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This study aims to optimize injection molding process parameters to reduce defects, including warpage and short shots, in the manufacturing of Set-Top Box components. The Design of Experiments (DoE) methodology, specifically the Taguchi approach with a L8 orthogonal array, was employed to investigate six critical parameters: flow rate, melt temperature, mold temperature, holding pressure, gate diameter, and runner diameter. The research utilized Analysis of Variance (ANOVA) to assess the statistical significance and impact of each parameter on the faults. The findings indicated that melt temperature, mold temperature, and holding pressure substantially affect warpage, with melt temperature contributing to 48.08% of the fluctuation. The mold temperature and holding pressure accounted for 21.37% and 6.90%, respectively. The study emphasizes the necessity of optimizing these parameters to mitigate warpage and short shots, therefore enhancing the quality and dimensional stability of injection-molded components. The results provide actionable recommendations for improving product quality and efficiency in injection molding operations, facilitating additional research on process optimization. [ABSTRACT FROM AUTHOR]

AlN, with its ultra-wide bandgap, is highly attractive for modern applications in deep ultraviolet light-emitting diodes and electronic devices. In this study, the surface and cross-sectional properties of AlN films grown on flat and nano-patterned sapphire substrates are characterized by a variety of techniques, including photoluminescence spectroscopy, high-resolution X-ray diffraction, X-ray photoelectron spectroscopy, ultraviolet photoelectron spectroscopy, and Raman spectroscopy. The results indicate that different sapphire substrates have minimal impact on the photoluminescence spectrum of the epitaxial films. As the temperature increased, the radius of curvature of the AlN films increased, while the warpage decreased. The AlN films grown on nano-patterned substrates exhibited superior quality with less surface oxidation. During the growth of AlN thin films on different types of substrates, slight shifts in the energy bands occurred due to differences in the introduction of carbon-related impurities and intrinsic defects. The Raman shift and full width at half maximum (FWHM) of the E2(low), A1(TO), E2(high), E1(TO), and E1(LO) phonon modes for the cross-sectional AlN films varied with the depth and temperature. The stress state within the film was precisely determined with specific depths and temperatures. The FWHM of the E2(high) phonon mode suggests that the films grown on nano-patterned substrates exhibited better crystalline quality. [ABSTRACT FROM AUTHOR]

Making molds in the injection molding manufacturing process is one of the basic steps that functions to prevent product defects during the production process. The product defects that most often occur in this manufacturing process include shrinkage and warpage defects. This research will discuss the mold design for the APC SF 11x4.7 propeller product with a twist variation of 45o and minimum shrinkage and warpage values. Glass Fiber Reinforced Polypropylene (GFRPP) will be used as the propeller product material. The entire design process to testing will be carried out using software assistance. The Taguchi method with an L9 orthogonal array matrix (34) was used in this research. where L9 explains that the experiment will be carried out nine times, and 34 means there are three levels and four main factors. The four main factors consist of packing pressure, packing time, melting temperature and injection pressure. The Taguchi method is used with the aim of making it easier to find the variation value that produces the lowest shrinkage and warping defects in the product. The simulation results show that the variation with the smallest shrinkage value produces a value of 7.9% and the variation with the smallest warpage value produces a value of 1.051 mm

Cycloaliphatic epoxides exhibit post‐light irradiation heat‐induced polymerization, creating warp‐resistant green bodies during sintering. However, their use in light polymerization three‐dimensional (3D) printing is limited by slow photo‐curing speeds. In this study, a photo‐cationic polymerizable ceramic slurry was developed for 3D printing by mixing oxetane with cyclo‐aliphatic epoxide. This mixture improved photo‐curing speed, reduced resin viscosity, and enhanced the ceramic slurry's solid content. Additionally, we optimized the slurry by considering the specific and content ratio of photosensitizers and light absorbers. The optimized slurry polymerized unreacted functional groups in the polymer, improving the fracture strength of the green bodies through enhanced crosslinking density and uniformity in each layer. Ultimately, a sintered body without warpage was produced by the improved green bodies. This approach provides a solution related to controlling the photocuring speed and expands the potential applications of 3D printing in areas where the precision and stability of the printing material are required. [ABSTRACT FROM AUTHOR]

Chip bonding, an essential process in power semiconductor device packaging, commonly includes welding and nano-silver sintering. Currently, most of the research on chip bonding technology focuses on the thermal stress analysis of tin–lead solder and nano-silver pressure-assisted sintering, whereas research on the thermal stress analysis of the nano-silver pressureless sintering process is more limited. In this study, the pressureless sintering process of nano-silver was studied using finite element software, with nano-silver as an interconnect material. Using the control variable method, we analyzed the influences of sintering temperature, cooling rate, solder paste thickness, and solder paste area on the residual stress and warping deformation of power devices. In addition, orthogonal experiments were designed to optimize the parameters and determine the optimal combination of the process parameters. The results showed that the maximum residual stress of the module appeared on the connection surface between the power chip and the nano-silver solder paste layer. The module warping deformation was convex warping. The residual stress of the solder layer increased with the increase in sintering temperature and cooling rate. It decreased with the increase in coating thickness. With the increase in the coating area, it showed a wave change. Each parameter influenced the stress of the solder layer in this descending order: sintering temperature, cooling rate, solder paste area, and solder paste thickness. The residual stress of the nano-silver layer was 24.83 MPa under the optimal combination of the process parameters and was reduced by 29.38% compared with the original value of 35.162 MPa. [ABSTRACT FROM AUTHOR]

