Mold Printing Research Articles

The introduction of modern techniques in 3D printing of sand cores and moulds – a review

Growing technological innovation has led to faster, easier, and more efficient methods of getting things done. Owing to increasing requests for parts and the need to enhance 3D printing of sand cores and moulds and their conventional counterparts, Artificial intelligence (AI) and Smart systems are expected to address the existing challenges in using these techniques. Conventional metal-casting techniques often necessitate the application of tools in the design of patterns, cores, dies and moulds. Also, specialised skills are needed for pattern-making in wood, plastic or other materials. Metallurgical models dealing with shrinkage rates, machining, draft allowances and solidification in diverse metals, are essential considerations in pattern designing. Furthermore, the possibility of using 3D sand core and mould printing in high-tech applications necessitates minimal error or error-free production of parts. Therefore, this review explores how AI and Smart systems could be introduced into conventional and 3D printing to make the techniques suitable for high-tech applications, such as in the biomedical, aerospace and automotive industries.

Rapid Micromolding of Sub-100 µm Microfluidic Channels Using an 8K Stereolithographic Resin 3D Printer.

Engineering microfluidic devices relies on the ability to manufacture sub-100 micrometer fluidic channels. Conventional lithographic methods provide high resolution but require costly exposure tools and outsourcing of masks, which extends the turnaround time to several days. The desire to accelerate design/test cycles has motivated the rapid prototyping of microfluidic channels; however, many of these methods (e.g., laser cutters, craft cutters, fused deposition modeling) have feature sizes of several hundred microns or more. In this paper, we describe a 1-day process for fabricating sub-100 µm channels, leveraging a low-cost (USD 600) 8K digital light projection (DLP) 3D resin printer. The soft lithography process includes mold printing, post-treatment, and casting polydimethylsiloxane (PDMS) elastomer. The process can produce microchannels with 44 µm lateral resolution and 25 µm height, posts as small as 400 µm, aspect ratio up to 7, structures with varying z-height, integrated reservoirs for fluidic connections, and a built-in tray for casting. We discuss strategies to obtain reliable structures, prevent mold warpage, facilitate curing and removal of PDMS during molding, and recycle the solvents used in the process. To our knowledge, this is the first low-cost 3D printer that prints extruded structures that can mold sub-100 µm channels, providing a balance between resolution, turnaround time, and cost (~USD 5 for a 2 × 5 × 0.5 cm3 chip) that will be attractive for many microfluidics labs.

Simplified Model Predicts Binder Behavior in Sand Mold Printing

Binder jetting is a crucial process in additive manufacturing (AM) and is widely used in sand mold casting. This study explores the challenges of simulating binder droplets in ANSYS Fluent, including complexity and computational time. To overcome these challenges, we propose a geometric approach that models the binder droplet as a circular shape instead of an actual droplet. Additionally, the dynamic mesh feature is employed to transform the initial boundary condition into a wall condition at a specified time interval (Δt). This simplified approach eliminates the need to simulate actual droplets, leading to significant computational resource and time savings. By adopting this geometric approach, we can accurately predict the diffusion and penetration behavior of binder droplets with varying materials and volumes in porous media with different porosities. Through data analysis, it was found that the main variables affecting the diffusion diameter and penetration depth are binder volume and porosity. The successful implementation of this simplified model enables researchers and engineers to expedite the simulation of binder behavior, facilitating process optimization and enhancing the understanding of binder jetting technology in the field of additive manufacturing.

Computer Vision Method for In Situ Measuring Forming Accuracy of 3D Sand Mold Printing

The three-dimensional sand mold printing technology (3DSP) for casting sand molds via a binding jet is a breakthrough in the casting mold-making process. It is a favorable combination of digital forming technology and sand casting, which is a significantly interesting research area in the foundry industry. This study has proposed an edge extraction approach for the forming region in the sand bed image. With the edge information, the study measures the forming accuracy of the printed molds, which offers a basis for assessing the forming quality after 3DSP. The extracted edges essentially match the original image through the validation of cube printing. The error between the measured and actual size is below 0.6 mm, and the standard deviation of the straight line edge is below 0.170 mm, which fulfills the accuracy requirements for 3D sand mold printing.

