Melting Machine Research Articles

Transforming Bale Twine into Useful Products with an Affordable Melting Machine: Closed-Loop for Recycling Plastics

The escalating use of plastic materials in agricultural practices has substantially increased the amount of plastic waste directed to landfills, leading to significant environmental and ecological challenges. Conventional disposal methods have been found to release hazardous pollutants, including microplastics and toxic chemicals, exacerbating these concerns. This study aims to address the environmental impact of agricultural plastic waste by exploring advanced reprocessing technologies and characterising the processed waste to assess its physical, mechanical, and thermal properties. Synthetic polymer-based bale twine (BT) waste, commonly used in livestock farming, was processed using an economically viable melting machine developed by Ritchie Technology. The BT and processed bale twine (PrBT) were analysed to understand their properties. Fourier transmission infrared spectroscopy revealed that the waste primarily consisted of polypropylene (PP). Thermal analysis indicated that the melting temperature of the PrBT was 162.49 °C, similar to virgin PP. Additionally, tensile testing revealed that the PrBT had an ultimate strength of 13.06 MPa and a Young’s modulus of 434.07 MPa. The PrBT was further transformed into a bench that can be applicable in outdoor applications. Furthermore, the PrBT was extruded into 3D printable filament. Therefore, it is evident that bale twine waste can be given a second life through an economically viable technology.

Achieving excellent strength and ductility of 24CrNiMoY alloy steel fabricated by high power selective laser melting technology

In order to increase the productivity, new generation of selective laser melting (SLM) machines are evolving towards higher power lasers. In this paper, the microstructure evolution and mechanical properties of 24CrNiMoY alloy steel fabricated by high power selective laser melting (HP-SLM) have been reported. The results show that with the optimized laser power over 400 W, the powder layer thickness can be increased to 60 μm, and the theoretical productivity reaches 7.2 mm3/s, which is more than two times of the normal SLM technology. As the laser energy density increases, the structure of melt pool changes from a thermal conduction mode to a keyhole mode, and the microstructure mainly consists of martensite, bainite and pre-eutectic ferrite, and the phase composition of the specimen is α-Fe phase and a small amount of Fe3C,with fine grain size and irregular orientation. When the laser energy density is 68 J/mm3, the microhardness of the specimen is 410HV0.2, the tensile strength reaches 1121 MPa and the percentage elongation after fracture is 11.5%, which realizes a good match between strength and ductility. The fine tempered martensite and lower bainite in the microstructure is the key to excellent strength and ductility. This research is of guiding significance and serves as a technical reference for understanding the microstructure evolution and mechanical properties of HP-SLM 24CrNiMoY alloy steel.

A Mathematical Programming Model for Minimizing Energy Consumption on a Selective Laser Melting Machine

The scheduling problem in additive manufacturing is receiving increasing attention; however, few have considered the effect of scheduling decisions on machine energy consumption. This research focuses on the nesting and scheduling problem of a single selective laser melting (SLM) machine to reduce total energy consumption. Based on an energy consumption model, a nesting and scheduling problem is formulated, and a mixed integer linear programming model is proposed. This model simultaneously determines part-to-batch assignments, part placement in the batch, and the choice of build orientation to reduce the total energy consumption of the SLM machine. The energy-saving potential of the model is validated through numerical experiments. Additionally, the effect of the number of alternative build orientations on energy consumption is explored.

Influences of Different Selective Laser Melting Machines on the Microstructures and Mechanical Properties of Co–Cr–Mo Alloys

Dental prostheses have been fabricated using various selective laser melting (SLM) machines; however, the impact of the type of machine on the microstructure and mechanical properties of Co–Cr–Mo alloys remains unclear. In this study, we prepared samples using two SLM machines (the small M100 and mid-sized M290) with different beam spot sizes (40 and 100 µm, respectively). The microstructures and tensile properties of the heated (1150 °C for 60 min) and as-built samples were evaluated. The grain sizes of the M100 samples were smaller than those of the M290 samples due to the small beam spot size of the M100 machine. Both heated samples exhibited recrystallized equiaxed grains; however, the amount of non-recrystallized grains remaining in the M290 sample exceeded that in the M100 sample. This suggests that the M100 samples recrystallized faster than the M290 samples after heating. The elongation of the M100 samples was higher than that of the M290 samples in the as-built and heated states, owing to the smaller grain size of the M100 samples. A comparison of the M100 and M290 SLM machines indicated that the M100 was suitable for producing dental prostheses owing to its good elongation and rapid recrystallization features, which shorten its post-heat-treatment duration.

