Cast Parts Research Articles

Morphology Distribution in Injection Molded Parts.

A more sustainable use of plastic parts makes it necessary to replace current plastic parts with recyclable components, also allowing the modulation of the part properties through the process. Injection molding is one of the most widely used technologies for obtaining rigid plastic parts, so it is crucial to understand how to tailor properties by adopting the correct processing conditions. One way is to perform annealing steps directly inside the mold: in-mold annealing improves the structural integrity and durability of the material, reduces defects, increases the resistance of parts against certain chemicals, reduces wear and tear, increases ductility, and lowers brittleness. In this work, several in-mold annealing steps were conducted, changing the mold temperature and annealing duration selected on the basis of the half crystallization time of the adopted isotactic polypropylene. The typical molded part morphology, composed of oriented layers at the surface, transition zones, and spherulitic core, is strongly affected by in-mold annealing. In particular, the thickness of the oriented layer, which forms in the early phase of the process, decreases, and the spherulites increase in size. Concerning mechanical behavior, the orientation degree mostly determines the elastic modulus value close to the surface, whereas the conditions under which crystallization occurs determine the modulus in the core.

Thermal Analysis of Ductile Iron: A New Way to Predict the Mechanical Properties

Thermal analysis is characterized by the recording and evaluation of the temperature curve over time. Due to the correlation between transformation temperatures and chemical composition, thermal analysis is used to determine the carbon and silicon content. Furthermore, the aim is to be able to predict mechanical properties by thermal analysis. However, all current prediction methods refer to the cooling conditions in the investigated casting area and do not allow any transfer to other cooling conditions. There is a lack of a direct and automatic prediction of the mechanical properties from the thermal analysis before casting and transfer to other cooling conditions. For this study, cooling curves from the last 10 years at the Foundry Institute at RWTH Aachen University were evaluated and correlated with the mechanical properties from castings with three different thermal modules. The results of this empirical regression analysis are equations for the investigated mechanical parameters, which can be automatically filled with the characteristic times and temperatures of a thermal analysis in the casting process and the thermal modulus from the casting. For this modulus, the user can insert a corresponding value of the structural casting part that is relevant to the quality requirements in the foundry.

Adaptive Tool Trajectory Generation for Robotic Deburring using Structured Light 3D Camera sensor

Sand casting usually implies some flash or burr on the cast parts that are unevenly distributed and variations in size and mass. Furthermore, the cast part itself can also have significant geometric deviations caused by sand casting process variations. Effective automated deburring needs to be fast and accurate, adapted to individual parts’ burr size and the actual geometry of the cast part. This paper reports on an experimental study of adaptive one-of-a-kind automated pre-programming for robotic deburring using structured light 3D machine vision optical measurements for tool trajectory generation. Each individual cast part is scanned to create a 3D mesh that is used to generate the tool trajectory. The method is verified in an experimental setup with a robot manipulator with a pneumatic spindle and carbide cutting tool. This study can serve as an example on how vision sensors and advanced algorithms can be applied to achieve productive and adaptive manufacturing processes and systems.

Use of rice husk as hot tipping on steel casting parts

The use of feeding aids in the foundry process has become widespread globally recent decades, leading to increased efficiency. This article examines the characterization of rice husks, their ashes, and their positive impact as hot topping on the efficiency of open risers in casting cylindrical parts made of AISI 1045 steel. The rice husks were analyzed through X-Ray Diffraction test, Thermal-Gravimetric Analysis, and Differential Thermal-Gravimetric Analysis, while the ashes were characterized using X-Ray Diffraction. The analyzed rice husks were found to contain cellulose and low crystallinity silicon, whereas the ashes primarily consisted of cristobalite and tridymite. It was observed that the thermal decomposition of rice husks occurs in three stages, with approximately 81% of the mass lost during their combustion as hot topping on liquid steel. The location of cavities contraction in the risers of casting parts was made through longitudinal cut of the part-riser system. The increase in the rice husks topping layer thickness positively influences the concentration of these cavities on the upper surface and enhances the feeder's efficiency.

