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There are several ways to assess machinability, viz. forces that are working during machining, the surface roughness of machined part, chip formation, and tool performance. This article aims to observe the machinability from the tool performance perspective when machining with minimum quantity lubrication (MQL). The MQL device can either be time-controlled or temperature-controlled using an Arduino. The machining was carried out on a conventional lathe toward a bar of AISI 4330 using carbide coated insert tools. The experiments were carried out using Taguchi design L9, by the varying depth of cut, coolant composition and method of applying the coolant. Tool performance was evaluated by tool deterioration value. There are four levels of tool deterioration according to its severities after machining. Analysis of variance shows that depth of cut more influence to the tool performance than the coolant application method by 32.69% and 12.82% each, respectively. However, it is proof that MQL with temperature-controlled would contribute to the minimum tool deterioration.

The synthesis of nanoparticles using thermal DC plasma method is a simple method for ease of installation and high efficiency is due to the rate of precursor that can be controlled. Micro-sized aluminum powder is synthesized using thermal DC plasma undergoing a process of evaporation as it passes through high temperature plasma flame, where kemuadian oxidized aluminum particles which evaporates the particles are split and binds with oxygen to form aluminum oxide or also known as alumina (Al2O3). In this experiment, the flow rate of oxygen plasma parameters at 35 SCFH (Standard Cubic Feet per Hour) and 20 amperes flows with precursors rate variation of 1.16 g / min, 3.19 g / min, and 3.5 g / min. Precursors used is 88 micro sized aluminum powder. To determine the morphology of nanoparticles of alumina testing scanning electron microscopy (SEM), the morphology form of nanosphere. Results of the analysis showed that the rate of precursor low causing agglomeration level slightly while the higher rate of precursor agglomeration rate also increased. At the rate of precursor 1.16 g / min, nanoparikel undergo agglomeration with an average particle size of 36.55 nm, and then at a rate of 3.19 gr precursor / mnt an average particle size of 46.49 nm, and at a rate of 3.5 gr / mnt an average particle size of 46.49 nm. The powder nanoparticles were then characterized using X-ray defraksi (XRD) where all alumina nanoparticles were synthesized showed alumina phase that is formed is a phase δ-Al2O3. Keywords: Alumina nanoparticles, DC Thermal Plasma, morphology, precursor rate, nanoparticles size, SEM, XRD.

Column flotation is commonly used in cleaner circuits at the ore beneficiacy industry. However, this research wants to apply the column to the rougher circuit as an alternative to the mechanical flotation due to its energy efficiency which is 80% more efficient. This research was conducted using column and mechanical flotation cells to observe their metallurgical performance as a rougher circuit. The feed is sphalerite ore at size -140+230# with variables of % solid 7.5;10; 12.5; 15 and doses of frother 20;30;40; and 50ppm. Reagents used include OrePrep, Potassium Amyl Xanthate 500g/ton, copper sulfate 500g/ton, and soda ash 500g/ton. Flotation process is carried out 5 minutes for conditioning and 10 minutes for aeration. The results obtained the recovery value and grade. The results from the experiment, it can be concluded that the recovery obtained by mechanical is superior, and for column flotation grade is superior. In the variation of solid percent and frother dose, recovery increases to the maximum point and then decreases because no signifant effect after maximum point. The recommended variables for mechanical flotation are 12.5 solid% and 50ppm frother dose, because the recovery worth 75.462%. For column flotation, 15% and 40ppm, obtain the highest recovery 53.439%.