Jae-Seob Kwak

Magnetic force improvement and parameter optimization for magnetic abrasive polishing of AZ31 magnesium alloy

Abstract The magnetic force acting on workpiece to be machined plays a significantly important role in magnetic abrasive polishing process. But in a case of polishing nonferrous materials, the strength of magnetic force is very low and it leads lower polishing efficiency. The magnesium alloy that has superior mechanical properties for industrial application such as a lightweight and high specific strength is one of the most famous nonferrous materials. An improving strategy of the magnetic force for the AZ31 magnesium alloy installed with a permanent magnet was proposed and experimental verification was carried out. For the proposed strategy, the effect of process parameters on the surface roughness of the AZ31 magnesium alloy was evaluated by a design of experimental method.

Mathematical model determination for improvement of surface roughness in magnetic-assisted abrasive polishing of nonferrous AISI316 material

Abstract The new magnetic-assisted abrasive polishing process for non-ferrous materials was proposed in order to increase the magnetic flux density which directly influences the contact force between the workpiece and the abrasives. The permanent magnets were installed under the workpiece and their effects were verified by the experiments. The effect of polishing factors on the improvement of surface roughness was evaluated based on the Taguchi experimental method, and the optimal conditions for polishing AISI316 stainless steel were determined. The predicting model for improving surface roughness was developed and the validity of the developed model was tested. The results show that the permanent magnets are very useful in improving the surface roughness in the magnetic-assisted abrasive polishing process.

A Study of Micro-Channel Fabrication by Micro-Milling and Magnetic Abrasive Deburring

This This study aims to verify burr formation and to remove the burrs in micro-channel fabrication using micro-machining tools. The machining processes are combined with micro-milling and magnetic abrasive deburring for AISI316 stainless steel. Depending on the micro-milling conditions that are applied, burrs are formed around the side walls. Magnetic abrasive deburring is used to remove these burrs. AISI316 stainless steel is a nonferrous material and its magnetic flux density, which is an important parameter for efficient magnetic abrasive deburring, is low. To enhance this magnetic flux density, we design and build a magnetic array table. The effect of removing burrs is evaluated via SEM and a surface tester.

Notice of Retraction Parameter optimization in magnetic abrasive polishing for magnesium plate

This study aims to finish effectively the thin magnesium (AZ31) alloy plate that is usually very difficult to be polished by the conventional cutting processes because of their explosive and fragility properties. Reaction components on the workpiece surface roughness were measured after the magnetic abrasive polishing of the magnesium alloy plate. Taguchi experimental design method was adopted for evaluating the effect of the process parameters on the improvement of the surface roughness by the magnetic abrasive polishing. The process parameters were the applied current to the inductor, the working gap between the workpiece and the inductor, the rotational speed and the feed speed. Optimal conditions for better surface roughness were determined using the S/N ratio. As a result, it was seen that the magnetic abrasive polishing was very useful for finishing the thin magnesium alloy plate.

Evaluation of wheel life by grinding ratio and static force

A degree of sharpness in wheel grains affects the surface roughness and dimensional accuracy in the grinding process. If a wheel with dull grains is used, the grinding force is increased and the surface roughness is deteriorated. In ovder to produce a precision component economically, the magnitude of the wear amount in the grinding wheel has to be limited. In this study, experimental evaluation of a wheel life varying with the grinding ratio and static grinding force was conducted. The grinding ratio and grinding force were measured to seek the grinding performance of the WA wheel. The relationship between the grinding ratio and static grinding force was presented.

Tool Wear Rate and Accuracy of Patterns in Micro Prismatic End-milling

Micro prism pattern is applying in order to get increase of luminance, control the light, and so forth especially in optics and display industry. Most patterns are fabricated by lithography, planning, and EDM, but they have limitations on the productivity or the unit cost of produce. However, ultra ...

New Seat Design and Finite Element Analysis for Anti-Leakage of Globe Valve

The valves used to control or shut off the flow through a pipeline can be divided into many different types, including gate valves, globe valves, and check valves. Globe valves, in particular, have excellent properties, and because they can easily control the flow under high-pressure conditions, they are generally used in LNG ship and steam pipelines. In this paper, a method for changing the shape of a seat was suggested to solve the valve leakage problem from a structural perspective. In addition, the stress distribution and directional deformation were compared for each model. The suggested models were thus validated, and the optimized seat structure, which includes a self-supporting capability for decreasing the amount of leakage, was determined.