Predictive tools for the cooling rate-dependent microstructure evolution of AISI 316L stainless steel in additive manufacturing

This study presents a thorough evaluation of advanced predictive tools for the solidification microstructure of AISI 316L stainless steel, taking into account both chemical composition and cooling rate. In order to achieve a broad range of cooling rates comparable to prominent additive manufacturing processes, autogenous laser welds were carried out on the steel plate by means of powderless directed energy deposition (DED) and selective laser melting (SLM) machines. Computational analysis of cooling rates and metallographic investigations revealed that DED welds solidify at moderate rates, exhibiting a primary ferrite (FA) solidification mode. Conversely, SLM welds solidify at significantly higher rates, showing dual solidification modes: initial austenite (A) at the fusion boundary and subsequent ferrite (F) at the interior. The WRC-1992 constitution diagram predicts the FA mode in accordance with the findings in the DED welds. An implicated Schaeffler diagram, proposed for a comparable cooling rate, also predicts the same mode. An artificial neural network model, referred to as ORFN, consistently predicts the variation of ferrite content within the DED welds based on the cooling rate variation. The dual mode observed in the SLM welds aligns with established knowledge regarding the alteration of stainless steel solidification under extremely high cooling rates. While the occurrence of the A mode at the fusion boundary is anticipated according to implicated Schaeffler diagrams for extremely high cooling rates, the transition to the F mode is not addressed explicitly.

PERAN BANK SAMPAH TEMATIK BUMI BEKO LESTARI DESA BUMIWANGI DALAM MENGELOLA SAMPAH MENJADI RUPIAH

Waste is not a source of problems but a potential environmental resource. There are still relatively many Indonesian people who do not understand waste processing. Only a small number of community groups care and are responsive to waste problems. Bumi Beko Lestari Thematic Waste Bank (BST BBL) is a group of people who have succeeded in turning waste into blessings. Even though its operations are still at the community unit (RW) area level, its business from household rubbish can bring in large sums of rupiah. Maggot, kasgot, and paving blocks are superior products produced by BST BBL. In fact, his business was flooded with orders because there were people who ordered several kilos of maggots but could not be served due to limited resources and funds. Likewise, when someone requests a relatively large quantity of plastic paving block orders, it cannot be fulfilled due to limited equipment. This service aims to strengthen the community's way of thinking about waste management which can bring economic benefits, providing assistance so that BST BBL can improve its quality, both services and products. The activity steps begin with a waste management strengthening workshop involving local residents and students and assistance to BST BBL with the hope that the quality of service and production can be maintained by implementing technology in the form of a faster and more precise plastic melting machine. In conclusion, the public is increasingly aware of the waste that can bring in rupiah and BST BBL can operate more quickly in processing waste into paving blocks.

Recycling selective laser melting alloy powder on cobalt chromium-to-ceramic bond strength

Statement of problemReusing the powder in selective laser melting machines after multiple cycles is a cost-effective procedure for dental laboratories. However, information on the metal-ceramic bond strength of the framework fabricated by using recycled powder is lacking. PurposeThe purpose of this in vitro study was to investigate how the bonding agent and repeated alloy powder reuse affected the metal-ceramic bond strength of cobalt chromium frameworks fabricated by using selective laser melting. Material and methodsFour square and 40-bar-shaped cobalt chromium frameworks were fabricated by selective laser melting. Half were produced by using virgin alloy powder (Group V; nsquare=2, nbar=20), and half with 30-times reused powder (Group R; nsquare=2, nbar=20). The particle size of each powder was measured by using scanning electron microscopy, and its phase composition was characterized by using radiograph diffraction. Each group was divided into 2 subgroups (Group W [Wash Opaque] and Group N [NP-Bond]) according to the brand of bonding agent used. After ceramic application, the metal-ceramic bond strengths were evaluated by using 3-point bend tests. The bonding agents’ chemical composition was analyzed by using radiograph fluorescence. Bond strength data were analyzed by using a 2-way analysis of variance (α=.05). ResultsMean ±standard deviation bond strengths did not differ significantly (P>.05) between Groups V (31.25 ±4.65) and R (30.88 ±4.78). Group W (35.34 ±1.78) had significantly higher bond strength than Group N (26.80 ±1.74; P<.001). Radiograph diffraction analysis found that the phase composition of all powders was similar. The bonding agent in Group W contained cerium, whereas, that in Group N did not. ConclusionsMetal-ceramic bond strength was unaffected by alloy powder reuse. However, the bonding agent brand may affect the bond strength of cobalt chromium frameworks fabricated by using selective laser melting.