In practical applications, polyurethane (PU) foam must be rigid to meet the demands of various industries and provide comfort and protection in everyday life. PU foam components are extensively used in structural foam, thermal insulation, decorative panels, packaging, imitation wood, and floral foam, as well as in models and prototypes. Conventional technology for producing PU foam parts often leads to defects such as deformation, short shots, entrapped air, warpage, flash, micro-bubbles, weld lines, and voids. Therefore, the development of rigid PU foam parts has become a crucial research focus in the industry. This study proposes an innovative manufacturing process for producing rigid PU foam parts using silicone rubber molds (SRMs). The deformation of the silicone rubber mold can be predicted based on its wall thickness, following a trend equation with a correlation coefficient of 0.9951. The volume of the PU foam part can also be predicted by the weight of the PU foaming agent, as indicated by a trend equation with a correlation coefficient of 0.9824. The optimal weight ratio of the foaming agent to water, yielding the highest surface hardness, was found to be 5:1. The surface hardness of the PU foam part can also be predicted based on the weight of the water used, according to a proposed prediction equation with a correlation coefficient of 0.7517. The average surface hardness of the fabricated PU foam part has a Shore O hardness value of approximately 75. Foam parts made with 1.5 g of water added to 15 g of a foaming agent have the fewest internal pores, resulting in the densest interior. PU foam parts exhibit excellent mechanical properties when 3 g of water is added to the PU foaming agent, as evidenced by their surface hardness and compressive strength. Using rigid PU foam parts as a backing material in the proposed method can reduce rapid tool production costs by about 62%. Finally, an innovative manufacturing process for creating large SRMs using rigid PU foam parts as backing material is demonstrated. [ABSTRACT FROM AUTHOR]

Warpage deformation is a typical phenomenon for polymer injection-molded parts, mainly caused by unbalanced cooling, and it is inevitable. Complex process parameters usually lead to uncontrollable thermal behavior of the polymer materials during injection molding and significant experimental errors. This work presents an experimental mold with a flat mold cavity and nine local heating sections to determine the exact effect of temperature difference on the thermal deformation of injection molded parts. Through local heating at different positions, different warpage deformation was caused. Experimental results demonstrated the relationship between the local temperature and the local thermal warpage. The predicted results of local temperature distribution by numerical simulation presented a strong negative correlation with the experimental results (R2 = 67%); however, the warpage prediction results by numerical simulation were moderate (R2 = 35%). Machine learning with neural networks was further conducted based on the experimental results. When more data was given with a suitable neural network structure, the model prediction accuracy of warpage could be up to 97%, while for the extrapolation test, the prediction accuracy could also be up to 89%. This local thermal heating technique and neural network modeling method can be applied in further theoretical investigation of warpage of injection molded parts and support the development of new models with high accuracy in predicting warpage deformation. [ABSTRACT FROM AUTHOR]

The finite element method combined with the experiment analyzed the evolution mechanism of the plastic strain state and warping deformation of the TA2/Q345R composite plate during heat treatment. Then, the factors influencing plastic strain state and shape warping in the composite plate were discussed. The results show that during the heat treatment process, the composite plate’s internal strain state and macroscopic shape state are impacted by the thermal strain and bending strain between the heterogeneous metal layers, and both are in a continuous dynamic variation state. Therefore, the ultimate deformation behaviour of the composite plate depends on the accumulation and inheritance of plastic deformation during heat treatment. There is a critical value of the composite ratio and the total thickness of the composite plate, respectively, which determines the direction of the warpage after heat treatment. [ABSTRACT FROM AUTHOR]

Warpage in semiconductor packages is a critical issue that affects their reliability and performance. This study aims to minimize the warpage of a bi-material dummy package by optimizing the post-mold curing (PMC) temperature profile. A warpage simulation model was developed considering the viscoelastic properties and cure shrinkage behavior of the epoxy molding compound (EMC). A compression molding monitoring system was also developed to analyze the cure behavior of the EMC. The gelation point of the EMC during compression molding was determined using a dielectric sensor, while cure shrinkage behaviors were analyzed using a fiber Bragg grating sensor. Viscoelastic properties were characterized through stress relaxation tests, and thermal properties were measured using three-dimensional digital image correlation. The developed simulation model was used to optimize the PMC temperature profile using a genetic algorithm. Experimental validation showed that the optimized temperature profile reduced the warpage from ∼1519 μm to 486 μm compared to a linear profile. The findings of this study have broader implications for the design and manufacturing of semiconductor packages, as the proposed approach can be applied to minimize warpage and improve package reliability.