Experimental Verification of Characteristics of Magnetic Abrasive Polishing Combined with Ultrasonic Vibration

In this paper, we propose an ultrasonic magnetic abrasive polishing (US-MAP) technique to effectively machine a high-strength material, and we prove the efficiency of hybrid finishing. We use Taguchi`s experimental method to determine the influence of each parameter. Based on the results, US-MAP exhibited a higher polishing efficiency than traditional MAP, and a suitable frequency for hybrid finishing was 28 kHz. When investigating the effect of the parameters on the surface roughness, the ultrasonic amplitude had the greatest effect. However, when machining with 55-μm amplitude, the machining efficiency decreased as the magnetic flux density varied.

Study on Effect of Particle Size of Ferrous Iron and Polishing Abrasive on Surface Quality Improvement

이런 소재의 가공은 주로 연삭가공에 의해 이루어지는데 금형의 복잡한 형상 때문에 연삭숫돌의 제작이 어렵고, 일반적인 연삭가공으로는 균일한 표면을 얻기가 매우 힘들다. 이를 해결하기 위한 방안으로 전자석을 이용한 자기연마법이 적용되고 있다. 전자석으로 구성된 Key Words: Magnetic Abrasive Polishing(자기연마), Ferrous Particles(자성입자), Mixture(혼합물), Polishing Abrasives(연마입자), Particle Size(입자크기), Surface Roughness(표면거칠기) 초록: 자기연마가공은 연마입자와 자성입자를 혼합한 공구의 유연성을 이용하여, 공작물 표면을 폴리싱 하는 특수가공법이다. 기존 연구의 대부분은 가공 정밀도를 향상시키기 위해서 연마입자의 크기를 달 리 하는 것에 관한 내용들이다. 그러나 자기연마 가공에서는 연마입자의 크기뿐만 아니라, 자성입자의 크기도 가공에 많은 영향을 미칠 것으로 판단되며 이에 대한 연구가 반드시 필요하다. 따라서 본 연구에서는 크기가 다른 자성입자들을 사용하여 자기연마가공의 효과를 평가하였다. 자성입자는 철 분말을 사용하였으며, 직경이 평균 8, 78, 250㎛의 크기이다. 공작물의 표면거칠기 향상 정도를 비교하여 자성입자의 크기가 자기연마가공의 정밀도에 미치는 효과를 평가하였다. 자성입자의 크기는 표면거칠기 의 향상에 많은 영향을 미치며, 직경이 78㎛일 때 가장 좋은 표면거칠기의 향상을 나타내었다. Abstract: Magnetic Abrasive Polishing (MAP) process is a nontraditional method for polishing the surface of workpiece by using the flexibility of tool. At present, a mixture of polishing abrasives and ferrous particles is used as the tool in the MAP process. Previously, an experiment was conducted with different sizes of polishing abrasives with an aim to improve the polishing accuracy. However, the sizes of ferrous particles are also expected to have a dominant effect on the process, warranting a study on the effect of the size of ferrous iron particles. In this study, an experiment was conducted using three different sizes of ferrous particles. Iron powder of average diameters 8, 78 and 250㎛ was used as ferrous particles. The effect of each ferrous particle size was evaluated by comparing the improvements in surface roughness. The particle size of a ferrous iron was found to play a significant role in MAP and particles of 78㎛ facilitated the best improvement in surface roughness.

Study on Abrasive Adhesion and Polishing Effect in Wet Magnetic Abrasive Polishing

In a conventional magnetic abrasive polishing process, the polishing abrasives are mixed with ferrous particles and slight cutting oil to form a cluster of abrasives. However, when a tool rotates at a high revolution speed, most of the polishing abrasives are scattered away from it due to the increase in centrifugal force. This phenomenon directly reduces the polishing efficiency. The use of a highly viscous matter such as silicone gel instead of cutting oil for mixing is one method to solve this problem and increase abrasive adhesion. Another method to avoid high abrasive scattering is the application of wet magnetic abrasive polishing (WMAP). In WMAP, abundant mineral oil is preliminarily applied to the workpiece surface. This study experimentally evaluated the effect of WMAP on abrasive adhesion. The relationship between the amount of working abrasives and polishing conditions was characterized. Despite the lower adhesion ratio of polishing abrasives, the surface roughness was found to be significantly improved as the result of WMAP. § 이 논문은 2014 년도 대한기계학회 생산 및 설계공학부문 춘계학술대회(2014. 4. 24.-25., 라마다프라자호텔) 발표논문임 † Corresponding Author, jskwak5@pknu.ac.kr C 2014 The Korean Society of Mechanical Engineers