Study on Cracking Causes of One 500 kV SSY Type Equipment Clamp

One SSY type equipment clamp serviced in a 500 kV station was found to be cracked. In this paper, the crcaked cause and mechanism is investigated by means of macroscopic morphology observation, fracture surface morphology observation, X-ray digital detection, metallographic observation. The results indicated that the main reason for the fracture of the equipment clamp this time is that the terminal board is a cast part, which contains a large number of casting defects such as porosity and shrinkage, resulting in a decrease in its effective cross-sectional area and load-bearing capacity. In addition, insufficient modification treatment of the terminal board led to insufficient toughness due to needle or rod-shaped eutectic silicon in the organization. Finally, under the combined action of dynamic load and self weight caused by the swinging of the wire in the wind, the terminal board was brittle fractured along the bolt hole with obvious stress concentration effect.

Scheduling Molds Manufacturing Processes through Process Mining

The molds industry, being a highly competitive sector, is constantly driven by organizations looking to optimize their business processes to gain a competitive edge. To access advanced management tools, there has been a strong push for integrating Industry 4.0 technologies, which in turn has resulted in a significant increase in the amount of manufacturing process data, enabling more accurate and real-time analysis of processes. However, challenges persist due to the unpredictable and ad-hoc nature of this industry’s business processes. As a result, effective resource management has become a crucial aspect that organizations are actively addressing. In this study, our objective is to leverage process mining algorithms and complement them with a genetic algorithm to generate efficient scheduling solutions to produce mold parts on factory floors. By analyzing existing data and identifying the workflows through process mining, we seek to gain a more realistic perspective on the mold manufacturing business process. Through this analysis, our aim is to uncover meaningful workflows and sequences for producing mold parts, ensuring that critical activities are appropriately incorporated while minimizing unnecessary repetitions. By identifying these purposeful sequences, we can provide the factory floor with schedules that optimize resource usage and enhance the overall efficiency of mold manufacturing processes.

Studying the new modes of deposition of plasma coatings

Problem. This paper considers using ion-plasma spraying of mold surfaces. This makes it possible to replace scarce and expensive tungsten-containing steels with other materials. Purpose. The purpose is to study the possibility of using the KIB method to increase the stability of die-casting molds, to establish the possibility of replacing scarce, expensive tungsten-containing steels with other materials. Materials and methods. 4Х5МФС and 5ХНМ steel grades were chosen as materials for copper alloy die-casting molds in this work. The choice of these steel grades is due to the fact that these steels do not contain tungsten due to its sharply increased scarcity and limited molybdenum content, and they also meet the requirements for the substrate material on which the titanium nitride coating is applied. Coatings were applied to samples for laboratory tests and die-casting mold parts by the condensation method with ion bombardment. Titanium nitride is applied at different partial nitrogen pressures – from 3×10-3 to 1 Pa to determine the required nitrogen pressure, which ensures that the working surfaces of mold parts receive coatings with the best performance characteristics. The coatings obtained at different nitrogen pressures differ in the amount and size of the droplet phase. Results of experiments. The largest amount of the droplet phase containing α-Ti is observed in coatings obtained at nitrogen pressures of 3×10-3 Pa, 3×10-2 Pa. An increase in nitrogen pressure (4×10-1 Pa, 1 Pa) significantly reduces the level of microdistortions of the crystal lattice in the coating, and its plasticity increases. In this regard, the coating's brittleness is reduced at a sufficiently high hardness. Results. The titanium nitride coating obtained at a nitrogen pressure of 1 Pa is the most effective in protecting the working surfaces of mold parts from destruction. Laboratory tests have shown that the titanium nitride coating applied under optimal process parameters increases the corrosion resistance of mold parts to which it is applied by 3 times and the scale resistance by 2-4 times.