The thermal balance of injection molds is defined by the cooling channel layout. However, the fluid tempering of injection molds underlies certain restrictions concerning the thermal dynamic and the local limitation of the zone of influence. The optimal heat balance within the mold to minimize warpage cannot be solely achieved with conformal cooling channels. Ceramic heating coating systems applied by Thermal Spraying on the cavity wall are a novel tempering method for high heating rates and offer the possibility of a more local heat input. In terms of the thermal mold design, the position and size of local heating coating systems need to be determined. A methodology is proposed, which connects the optimization of part warpage by defining the necessary local heat flux within the mold with the determination of the heating coating placement. Due to the dependence of the coating placement on the heating time and the power, different decision criteria of these parameters are discussed with regard to the process efficiency. The developed methodology can calculate the necessary heating power distribution to homogenize the surface temperature and freeze time. A second step discretizes the heating power distribution to certain manufacturable heating zones. [ABSTRACT FROM AUTHOR]

Double‐injection molding involves the use of two injection units, A and B, which can combine two different plastics into one part in a single injection molding process. Double‐injection molding can promote the recycling of plastic waste as well as improve the performance and dull appearance of plastic products made from recycled materials. However, the warpage of parts is a significant challenge in double‐injection molding. Warpage is significantly affected by the properties of the recycled material and injection molding process. In this study, the relationship between the warpage of double‐injection‐molded parts using raw and recycled materials was studied through uniform design experiments. To investigate the processes and warpage, the material was recycled several times, and its properties were tested. A regression model was established to describe the quantitative relationship between the important parameters and warpage. The number‐average molecular weight and weight‐average molecular weight exhibited the largest decrease after the first recycling cycle with a 21.11% and 41.11% decrease, respectively. The melting temperature decreased from 164.61 to 159.35°C, and the crystallinity did not change significantly. The processing parameters varied with the change in the properties of PP recycled materials, with the melt temperature decreased from 225 to 210°C. In addition, the number of recycling cycles and holding time for B were the most important factors influencing the warpage of double‐injection‐molded parts, followed by holding time for A and melt temperature for A. Warpage can be reduced by increasing holding times B and A. The experimental results provide important data for reducing the warpage of double‐injection‐molded parts with recycled materials. Highlights: Double‐injection‐molded parts containing recycled materials were prepared.Recycling enhanced the filling capacity of polypropylene.The regression model of warpage with variables was established.Warpage can be improved by adjusting processes and materials. [ABSTRACT FROM AUTHOR]

The food industry holds immense promise for 3D printing technology. Current research focuses mainly on optimizing food material composition, molding characteristics, and printing parameters. However, there is a notable lack of comprehensive studies on the shape changes of food products, especially in modeling and simulating deformations. This study addresses this gap by conducting a detailed simulation of the starch gel printing and deformation process using COMSOL Multiphysics 6.2 software. Additive manufacturing (AM) technology is widely acclaimed for its user-friendly operation and cost-effectiveness. The 3D printing process may lead to changes in part dimensions and mechanical properties, attributable to the accumulation of residual stresses. Studies require a significant amount of time and effort to discover the optimal composition of the printed material and the most effective deformed 3D structure. There is a risk of failure, which can lead to wasted resources and research delays. To tackle this issue, this study thoroughly analyzes the physical properties of the gel material through COMSOL Multiphysics 6.2 software, It simulates the heat distribution during the 3D printing process, providing important insights into how materials melt and solidify. Three-part models with varying aspect ratios were meticulously designed to explore shape changes during both the printing process and exposure to an 80 °C environment, employing NMR and rheological characterization. Using the generalized Maxwell model for material simulation in COMSOL Multiphysics, the study predicted stress and deformation of the parts by analyzing solid heat transfer and solid mechanics physical fields. Simulation results showed that among three models utilizing a gel-PET plastic membrane bilayer structure, Model No. 1, with the largest aspect ratio, exhibited the most favorable deformation under an 80 °C baking environment. It displayed uniform bending in the transverse direction without significant excess warpage in the edge direction. In contrast, Models No. 2 and No. 3 showed varying degrees of excess warpage at the edges, with Model No. 3 exhibiting a more pronounced warpage. These findings closely aligned with the actual printing outcomes. [ABSTRACT FROM AUTHOR]

There are multiple factors that contribute to the warpage problems where molten part is distorted during solidification in rotational molding. A novel warpage simulation model is developed accounting for the effect of various process parameters like crystallinity change, temperature‐dependent polymer properties, and cooling rate. The polymer material properties were readily not available; they were constructed from literature data with adaptation to the process condition and their significance on simulation results is discussed in detail. A systematic detailed simulation analysis of warpage in box part was done and results were compared with experimental values published in literature. The warpage magnitude under seven different cooling methods are presented. It was found that externally water cooled parts exhibited maximum warpage which is also corroborated by literature data while the parts cooled by water on either sides of the part show reduction in warpage. The warpage simulation results show an agreement with deviation ranging from 1.2% to 69% with experimental values. Highlights: A novel thermal expansion coefficient approach was adopted for the first time to develop warpage simulation of rotationally moulded parts.Inclusion of temperature‐dependent thermo‐mechanical properties of polymer in the simulation model.The cooling rate is directly proportional to the warpage in the parts.Validating warpage simulation results for seven different cooling methods with experimental measurements.Maximum warpage is seen where the highest temperature difference exists between part and mould. [ABSTRACT FROM AUTHOR]

