Hollow Mold Research Articles

(Invited) 3D Printing-Assisted Casting of Conducting Polymers for Bioelectronics

3D structured conducting polymers, known for their high conductivity, low impedance, and tunable form factor, are promising candidates for various bioelectronics applications. However, achieving a balance between structural complexity, electrical conductance, and processing generality has been challenging in these materials. In this talk, I will discuss our efforts to address this trade-off through 3D printing-assisted casting. Light-based 3D printing is used to create hollow molds, providing structural complexity and design freedom, whereas the casting nature imparts material versatility. The casting molds are made of superabsorbent polymers and printed in a partially hydrated state. Their dehydration provides significant enhancement in feature resolution and excellent thermal and mechanical properties, making them versatile for casting. After casting, over-hydration of the molds facilitate their energy-efficient removal. Using poly(3,4-ethylenedioxythiophene) (PEDOT) as a model system, complex architectures such as octet and truncated octahedron can be achieved. Compositing silver flakes with PEDOT through a thermal injection process leads to prints with conductivity over 6000 S/cm and high environmental stability. This method can potentially be applied to other hard-to-print soft materials and composites.

Study on the Mechanical Properties of 3D-Printed Sand Mold Specimens with Complex Hollow Structures.

Casting, as a fundamental process in metal forming, finds widespread applications in the manufacturing industry. The advent of 3D printing hollow sand mold technology presents a novel method for casting technology to revolutionize traditional dense sand molds, offering increased flexibility in achieving quality control and improvement in casting processes. Consequently, this study delves into an examination of the mechanical strengths of 3D-printed sand molds with complex hollow structures and further investigates the influence of hollow sand mold concession on castings. The results indicate that compressive and high-temperature residual tensile and bending strengths vary in hollow structures. Multi-layer shells have greater high-temperature residual tensile, compressive, and bending strengths than truss hollow sand molds with roughly the same hollow volume fraction. Compared to dense sand molds, hollow sand molds, which have a lower mechanical strength, have better retractability, which helps reduce the residual stress and crack tendency of castings. The breaking of hollow structures is limited to local areas, unlike the penetrative cracking of dense sand molds. The I-beam-shaped casting test results indicate that a hollow structure is beneficial for the preservation of the integrity of a sand mold during the casting process. Compared to dense and truss hollow molds, a multi-layer shell hollow sand structure has the comprehensive advantages that it improves retractability while maintaining strength relatively well, reduces the residual stress, and avoids cracks in castings and itself.

Effects of hollow sand mold on the microstructure and mechanical properties of a low pressure aluminum alloy casting

The hollow mold revolutionizes conventional dense mold design as it can optimize the solidification and cooling processes of casting and offer potential to improve performance of castings. In this paper, the effect of hollow mold structures on the microstructure and mechanical properties of a low pressure thin-walled aluminum alloy conical cabin casting was investigated. A hollow mold combined by four sectors with different shell thicknesses was tactfully designed. The hollow mold structures delayed the cooling and solidification of casting. They significantly reduced the pore defect from 0.4 % to 0.03 % at the lower, from 0.68 % to 0.04 % at the middle and from 0.3 % to 0.03 % at the top, compared to dense mold. In the lower and middle areas of casting, improvements of 1.0 % and 1.1 % in mechanical properties were respectively achieved when applying 50 mm-thick-shell hollow sand molds compared with using dense sand mold, while an improvement of 1.1 % was achieved in the upper area of casting with 70 mm-thick-shell. This allows designers to create hollow molds with different shell thicknesses depending on the position in the casting to meet specific needs. For example, thin shell for the bottom to achieve high fluid flow and feeding while thick shell for the top for improved cooling. For castings with wall thickness of 10 mm–20 mm, the most effective shell thickness for the hollow mold is 50 mm–70 mm. The hollow mold provides the feasibility to differentiated semi-quantitatively control the solidification and cooling processes of castings, which can be applied in production of high-end castings in the future.

Studying the impact of geometrical and cellular cues on myogenesis with a skeletal muscle-on-chip.