Influence mechanism of injection process parameters on iridescent pattern defects on optical molded parts

AbstractIridescent patterns are insufferable molding defects during mass manufacturing of polymer optic devices by using injection molding (IM) technique and seriously affect the appearance and imaging performance of parts. However, at present, the research on the factors affecting iridescent pattern defects is lacking, resulting in the difficulty of obtaining effective methods to weaken iridescent pattern defects. This article aims to clarify the correlation mechanism between injection process parameters and iridescent patterns and provide a theoretical basis for reducing iridescent pattern defects. Based on the process characteristics of IM and the optical mechanism of iridescent patterns, the correlation between iridescent patterns and influencing factors such as optical characteristics and the material structure is established. The influence mechanism of process parameters on iridescent patterns is further clarified by experiments. The results show the iridescent pattern color is related to the retardation, while the iridescent pattern brightness is affected by the retardation and transmittance. Process parameters change the retardation and transmittance by varying factors such as the thickness, birefringence, and crystallinity. Higher mold temperature, reasonable melt temperature, injection speed, and holding pressure are conducive to reducing the colorful fringe area and iridescent pattern brightness, thereby weakening the iridescent patterns on the part.

Modeling De-Coring Tools with Coupled Multibody Simulation and Finite Element Analysis

De-coring is an essential process in the casting process chain, determining the quality and cost of production. In this study, a coupled multibody system (MBS) and finite element modeling (FEM) technique is presented to study the mechanical loads during the de-coring process. The removal of cast-in sand cores from the inner regions of the cast part by de-coring or knocking out is a complex process with dynamic loads. Currently, the process relies upon empirical knowledge and tests. Inorganic sand cores pose additional challenges in the success of the de-coring process. Increasing complexity in geometry and stringent environmental regulations compel a predictive process in the earlier stages of design. Predicting the process’ success is challenged by the dynamic non-linearities of the system. The dynamic characteristics and the interaction between hammer and casting were studied here for the first time using an industrial-based test rig, and a novel modeling approach was formulated. The results of the developed model are in good compliance with the experiments. The methodology presented in this study can be used to include a varying number of hammers and loads. The proposed approach presents the possibility to discretize the process and qualitatively assess the process parameters for optimization.

Deep learning–based inline monitoring approach of mold coating thickness for Al-Si alloy permanent mold casting

AbstractIn the permanent mold casting process, the distribution of mold coating thickness is a significant variable with respect to the coating’s thermal resistance, as it strongly influences the mechanical properties of cast parts and the thermal erosion of expensive molds. However, efficient online coating thickness measurement is challenging due to the high working temperatures of the molds. To address this, we propose an indirect monitoring concept based on the analysis of the as-cast surface corresponding to the coated area. Our previous research proves linear correlations between the as-cast surface roughness parameter known as arithmetical mean height (Sa) and the coating thickness for various coating materials. Based on these correlations, we can derive the coating thickness from the analysis of the corresponding as-cast surface. In this work, we introduce a method to quickly evaluate the as-cast surface roughness by analyzing optical images with a deep-learning model. We tested six different models due to their high accuracies on ImageNet: Vision Transformer (ViT), Multi-Axis Vision Transformer (MaxViT), EfficientNetV2-S/M, MobileNetV3, Densely Connected Convolutional Networks (DenseNet), and Wide Residual Networks (Wide ResNet). The results show that the Wide ResNet50-2 model achieves the lowest mean absolute error (MAE) value of 1.060 µm and the highest R-squared (R2) value of 0.918, and EfficientNetV2-M reaches the highest prediction accuracy of 98.39% on the test set. The absolute error of the surface roughness prediction remains well within an acceptable tolerance of ca. 2 µm for the top three models. The findings presented in this paper hold significant importance for the development of an affordable and efficient online method to evaluate mold coating thickness. In future work, we plan to enrich the sample dataset to further enhance the stability of prediction accuracy.