We discuss a technique for investigating changes in complex topography and shape of structures using geomorphometric methods to study surfaces of wafers and membranes formed by the Bosch process. The wafers were analyzed before and after the deposition of the SiO2 layer. The membranes were analyzed during the bulge testing. The study was carried out using maps of the catchment area and principal curvatures taking into account artifacts of the approximation of experimental data. We found a correspondence between the distribution of lines connecting the highest surface areas before and after the deposition of the SiO2 layer on the wafers. For membranes with structure: Al(0.8 μm)/SiO2(0.6 μm)/Al(1.1 μm), pSi*(0.8 μm)/SiNx (0.13 μm)/SiO2, Al(0.6 μm) we also found that features of membrane boundaries are mainly caused by their initial shape rather than change under the action of an applied pressure. The advantages of geomorphometric methods for studying changes in the shape of wafers and thin-film membranes in technological processes for the manufacturing of microelectronic devices are shown in comparison with traditional methods for analyzing surface topography maps. [ABSTRACT FROM AUTHOR]

Material extrusion (MEX) continues to be a pivotal additive manufacturing (AM) process, involving the selective heating and layer-by-layer deposition of material. However, conventional finite-element models (finite-element analysis) face limitations in accurately simulating the MEX process, highlighting the need for experimental validation. This paper highlights an advanced material modeling technology that streamlines the development of composite parts using large format AM (LFAM). It specifically focuses on a thermoplastic acrylonitrile butadiene styrene (ABS) matrix composite material enriched with 20% short carbon fibers. The study employs integrated computational materials engineering, integrating (i) the manufacturing process, (ii) the material's microstructure, (iii) homogenization techniques, and (iv) the performance of the final part. The development of a digital twin for pellet extrusion is proposed, emphasizing the importance of micro-structure characterization to account for warpage and residual stresses that lead to part distortion. The demonstrator manufactured for this study is a wind turbine mold of a blade section. Experimental tests revealed an elastic modulus of 5.5 GPa and a hardening modulus of 2.4 GPa for the composite. The numerical microscopic model showed a 16% error in the elastic modulus compared to experimental results. The study concludes that the homogenization techniques are effective in predicting the elastic properties but lack accuracy in the plastic region. The application of the model to the LFAM process of pellet extrusion is demonstrated, with simulation results showing a maximum deformation close to the center of the wind turbine blade mold. [ABSTRACT FROM AUTHOR]

When the dissimilar metal composite plate accumulates inconsistent deformation to a certain degree during the heat treatment process, it indicates bad plate morphology such as warpage. Therefore, it is crucial to explore the mechanism of coordinated deformation between layers under thermal–mechanical coupling during heat treatment. This study investigates the interlayer coordinated deformation mechanism of the stainless-steel clad plate (304/Q235 stainless-steel clad plate) under thermal–mechanical coupling by using three heat treatment methods: rapid cooling process, rapid cooling in the high-temperature stage + slow cooling in the low-temperature stage, and rapid cooling + tempering process. And this study enlightens that the temperature field distribution and the longitudinal stress–strain distribution are obtained by using the Abaqus software. The effects of different tensile and thickness ratios on the residual stress are analyzed. The final experiment found that the maximum longitudinal stress and plastic strain appear on the upper and lower surfaces during heat treatment. The rapid cooling heat treatment process has light warpage and good shape. When the thickness ratio of the composite plate is 1:4, the warpage is the lightest. The increase of set tension will increase the compressive stress value in the residual stress. In contrast, the tensile stress value will decrease. [ABSTRACT FROM AUTHOR]

We investigate the microstructural evolution of electrochemically deposited poly-crystalline Cu films during subsequent thermal process cycles at mild maximum temperatures, compatible with the integration in advanced metallization schemes for electronic device manufacturing. The modifications induced by the thermal budget have been characterized at different scales (from the film-substrate interface to the wafer scale) with different complementary techniques: X-ray Diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), and dynamical warpage measurements. Moreover, the film internal grains' evolution has been modelled by a tri-dimensional on-cell model, derived by the Pott-like multi-states configurational energy dependence, able to consider multiple orientation of the grains and densification kinetics in the canonical ensemble. Finally, a macroscopic model of the warpage dependence on the process conditions is discussed. The presented joint theoretical and experimental analysis provides a complete and consistent scenario of the grain densification phenomenon and its impact for the Cu film microstructure and the composite system morphology, indicating several strategies for the integration of the process in real device structures. [ABSTRACT FROM AUTHOR]

The paper considers the main types and causes of surface damage that lead to the destruction and failure of large-sized bearings of motor-wheel reducers (MWR) of BELAZ mining dump trucks. The disadvantages of 20Х2Н4A (20Kh2N4A) steel currently used for the manufacture of large-sized MWR bearings are given. It is shown that using this steel it is problematic to achieve a high and uniform distribution of microhardness values over the thickness of the hardened layer. The analysis of the destruction of this type of bearings made of 20Kh2N4A steel largely determining the required life of the motor-wheel reducers, is carried out. The obtained research results indicate the need to use new grades of steels for the manufacture of largesized MWR bearings.