In the skeletal muscle tissue, cells are organized following an anisotropic architecture, which is both required during myogenesis when muscle precursor cells fuse to generate myotubes and for its contractile function. To build an in vitro skeletal muscle tissue, it is therefore essential to develop methods to organize cells in an anisotropic fashion, which can be particularly challenging, especially in 3D. In this study, we present a versatile muscle-on-chip system with adjustable collagen hollow tubes that can be seeded with muscle precursor cells. The collagen acts both as a tube-shaped hollow mold and as an extracellular matrix scaffold that can house other cell types for co-culture. We found that the diameter of the channel affects the organization of the muscle cells and that proper myogenesis was obtained at a diameter of 75 μm. In these conditions, muscle precursor cells fused into long myotubes aligned along these collagen channels, resulting in a fascicle-like structure. These myotubes exhibited actin striations and upregulation of multiple myogenic genes, reflecting their maturation. Moreover, we showed that our chip allowed muscle tissue culture and maturation over a month, with the possibility of fibroblast co-culture embedding in the collagen matrix.

Chimney Structure of Hollow Sand Mold for Casting Solidification

The hollow sand mold can affect the cooling of the casting during the solidification process. A chimney structure of a hollow sand mold that mainly consists of a two-layer shell with through channels was proposed. The design method was proposed for the chimney structure. Due to the chimney effect, cool air can enter the chimney from the bottom entrance, and hot air flows out from its top opening. Air transfers heat from the sand mold and forms a temperature gradient from bottom to top. A hollow sand mold with a chimney structure was applied to the wedge plate casting. During the solidification process, natural cooling and forced air cooling through open channels were applied. The effects of the chimney on the microstructure, mechanical properties, and residual stress of the castings under these two different cooling conditions were analyzed and compared with those of the casting in a dense mold. During the solidification stage of the castings, the chimney structure prolonged their solidification time. After solidification, the chimney structure under forced air condition increased the cooling rate of the castings by 61% and the temperature gradient along the vertical direction by a factor of three. The Si content in the Al matrix increased by 20.4%, and the tensile strength increased by 32.66%.

Experimental study on seismic performance of shear wall with precast concrete hollow molds

AbstractA new type of connection between shear walls is proposed for the shear wall with precast concrete hollow molds (PCHM). The overlapping reinforcements are inserted into the PCHM before pouring concrete into the hollow in this method. Full‐scale test specimens are tested under low cyclic loading test to analyze their seismic performance, such as failure modes, hysteretic characters, stiffness degradation, energy dissipation, and ductility. For the precast specimen, although the penetrating crack appears at the horizontal connection, there is no large slippage leading to anchorage failure and disengagement of interfaces. Generally, compared with cast‐in‐situ shear walls, shear walls with PCHM have no large difference in bearing capacity, failure mode, stiffness degradation, energy dissipation and ductility. Therefore, the proposed shear wall with the new type of connection method is worth popularizing and utilizing in practical engineering projects with similar design procedure to cast‐in‐situ structures.

PENGARUH PENAMBAHAN SERBUK GAHARU (Aquilaria malaccensis) TERHADAP KARAKTERISTIK BRIKET ARANG AROMATERAPI DARI LIMBAH ARANG SERBUK KAYU CAMPURAN

This studygaims to analyze the characteristics of aromatherapy charcoal briquettes from mixed wood charcoal powder waste and agarwood wood carried out organoleptic tests in the form of the old ability to burn briquettes to ash when aromatherapy charcoal spreads in a room. The results of the study showed that of the highest charcoal briquette density average value was (0.90 gr/cm3) and the lowest (0.82 gr/cm3), highest moisture content value of (9.33%) and the lowest of (8.46%). Value of flying substances levels (47.9%) and the lowest is (40.66%). Value of the highest ash content characteristics of (40.37%) and the lowest (33.28%). Testing the highest average value of bonded carbon characteristics is 28.82% and the lowest is (9.305%). Value of the highest heating characteristics (4174,696 cal/gr) and the lowest (3784,976 cal/gr). From all the results of the testing of the characteristics of the aromatherapy charcoal briquettes from the mixture of wood charcoal powder and agarwood powder waste on average do not meet ASTM testing standards. The organoleptic test of mold without holes that most quickly consumes aromatherapy at a concentration of 6 grams with 5 minutes and the longest smell of aromatherapy is 12, 18, and 24 grams with 7 minutes with an average of 46 minutes. And organoleptic test with the fastest hollow molds smelled at concentrations of 12 grams, 18 grams, 24 grams at 15 seconds, and on average each concentration had a scent that runs out at 7 minutes with an average of 55 minutes long liters of briquettes.Keywords : Characteristics of Charcoal Briquettes; Organoleptic Test; Mixed Wood Charcoal Waste and Agarwood

The development of rotational molding of waste bamboo powder with LLDPE plastic powder