Determination of the elastoplastic properties of Ti-6Al-4V alloy manufactured by electron beam melting

PurposeThis study aims to evaluate and assess the elastoplastic properties of Ti-6Al-4V alloy manufactured by Arcam Q20 Plus electron beam melting (EBM) machine by a tensile test campaign and micro computerized tomography (microCT) imaging.Design/methodology/approachASTM E8 tensile test specimens are designed and manufactured by EBM at an Arcam Q20 Plus machine. Surface quality is improved by machining to discard the effect of surface roughness. After surface machining, hot isostatic pressing (HIP) post-treatment is applied to half of the specimens to remove unsolicited internal defects. ASTM E8 tensile test campaign is carried out simultaneously with digital image correlation to acquire strain data for each sample. Finally, build direction and HIP post-treatment dependencies of elastoplastic properties are analyzed by F-test and t-test statistical analyses methods.FindingsModulus of elasticity presents isotropic behavior for each build direction according to F-test and t-test analysis. Yield and ultimate strengths vary according to build direction and post-treatment. Stiffness and strength properties are superior to conventional Ti-6Al-4V material; however, ductility turns out to be poor for aerospace structures compared to conventional Ti-6Al-4V alloy. In addition, micro CT images show that support structure leads to dense internal defects and pores at applied surfaces. However, HIP post-treatment diminishes those internal defects and pores thoroughly.Originality/valueAs a novel scientific contribution, this study investigates the effects of three orthogonal build directions on elastoplastic properties, while many studies focus on only two-build directions. Evaluation of Poisson’s ratio is the other originality of this study. Furthermore, another finding through micro CT imaging is that temporary support structures result in intense defects closer to applied surfaces; hence high-stress regions of structures should be avoided to use support structures.

A Design of Plastic Melting Equipment Waste Bank Scale Using Quality Function Deployment Method

The COVID-19 pandemic has triggered the rise of online purchases, resulting in the accumulation of plastic packaging waste. Plastic is most widely used because it is lightweight, flexible, cheap and easy to obtain, but its waste is difficult to decompose, which has an impact on the environment. Eco-bricking is one way that waste banks often reduce the amount of plastic waste. The obstacle in making eco-bricks is sore hands and calluses because it takes a lot of energy to compact the plastic. On the other hand, there is a lot of concentrated cooking oil waste that is still untreated, causing difficulties when disposing of it. Through this research, the design of a waste bank scale plastic melting machine is carried out with the raw materials of plastic bags and concentrated cooking oil into new materials that are more useful. The Quality Function Deployment (QFD) method with an Ergonomics approach is the basis for the stages of making product design from collecting consumer voices to making detailed tool designs. The operation of the tool uses simple technology so that it is easy to use by members of the Gurami Semanu waste bank. A total of 34 respondents will be the basis for determining product design. The results of the design of a bank-scale plastic melting tool in the form of a lidded stainless steel pot with a stirrer. The heater used for melting uses LPG gas with automatic operation using a button.

Pengendalian Kualitas Menggunakan Metode Seven Tools Dan Kaizen Produk Polypropylene Pada PT KMPI