Chip bonding, an essential process in power semiconductor device packaging, commonly includes welding and nano-silver sintering. Currently, most of the research on chip bonding technology focuses on the thermal stress analysis of tin–lead solder and nano-silver pressure-assisted sintering, whereas research on the thermal stress analysis of the nano-silver pressureless sintering process is more limited. In this study, the pressureless sintering process of nano-silver was studied using finite element software, with nano-silver as an interconnect material. Using the control variable method, we analyzed the influences of sintering temperature, cooling rate, solder paste thickness, and solder paste area on the residual stress and warping deformation of power devices. In addition, orthogonal experiments were designed to optimize the parameters and determine the optimal combination of the process parameters. The results showed that the maximum residual stress of the module appeared on the connection surface between the power chip and the nano-silver solder paste layer. The module warping deformation was convex warping. The residual stress of the solder layer increased with the increase in sintering temperature and cooling rate. It decreased with the increase in coating thickness. With the increase in the coating area, it showed a wave change. Each parameter influenced the stress of the solder layer in this descending order: sintering temperature, cooling rate, solder paste area, and solder paste thickness. The residual stress of the nano-silver layer was 24.83 MPa under the optimal combination of the process parameters and was reduced by 29.38% compared with the original value of 35.162 MPa.

Warpage is one of the prominent issues in Fused Filament Fabrication. The cause of this is the rapid cooling of the polymer during extrusion. The residual thermal stresses accumulated within the print part result in a shape distortion and subsequent detachment of the object from the print bed. In this study, both experimental and numerical approaches were used to identify the stresses due to thermal shrinking that occurs in soft polymers such as wax. A temperature sweep test was performed using a rotational rheometer to measure the magnitude of axial forces that are generated due to the thermal shrinking of a thin layer of 3D printable wax. The thermal stresses responsible for warpage were computed analytically and using the FEA. It was found that due to thermal processes, the stress magnitude can reach a value of 1.17 MPa. This value is enough to cause the plastic deformation in the wax part having a thin elongated shape. In addition, Taguchi's robust design has identified two major FFF parameters that impact the warpage in amorphous soft polymers. They are the printing speed and the print bed temperature. To achieve a low level of warpage, it is important to make sure that the layer deposition occurs at medium speeds and the print bed temperature is moderately high according to the findings of this study. [ABSTRACT FROM AUTHOR]

Analyses in the present work focus on understanding the influence of the WAAM (wire arc additive manufacturing) deposition pattern and travel speed on residual stress and warpage in aluminum alloy. The thermal profiles are analyzed using thermomechanical FE simulations. Analysis shows that the out–in deposition pattern leads to the highest level of residual stress and warpage. It is also found that an increase in the travel speed decreases the peak temperature and thermal gradient during the AM deposition, which results in a lower level of residual stress generation. A comparison of results for the line-type patterns (raster and alternate) suggests that the deposition interval between each deposition has little influence on thermal profiles, residual stress generation, and warpage. However, the contour-type patterns significantly affect the heat transfer, thermal gradient, and cooling rate during the AM deposition. [ABSTRACT FROM AUTHOR]

Injection molding (IM) is an ideal technique for the low-cost mass production of moderately thick plane lenses (MTPLs). However, the optical performance of injection molded MTPL is seriously degraded by the warpage and sink marks induced during the molding process with complex historical thermal field changes. Thus, it is essential that the processing parameters utilized in the molding process are properly assigned. And the challenges are further compounded when considering the MTPL molding energy consumption. This paper presents a set of procedures for the optimization of injection molding process parameters, with warpage, sink marks reflecting the optical performance, and clamping force reflecting the molding energy consumption as the optimization objectives. First, the orthogonal experiment was carried out with the Taguchi method, and the S/N response shows that these three objectives cannot reach the optimal values simultaneously. Second, considering the experimental data scale, the back propagation neural network updated by the particle swarm optimization method (PSO-BPNN) was applied to establish the complex nonlinear mapping relationship between the process parameters and these three trade-off objectives respectively. Then, the Pareto optimal frontier of the multi-objective optimization problem was attained by multi-objective particle swarm optimization using a mutation operator and dominance coefficient algorithm (OMOPSO). And the competitive relationship between these objectives was further confirmed by the corresponding pairwise Pareto frontiers. Additionally, the TOPSIS method with equal weights was employed to achieve the best optimal solution from the Pareto optimal frontier. The simulation results yielded that the maximum values of warpage, sink marks, and clamping force could be reduced by 7.44%, 40.56%, and 5.56%, respectively, after optimization. Finally, MTPL products were successfully fabricated. [ABSTRACT FROM AUTHOR]

