Papers by Keyword: Material Removal Rate (MRR)

Abstract: Open-air type numerically controlled plasma chemical vaporization machining (NC-PCVM) is promising technique to fabricate the ultra-precision optical components and to finish the functional materials. The objective shape is fabricated by controlling the scanning speed of the localized plasma because removal volume is proportional to the dwelling time of the plasma on the workpiece surface. To achieve deterministic figuring with shape accuracy of nanometer level, it is essential to keep volumetric material removal rate (MRR) constant during and batch to batch processing. The removal rate is proportional to the density of fluorine radical generated by plasma. So, we control the electric power to keep the removal rate constant during the process based on the fluorine atomic density obtained by optical emission actinometry. We report the relationship between MRR and fluorine atomic density measured by optical emission actinometry.

Abstract: Ultrasonic vibration assisted processing is well known for the improvement in machined surface quality and processing efficiency due to the reduced forces and tribology-generated heating when grinding hard-brittle materials. We transplanted this philosophy to chemo-mechanical fixed abrasive polishing of optical glass, namely fused silica, in an attempt to improve surface roughness and/or material removal rate. Experiments were conducted to elucidate the fundamental characteristics of chemo-mechanical fixed abrasive polishing of fused silica in the presence and absence of ultrasonic vibration on a setup with an in-house built gadget. The experimental results show that ultrasonic vibration assisted chemo-mechanical fixed abrasive polishing can yield increased material removal rate while maintaining the surface roughness of manufactured optics compared to conventional fixed abrasive polishing without ultrasonic vibration. The mechanism of material removal in fixed abrasive polishing was also delved. We found that the glass material is removed through the synergic effects of chemical and mechanical actions between abrasives and glass and the resultant grinding swarf contains ample Si element as well as Ce element, standing in stark contrast to the polisher that contains abundant Ce element and minor Si element.

Abstract: Laser ablation is a new, very flexible process for micro-fabrication of micro-moulds and other micro-system devices. This process is suitable for machining difficult-to-machine materials, like ceramics, dielectrics, carbide and hardened steel with excellent productivity and surface. The paper presents the investigation on the material removal rate of aluminium 5754 using a nanosecond Nd:YAG laser with a wavelength of 1064 nm.

Abstract: Powder-mixed dielectric fluid is one of the innovations of electro-discharge machining (EDM) which seeks to improve the process outputs by addition of powders to the dielectric during machining. In the present study, the influence of TaC powder in kerosene dielectric fluid on EDM process outputs was investigated. Experiments were conducted with the outputs as material removal rate (MRR), surface roughness (Ra) and micro-hardness. During the EDM, the discharge current was varied between 2.5 and 6.5 A, while powder concentration ranges between 5.0 and 15.0 g/l. Results indicate that the highest MRR of 0.38 g/min was obtained with TaC concentration of 15 g/l at the current of 6.5 A. TaC powder addition does not affect both the MRR and Ra at lower current. However, the level of micro-hardness attained was influenced by TaC powder concentration in dielectric fluid, the highest being 1,040 Hv with 5.0 g/l at the current of 2.5 A.

Abstract: Manufacturing companies define the qualities of thermal removing process based on the dimension and physical appearance of the cutting material surface. Therefore, the roughness of the surface area of the cutting material and the rate of the material being removed during the manual plasma arc cutting process was importantly considered. Plasma arc cutter Selco Genesis 90 was used to cut the specimens made from Standard AISI 1017 Steel manually based on the selected parameters setting. Two different thicknesses of specimens with 3mm and 6mm were used. The material removal rate (MRR) was measured by determining the weight of the specimens before and after the cutting process. The surface roughness (SR) analysis was conducted to determine the average roughness (Ra) value. Taguchi method was utilized as an experimental layout to obtain MRR and Ra values. The results reveal that for the case of manual plasma arc cutting machining, the SR values are inversely proportional to the MRR values. The quality of the surface roughness depends on the dross peak that occurred during the cutting process.

Abstract: EDM machinability of PCD was investigated using a copper electrode giving ultrasonic vibrations. In this series of EDM experiments, three types of ultrasonic vibration modes were selected (axial vibration, flexural vibration and complex vibration). From the experimental results, it was found that EDM efficiency became 3 times higher than the ordinary EDM (no vibration given to the electrode) under the two specific vibration modes, namely, 1) the axial vibration (large) mode and 2) the complex vibration (axial vibration: large + flexural vibration: small) mode. Furthermore, it was shown that the effects resulted from not only the cavitation effect of the working fluid but also the vibrational action of the electrode itself.

Abstract: The SiC crystal substrate has been widely used in the area of microelectronics, photonics and new materials, such as semiconductor lighting, integrated circuits, and so on. In this paper, the influences of the lapping parameters, such as the rotational velocity of the lapping platen and the carrier and the polishing pressure on the material removal rate (MRR) and surface roughness Ra of SiC crystal substrate (0001) C surface based on the diamond particle in lapping. This study results will provide the reference for developing the abrasive paste, optimizing the process parameters and researching the material removal mechanism in lapping of SiC crystal substrate.

Abstract: In this paper an attempt has been made to investigate the performance of an electrode made through powder metallurgy (PM) of copper tungsten during electrical discharge machining (EDM). Experimental results are presented on electrical discharge machining of AISI D2 hardened steel in kerosene with a copper tungsten (Cu35% - W65%) tool electrode made through PM method with a constant duty factor of 80%. In term of high performance EDM process, higher peak current (>20A) and pulse duration (>400µs) with a high machining efficiency were used. Experimental results have shown that machining at a peak current of 40A and pulse duration of 400µs yields the highest material removal rate (MRR) whereas machining at a peak current of 20A and pulse duration of 400µs yields the lowest tool wear rate (TWR). The lowest surface roughness appears at the lowest material removal rate which is at a peak current of 20A and pulse duration of 600µs. The optimum machining performance can be performed by the combination of pulse duration and peak current at 600µs and 40A respectively.

Abstract: Powder mixed near dry electrical discharge machining (PMND-EDM), which uses gas-liquid-powder mixture as three phase dielectric medium to remove materials, is proposed. Compared with dry EDM, much higher material removal rate (MRR) is achieved in PMND-EDM. The mechanism of PMND-EDM is analyzed and reasons for its MRR improvement are illustrated. Comparative experiment is done in compressed air and three phase dielectric medium, respectively. MRR is calculated. And discharge voltage waveforms are obtained by oscilloscope. It is shown that three phase dielectric medium can improve MRR effectively.

Abstract: Particle reinforced metal matrix composites (SiCp/Al composites) have proved to be extremely difficult to machine with traditional cutting processes due to serious tool-wear and high machining cost, which lead to the low machining efficiency. This paper presents the results of an experimental research on mill-grinding of SiC particle reinforced aluminum matrix composites. Based on the Taguchi experimental design method, study on the material removal rate was carried out to gain the optimal processing parameters combination by using the analysis of S/N ratio. The detailed effect of wheel speed on material removal rate through single factor experiment was also studied. Though analysis of S/N ratio and variance, the depth of cut has greatest effect on the material removal rate, followed by feed rate. And grinding wheel speed has least effect on it. But the depth of cut and feed rate affect on the material removal rate nonlinearly. In the range of machining parameters applied, the optimal processing parameters combination gained is A2B3C3, namely, v_s=11.77m/s, v_w=100mm/min, a_p=0.8mm. Material removal rate increased at first and then there was a decreasing trend with increasing wheel speed.