PT KMPI is an industrial company that produces textiles and plastics, including plastic products made of polypropylene (PP). The problem that occurs in PT Kusuma Mulia Plasindo Infitex is the quality of the products that still have defects, based on the results of the analysis in February 2023 with a total production of 76,596 kg there are rejects data of 4,695 kg and the percentage of product defects that occur is 6.1%. The objective of this study is to determine the predominant types of defects that influence the factors that cause defects. This study uses the seven tools method to find the root cause of the problem to be solved, as well as the Kaizen Five-M checklist and the Kaizen Five Step Plan to suggest improvements to the company. Based on the results of data processing, there are three types of defects, namely wrinkle defects with a percentage of 43% for a total defect of 2039 kg, medium wrinkle defects with a percentage of 45% for a total defect of 2094 kg, and thick-thin defects with a percentage of 12% for a total defect of 562 kg. From the fishbone diagram, it can be seen that the occurrence of defects is caused by several factors, namely people, materials, methods and machines. Suggested improvements using the Kaizen Five-M checklist analysis are training and monitoring of production, implementation of SOPs (Standard Operating Procedures) established by the company, such as dosing the mixture of plastic seeds with addictive substances at a ratio of 25 Kg. 1 oz. and Kaizen management control: 1 Ons and Kaizen five-step plan management controls, namely Seiri, Seiton, Seiso, Seiketsu, Shitsuke. This includes pre-job briefings and periodic assessments, and the establishment of standard operating procedures for the supervision of single-table melting machines with a melting temperature of 160-166oC.

Fabrication and mechanical properties of Bi-added Ti–Cr alloys for biomedical applications

The potential of the Bismuth (Bi) addition was evaluated for the development of biocompatible metastable β (bcc) Ti alloys from the viewpoints of mechanical properties and phase stability. The basic alloy was Ti–5 mol% Cr, and 0–9 mol% Bi was added in nominal composition. A Ti–Bi binary alloy was also selected. The alloys were fabricated using a standard laboratory-scale arc melting machine under an Ar atmosphere. The weight loss was significant during melting due to Bi evaporation. The measured Bi content is linearly proportional to the Bi nominal composition with MCBi = 2/3 NCBi, allowing the prediction and control of Bi content of the alloy. Then, the microstructure, workability, and mechanical properties were systematically investigated. The phase constitution of the Ti–5Cr binary alloy was β + α′ (hcp) + ω (hexagonal). The presence of the athermal ω phase resulted in significantly poor cold workability and poor ductility. It was also found that the addition of Bi to the Ti–5Cr alloy stabilized the β phase and suppressed the ω phase formation. The phase stability of Ti–Cr–Bi alloy is discussed using Mo equivalent and electron-to-atom (e/a) ratio. Ti–5Cr–1.6Bi alloy showed improved workability and ductility. However, with further increasing Bi addition, the Ti–5Cr–3.7Bi alloy showed no plastic deformation, and the Ti–5Cr–6.1Bi alloy was broken even during hot-rolling. Thus, it is concluded that ∼2 mol% Bi addition is suitable and that such a small amount of Bi addition is an attractive candidate for the development of β Ti alloys.

Investigating the accuracy of mandibulectomy and reconstructive surgery using 3D customized implants and surgical guides in a rabbit model

BackgroundThis study aimed to analyze the accuracy of the output of three-dimensional (3D) customized surgical guides and titanium implants in a rabbit model, and of mandibulectomy, reconstructive surgery, and surgical outcome; additionally, the correlation between surgical accuracy and surgical outcomes, including the differences in surgical outcome according to surgical accuracy, was analyzed.ResultsThe output of implants was accurately implemented within the error range (− 0.03–0.03 mm), and the surgical accuracy varied depending on the measured area (range − 0.4–1.1 mm). Regarding surgical outcomes, angle between the mandibular lower borders showed the most sensitive results and distance between the lingual cusps of the first molars represented the most accurate outcomes. A significant correlation was noted between surgical accuracy in the anteroposterior length of the upper borders pre- and postoperatively and the angle between the mandibular lower borders (regression coefficient = 0.491, p = 0.028). In the group wherein surgery was performed more accurately, the angle between the mandibular lower borders was reproduced more accurately (p = 0.021). A selective laser melting machine accurately printed the implants as designed. Considering the positive correlation among surgical accuracy in the mandibular upper borders, angle between the mandibular lower borders, and more accurately reproduced angle between the mandibular lower borders, the angle between the mandibular lower borders is considered a good indicator for evaluating the outcomes of reconstructive surgery.ConclusionTo reduce errors in surgical outcomes, it is necessary to devise a positioner for the surgical guide and design a 3D surgical guide to constantly maintain the direction of bone resection. A fixed area considering the concept of three-point fixation should be selected for stable positioning of the implant; in some cases, bilateral cortical bone fixation should be considered. The angle between the mandibular lower borders is a sensitive indicator for evaluating the outcomes of reconstructive surgery.