The objective of this study was to assess the effect of bamboo powder addition and the treatment of its surface on the properties and structure of rotationally molded (rotomolded) polypropylene. In this study we can transform plastic and bamboo powder into a product by putting the raw materials into hollow mold and then cover the mold. The mold is rotated along two axes by burning with high temperature to make liquid plastic flows evenly along the inner surface of the mold with gravity. The results of this research had shown that, by using LLDPE plastic 4 kg, bamboo waste powder 1 kg size of 0.15: 0.30: 0.85 mm tested with humidity 10:15:20% mixed and then molded, it was found that the moisture of waste bamboo powder had a direct effect on molding. If the moisture in the bamboo powder is more than 20%, the work will not be molded. It shown look like a lump. The moisture content less than 15% can be molded as a product. In terms of the size used in this test 0.15: 0.30: 0.85 can be molded well in the range of moisture, not more than 15%.

Development of Intricate Aerogel Articles Using Fused Filament Fabrication

A fused filament fabrication process is used for conversion of polyimide aerogels into bicontinuous gyroid structures to obtain enhanced elasticity. A sacrificial hollow mold in an inverse gyroid shape is first fabricated from high impact polystyrene and is filled with the polyimide sol. After the sol–gel transition, the mold is dissolved in a solvent to yield the gel structure of a gyroid shape. The gel is supercritically dried to recover a free-standing aerogel structure with ultrahigh porosity (98.9%) and low bulk density (0.0146 g/cm3). The bicontinuous gyroid structure of the aerogel offers significant elasticity and high elongation at break compared to an otherwise brittle monolithic aerogel of polyimide. The ability to create intricate aerogel structures opens up a large potential in applications such as sensor housing and acoustic barriers of arbitrary shape and size and load-bearing porous thermally insulating structures that allow breathing.

Auricle shaping using 3D printing and autologous diced cartilage.

ObjectiveTo reconstruct the auricle using a porous, hollow, three‐dimensional (3D)‐printed mold and autologous diced cartilage mixed with platelet‐rich plasma (PRP).MethodsMaterialise Magics v20.03 was used to design a 3D, porous, hollow auricle mold. Ten molds were printed by selective laser sintering with polyamide. Cartilage grafts were harvested from one ear of a New Zealand rabbit, and PRP was prepared using 10 mL of auricular blood from the same animal. Ear cartilage was diced into 0.5‐ to 2.0‐mm pieces, weighed, mixed with PRP, and then placed inside the hollow mold. Composite grafts were then implanted into the backs of respective rabbits (n = 10) for 4 months. The shape and composition of the diced cartilage were assessed histologically, and biomechanical testing was used to determine stiffness.ResultsThe 3D‐printed auricle molds were 0.6‐mm thick and showed connectivity between the internal and external surfaces, with round pores of 0.1 to 0.3 cm. After 4 months, the diced cartilage pieces had fused into an auricular shape with high fidelity to the anthropotomy. The weight of the diced cartilage was 5.157 ± 0.230 g (P > 0.05, compared with preoperative). Histological staining showed high chondrocyte viability and the production of collagen II, glycosaminoglycans, and other cartilaginous matrix components. In unrestricted compression tests, auricle stiffness was 0.158 ± 0.187 N/mm, similar to that in humans.ConclusionAuricle grafts were constructed successfully through packing a 3D‐printed, porous, hollow auricle mold with diced cartilage mixed with PRP. The auricle cartilage contained viable chondrocytes, appropriate extracellular matrix components, and good mechanical properties.Levels of EvidenceNA. Laryngoscope, 129:2467–2474, 2019

Controlled cooling of an aluminum alloy casting based on 3D printed rib reinforced shell mold

3D printing technology has been used for sand molding and core printing, but they simply substitute the traditional molding and core making method without changing the shape or size of the sand mold (core) and their dense structure. In this study, a new type of hollow mold based on 3D printing is presented. The new type of mold is a rib reinforced thickness-varying shell mold. This mold design can realize the controlled cooling of castings, i.e., different cooling rates at different areas, and improve the temperature uniformity of a casting after its solidification. Therefore, the performance of castings can be improved and their residual stress and deformation can be reduced. This kind of new mold was applied to a stress frame of A356 aluminum alloy. The 3D printed rib reinforced thickness-varying shell mold was compared with the traditional dense mold, and the castings obtained by these two kinds of molds were also compared. The experimental results showed that the rib reinforced shell mold increased the cooling rate of the casting by 30%, tensile strength by 17%, yield strength by 11%, elongation by 67%, and decreased its deformation by 43%, while sand consumption was greatly reduced by 90%.

