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Powder addition reinforcement (PAR) has shown its ability to enhance the mechanical properties of polymers prepared with fused filament fabrication (FFF). However, this technique was less reliable owing to the frequent printing failures caused by nozzle clogging. In this research, a novel delivery method for Fe3O4powder was introduced and coupled to the FFF process for preparing PLA/Fe3O4composite. The tensile and flexural properties of the resulting composite were then determined. The result showed that the addition of Fe3O4powder increased both the tensile and flexural strengths of the composite. The highest strength of PLA/Fe3O4composite was obtained in the specimen with 1 wt% Fe3O4powder content, where their tensile and flexural strengths increased by 59.92% and 53%, respectively, with the addition of such amount of powder particles. However, higher powder contents led to deterioration of the composite strength. The microstructure of the composite apparently showed that the presence of Fe3O4powder yielded a less porous structure in this material and improved the bonding between the printed rasters and layers within the composites, thereby enhancing their tensile and flexural properties.

Digital light processing (DLP) technology has been developed based on stereolithography (SLA) 3D-printing principle. The biodegradable and low-cost polylactic-acid (PLA) has so far been used as polymeric material for photopolymer resin in SLA and DLP. To achieve functional SLA-processed product, the properties of such PLA has been improved, with the aim to make it flame retardant, less viscous, and having light transmittance characteristics. In this study, the liquid raw PLA photopolymer was changed by adding different contents of Ammonium Phosphate (APP), melamine cyanurate (MCA), Aluminum Tri-hydroxide (Al2O3) and Nano-silicon dioxide (SiO2) additives. The solid PLA nanocomposite specimens were printed by using DLP device according to the standard geometry for burning test UL-94 to evaluate its flame-retardant property. In addition, the printing product and residue after burning test was analyzed for their morphological characteristic by using SEM. The results showed that the low weight fraction of MCA showed excellent performance. PLA/MCA successfully kept green body form until the sintering temperature of stainless steel was achieved. It can become a reference for application DLP 3D printing products in the casting and sintering process.

Although Fused Filament Fabrication (FFF) technology has gained popularity and is used extensively since the last decade, the low mechanical properties of the resulting product have been recognized as the major limitation of this technique. The anisotropic nature of the printed products due to the layered structure and many cavities that are present inside the printed parts are among the main causes of this problem. In this study, the powder addition reinforcement (PAR) method had been developed by introducing reinforcing powder into the polylactic acid (PLA) as the base material during the printing process so that nozzle clogging can be avoided and powders can be placed between the layers. In this work, iron oxide nanoparticles (Fe2O3) were used as a reinforcing powder. The addition of this powder was carried out by using two methods, namely brushing and compressed air-assisted techniques. The results showed that the compressed-air assisted technique demonstrated better results in terms of mechanical properties. In this case, the tensile strength of the composite with the compressed-air assisted technique was higher by 28.95% than that of the PLA and by 5.53% - 25.2% than that of the brushing method. Finally, this study showed that the compressed air-assisted method is the potential to be developed in the future as a powder addition reinforcement technique in the FFF process.

Fused filament fabrication (FFF) has nowadays become a popular 3-dimensional (3D) printing technique for the fabrication of polymeric components with customized and complex-shape design, including biomedical implants. However, the use of this technique is often constrained by the limited number of polymeric materials that can be printed to form the final product. Despite excellent wear resistance and widely used as the acetabular component of a joint prosthesis, ultra-high molecular weight polyethylene (UHMWPE) is among such the rarely-found filament material in the market. In this research, preliminary work to fabricate UHMWPE filament for the FFF processing is carried out by using extrusion. The influences of extrusion temperature, addition of polyethylene glycol (PEG), and rotational speed of the extruder’s screw on the physical, chemical, and mechanical properties of the extruded UHMWPE filament were determined. The result demonstrated no change in the chemical compositions of the filament due to the processing parameters applied, as noted from the FTIR spectra. The result of the tensile test showed that the highest tensile strength of UHMWPE filaments could reach 23.5 MPa.

Fused Filament Fabrication (FFF) continues to experience improvements in terms of its flexibility and functionality, therefore it attracts public attention to use this technology. Multi-Material Additive Manufacturing (MMAM) is an approach in the FFF technology that allows the manufacturing of 3D-printed products composed of two or more materials in a single printing process. MMAM enables the user to apply various configurations to obtain a 3D-printed material with adjustable properties. This study aims to determine the effect of core material on the Shore hardness of the FFF printed parts with the MMAM approach. There were two types of materials combined with the MMAM approach in this work, namely polylactic-acid (PLA) and thermoplastic elastomer (TPE). The Shore hardness test was conducted according to the ASTM D2240-15 standard. The results showed that the thickness of the core material inserted into the printed material had a significant effect on the hardness value of printed multi-material parts. In addition, the hardness value was highly dependent on the modulus of elasticity of the material. Therefore, the hardness value changed following the proportion of the printed material.

