Mold Cavity Research Articles

Arc-directed energy deposition for hot forging mold cavity with conformal cooling channels

Arc-directed energy deposition for hot forging mold cavity with conformal cooling channels

FLAKE POWDER METALLURGY APPROACH FOR PRODUCTION OF Al–Al2O3COMPOSITES WITH ENHANCED PROPERTIES

Flake Powder Metallurgy (FPM) is utilized for the processing of Al–Al2O3composites. The effects of contents of 1-[Formula: see text]m-sized alumina (0, 3, 6 and 9 vol.%) on the microstructure, hardness, porosity and wear behavior of these composites are investigated. The as-received aluminum powder particles are milled in a planetary ball mill for different time durations (0.5, 1, 1.5 and 2 h), and the resultant flake powders are characterized by sieving, SEM, optical microscopy and XRD to determine their particle size, morphology and grain size. Al flakes and different amounts of Al2O3powders are stacked into the mold cavity using a floating column filled with alcohol. Then the compacts are cold pressed at 750 MPa and sintered in a tube furnace at 655∘C for 60[Formula: see text]min. For comparison, reference samples from as-received aluminum powders are also fabricated. SEM studies showed a uniform distribution of alumina particles within the matrix of FPM-processed composites. These composites, despite their higher porosity, exhibited higher hardness levels and improved wear properties in comparison with the conventionally produced powder metallurgy (PM) counterparts. This is due to: (i) the special morphology of the flake powders that contributed to a more uniform distribution of alumina within the matrix and (ii) their smaller grain size due to work hardening that occurred during milling, which resulted in higher hardness values.

Mechanism of laser-inducing hierarchical surface structures improving bonding strength of metal-plastic hybrids

The mechanism of laser-inducing hierarchical metal surface structures was investigated both experimentally and numerically, providing insights into improving bonding strength of metal-plastic hybrids (MPHs). For this purpose, metal sheets were first treated with the nanosecond pulsed laser to induce surface microstructures, followed by being put into the mold cavity, and jointed with plastic via the injection molding process. Both aluminum and titanium alloys were adopted as the metals and the glass fiber reinforced polyphenylene sulfide was chosen as the plastic material for MPHs. Specifically, laser parameters including the scanning speed, laser frequency, scan repetition, and modulation switch pulse-width were varied to investigate their impact on metal surface microstructure morphology and thus the MPH bonding strength. It is found that although having no clear trend while changing the laser parameters, the MPH bonding strength is strongly dependent on both surface morphology and material type of the metals. Finally, the process was optimized based on observations concerning the laser-inducing mechanism. The titanium alloy surfaces with bumpy morphology facilitated forming microscale mechanical interlocking between the metal and the plastic, leading to enhanced MPH bonding strength.

Effect of Hot Air Heating on The Cavity Temperature Distribution of Injection Mold

In this paper, the air-assisted mold temperature control (AMTC) is applied for heating the mold in the injection molding process. The simulation is run with the same boundary conditions in the experiment. The results shows that the AMTC can heat the surface mold plate to 171.6 °C. This temperature value is higher than the glass transition temperature of almost thermoplastic materials that used in the injection molding process. With the product thickness values of 0.1 mm, 0.3 mm and 0.5 mm, the heating rates were 6.3 °C/s, 6.39 °C/s and 6.58 °C/s, respectively. The increase in heating rate can be explained by the need for thermal energy to heat up the stamp volume that is inserted in the mold cavity for changing the product thickness. Also, the highest temperature at the top of the stamp which is nearest to the hot air gate, and the temperature is smaller when the area is far from the hot air gate.

Effects of Cavity Thickness and Mold Surface Roughness on the Polymer Flow during Micro Injection Molding.

In micro injection molding, the cavity thickness and surface roughness are the main effects factors of polymer flow in the die designing and affect the quality of molded products significantly. In this study, the effects of cavity thickness and roughness of cavity surface were investigated mainly on polymer flow during molding and on the roughness of molded products. The parts were molded in the cavities with the thickness from 0.05 mm to 0.25 mm and surface roughness from Ra = 46.55 nm to Ra = 462.57 nm, respectively. The filling integrities and roughness replication ratio of molded parts were used to evaluate the statements of polymer flow and microstructure replication during micro injection molding, respectively. The results showed that the filling integrity changing trends in the thinner cavities were obviously different or even opposite to those in the thicker cavities with the changing of cavity surface roughness instead of single trend in the conventional studies. For each cavity surface roughness, the filling integrity showed an upward trend with the increasing cavity thickness. In different cavity thickness, the maximum gap of filling integrity was 23.76 mm, reaching 544.94% from 0.05 mm to 0.25 mm. Additionally, the surface roughness ratio was slightly smaller than one before, reaching the polymer surface roughness limit around Ra = 71.27 nm, which was decided by the nature of the polymer itself. This study proposed the references for the design and fabrication of mold cavities and parts, and saved time and cost in the actual product manufacturing.