In this paper, the influence of different cooling processes on the stress, strain and shape warping of low carbon bainite steel Q690D during laminar cooling is analyzed, and a temperature stress–strain coupled finite element model of low carbon bainite steel Q690D is established. For the warping deformation of medium and thick plates, edge shielding, symmetrical cooling of upper and lower surfaces and head shielding are adopted for their length, width and thickness. The results show that when using edge occlusion, the best occlusion distance is 0.1 m; when the upper and lower surfaces are symmetrically cooled, the stress symmetry is basically realized; when head shielding is used, the best masking distance is 0.2 m. [ABSTRACT FROM AUTHOR]

In the process of preparing textile composites by resin transfer molding (RTM) method, both the upper and lower surface of the mold will interact with the composite parts due to the mismatch of thermal expansion coefficient between the mold and the part, resulting in warpage deformation. To address this key technical problem, this article first studied the effect of mold on the warpage deformation of composite material under different fiber volume fractions. Then a mold–part interaction modeling method for RTM process with nonthermoelastic deformation is proposed. By introducing shear layers between the upper and lower surfaces of the mold and the composite part, a finite element simulation model for predicting the curing deformation of the component is established and experimentally verified. The results show that the effect of mold–part interaction on the warpage deformation of the composite decreases with increasing fiber volume fraction. Meanwhile, the proposed modeling method can avoid complete material characterization, and the comparison between experimental and simulation results proves that the model can accurately simulate the curing deformation of composite components under the same process conditions. Finally, the analysis reveals that the interaction caused by thermal mismatch between the composites and the mold is less related to the intermediate layup, but mainly related to the fiber orientation of the layup layer in contact with the mold. Highlights: The warpage deformation law of the mold on the composites with different fiber volume fractions is investigated.A mold–part interaction modeling method for a resin transfer molding process with nonthermoelastic deformation is proposed, where the mold stretching effect is represented by the cumulative effect of the interaction between the two layers on the upper and lower surfaces of the part. [ABSTRACT FROM AUTHOR]

The high crystallinity and fast crystallization rate of polypropylene (PP) often result in severe warpage of final parts prepared by means of material extrusion additive manufacturing (MEAM). In this work, the effect of bed temperature (Tb) and nozzle temperature (Tn) on the dimensional accuracy and mechanical property of MEAM‐printed PP copolymer parts was investigated. It is found that raising Tb and Tn could significantly reduce the warpage of PP parts by regulating the crystallization behavior of PP. Specially, the amount of γ‐crystal grows obviously while the total crystallinity remains unchanged, as Tb or Tn increases. Moreover, the more the content of γ‐crystal, the lower the warpage height of PP samples is. Hence, a close correlation between the content of γ‐crystal and part deformation of MEAM‐printed PP parts is successfully established. This is mainly related to the large rigidity of γ‐crystal, which significantly reduces the volume shrinkage of PP during MEAM process. Besides, the raise of Tb or Tn also enhances the tensile strength, modulus and the elongation at break of PP parts. This wok provides an effective and convenient method for the manufacture of PP parts with good dimensional accuracy and excellent mechanical properties by means of MEAM techniques. [ABSTRACT FROM AUTHOR]

3D printing technology has subverted the traditional process manufacturing process. The main algorithms used in the model data processing is a key step that affects the accuracy of the model printing. This paper focuses on the 3D printing path planning algorithm. Analyze the realistic requirements for the coexistence of artistry and craftsmanship in 3D printing products and develop a design scheme. Visualize the 3D printing path planning suggested for contour information in the partition linear scanning corner filling algorithm. Set the 45° scanning direction of the X-axis, adjust the fitted spline curve function reciprocally, and even out the path of the printer in the corner of the partitioned scanning path. Improve printing accuracy. Combined with the experimental equipment to set up the 3D printer’s operating code, the proposed Hilbert filling curve method, combined with three groups of comparison tests, verified the accuracy improvement benefits of the composite scanning algorithm in this paper. Taking the experimental data of the uncovered box group as an example, the composite scanning algorithm of this paper changes the maximum warpage from 0.23mm to 0.16mm, which is an improvement of 30.43%, and the average warpage from 0.1675mm to 0.095mm, which is an improvement of 43.28%. The reduction and optimization of warpage not only shows the improvement of accuracy of 3D printing technology but also optimizes the shape of 3D products.