A phase-field model for liquid–gas mixtures: mathematical modelling and discontinuous Galerkin discretization

To model a liquid–gas mixture, in this article we propose a phase-field approach that might also provide a description of the expansion stage of a metal foam inside a hollow mold. We conceive the mixture as a two-phase incompressible–compressible fluid governed by a Navier–Stokes–Cahn–Hilliard system of equations, and we adapt the Lowengrub–Truskinowsky model to take into account the expansion of the gaseous phase. The resulting system of equations is characterized by a velocity field that fails to be divergence-free, by a logarithmic term for the pressure that enters in the Gibbs free-energy expression and by the viscosity that degenerates in the gas phase. In the second part of the article we propose an energy-based numerical scheme that, at the discrete level, preserves the mass conservation property and the energy dissipation law of the original system. We use a discontinuous Galerkin approximation for the spatial approximation and a modified midpoint based scheme for the time approximation.

The Release of Diazepam from Different Conventional and Hollow Type Suppository Bases

The objective of this study was to investigate the release profile of different fat and water soluble bases using diazepam as a model drug , and then to develop a satisfactory formula with a rapid release of diazepam from suppository bases .The study was conducted using theobroma oil ,glycerol-gelatin and glycerol-PEG1540 bases using conventional mold method for preparation .while the later base was utilized to incorporate diazepam ( buffered solution ) in a hollow type suppositories. The results indicated that all types of bases can be utilized to formulate diazepam as rectal suppositories with acceptable disintegration time ( 12, 10, 6, and 6min.), respectively . While 100% of the released drug had been shown different release profiles with different storage time ( 15, 30, and 45 days ) in a refrigerator at 5°C , best results were obtained , when glycerol- PEG1540 used as a base for both conventional and hollow type mold methods .However , a decrease in the release rate of the drug was seen with glycerol-gelatin and glycerol-PEG1540 and to a lesser extent for glycerol-PEG1540 prepared
 by hollow type method .
 Key words: Diazepam , Hollow type suppository

TU‐H‐BRC‐01: A New Fabrication Method for Secondary Skin Collimation Using 3D Scanner and 3D Printer

Purpose:Using secondary skin collimation (SSC) to protect the critical organ surrounding the tumors is always desirable for electron and/or ortho‐voltage treatments. However, the time‐consuming and labor‐intensive fabrication processes of current method (manually fabricate the lead mask) restrict the general use of SSC. The aim of this study is to develop a new SSC fabrication method using 3D scanning and 3D printing technologies in order to largely decrease the human labor involvement and fabrication time, also improve the fabrication accuracy.Methods:First, the patient surface was scanned with a 3D scanner (Structure Sensor, Occipital, CO). The raw scan data was subsequently transferred to a 3D modeling software (Rhinoceros, Ver. 5.0, McNeel North America, Seattle, WA). The tumor contour was then digitized and shielding region was determined by clinicians in the same software. The corresponding SCC conformed to the skin surface was then automatically generated by the software with the proper shielding thickness. The shell of the SCC (with hollow inside) was consequently printed by a 3D printer (Lulzbot TAZ, Aleph Objects, CO) using plastic material. Finally, the hollow mold of SCC was filled up with a melted cerrobend alloy. Once the cerrobend alloy cooled down, the fabrication of SCC was accomplished.Results:The results indicated the proposed method can achieve a much shorter time on making a SCC compared with tradition fabrication method. The processes of making a skin contour model for patients have been eliminated with the new method. SCC created by the new method possessed better accuracy and better conformality to patient's skin contours.Conclusion:In this study, we have demonstrated a new method for the SCC fabrication. It is anticipated that our method can be an alternative way to replace conventional manual‐based methods for electron and/or ortho‐voltage SCC fabrication.This research was supported by the Global Ph.D. Fellowship Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (Grant No. 2015H1A2A1034071), Republic of Korea.

Increasing the safety and efficiency of metal cooling in the process of fabricating a hollow mold

The results of heat exchange during the cooling of aluminum in a mold with a central core in the form of a heat pipe are presented and compared with the heat exchange data obtained in the case of an uncooled core. The novelty of the results is confirmed by patents. Heat pipes used for metal cooling make it possible to improve the ecological situation, to prolong the service life of the core and molds, and to increase reliability of the structures. The obtained results can be used when designing heat-pipe-based systems for metal cooling and crystallizers of machines.

An anthropomorphic phantom for quantitative evaluation of breast MRI.