The generation mechanism of demolding force based on themold‐partinterface contact mode in micro‐injection molding

AbstractDemolding is the key step of micro‐injection molding (μIM), which influences the molding quality of polymer parts to a great extent. The essence of demolding is to overcome interface interactions between the mold cavity surface and the part surface, which is closely related to factors such as the cavity surface topography and process parameters. However, a theoretical model predicting the demolding force of μIM is still lacking, resulting in the difficulty of improving the quality of demolding in μIM. Therefore, a comprehensive demolding force model is proposed to clarify the demolding mechanism of μIM. The model focuses on the adhesion behavior and friction behavior in the special contact mode formed by the replication effect of μIM. The theory proof and computation results indicate that the cavity surface topography determines the contact mode of the mold‐part interface (MPI), which in turn changes the real interface contact area, the composition mode of adhesion stress, and the friction forms, thereby affecting the adhesion and friction force during demolding. In addition, the process parameters can also change the contact mode of MPI as the process parameters have a great effect on the filling capacity and the degree of replication, thereby influencing the demolding process.

Razvoj modela za simulaciju livenja pri aluminotermijskom zavarivanju šina

Aluminothermic welding has been used to connect railway rails for over a century. This technique has the advantages of flexibility, weld compactness, and simplicity. External energy is not required for the procedure. Exothermic heat is produced by chemical reactions of aluminothermic elements. To create a quality welded connection, the mold and pouring system must provide uniform pouring of hot steel without turbulence, even heat dissipation or cooling, and an acceptable micro and macro structure of steel free of internal and external faults. The design of the mould was constantly changing, necessitating costly industrial experimentation. As a result, the mould's design was constantly evolving, necessitating the use of costly experimental procedures in industrial settings. The latest iteration of the model the casting cavity was improved by adding hoes in the sand and putting rails on both sides in order to more aquratly simuate heat transfer. Software programs are emulating conventional casting procedures for thermite steel casting in welded railway connections to save money and effort on costly and timeconsuming industrial testing. For the 49E1 rail, NovaFlow & Solid CV were utilized to simulate casting thermite steel in the mould cavity or weld junction.

On modelling conjugated heat transfer in the thin slab CC mold and solid shell formation under the applied EMBr

Continuous casting (CC) became one of the dominant steel production technologies throughout last decades. Better quality, energy savings and high production rates are the main aims of the research especially in the field of the thin slab casting (TSC). The electromagnetic brake (EMBr) is applied to control the highly turbulent flow after the fresh melt is fed through the ports of a submerged entry nozzle (SEN). The numerical modelling is a perfect tool to investigate the multiphase phenomena of the turbulent flow in the CC mold, heat transfer and solidification coupled with the effects of the magnetohydrodynamics (MHD). Traditionally the heat transfer in the CC mold during the numerical simulations is predefined by the heat flux profile which could be taken from the plant measurements, published data, or is described by the semi-empirical formulas. In all these cases the heat extraction in the CC mold cavity is strictly predefined and is not significantly influenced by the transient flow behavior. Moreover, the heat flux, used in a simulation, is frequently measured for the different flow pattern inside the mold. That is especially important when the EMBr effects on the solid shell formation are investigated. Thereby, the presented study considers the coupled heat transfer in the water-cooled copper mold, including the averaged thermal resistance between the slab and mold, implemented using OpenFOAM® open-source CFD software. The melt flow, the temperature field, and the induced electric current density are compared between the traditional approach (the applied heat flux) and the modelled heat transfer in the TSC mold. Different scenarios are studied without and with the applied magnetic field.