Design and CT imaging of casper, an anthropomorphic breathing thorax phantom

The goal of this work was to build an anthropomorphic thorax phantom capable of breathing motion with materials mimicking human tissues in x-ray imaging applications. The thorax phantom, named Casper, was composed of resin (body), foam (lungs), glow polyactic acid (bones) and natural polyactic acid (tumours placed in the lungs). X-ray attenuation properties of all materials prior to manufacturing were evaluated by means of photon-counting computed tomography (CT) imaging on a table-top system. Breathing motion was achieved by a scotch-yoke mechanism with diaphragm motion frequencies of 10−20 rpm and displacements of 1 to 2 cm. Casper was manufactured by means of 3D printing of moulds and ribs and assembled in a complex process. The final phantom was then scanned using a clinical CT scanner to evaluate material CT numbers and the extent of tumour motion. Casper CT numbers were close to human CT numbers for soft tissue (46 HU), ribs (125 HU), lungs (−840 HU) and tumours (−45 HU). For a 2 cm diaphragm displacement the largest tumour displacement was 0.7 cm. The five tumour volumes were accurately assessed in the static CT images with a mean absolute error of 4.3%. Tumour sizes were either underestimated for smaller tumours or overestimated for larger tumours in dynamic CT images due to motion blurring with a mean absolute difference from true volumes of 10.3%. More Casper information including a motion movie and manufacturing data can be downloaded from http://web.uvic.ca/~bazalova/Casper/.

Development of a 3D simulator for training the mouse in utero electroporation.

In utero electroporation (IUE) requires high-level training in microinjection through the mouse uterine wall into the lateral ventricle of the mouse brain. Training for IUE is currently being performed in live mice as no artificial models allow simulations yet. This study aimed to develop an anatomically realistic 3D printed simulator to train IUE in mice. To this end, we created embryo models containing lateral ventricles. We coupled them to uterus models in six steps: (1) computed tomography imaging, (2) 3D model segmentation, (3) 3D model refinement, (4) mold creation to cast the actual model, (5) 3D mold printing, and (6) mold casting the molds with a mix of soft silicones to ensure the hardness and consistency of the uterus and embryo. The results showed that the simulator assembly successfully recreated the IUE. The compression test did not differ in the mechanical properties of the real embryo or in the required load for uterus displacement. Furthermore, more than 90% of the users approved the simulator as an introduction to IUE and considered that the simulator could help reduce the number of animals for training. Despite current limitations, our 3D simulator enabled a realistic experience for initial approximations to the IUE and is a real alternative for implementing the 3Rs. We are currently working on refining the model.

Greyscale printing and characterization of the binder migration pattern during 3D sand mold printing

Binder jetting is an additive manufacturing process in which a liquid binder is deposited onto a sand bed to fabricate components of a desired geometry. After deposition, the permeation and migration of the liquid binder in the porous sand bed has a critical impact on the final performance of the printed part. The purpose of this two-part study is to determine whether greyscale printing can be adapted for use in binder jetting. First, using Furan resin as the liquid binder and silica particles for the sand bed, we fabricated six sets of samples with different droplet volumes and measured the resulting migration patterns and quantified them based on deposited liquid saturation. The migration patterns are then correlated with the dimension error, strength, and formability of the printed samples. The results show that a larger liquid saturation produces better strength and formability with the tradeoff of a significant decrease in dimension error. Within this quantitative framework, the authors then demonstrate that gray-level printing—adjusting the droplet size of the liquid binder independently at each print head—can achieve the desired dimension error, strength, and formability at any specific location. Future applications may include the binder jetting of ceramic and metallic powders.

Investigation of the effect of three-point bending testing parameters on the behavior of 3D printed sand

3D sand mold printing allows rapid and direct fabrication of complex-shaped molds and cores that helps to overcome the limitations of conventional casting. The manufactured molds and cores, having complex geometries, are subjected to severe thermomechanical loads during casting and thus must have sufficient rigidity to meet the technical requirements. Therefore, a mastery of their behavior and intrinsic sand properties becomes essential for a better dimensioning of molds and cores but also the simulation of casting processes. The bending is the most critical load type, for sand cores under casting conditions, and therefore needs to be characterized. This study proposes to investigate the effect of testing parameters, which are span-to-thickness and strain rate, on the three-point bending behavior of printed sand. The results showed that the elastic modulus increases with the rise of the span-to-thickness parameter and is not affected by the strain rate. The bending strength, for its part, is only affected by strain rate. The test results and DIC measurement made it possible to give recommendation for the optimal testing parameters.

Sustainability metrics for rapid manufacturing of the sand casting moulds: A multi-criteria decision-making algorithm-based approach

Additive Manufacturing has significantly developed over the years and is widely used in most industrial applications. Rapid Tooling refers to manufacturing the tools (moulds and dies) using Additive Manufacturing techniques. An essential application of Rapid Tooling is the 3D printing of sand moulds for castings. Metal casting is an energy-intensive process; and a lot of research has gone into the sustainability assessment of traditional sand castings. In this work, a robust decision-making approach is developed and implemented for sand mould manufacturing. Sustainability metrics for the mould production are formulated, and the conventional sand moulds are compared against the 3D printed sand moulds. A Multi-Criteria decision-making algorithm is implemented, and the effect of the batch size in the mould manufacturing is also studied. The discussed approach can help decision-makers choose the best mould manufacturing technique for the intended number of moulds to be manufactured.