Injection molds are production tools that require detailed analysis based on the quality of the resulting part, the impact on cycle times, and the expected production volume. Cooling channels also play a critical role in mold performance and product quality as they largely determine cycle time. Designs that incorporate conformal cooling channel (CCC) geometries that conform to or align with the part contour are currently being explored as an alternative to conventional cooling channel designs in injection molds. In this study, a simulation of CCC geometries was performed and their effects on mold temperatures and warpage were investigated. Two cross-sectional geometries, circular and square, were selected for a three-factor level design of experiments (DOE) analysis. The response variables used were mold temperatures and part warpage. A cup-shaped part with upper and lower diameters of 54 and 48 mm, respectively, a height of 23 mm and a thickness of 3 mm was used for the injection molded part. A comparison was also made between two materials for the injection mold, steel and polycarbonate. The DOE results showed that the distance between the CCC and the injected part and the diameter or side of the square have significant effects on the response variables for both systems (steel and polycarbonate molds). In addition, a comparison between conventional and conformal cooling channels was analyzed using a cup-shaped part and a less rigid part geometry. The finite element simulation results show a 9.26% reduction in final warpage in the cup-shaped part using CCCs compared with the conventional cooling methods in steel. When using parts with lower geometry stiffness, the use of CCCs reduced final part warpage by 32.4% in metal molds and by 59.8% in polymer molds. [ABSTRACT FROM AUTHOR]

Polyolefin-based thermoplastics such as polyethylene and polypropylene constitute a major fraction of the polymers employed in commodity applications due to their ease of processability, durability, and economic viability. Additive manufacturing (AM) of polyolefins offers both a viable path toward functional prototyping of design concepts and direct manufacturing of end-use parts. Melt-based AM of polyolefins is more challenging than other semicrystalline polymers (polyamides) due to the relatively high levels of volumetric shrinkage encountered during crystallization of such polymers that lead to significant issues related to warpage and interlayer adhesion. The focus of this review is to evaluate the latest state-of-the-art for processing polyolefins by powder bed fusion (PBF) and material extrusion (MatEx) AM modalities. Recent progress in processing neat, filled, and blends of polyolefins using PBF and MatEx are discussed to highlight the importance of the rheological and morphological characteristics of the polymer melt on the printed parts performance. The existing challenges to AM of polyolefins are emphasized and strategies to address the limitations are recommended through a better understanding of the associated process-structure-property relationships. A holistic approach spanning synthetic modifications for feedstock development, improved system design, and physics-guided process parameter selection is required to broadly adopt melt-based AM of polyolefins. [ABSTRACT FROM AUTHOR]

In plastic injection molding (PIM), the process parameters determine the quality and productivity of molded parts. The traditional injection molding process analysis method mainly relies on production experience. It is lack of advanced and rationality and seriously increases production costs. In this paper, a hybrid multiobjective optimization method is proposed to minimize the warpage, volumetric shrinkage and cycle time. The method integrates orthogonal experimental design, numerical simulation, and the metamodel method with multiobjective optimization. The orthogonal experiment chooses seven parameters as the design variables to generate sampling data and determines key factors that affect product quality by the numerical simulation. A gradient-enhanced Kriging (GEK) surrogate model strategy is introduced to construct the response predictors to calculate objective responses in the global design space. Multipopulation differential evolution (MPDE) is conducted to locate the Pareto-optimal solutions, where the response predictors are taken as the fitness functions. This study shows that the proposed GEK-MPDE method can reduce warpage, volumetric shrinkage and cycle time by 5.7 %, 4.7 %, and 18.1 %, respectively. It helps plastic industry to realize collaborative scheduling of multiple tasks between different production lines by providing a low-cost and effective dynamic control method. [ABSTRACT FROM AUTHOR]

The quality of injection molded polymer products can be compromised due to the occurrence of residual stresses inherent to the molding process. In order to determine the parameters that influence the dimensional changes and residual stresses of injection molded polypropylene; computer simulations, chemical, thermal and mechanical characterizations were performed. Statistically, we evaluated two conditions of part geometry (with and without rib), three holding pressures (25, 60 and 96 MPa) and three post-molding conditions (without restriction, with restriction followed by water, and with restriction followed by annealing). The specimens molded with ribs and lower holding pressures showed greater warpage, which agreed with the computer simulations. The smooth specimens submitted to annealing followed by air cooling showed lower warpage in relation to the other two post-molding conditions. The thermal analysis presented a lower degree of crystallinity in the samples without post-molding restrictions. The samples submitted to the annealing heat treatment showed an increase in impact strength, and there was no significant variation in the modulus of elasticity for the post-molding conditions evaluated. The ribbed specimens exhibited higher residual stresses than the smooth specimens. Samples with greater warpage had lower residual stresses. All samples showed a tensile-compression-tensile behavior along the hole depth. The results showed that the shrinkage values were not influenced by any of the parameters evaluated. However, on the warpage the factor that exerts the greatest influence is the geometry of the part, followed by the holding pressure; and the post-molding condition presented the least influence among the analyzed factors. [ABSTRACT FROM AUTHOR]