Acoustic Emission and Deep Learning for the Classification of the Mechanical Behavior of AlSi10Mg AM-SLM Specimens

In this research paper, the acoustic emission technique and a deep learning framework based on two types of pre-trained CNN models (alexNet and squeezeNet) and a new model are proposed to characterize and classify the mechanical behavior of AlSi10Mg components. Specimens are built in a Selective Laser Melting machine with different bed orientations along X, Y, Z, and 45 degrees. Tensile tests are performed, and AE signals are recorded from these tests. To characterize the elastic and plastic deformation stages, a time-frequency domain analysis was performed using CWT-based spectrograms. Three different categories of damage classification strategies were implemented, and CNN models were trained for each strategy. CNN models including AlexNet, SqueezeNet, and the new model were used. Several training modes were performed to determine the CNN model that can accurately classify AE data. Understanding the minimum set of AE signals needed to train the CNN while having 100% accuracy and understanding the parameters affecting the accuracy of a CNN and the training time for the efficient classification of AE signals are the main objectives of this work. The results obtained demonstrated that the new simplified CNN model proposed can accurately classify the AE signals in a short time compared to AlexNet and SqueezeNet.

Benchmark Test Artifacts for Selective Laser Melting - A Critical Review

Background: Selective laser melting is a best-established additive manufacturing technology for high-quality metal part manufacturing. However, the technology is yet to be accepted widely, especially in critical applications, due to the absence of a thorough understanding of the technology although several benchmark test artifacts have been developed to characterize the performance of selective laser melting machines. Objective: The objective of this paper is to inspire new designs of benchmark test artifacts to better understand the selective laser melting process, and to promote the acceptance of the selective laser melting technology. Method: The existing benchmark test artifacts for selective laser melting are analyzed comparatively, and the design guidelines are discussed. Results: The modular approach should still be adopted in designing new benchmark test artifacts in the future, and task-specific test artifacts may also need to be considered furtherly to validate machine performance for critical applications. The inclusion of the design model in the manufactured artifact, instead of the conformance to the design specifications, should be evaluated after the artifact is measured for the applications requiring high-dimensional accuracy and high surface quality. Conclusion: The benchmark test artifact for selective laser melting is still under development, and a breakthrough of the measuring technology for internal and/or inaccessible features will be beneficial for understanding the technology.

Utilization of Plastic Waste as Paver Block, Economic Potential, and Environmental Impact

One of the main factors that cause environmental damage in Indonesia is waste. Reducing waste by burning it directly without an incinerator will cause air pollution for the environment. CO2 is a substance produced by a complete combustion process. The amount of waste produced by Bandung Regency reaches 1,480.1 tons/day, with 20% of the waste being plastic waste. One way to utilize plastic waste is to recycle it into materials to produce paver blocks. Producing paver blocks requires a series of machines, such as crushing machines, plastic melting machines, and pressing machines. Plastic waste that has been sorted is put into a chopping machine and cut into 10 mm pieces. The plastic that has been cut is then melted down and printed, then re-pressed with a press machine. The type of plastic used in this research is polypropylene, with a melting point of 160-170°C. The size of the paver block produced is compatible with the market size. During the production of paver blocks, the CO2 concentration was monitored to see the effect of resin melting. In the analysis of paver blocks' economic potential, we found that the production cost using plastic waste is relatively expensive compared to conventional paver blocks. However, this type of paver block is not harmful to the environment. The results of this study indicate that plastic waste paver blocks can be used as paver block materials because they have quite an impact on the environment, although their economic value cannot compete with conventional paver blocks.

Geometry, Structure and Surface Quality of a Maraging Steel Milling Cutter Printed by Direct Metal Laser Melting.

This article considers the use of additive manufacturing to produce cutting tools for various machining operations, especially turning, milling, and drilling. The right geometry and material of the tool as well as coatings applied on cutting edges are crucial as they improve the life and performance of the tool. The study described here focused on a four-flute end mill made of maraging steel 1.2709 using a Concept Laser M2 Cusing Direct Metal Laser Melting (DMLM) machine. Before the printed tool was first used, it was examined to determine its dimensional and geometric accuracy, surface roughness, and surface structure. The measurement data showed that the tool required machining, e.g., grinding, to improve its geometry because the total runout of the shank and the cutting edge radius were too high, amounting to 120 μm and 217 μm, respectively. The cutting edges were sharpened to obtain a fully functional cutting tool ready to perform milling operations. The study aimed to check the dimensional and geometric accuracy of the 3D printed milling cutter and determine the optimal machining allowance for its finishing.