A review on the progress and challenges of binder jet 3D printing of sand moulds for advanced casting

Abstract 3D sand mould printing using binder jet technology can enable many technical improvements in casting practice, including part consolidation, design of parts to optimise the consumption of materials and hazardous chemicals, and on-demand and flexible size part manufacturing near the customer. Incorporating artificial intelligence in optimising the design of moulds, printing process parameters, and solidification processes may help automate a production facility and reduce labour time. Elimination of hazardous chemicals from industrial use may be a challenge. Therefore, an alternative technology to fuse the sand particles during printing or an environmentally friendlier alternative option for the binders and other consumables should be utilised with the 3D sand printing process. Properties of parts produced using 3D printed sand moulds have the potential to be better than the properties of parts produced using traditional casting due to this technology's benefits. This technology is an enabling technology for traditional casting processes rather than a competing technology. It is causing a paradigm shift in casting design because of the mould geometries achievable by using additive manufacturing to produce the sand mould. This paper reviews the first twenty years of research and challenges in developing 3D sand printing processes as an innovation for sustainable manufacturing.

OSMANLI KUMAŞ SANATINDA AHŞAP KALIP BASKI TEKNİĞİ

Geleneksel basmacılık sanatı, desenlerin tahta kalıp, fırça ve kalem gibi araçlar yardımıyla boyaların kumaş üzerine basılarak ya da elle çizilerek aktarılması ve desenlendirilmesi işlemidir. Yazmacılık sanatı olarak da bilinen bu sanat, XVI. yüzyıldan sonra Osmanlı İmparatorluğu'nda geniş bir kullanım alanı bulmuştur. İmparatorlıkta, düz kumaşları desenlendirmek için uygulanan kalıpla baskı tekniği; kaftan, yastık, yorgan yüzü, seccade, bohça, mendil, sofra altı, peşkir gibi pek çok üründe kullanılmıştır. En güzel örneklerine XVI, XVII, XVIII, ve XIX. yüzyıllarda rastlanılan baskılı kumaşlar, üstün nitelikleri ile sarayın tercih edilen eşyaları arasında yerini almış; kullanılan malzeme, renklerin haslığı, desenlerdeki incelik ve akıcılıkla döneminin en güzel örneklerini oluşturmuşlardır. Bu çalışma ile tarihsel süreç içerisinde Osmanlı kumaş sanatı kapsamında basmacılık sanatı ele alınacak,baskılı kumaş örnekleri teknik, desen ve renk özellikleri açısından incelenecektir.

Effect of process parameters on flexure strength and gas permeability of 3D printed sand molds

3D printed sand molds for the casting industry play a vital role in manufacturing intricate parts using a computer model. The possibility of producing fairly significant structural castings using a small job-box 3D sand mold printer is another advantage compared to the direct metal 3D printing processes. It is important to identify the relationship between the process parameters and the properties of the sand mold to produce a mold with the required strength, permeability and stiffness; to reduce gas emissions during casting and minimize the mass of combustible materials in the mold. Hence, it is possible to create an excellent casting by improving the design of such molds for liquid alloy filling and solidification. The relationship between the printing parameters and the properties of the mold can be a great tool for foundrymen, primarily to optimize the strength and permeability properties of these molds and therefore to provide exact boundary conditions for the solidification simulation prior to a casting trial. This paper reports on a study of a basic outline to quantify the role of the sand mold printing process parameters, particularly the recoater speed and print resolution, on the mold strength and permeability, and their impacts on the anisotropic behavior of the printed sand molds.

Investigation on moist silica sand’s circulation for sand mold printing with line-forming

Purpose This paper aims to investigate the circulation of moist silica sand to provide appropriate feeding modes and references for designing the coating device when printing sand mold with line-forming. Design/methodology/approach First, this paper briefly introduces sand mold printing with line-forming and the circulation problem brought by moist silica sand. The outlet may be choked due to poor flowability and solidification characteristic, resulting in poor dimensional tolerance and even production failure. Then, based on circulation modeling, a series of feeding modes is proposed to guarantee adequate feeding, avoid solidification and ensure successful fabrication. Finally, the GUI of control software is developed, including slicing, path planning and the function of virtual printing. Findings Several feeding modes of moist silica sand are put forward to avoid the choke. Research limitations/implications The authors will further investigate the flowability of furan no-bake sand based on experiments. Originality/value This paper is going to provide references for the novel design of nozzle, prototype and sand mold printing, influencing significantly on mold manufacturing and the casting industry. This research applies equally to equipment having the circulation of high moist particles with solidification features.