INCREASING THE DURABILITY OF EXTERIOR PARTS OF AGRICULTURAL MACHINERY USING COMPOSITE MATERIALS

The problem of ensuring the durability of machines is currently extremely relevant, since the aging of the fleet of machines is outpacing the pace of the necessary technical re-equipment. The use of traditional metal materials and outdated technologies in the designs of agricultural machines leads to an increase in the cost of their production, a decrease in resource and durability. The use of corrosion-resistant materials, such as polymer composites, for exterior elements allows to increase the durability of agricultural machinery and reduce corrosion-related damage. (Research purpose) To perform an analytical review of production methods by which it is possible to manufacture exterior parts of agricultural machinery from composite materials. (Materials and methods) It was determined that the material of this study is open information sources; the research method consists in the collection, study and comparative analysis of information. (Results and discussion) It was noted that the following technologies are used for the production of exterior parts of agricultural machinery: vacuum molding, contact molding, pressure impregnation, injection molding. Vacuum forming consists in the production of materials in hot form by the method of exposure to vacuum or low air pressure. Contact molding is a manual layering of reinforcing material and impregnation of each layer with resin. When impregnated under pressure, the fibrous billet is placed in the inner mold, leaving a gap that allows the resin to be injected and the fibers to be impregnated. The essence of injection molding is the forced filling of the working cavity of the metal mold with melt and the formation of the casting, which occurs under the action of the press piston. (Conclusions) Distinctive features of the exterior elements of agricultural machinery are their large overall dimensions and low requirements for the accuracy of shapes and sizes, which determines the scope of technologies possible for their manufacture. The least labor-intensive and simply implemented in a single production method is contact molding. In mass production, the most suitable method is injection molding.

Oxidické vrstvy a bifilmy v odliatkoch hliníkových zliatin

Surface of aluminium alloy melt is covered by an oxide layer when it is in contact with the surrounding atmosphere. When the oxide layer is retained on the surface of the melt it prevents the melt by hydrogen saturation. The oxide layer is harmful when it is submerged into the melt. The work focuses on the influence of the melt velocity on the bifilm formation, morphology of oxide layers and their influence on the porosity and filling the mold cavity.

Modular injection mould with a conformal cooling channel for the production of hydraulic filter housings

The article presents the idea, design, construction, and implementation of a production technology for hydraulic filter housings using a modular injection mould. The annual demand for filters for specialised marine hydraulics systems by HYDROMEGA averages about 1,000 pieces. Two sizes of filters with the same housing connection dimensions are used. Due to the small scale of production, the modular injection mould was designed and manufactured to press two types of a polyamide housing. Changing the shape of a moulded part requires removing or installing modules that change the die and punch dimensions, which reduces the costs of production of a single tool compared to the costs of production of two separate tools. The mould design process was supported by the numerical analyses of operation and processes of plastic injection, cooling, moulded part shrinkage, and mould cavity deaeration. A mould and a series of moulded parts were manufactured and verified positively for dimensions and durability.

Automatic design of conformal cooling channels with an asymmetric centre

In this paper, a compensation-based calculation method is proposed for designing a CCC with an asymmetric centre to make the temperatures of the core and cavity moulds uniform. By redefining the parting line, a heat accumulation centre can be obtained and the distance between a cooling channel and a plastic part can be calculated to ensure a more uniform temperature distribution, thereby reducing the severity of volumetric shrinkage and deformation. Two case studies with different characteristics were used for verifying the proposed method. One is a flat part large thickness difference; the other is a uniform thickness with a large curved surface. According to the analysis results obtained in the aforementioned cases, the CCC with an asymmetric centre not only reduces the temperature of molten plastic rapidly to the ejection temperature, but also effectively evens the temperature variation over the entire mould cavity.

СОВРЕМЕННЫЕ МЕТОДЫ ПРИ РЕМОНТЕ И ВОССТАНОВЛЕНИИ ДЕТАЛЕЙ МАШИН ДЛЯ ПОВЫШЕНИЯ ЭФФЕКТИВНОСТИ ТРАНСПОРТНО-ДОРОЖНОГО КОМПЛЕКСА

An experimental study of the technological process of obtaining a composite ABS - a metal-polymer part is considered. A method and device for the manufacture of composite parts based on the method of vacuum suction of a viscous metal polymer into a shell form are described. Recommendations are given on the technological modes of filling the mold, taking into account the presence of vibration in the process of filling the mold with a metal polymer, as well as the Reynolds number parameter for establishing a laminar flow of the metal polymer in the technological mold cavities. The study of the strength of the designed composite part was carried out using the finite element method of the APM FEM module. The calculations of the strength and stiffness of parts made of ABS, metal-polymer and metal made it possible to compare the strength characteristics of parts made by various methods. Relevant recommendations are given on the use of a composite part reinforced with a metal-polymer in the field of mechanical engineering.

Self-assembled micropillar arrays via near-field electrospinning.