Reinventing quality in foundry castings through gearbox housing optimization: A case study approach

The Indian Foundry cluster is a key player in the production of metal castings used across various industries, including automobiles, railways, machinery, sanitary appliances, pipes, gears, earth-moving equipment, cement, electric circuits, pumps, valves, and wind turbines. Grey iron is the predominant material, constituting around 68% of all cast parts. In this context, Kolhapur plays a pivotal role in the production of diverse castings in India, primarily focusing on grey iron and SG iron castings, both of which are ferrous materials. The Kolhapur Cluster of Foundries is expected to produce approximately 650,000 tonnes annually, contributing about 7% of India's total cast iron production. However, this cluster encountered challenges related to higher rejection rates for castings due to a variety of defects. One established foundry in Kolhapur faced stricter rejection standards for specific castings. To address these issues, a comprehensive case study was conducted to reduce rejection rates in this foundry. The primary focus of the study was on a specific casting, the Gearbox Housing, which had an initial average rejection rate of 13%. In some instances, this rejection rate spiked to as high as 18% in a single month, resulting in significant revenue losses for the company. The defects observed in Gearbox Housing castings were categorized into two main types: Methoding, Filling, and Solidification-related defects, which included issues like shrinkage porosity and hot tears. Sand and mold-related defects, such as sand inclusion, sand drop, and mold quality issues. The initial step in addressing these defects involved utilizing casting simulation techniques to analyze and tackle shrinkage and porosity issues. A new gating system was designed to enhance the casting process. In the subsequent stage of defect reduction, the Design of Experiment (DoE) tool was employed. This data-driven approach helped refine and optimize the manufacturing process to minimize defects and enhance the overall quality of Gearbox Housing castings. By implementing these strategies, the foundry in Kolhapur successfully reduced rejection rates, thereby safeguarding company revenue and ensuring the production of high-quality castings for various industrial applications.

Teleoperation mode and control strategy for the machining of large casting parts

Residual features of large casting parts in small batch are random in distribution, size, and shape. The manual mode is inefficient, dangerous, and labor-intensive. The automatic mode spends a lot of time on trajectory planning and programming. To overcome the challenges, a novel teleoperation machining mode and a modified master-slave control structure are proposed. Moreover, a hierarchical control strategy based on variable motion mapping (VMM) and elastic compensation (EC) is presented to improve machining efficiency by realizing the constant cutting force. The control laws of VMM, EC and interactive force are designed to reduce operator fatigue and mental burden. The forbidden virtual fixture (RVF) is generated by employing a six-degree-of-freedom (6-DoF) articulated measuring arm to constraint the movement of slave robot and protect the workpiece from being overcut. The velocity and acceleration constraints are formulated to avoid the impact of the slave robot. A large casting part (train bolster) is considered to carry out comparative experiments. The effectiveness of the teleoperation mode and control strategy are confirmed by experiment results, which strongly promotes the progress of unstructured workpiece manufacturing and provides a reference for other machining.

A comparative study on the microstructure, mechanical properties, wear and corrosion behaviors of SS 316 austenitic stainless steels manufactured by casting and WAAM technologies

Replacing the traditional casting method with wire arc additive manufacturing (WAAM) to produce complex shaped parts will lead to using cost-effective technology even for challenging engineering applications depending on their geometry and number of the parts to be produced. This work performed a comparative study on the stainless steel 316 parts manufactured by WAAM and sand casting to reveal the microstructural, mechanical, wear, and corrosion behaviors. The WAAM components were manufactured using three different cooling dwell times and compared in terms of microstructures with the as-cast and heat-treated cast parts to reveal the properties of the WAAM parts. It was concluded that WAAM is a viable engineering alternative to the casting technology. Results showed that the WAAM and cast parts revealed similar microstructures, including delta ferrite and austenite phases, but the cast parts had a coarser grain and lower amount of delta ferrite due to slower cooling during the solidification. The yield and tensile strength of WAAM parts showed an increasing trend with the increase in dwell time, and on average, their yield strength was ∼1.5 times higher than in cast parts due to the smaller grains and more elevated δ-ferrite content resulting from rapid cooling. Furthermore, the greatest wear resistance was obtained in the cast parts after solution annealing heat treatment followed by water quenching. In contrast the highest corrosion resistance was obtained from WAAM parts produced using a dwell time of 120 sec. In conclusion, WAAM technology can be an excellent alternative to casting technology for producing stainless-steel parts with optimized process parameters.