Permeability and mechanical properties of gradient porous PDMS scaffolds fabricated by 3D-printed sacrificial templates designed with minimal surfaces

In the present study, polydimethylsiloxane (PDMS) porous scaffolds are designed based on minimal surface architectures and fabricated through a low-cost and accessible sacrificial mold printing approach using a fused deposition modeling (FDM) 3D printer. The effects of pore characteristics on compressive properties and fluid permeability are studied. The results suggest that radially gradient pore distribution (as a potential way to enhance mechanically-efficient scaffolds with enhanced cell/scaffold integration) has higher elastic modulus and fluid permeability compared to their uniform porosity counterparts. Also, the scaffolds are fairly strain-reversible under repeated loading of up to 40% strain. Among different triply periodic minimal surface pore architectures, P-surface was observed to be stiffer, less permeable and have lower densification strain compared to the D-surface and G-surface-based pore shapes. The biocompatibility of the created scaffolds is assessed by filling the PDMS scaffolds using mouse embryonic fibroblasts with cell-laden gelatin methacryloyl which was cross-linked in situ by UV light. Cell viability is found to be over 90% after 4 days in 3D culture. This method allows for effectively fabricating biocompatible porous organ-shaped scaffolds with detailed pore features which can potentially tailor tissue regenerative applications. Statement of SignificancePrinting polymers with chemical curing mechanism required for materials such as PDMS is challenging and impossible to create high-resolution uniformly cured structures due to hard control on the base polymer and curing process. An interconnected porous mold with ordered internal architecture with complex geometries were 3D printed using low-cost and accessible FDM technology. The mold acted as a 3D sacrificial material to form internally architected flexible PDMS scaffolds for tissue engineering applications. The scaffolds are mechanically stable under high strain cyclic loads and provide enough pore and space for viably integrating cells within the gradient architecture in a controllable manner.

Reduced consumption of materials and hazardous chemicals for energy efficient production of metal parts through 3D printing of sand molds

Metals remain essential structural materials for many demanding engineering applications requiring high strength at elevated temperatures and good performance in environments subjected to high thermal fluctuations such as often encountered in the automotive, rail and aircraft industries. The sand-casting process is one of the most preferred methods of producing complex and intricate shaped components out of metals with good strength at elevated temperatures. Unfortunately, the sand casting process also leads to the direct and indirect production of carbon dioxide. Three-dimensional sand mold printing has been revolutionizing traditional production methods by reducing the unnecessary consumption of metal and chemicals when manufacturing a part through sand casting. This paper explores the opportunities that are emerging in the area of 3D printing of sand molds and the positive impact that these new technologies and practices are having on the environmental impact of current sand-casting processes. The paper demonstrates that 3D printing of sand molds enables new manufacturing strategies reducing the direct CO2 emissions and reducing the amount of metal required by enabling design optimization of both the component and mold/core assembly. Further benefits will be realized through the development of environmentally friendly binder systems.

Experimental investigation on the flow properties of sand granules in the process of sand mold printing

PurposeThis paper aims to determine how the viscosity and curing agent content affect the flowability of moist silica sand granules. In addition, a coating device was designed according to the flow properties of silica sand granules.Design/methodology/approachThe flowability of silica sand granules premixed with two curing agents of different viscosities is studied using a Jenike shear apparatus. An open-ended device was used in discharge testing of sand granules with a design based on the variable dip angle of the two plates and variable outlet size.FindingsThe test results show that increasing the curing agent content would significantly decrease the flowability of silica sand granules, and a curing agent of higher viscosity has a greater effect on the flowability of silica sand. The presence of a curing agent strengthens the cohesion among sand granules, lubricates them and restrains their deformation. The shape function of the coating device was obtained by theoretical derivation.Practical implicationsThe flow properties provide a valuable theoretical guidance for the design of coating device for sand mold printing.Originality/valueThis paper deals with experimental work on flow properties of silica sand granules with different viscosities and curing agent content. The shape function of a wedge-shaped coating device is obtained based on experimental data.