Self-assembly in near-field electrospinning is reported for the first time in this paper, which realized the conversion from two-dimensional planar printing to three-dimensional (3D) structures. Repeatedly stacked fibres formed a micropillar array structure (MPAS) with intervals on the deposition paths by adding carbonyl iron powder particles to a polyethylene oxide (PEO) solution. The growth process of the self-assembled MPAS is documented, and the mechanism of the self-assembled MPAS is proposed. In addition, the effects of substrate speed and injection speed on self-assembly were investigated. Electric field distribution simulations show that the electric field strength around the MPAS is enhanced by nearly ten times so that the micropillar can attract the jet for further deposition. Self-assembly can obtain MPASs with arbitrary paths on different substrates, and the interval of the MPAS can be controlled by using bulging substrates. Furthermore, a self-assembled MPAS has been successfully used to prepare mold cavities, which can be used to prepare MPASs of other materials. Due to their small feature size, large surface area and structural periodicity, micropillar arrays will have promising applications, such as hydrophobicity of surfaces and electrochemical detection. Self-assembly in near-field electrospinning can significantly reduce the preparation cost of an MPAS and provide new processes and ideas.

Thermal behaviour of resin inserts for micro injection moulding: a FEM analysis

One of the future challenges is to satisfy a manufacturing market in which the raw material and its storage are increasingly limited, while the need for product diversification is growing. In this context, the global market, especially in the biomedical sectors, sees a growing interest in the miniaturization of products and features for which micro injection moulding (µIM) seems to be ready. Improvement in mould flexibility in terms of reconfigurability of the cavity mould and features is requested to µIM. A tailored insert approach for the micro mould has been adopted to study different materials and micro manufacturing technologies to produce the inserts with such extreme features. Novel high temperature resins for additive manufacturing, able to withstand temperatures up to 250°C, are used to realize inserts for µIM prototyping and small batches. A numerical simulation of the process to produce a 400µm thick thin plates of polymethylmethacrylate (PMMA), a typical benchmark and polymer for microfluidic applications, has been conducted to evaluate the thermal behavior of the resin insert on the molten polymer with respect to the steel one. The results evidenced an isolating behavior of the resin which reduces the thermal dissipation with consequent lower viscosity also during the packing pressure. To validate the results an experimental campaign, was made using both a steel insert and a high-temperature resistance resin insert. The part produced with the resin insert presented diffused flash, a defect usually correlated to high melt temperature and high injection pressure.

Preliminary DOE Analysis of the Polishing Process of AISI P20 Mould Steel by Ultrasonic Erosion, Using Alumina and Diamond Hard Particles

The present work examines the surface finishing of AISI P20 tool steel, average hardness of 31.5 HRc, in the polishing process by ultrasonic erosion by loose abrasive particles. The study was performed in laboratory equipment, using various alumina and diamond hard particle sizes, ultrasonic frequencies and times. P20 steel is widely employed in the fabrication of polymer injection mould cavities due to its good machinability, homogeneous microstructure, hardness, corrosion and abrasion wear resistance. Mould cavity polishing processes represents the second longest manufacturing process time required to achieve the mould surface finish for good quality polymer parts. This time-consuming and largely artisanal polishing process contributes to high mould costs. Thus, several studies have been carried out in the literature to automate the mould polishing process, aiming to reducing surface roughness and polishing time. Present investigation was carried out in a surface cleaning equipment by the ultrasonic technique with commercial paste of abrasive hard particles used in mould polishing. Three factors were investigated: abrasive particle size, ultrasonic frequency and polishing time. The investigated alumina particle sizes were 0.05, 0.3, and 1.0 micron and the diamond particle size was 1.5 micron, which are the common sizes available in commercial paste for polishing metallography samples. The studied frequencies of the ultrasonic polishing process were 28 and 40 kHz, and the times of polishing process were 15, 30, and 45 minutes. Analysis of variance (ANOVA) of factor effects and two types of DOE analysis were employed to obtain the roughness Ra outcomes by empirical response surface modelling: 3x3 partial factorial design and 4x2 factorial design were used to investigate the surface roughness. The response surface modelling results indicate that the minimum surface roughness Ra of 0.21 micron obtained by ultrasonic polishing correspond to the frequency of 40 kHz, 20 minutes of polishing and alumina particle size of 0.7 microns.

