This study aims to investigate the surface roughness and the time consume printing on PLA material using FDM 3D printing on differences in layer height. A 3D printer machine, Creality Ender 3 was involved to manufacture the specimen. Furthermore, they tested with the SurftestSJ-301 Mitutoyo device to determine the roughness of surface object. The height of the test specimen layer varies from 0.05 mm to 0.25 mm with the increment of 0.5 mm for each variation, while the layer angle keep constant at zero degree (0°). Surface roughness and print time are analysed to determine the best design parameters. The test results show that, the greater of layer height has the rougher of the surface. In addition, the printing time is inversely proportional to surface roughness. The smallest of surface roughness occurs on the 0.05 mm of layer height, whereas the lowest occurs on the 0.25 mm of layer height. In addition, the optimize parameter occurs on 0.15 mm and 0.2 mm of layer height which surface roughness and printing time are 9.11 μm and 158 min respectively (Lh 0.15 mm), while the layer height of 0.20 mm for 120 min and 10.48 μm.

Many studies were conducted to maintain the environment by reducing the waste, especially pineapple peel waste. This study aims to explore the effect of various pressure of the homogenization process on bacterial cellulose membrane surface morphology and structure produced using extract of pineapple peel waste. The methods include the preparation of pellicle samples from the product of the fermentation process of Acetobacter xylinum using a medium from the extract of pineapple peel waste. Bacterial cellulose pellicles were crushed using a blender. Mashed bacterial cellulose pellicle then homogenized in High-Pressure Homogenizer with pressure variation of  0 bar, 150 bar, 300 bar, 450 bar, dan 600 bar then cast into a mold. The bacterial cellulose solutions were dried in an oven at 60°C for 8 hours. The dried bacterial cellulose membrane was analyzed using XRD for the structure and SEM analysis for the morphology. The results indicate that the crystalline properties of BCM were shifted after being treated by various pressure processing in a High-Pressure Homogenizer. It was found that the High-Pressure Homogenizer with higher pressure reduced the peak intensity, decreased crystalline index from 87% to 70%, and decreased the degree of crystalline from 88% to 77%  without changing the cellulose structure. The higher pressure of the homogenization process causes the porosity of the membrane to be decreased.

AbstractThe machinability information of Zr-based bulk metallic glasses (BMGs) are recently limited but essential to provide technological recommendation for the fabrication of the medical devices due to the material’s metastable nature. This study aims to investigate the material removal rate (MRR) and surface roughness under different current and pulse-on time of newly developed Ni- and Cu-free Zr-based BMG using sinking-electrical discharge machining (EDM). By using weightloss calculation, surface roughness test and scanning electron microscopy (SEM) observation on the workpiece after machining, both MRR and surface roughness were obtained to be increased up to 0.594 mm3/min and 5.50 μm, respectively, when the higher current was applied. On the other hand, the longer pulse-on time shifted the Ra into the higher value but lower the MRR value to only 0.183 mm3/min at 150 μs. Contrary, the surface hardness value was enhanced by both higher current and pulse-on time applied during machining indicating different level of structural change after high-temperature spark exposure on the BMG surface. These phenomena are strongly related to the surface evaporation which characterize the formation of crater and recast layer in various thicknesses and morphologies as well as the crystallization under the different discharge energy and exposure time.

Sand for mould must comply with requirements for casting moulding, this sand mould must have enough permeability and strength. Permeability is the capability to remove air from the mould cavity. Sand from volcanoes is very easy to get and costs less than silica sand. One of the sands that can be used is Mount Semeru, which has only been used as a building material. The use of volcanic sand has been using clay as a binder. In order to improve the quality of the mould, in this research, we was carried out using phenolic resins as a binder. The sand used in this research is sand from Semeru Mountain which is obtained from the Pasirian area of Lumajang Regency. The sand sizes for the mould are 20, 40 and 60 mesh, the sand sizes for the mould are 20, 40 and 60 mesh. The sand binder used is phenolic resin mixed with water with a ratio of 2 resins to 1 water. Permeability testing uses a sand mould specimen in the form of a tube in accordance with SNI 15-0312-1989 standards. The highest permeability occurs in sand moulds with a mesh grain sand 20 (321.67 cm3/minute), The highest compressive strength is found in moulds with 60 mesh (4.13 MPa).

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