Compensated printing and characterization of the droplet on the binder migration pattern during casting sand mold 3D printing

With its unique advantages, binder jetting additive manufacturing technology has shown significant development potential in the additive manufacturing of complex casting sand mold. After droplet deposition, the permeation and migration of the liquid binder in the porous powder bed have a critical impact on the final performance of the printed sand mold. Taking the piezoelectric printhead as the research object, using Furan resin as the liquid binder and silica particles for the powder bed, the effect of binder content on the dimensional accuracy and mechanical properties of the formed sand mold parts was discussed. Several samples were printed with different volumes of droplets, and the droplet diffusion mode, dimensional accuracy, mechanical properties, and formability were measured, respectively. These indicators were quantified based on the different binder saturation, by comprehensively considering the correlation between the indicators. The methods of grayscale printing and layer thickness compensation are given to improve the product quality. The results show that a more extensive liquid saturation produces better strength and formability with the tradeoff of a significant increase in dimension error. However, by independently adjusting the droplet amount of the liquid binder at each printhead, the desired dimension inaccuracy, strength, and formability can be achieved at each precise place. The future application can be implemented in the binder jetting of precision casting sand mold 3D printing to accelerate its industrial development.

Binder Content and Storing Conditions of Inorganically-Bound Foundry Cores Determine the Intensity and Onset Time of Gas Release in Metal Casting

Organically-bound foundry cores are substituted by inorganically-bound cores increasingly. This trend is due to regulatory efforts, workplace safety issues, and increasing costs for waste deposits. Changing the binder system reduces the emissions to mostly water vapor, solving health and safety issues. Yet, the difference in the behavior of the gas phase, namely, the condensation potential of water, changes the casting process drastically. In contrast with the continuous generation and discharge of combustion products in the case of organic binders, water accumulates within the foundry core. Only once the cold spots of the core reach boiling temperature noteworthy amounts of vapor are created, increasing the chance for gas defects of the cast parts. Countermeasures have to be taken when designing the core’s geometry. We conducted the following research to improve the understanding of core gas release and its interactions with the foundry core’s binder content and storage conditions. Both binder content and relative humidity during storage were varied in three steps. Their influence on the core gas amount, time of gas generation, and gas permeability of the cores were investigated. The experiments were performed in the institute’s Induction Analysis Furnace and an aluminum melt bath. We found a strong dependency of storage humidity, further increased by increasing binder content on the gas amount and time of the gas release.

TECHNOLOGICAL ANALYSIS OF INCREASING THE CORROSION RESISTANCE OF CAST PARTS

Corrosion is a significant challenge faced by industries that utilize cast parts in various applications. The deterioration of cast components due to corrosion leads to significant economic losses, safety hazards, and environmental concerns. This abstract presents a technological analysis focusing on enhancing the corrosion resistance of cast parts through various methods and techniques.

Investigation on effect of carbon equivalent and inoculation on the solidification and shrinkage tendency of ductile cast iron using thermal analysis

PurposeThe foundry industry incurs additional costs as a result of defective castings. Shrinkage defects are a frequent problem in ductile iron castings. It is still essential to understand how shrinkage porosity varies in size when the ductile iron composition changes. This information can be used to produce high-quality cast parts and determine the best processing conditions. The objective of this research paper is to examine the effect of carbon equivalent and inoculation on the morphology of the shrinkage defect using thermal analysis.Design/methodology/approachThis study focuses on certain thermal analysis parameters, such as the angle of the first derivative curve at the solidus temperature, recalescence and its relationships to graphite nucleation and shrinkage tendency. The results of thermal analysis in terms of the cooling curve and its derivative parameters, and thorough characterizations of the shrinkage observed in cup castings produced with various melt compositions and inoculation are presented in the current study.FindingsThe proportion of caved surfaces and macro shrinkage porosity defects has been reduced as the carbon equivalent of melt increases from hypoeutectic to a hypereutectic composition. The composition that is slightly hypereutectic has the lowest shrinkage propensity. Although inoculation reduces shrinkage, the importance of this parameter differs depending on the carbon equivalent.Originality/valueThe percentage of macro shrinkage porosity and the angle that the cooling rate curve forms are strongly correlated. It is found that the macro shrinkage size decreases as the angle of the first derivative curve at the solidus temperature is reduced. Further, lower macroporosity is produced by a metal that has a higher nodule count in association with a greater cooling rate toward the end of the solidification process.