A comprehensive understanding of powder flow is essential, particularly in the synthesis of additives in the solid free-forming process and dosage dispensing in pharmaceutical industries. The vibration method is the most widely used for inducing powder flow. In this method, a hopper containing powder is vibrated by a piezoelectric system to allow powder flow. However, there are several drawbacks in this method, particularly in the degree of consistency of the resulting flow. This occurs because the vibration characteristics created have a single axis direction, resulting in which can lead to powder compaction. To resolve this problem, this research is conducted to determine the flow properties of titanium powder dispensed by 2-axis vibration. The titanium (Ti) powder having a size of less than 74 μm in the powder hopper was vibrated for 15 min by a DC motor and the weight of the dispensed powder was measured to evaluate the consistency of the resulting powder flow. The result shows that the powder flow generated by the DC motor was consistent during the period of dispensing. However, the powder flow rate dropped up to 8.6% during 5-10 min of dispensing at a speed of 1800 rpm. In conclusion, the 2-axis vibration by using a DC motor could prevent the powder compacting phenomenon and ensure a consistent flow of micro-sized powders during the dispensing process.

Direct chill (DC) casting has been considered as one of the promising casting methods that can be used to produce aluminum alloys billet. The process is conducted by pouring aluminum metal into a water-cooled mold. The billet shell begins to form when molten aluminum contact directly with the mold (this is also known as primary cooling). Afterward, the starting block is pulled downwards at a specified casting speed to achieve desired aluminum billet. The start-up phase during the DC casting process is considered a crucial step since it may determine the formation of defects in the casting products. This research aims to investigate the casting defects on the aluminum alloy that were formed during the start-up process of DC casting. The results show that the billet failed to form following the downward movement of starting block. Meanwhile, the billet tended to stick to the mold wall due to several factors, such as too low a pouring temperature, a less-round mold shape, the poor quality of the hot top and graphite ring, and the water that entered the mold during the casting process. It also noted several markers of the casting defects that occurred during the DC casting process such as liquation or bleeding, cold folding, billet stuck in the mold, butt structure, and rough billet surface.

This research aims to evaluate horizontal and vertical constrained rod casting (CRC) molds on hot tearing susceptibility (HTS) of Al-xCu casting alloys with 2.2, 3.6, 7.5, and 12.5 percent Cu. The hot tears on the casting product were observed using a macroscopic approach. In addition, the hot tearing susceptibility of each casting product prepared using these molds was evaluated using the HTS formula. The results show that the vertical CRC mold has a higher HTS value than the horizontal CRC mold. The rod length is a significant factor in causing hot tearing. Longer rods are more susceptible to hot tearing. The horizontal CRC mold provides a clearer effect of rod length and Cu composition on the average HTS value. In the vertical CRC mold, the effect of Cu composition on the average HTS value is less clear. Therefore, it is highly recommended to use horizontal CRC mold for HTS testing of aluminum casting alloys.

Electropolishing has been widely used for surface finishing of metallic products in the industry, owing to its excellent capability of producing metallic components with a homogeneously smooth surfaces. However, this treatment is often constrained by the long duration required for the processing. Therefore, an improvement in this process is needed. The aim of this research is to introduce the use of electropolishing with circulated electrolytes for improving the surface finish of brass. In this work, electropolishing was carried out by using circulated H2SO4 electrolyte for 10 to 30 min in a customized electropolishing chamber. The effect of this treatment on surface morphology, surface roughness, and thickness reduction of the brass specimen was determined. The results showed a better capability of electropolishing with circulated electrolyte in decreasing the brass roughness, i.e., by 84%, than that without electrolyte circulation which only reached 45% during 30 min of the treatment.

The composition profile and the microstructure formation of unidirectionally solidified Al–4.5 wt% Cu sample was investigated. The thermal analysis technique determined the vertical Bridgman’s test sample solidification parameters. Characterization of microstructures was conducted with an optical microscope, and Image-J software determined the α-Al area. Energy-dispersive X-ray spectroscopy was used to assess the composition. The composition profile was confirmed with the actual density and micro-hardness value. The results show that the composition of Cu varies between 4.93 and 3.99%, along with the 98.3% drop in the cooling rate. The reduction of Cu composition is in line with the α-Al area, actual density, and micro-hardness value. Two different morphologies of eutectics are found, fine internal fragments in 1.12 to 2.4 °C/s (less than 35 mm) and the lamellar in 0.04 to 0.06 °C/s cooling zone (more than 35 mm).

Surface mechanical attrition treatment (SMAT) has been recognized as a potential surface treatment for improving the strength and the wear resistance of magnesium (Mg) and its alloy. However, this treatment potentially increases the degradation rate of these particular materials. Therefore, additional treatments might be needed to overcome such limitation of the SMAT. In this research, the influence of polishing on the degradation of the SMAT-processed AZ31B Mg alloy was investigated. Weight losses measurement and pH monitoring were carried out to determine degradation behavior of the Mg alloy during an immersion test in 3.5 wt.% NaCl solution. The results showed that the degradability of the Mg alloy decreased with the application of polishing to remove the rough surface layer and the Fe contaminant on the material surface generated by the SMAT. Based on all the findings in this work, it can be concluded that the SMAT is indeed a promising technique for lowering the degradability of AZ31B Mg alloy, but such an advantage was masked by the increased roughness and contamination of the alloy surface with this treatment.

•Wind as renewable energy has several disadvantages, e.g. high installation costs.•As solution, VAWT Savonius as a small-scale turbine is used as harvesting instrument.•Effects of Reynolds number on the performance of Savonius wind turbines are investigated.•Modification by applying slotted blades on the turbine is considered in this work.•The highest power coefficient is achieved by modification of 3 mm slotted with Re = 1.44 × 104.