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One of the most important steps in the extrusion processing of ceramic inks is the initial drying of the ceramic parts. This study aimed to investigate the drying behaviour of an Al2O3-based ceramic ink optimised to be processed by extrusion processing methods, e.g., direct ink writing. Carboxymethylcellulose (CMC) was singly added to a suspension of deionised water and Al2O3 (50:50 wt.%) to perform as a dispersing and plasticising agent. To assess moisture loss as a function of time, the ceramic inks were extruded into two types of polymeric moulds: one with a completely closed profile producing cylindrical samples (disks) and one with an open profile producing ceramic bars. After the injection of the inks, the moulds were exposed to different controlled temperatures (20 and 40 °C) for up to 180 h; moisture loss and warpage were periodically measured, and exponential mathematical expressions (moisture loss × drying time) were obtained. The Al2O3-bars dried for 24 h in open moulds at 20 and 40 °C presented longitudinal warpages of 4.5% and 9%, respectively, while the Al2O3 disks dried in closed moulds presented warpages of 3.5% and 7% in these same temperatures (20 and 40 °C, respectively). The samples were sintered at 1610 °C for 4 h and characterised by scanning electron microscopy (SEM), relative density (Archimedes principle), and X-ray diffraction (XRD), presenting a relative density of 92.3 ± 0.5%, α-Al2O3 as crystalline phase and grain with equiaxed morphology varying between 1 and 5 μm.

It is known that products made of polymer materials or especially polymer materials with glass fiber and carbon fiber are used in many different areas such as automotive, aerospace, and defense. At this point, studies in the literature have gained momentum due to the combination of fiber-reinforced polymer materials emerging as a result of technological developments and industrial demands, and the fused deposition modeling (FDM) method providing the production of parts in desired sizes and complexity. Residual stresses and distortions occurring in polymer-based composite parts produced with FDM are among the problems that should be minimized. In this study, the influences of fiber ratio (%10, %15, and %20), infill rate (%20, %50, and %80), and infill pattern (line, honeycomb, and triangle) on the residual stresses and warpages generating in impact test specimens produced from glass fiber reinforced ABS filaments by fused deposition modeling were tried to be determined with the Digimat 2021 program. As a result of the findings, it was determined that the distortion values decreased and the thermal residual stress values went up with the increase in fiber ratio and infill rate. In addition, it can be reported that the distortions that bring out as a result of the separation of the produced parts from the production platform are caused by the high deformations condensing at the lower corner points of the parts.

Abstract A correlation effect between particle size of kaolin clay and injection moulding process parameters on impact strength, shrinkage and warpage of high-density polyethylene/kaolin clay (HDPE/KC) composites was carried out using analysis of variance (ANOVA). Kaolin clay with particle sizes of < 75, 75–106 and 106–150 μm was used. The process parameters that were taken into consideration were injection temperature, packing pressure and packing time. In general, experimental results showed that the impact strength and shrinkage of the HDPE/KC composites clearly depended on the injection temperature. However, no clear dependency of the warpage on the injection temperature was observed. Furthermore, clay particle size showed to have an influence only on the shrinkage of the composites, where smaller clay particle size led to injected composite parts with relatively less shrinkage. ANOVA showed that the effect of injection temperature on shrinkage of composites containing clay particle sizes of < 75 and 106–150 μm was statistically significant (p = 0.01 and 0.04, respectively). However, the effect of injection temperature on shrinkage of the composite made with clay having particle sizes of 75–106 μm was not significant (p = 0.07). ANOVA also indicated that the injection temperature effect on the impact strength of composites that contain clays with particle sizes of < 75 μm and 75–106 μm was significant (p = 0.03 and p = 0.01, respectively), whereas the injection temperature effect on the impact strength of the composite containing clay with a particle size of 106–150 μm was not significant (p = 0.17). Contrary to shrinkage and impact strength, the effect of the studied parameters on the warpage was not statistically significant, which was in good agreement with the experimental observations.

The current work investigates the auxetic tensile deformation behavior of the inversehoneycomb structure with 5 × 5 cells made of biodegradable poly(butylene adipate-coterephthalate) (PBAT). Fused deposition modeling, an additive manufacturing method, was used to produce such specimens. Residual stress (RS) and warpage, more or less, always exist in such specimens due to their layer-by-layer fabrication, i.e., repeated heating and cooling. The RS influences the auxetic deformation behavior, but its measurement is challenging due to its very fine structure. Instead, the finite-element (FE)-based process simulation realized using an ABAQUS plug-in numerically predicts the RS and warpage. The predicted warpage shows a negligibly slight deviation compared to the design topology. This process simulation also provides the temperature evolution of a small-volume material, revealing the effects of local cyclic heating and cooling. The achieved RS serves as the initial condition for the FE model used to investigate the auxetic tensile behavior. With the outcomes from FE calculation without consideration of the RS, the effect of the RS on the deformation behavior is discussed for the global force–displacement curve, the structural Poisson's ratio evolution, the deformed structural status, the stress distribution, and the evolution, where the first three and the warpage are also compared with the experimental results. Furthermore, the FE simulation can easily provide the global stress–strain flow curve with the total stress calculated from the elemental stresses. [ABSTRACT FROM AUTHOR]