized analytical system for the determination of zinc (II) in pharmaceutical samples taking the advantage of the colorimetric reaction of zinc (II) and xylenol orange in acetate buffer at pH 5.5. The microfluidic device is a convenient way to quantify zinc (II) over a wide dynamic range, 0.2–2.5 µg mL−1, with good linearity (R2 0.9940).

Design Development of Unitized Titanium Structure

Traditional airframe primary structure is fabricated from wrought product forms that are transformed by machining, forming, and joining into structural components. These individual parts are assembled together by fasteners to create the airframe. Significant cost and cycle-time savings can be achieved by switching from multipiece builtup assembly to a single-piece net shape casting. The reduction in number of discrete parts provides a significant reduction in both direct and indirect costs. In particular, the inherent low material costs and excellent producibility characteristics of cast metallic parts may provide a significant contribution to the goal to reduce acquisition costs. Under the program reported herein, and in conjunction with a casting vendor, prototype titanium (Ti-6Al-4V) cast airframe components were designed and fabricated. The typical overall dimensions of each casting are 50inches×40inches×30inches, and weigh approximately 190 pounds per casting. The castings were modeled on generic aircraft fuselage structure, that incorporated smooth inner moldline surface and integral webs and keels, capped by a T-element, web stiffeners, access holes, and other detail features. Multiple castings are joined to create the airframe structure. A rapid prototyping method was utilized to create the pattern, which eliminated the requirement for expensive metal tooling. The prototype castings successfully demonstrated the producibility of this generic airframe structure.

Low-cost, fly-ash-containing aluminum-matrix composites

In recent years there has been considerable activity in the development of metal-matrix composites, especially for aerospace, ground transportation, and the leisure industry. Short-fiber-reinforced pistons and cylinder blocks have been marketed by Japanese companies for several years. It is likely that in the near future cast particulate composites like aluminum-graphite, aluminum-silicon carbide, and aluminum-alumina will find widespread applications as brake rotors, drive shafts, cylinder liners, connecting rods, and wrist pins. The cost of metal-matrix composites has been one of the major barriers toward their widespread application. This paper describes the development of cast aluminum-fly ash particle composites (ash alloy). Incorporation of fly-ash particles, which are a waste by-product of coal-based power generation, reduces the cost of aluminum castings by acting as a filler; decreases their density, and increases their hardness, abrasion resistance, and stiffness. Several prototype castings have been made from aluminum-fly ash composites to demonstrate their castability. With sustained research and the support of manufacturing organizations, these alloys can find widespread applications as low-cost aluminum composite components.

Towards Improving the Properties of Plaster Moulds and Castings

The plaster moulding process is commonly used for casting prototypes of aluminium components designed for subsequent production by die casting. Plaster moulded prototype castings possess dimensional tolerances and surface quality comparable to die castings, but without the high tooling costs and lead times. Unfortunately, the mechanical properties of plaster castings are significantly inferior to their die cast counterparts. This is due primarily to the low thermal conductivity of plaster which extends casting solidification time significantly compared to die or even sand casting processes. Long solidification times result in large grained castings demonstrating low strength and hardness. This work is an experimental investigation into the effects of various levels of silica sand and carbon fibre additions on the properties of foaming plaster moulds and associated aluminium castings. Data and statistical analyses are presented and conclusions drawn regarding the wet and dry strength of plaster moulds as a function of sand and carbon fibre content. Likewise, conclusions regarding the associated casting characteristics such as surface finish, solidification time, hardness and tensile strength are presented. The effectiveness of silica sand and carbon fibre additions with respect to improving the properties of plaster moulded prototype castings is also discussed.

Evaluation of Structural Steel Castings for the Hutton Tension Leg Platform

The use of steel castings as major structural elements of the Hutton tension leg platform represents a relatively novel concept. In order to ensure that these castings would provide adequate service, an extensive testing program was undertaken to assess variations in chemical composition and mechanical properties of prototype castings. In addition, a rigorous acceptance procedure for production castings was developed. The results of these programs showed that steel castings possessed adequate strength and toughness. Also, a welding procedure was developed which consistently produced sound weld repair and satisfactory joints between cast and plate steel.