In this study, the authors aim to develop a physical, tissue-mimicking phantom for quantitative evaluation of breast MRI protocols. The objective of this phantom is to address the need for improved standardization in breast MRI and provide a platform for evaluating the influence of image protocol parameters on lesion detection and discrimination. Quantitative comparisons between patient and phantom image properties are presented. The phantom is constructed using a mixture of lard and egg whites, resulting in a random structure with separate adipose- and glandular-mimicking components. T1 and T2 relaxation times of the lard and egg components of the phantom were estimated at 1.5 T from inversion recovery and spin-echo scans, respectively, using maximum-likelihood methods. The image structure was examined quantitatively by calculating and comparing spatial covariance matrices of phantom and patient images. A static, enhancing lesion was introduced by creating a hollow mold with stereolithography and filling it with a gadolinium-doped water solution. Measured phantom relaxation values fall within 2 standard errors of human values from the literature and are reasonably stable over 9 months of testing. Comparison of the covariance matrices of phantom and patient data demonstrates that the phantom and patient data have similar image structure. Their covariance matrices are the same to within error bars in the anterior-posterior direction and to within about two error bars in the right-left direction. The signal from the phantom's adipose-mimicking material can be suppressed using active fat-suppression protocols. A static, enhancing lesion can also be included with the ability to change morphology and contrast agent concentration. The authors have constructed a phantom and demonstrated its ability to mimic human breast images in terms of key physical properties that are relevant to breast MRI. This phantom provides a platform for the optimization and standardization of breast MRI imaging protocols for lesion detection and characterization.

Technology of High-Speed Milling Process and Programming Optimization for Beverage Bottle Hollow Mold

From the perspective of optimization of high-speed milling process, this paper has described the programming strategies of the mold high speed machining, including appropriate method of selection of high-speed machining, tool cut-in, cut-out and the control of the way of tool shifting. Taking mold cavity as the bottles as processing objects, it has discussed the quality and efficiency of processing of the mold angle which encountered frequently in processing. And it has developed the strategies of processing and set the parameters, then completed the programming of high-speed processing.

Development of Metal Resin Concrete for Metallic Mold. 1st Report, Injection Molding for Plastics.

It has been pointed out that it is difficult to manufacture hollow molds, free curved surfaces and large molds. Therefore, much time and high cost are involved in the production of injection molds for such plastics. In this paper, a new material, for metal resin concrete, has been developed as a material for the injection mold. This material consists of heat-proof epoxy resin and a steel aggregate. It is concluded from the results that metal resin concrete has sufficient stiffness, high compressive strength, excellent copying characteristics and heat shock resistance to be used as material for the injection mold.

Science Fiction

In an earlier study, De la féerie à la science-fiction, I tried to show the internal consistency and the chronological succession of fairy tales, fantastic stories and works of scientific anticipation or extrapolation. They represent three styles of the imaginary, and illustrate, each in its own way (“like hollow molds,” I said), the chief epochs of man's changing situation on his planet, as he himself saw it, more or less naively, in each case. First he depicted himself as powerless and wonderstruck; then confident in science and technology, he considered himself the fortunate conqueror of the planet; and finally he saw himself as isolated and marginal in the immensity of space—just at the very time when he was learning to move about in it.

Control and Distribution of Uranium in Coral Reefs During Diagenesis

ABSTRACT The concentration of about 2 ppm of uranium in the aragonitic skeletons of modern scleractinian corals which we studied is a constant value, regardless of occurrence, anatomy, or taxonomy. The presence of cement of aragonite or high-magnesian calcite usually raises the concentration of bulk samples to about 3 ppm. Modern corals may contain up to 50% of cementing minerals. Organisms, such as corals and coralline algae, while secreting their skeleton, discriminate against the uptake of uranium, whereas the uptake of uranium by mineral cements is less restrained. Aragonite cement contains about 3.6 ppm and high-magnesian calcite cement 2.6 ppm uranium. During leaching by freshwater, the aragonite of the skeletons of corals dissolves out. This creates hollow molds which fill with drusy low-magnesian calcite. In emergent reefs from the shores of the Red Sea which display the effects of progressive diagenesis this calcite is enriched in uranium (3.9 ppm) beyond that found in marine cements. Second-generation calcite which fills original voids in the corals from the emergent reefs contains a lower level of uranium concentration (1.3 ppm). The level of concentration of uranium in low-magnesian calcite of diagenetically altered corals is a function of the availability of uranium in meteoric waters. In aragonite as well as in high- and low-magnesian calcite uranium replaces calcium or occupies lattice vacancies in the crystal lattice.