Research on the effect of the waveform on the droplet injection behavior of a piezoelectric printhead and the forming accuracy of casting sand molds

Injection behaviors of printheads are concerned by engineers since they affect the whole working performances and the printing quality of 3D printing device. In view of the quality instability issue for sand molds caused by the fluctuation of the droplet injection performance, a study on the relationship of the driving waveform parameters with the droplet injection performance of a casting sand mold printhead and the printing quality of the sand mold was carried out. Comprehensively considering the applied background of 3D printing in casting sand molds and using the separation of variables method, the quantitative relationship between the driving waveform parameters and the droplet injection characteristics was set up, and the injection performance of the printhead under the current waveform was evaluated through experiments. This article puts forward an optimal waveform for use in casting sand printing. Based on the analysis of existing conclusions, by using special equipment for casting sand mold 3D printing, the printing quality of the sand mold under the new waveform and the current waveform was studied via a comparison experiment. The results show that the new waveform is more suitable for sand mold printing of high-viscosity fluid, as it avoids the presence of satellite droplets. The qualification rate in terms of the sand mold size is enhanced by 44%, and the mechanical properties of the sand mold are effectively improved. This study provides a reliable basis for ensuring dimensional accuracy in the application of 3D printing technology in the precision casting field.

A patient-specific three-dimensional couplant pad for ultrasound image-guided radiation therapy: a feasibility study

BackgroundA wide application of ultrasound for radiation therapy has been hindered by a few issues such as skin and target deformations due to probe pressure, optical tracking disabilities caused by irregular surfaces and inter-user variations. The purpose of this study was to overcome these barriers by using a patient-specific three-dimensional (3D) couplant pad (CP).MethodsA patient skin mold was designed using a skin contour of simulation CT images and fabricated by a 3D printer. A CP was then casted by pouring gelatin solution into a container accommodating the mold. To validate the use of the CP in positioning accuracy and imaging quality, phantom tests were carried out in our ultrasound-based localization system and then daily ultrasound images of four patients were acquired with and without the CP before treatment.ResultsIn the phantom study, the use of CP increased a contrast-to-noise ratio from 2.4 to 4.0. The positioning accuracies in the US scans with and without the CP were less than 1 mm in all directions. In the patient study, the use of CP decreased the centroid offset of the target volume after target position alignment from 4.4 mm to 2.9 mm. One patient with a small volume of target showed a substantial increase in the inter-fractional target contour agreement (from 0.07 (poor agreement) to 0.31 (fair agreement) in Kappa values) by using the CP.ConclusionsOur patient-specific 3D CP based on a 3D mold printing technique not only maintained the tracking accuracy but also reduced the inter-user variation, as well as that could potentially improve detectability of optical markers and target visibility for ultrasound image-guided radiotherapy.

Research on the method for improving mechanical properties of sand mold based on 3D printing process

Aiming at the problem of strength instability of casting sand mold under immature process, a study on the strength influence factors and the method for improving the performance of casting sand mold. With the same typical casting sand mold printing process as the experimental conditions, the comparison experiments were carried out from the change of the 3D printing process parameters, the increase of the mechanical vibration to increase the sand density and the introduction of the heat source to speed the sand mold curing speed, The influence of the above methods on the strength of printing sand mold is analyzed. Comparative experimental research shows that the test methods have effectively improved the strength of the sand mold, and the combination of that three methods has a better effect. The research results provide guidance and direction for further promoting the application of 3D printing technology in the foundry industry, and provide a theoretical basis for the application of 3D printing sand in different casting situations.

Quantitative transrectal shear wave elastography undergoing salvage extraperitoneal laparoscopic radical prostatectomy following failed radiotherapy.

To evaluate pre-surgical quantitative transrectal shear wave elastography (SWE) in the detection and characterisation of radioresistant prostate cancer. Twelve men with recurrent prostate cancer following external beam radiotherapy were included in a prospective protocol-driven study. All underwent MR imaging and quantitative shear wave elastographic assessment of recurrent disease prior to salvage laparoscopic radical prostatectomy procedures. Images were used to construct 3D mold printing and histopathological processing of surgical specimen. Statistical analyses including ROC were generated using software programmes. There were 48 cancer foci identified on final histopathology using patient-specific mold-based approach in 12 patients. Mean number of lesion was 3.4 (range 2-4). Quantitative transrectal SWE showed a sensitivity and specificity 0.77 (95% CI 0.627-0.880) and 0.82 (95% CI 0.642-0.942), respectively. The diagnostic accuracy increased with increasing size of the lesions with overall AUC of 0.89. In our series, quantitative transrectal SWE showed a good diagnostic accuracy in the detection and characterisation of recurrent prostate cancer following failed radiotherapy treatment. These findings may help in targeting biopsies or future focal treatment options.