Alumina-based ceramic cores prepared by vat photopolymerization and buried combustion method

Alumina (Al2O3)-based ceramic cores are extensively employed to form cavities within complex or difficult-to-form casting parts. As a conventional manufacturing process, investment casting requires molds and is labor-intensive. Therefore, it is crucial to develop a direct method for preparing Al2O3-based ceramic cores at a low cost. As an AM process, vat photopolymerization (VPP) can produce high-quality parts with smooth surface finish and fine details. Therefore, extensive attentions have been attracted to processing ceramic materials by VPP. Despite these benefits, the layer-by-layer accumulation strategy of VPP inevitably induces low bonding strength between adjacent layers, and induces cracks in the sintered parts. To mitigate these problems, burying VPP-printed Al2O3 green bodies into silica has been proposed in this investigation. Results show that cracks and deformation problems have been reduced when the buried combustion method is adopted. To create Al2O3-based ceramic cores with desired porosity and flexural strength properties, process parameters have been optimized. A systematic study on how the inclusion of SiO2 particles and variations in sintering temperature impact the microstructure and mechanical properties of Al2O3-based ceramic cores fabricated through VPP printing is presented. Based on experimental results, a 1300 ℃ sintering temperature is selected to produce appropriate shrinkages (4%∼8%), open porosity of over 20%, and flexural strength ranging from 20 to 50 MPa of ceramic cores.

Microstructure and properties of the GEWZ522K casting magnesium alloy based on the Mg–Gd–Nd–Y–Zn–Zr system

The article discusses the solidification and phase composition of the (wt.%) Mg–4.8Gd–2.1Nd–1.6Y–0.4Zn–0.6Zr (GEWZ522K) casting alloy. It is demonstrated that in the as-cast state, the alloy structure comprises primary zirconium particles, dendrites of the magnesium solid solution (αMg), and eutectic intermetallic phases located between dendritic branches. Following solution heat treatment at t = 530±5 °C, the alloy transitions into a single-phase state and can be significantly strengthened through artificial aging after quenching. It is recommended to apply alloy aging at t = 250 °C for 8–10 h or at t = 200 °C for 15–18 h. This approach leads to the maximum strengthening of the alloy, with the best mechanical properties achieved for the alloy aged at t = 250 °C. Regardless of the aging method used, the ultimate tensile strength (UTS) of the samples surpasses 300 MPa, which significantly exceeds that of commercial casting alloys according to GOST 2856-79. The measured corrosion rate for the GEWZ522K alloy is 7.5±0.4 mm/year, that slightly higher than that for the less alloyed commercial alloy ML10 (approximately 2.5 mm/year) tested under similar conditions. Furthermore, the alloy was subjected to tests for ignition resistance when in contact with air. It was observed that with continuous airflow over the specimen’s surface, ignition centers appear at t = 625 °C due to the breakdown of the oxide film, causing the alloy to nearly completely melt. Therefore, the GEWZ522K alloy can be employed as a high-strength casting alloy. However, during the operation of cast parts, particular attention must be paid to safeguarding the surface of these parts against corrosion.

Solidification analysis for variable thickness aluminum castings: simulation and chill design insights

Manufacturing high-quality casting parts with complex geometries requires high engineering skill and precision. One essential quality concern is isolated hot spots within the castings, often in thick sections. Each hot spot must be consistently fed or mitigated through directional solidification techniques. The impact of various mold sands and the geometry of chill parts on solidification direction was investigated using specialized casting and general-purpose simulation programs. A parametric optimization method was employed to analyze directional solidification to adjust the geometry of the chill parts. The results indicate that employing diverse mold sands to enhance cooling in the thick sections was a viable strategy for achieving directional solidification in parts where the feeding pathway is obstructed due to changes in cross-section. Furthermore, the study revealed that intricate details in the chill part’s geometry are not critical; however, a minimum volume (or weight) was necessary for adequate directional solidification. Lastly, an easily applicable mathematical model has been developed to determine the required volume of chill parts to ensure successful directional solidification.