Modeling the Effect of Pour Height, Casting Temperature and Die Preheating Temperature on the Fluidity of Different Section Thicknesses in Permanent Mold Casting of Al12Si Alloys

The first and most important step of the casting method is that the liquid metal completely fills the mold cavity. One of the common mistakes in the casting process is that the liquid metal does not fully fill the mold cavity. For this reason, there is a need to improve the fluidity properties of aluminum alloys, the usage area of which is expanding thanks to its many advantageous properties. The aim of this study is to examine the parameters affecting the fluidity in the casting of Al12Si alloy by modeling techniques. The effects of varying pouring height, casting temperature and mold preheating temperature on fluidity in different section thicknesses were investigated in permanent mold casting. A specially designed mold with 2 mm, 4 mm, 6 mm and 8 mm section thickness was used in the study. Modeling studies were carried out with the FlowCast filling module, which is integrated into the SolidCast Casting simulation program. When the results are examined; It has been determined that all parameters play an active role on fluidity and different filling levels in different section thicknesses.

Nanoscale deformation of crystalline metals: Experiments and simulations

In the present work, we performed experiments and molecular dynamic simulations to study the atomic physical process and deformation mechanism involved in nanoscale deformation of crystalline metals. By contact deforming bulk metals using hard molds with different cavity sizes at various temperatures and different stress levels, the flow of metals (e.g., Au and Ag) into nanocavities is quantified by the aspect ratio of molded micro-/nanorods, based on which the dependence of deformability on cavity size, temperature and stress is revealed. It is found that the critical forming pressure is determined by the entering barrier. Once the entering barrier can be overcome, quantified by the aspect ratio of metal nanorods, the molding efficiency increases with the cavity size decreasing. Moreover, three deformation modes are uncovered in the nanoscale plastic flow of metals and directly related with the atomic physical processes, i.e. atomic diffusion, dislocation nucleation, multiplication and movement. In the dislocation dominated temperature regime, a transition of deformation mode from burst growth to continuous growth is observed as the cavity size increases. When the mold cavity size is very small (100-101 nm), the metal atoms flowing in a mold cavity will arrange amorphously even at low temperature, which usually only occurs at high temperature for large cavity sizes. Therefore, reducing the size shows the same effect as increasing the temperature, making nanomolding easier.

Evaluation of the Influence of Process Parameters on the Mechanical Properties of Castings during High Pressure Die Casting

The article is devoted to the influence of mold filling parameters by the HPDC - High Pressure Die Casting method on the mechanical and structural properties of castings intended for technology and mechanization means in forestry. Three groups of AlSi10MnMg alloy samples were formed for the experiment. Three different settings of mold cavity filling parameters were chosen. Two castings were made from each setting. Two samples were taken from two places on the casts. Thus, 12 pieces of samples were used for the experiment. An analysis of their mechanical properties was performed using a static tensile test. tensile strength, yield strength and ductility were evaluated. The microstructure was evaluated by light optical microscopy. The influence of process parameters on the quality of the casting was monitored from the point of view of the occurrence of errors, defects and the method and size of the exclusion of structural phases. The experimental results showed that the best results were obtained when the process parameters of the first group of samples were set. Their values are the closest to the customer's requirements.

The Effect of the Extrusion Method on Processing and Selected Properties of Poly(3-hydroxybutyric-co-3-hydroxyvaleric Acid)-Based Biocomposites with Flax and Hemp Fibers.

The paper presents a comparative analysis of two extrusion methods of biocomposites with a poly(3-hydroxybutyrate-co-3-hydroxyvalerate acid) (PHBV) matrix filled with flax and hemp fibers in terms of biopolymer production, its processing in the further injection process, and an evaluation of the mechanical and functional properties of the products. Biocomposites containing 15% by weight of the filler were produced using single- and twin-screw extruders. The biocomposites were then processed by injection molding and then, among other things, the pressures in the mold cavity during processing were analyzed. The produced samples were tested by means of the following tests: uniaxial tensile strength, hardness, and impact tensile strength. The biocomposite's microstructure was also analyzed using scanning electron microscopy (SEM), as were the shrinkage and water absorption of the manufactured products. In addition, thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC) tests were performed. It was found that the extrusion method changed significantly the geometry of the filler fibers and the processing capabilities of the manufactured materials. Significant differences in the mechanical and functional properties of the obtained biocomposite products were also found. On their basis, the advantages and disadvantages of both extrusion methods were discussed. Most of the obtained properties of injection products indicate the choice of single-screw extrusion. The products were characterized by slightly better mechanical properties and lower processing shrinkage. In turn, composites obtained by the screw method were characterized by lower water absorption and lower viscosity of the composite during injection molding.