Study of anisotropy through microscopy, internal friction and electrical resistivity measurements of Ti-6Al-4V samples fabricated by selective laser melting

PurposeThis paper aims to investigate the microstructural anisotropy of Ti-6Al-4V samples fabricated by selective laser melting.Design/methodology/approachSpecimens are fabricated through a Renishaw AM400 selective laser melting machine. Three microstructures (as-built, 850°C annealed and 1,050°C annealed) and two building orientations, parallel (PA) and perpendicular (PE) to the building platform, are considered. Starting from in-depth microscopic observations and comprehensive electron backscattered diffraction imaging, the study addresses non-conventional techniques such as internal friction and electrical resistivity measurements to assess the anisotropy of the fabricated parts.FindingsMicroscope observations highlight a fine texture with columnar grains parallel to the building direction in the as-built and 850°C annealed samples. Besides, coarse grains characterized the 1,050°C annealed specimens. Internal friction measurements pointed out the presence of internal stress while storage modulus analyses appear sensitive to texture. Electrical resistivity is resulted to be dependent on grain orientation.Originality/valueThe work uses some novel characterization techniques to study the anisotropy and internal stresses of Ti-6Al-4V samples processed by selective laser melting. Mechanical spectroscopy results suitable in this kind of study, as it mimics the operating conditions of the material.

Effect of laser-induced ultrasound treatment on material structure in laser surface treatment for selective laser melting applications

A new mechanism for controlling the microstructure of products in manufacturing processes based on selective laser melting is proposed. The mechanism relies on generation of high-intensity ultrasonic waves in the melt pool by complex intensity-modulated laser irradiation. The experimental study and numerical modeling suggest that this control mechanism is technically feasible and can be effectively integrated into the design of modern selective laser melting machines.

In Situ Monitoring of Powder Bed Fusion Homogeneity in Electron Beam Melting.

Increasing attention has been devoted in recent years to in situ sensing and monitoring of the electron beam melting process, ranging from seminal methods based on infrared imaging to novel methods based on backscattered electron detection. However, the range of available in situ monitoring capabilities and solutions is still quite limited compared to the wide number of studies and industrial toolkits in laser-based additive manufacturing processes. Some methods that are already industrially available in laser powder bed fusion systems, such as in situ detection of recoating errors, have not yet been investigated and tested in electron beam melting. Motivated by the attempt to fill this gap, we present a novel in situ monitoring methodology that can be easily implemented in industrial electron beam melting machines. The method is aimed at identifying local inhomogeneity and irregularities in the powder bed by means of layerwise image acquisition and processing, with no external illumination source apart from the light emitted by the hot material underneath the currently recoated layer. The results show that the proposed approach is suitable to detect powder bed anomalies, while also highlighting the link between the severity of in situ detected errors and the severity of resulting defects in the additively manufactured part.

A hybrid learning-based meta-heuristic algorithm for scheduling of an additive manufacturing system consisting of parallel SLM machines

Additive manufacturing (AM) has been recognised as a promising technology under the context of Industry 4.0, which is reshaping manufacturing paradigms. A prominent type of AM machine is the selective laser melting (SLM) machine, in which several parts may form a job and be produced concurrently. This paper aims to investigate a scheduling problem in an AM system with non-identical parallel SLM machines. Since, in this system, there might be differences in the material types of parts, the required setup time between two consecutive jobs on the relevant machine is dependent on their material types. Accordingly, a bi-objective mathematical model is extended for the problem, considering the makespan and the total tardiness penalty as two objective functions. Due to the high complexity of the problem, an efficient hybrid meta-heuristic algorithm is developed by combining the non-dominated sorting genetic algorithm (NSGA-II) with a novel learning-based local search founded on the k-means clustering algorithm and a regression neural network. The local search enhances the exploitation ability of the NSGA-II while intelligently being taught during the solving procedure. Finally, the superiority of the proposed hybrid algorithm is demonstrated through a computational experiment.