Min-Seog Choi

Simulation for the prediction of surface-accuracy in magnetic abrasive machining

A new machining technique, magnetic abrasive machining which uses magnetic force as a machining pressure, has been developed recently for the efficient and precision finishing of surfaces. The process is controllable because the machining pressure is controlled only by the current that is input to the coil of solenoid, but it needs the monitoring of the surface roughness for the automation of the process and for the achieving of machining efficiency by preventing over-finishing of the surface. For this, in the present study, the surface roughness is predicted as a function of finishing time by a model that has been derived from the removed volume of material. Thus, it is possible, from the surface-roughness model, to predict the time when existing scratches are completely removed. The simulation results are confirmed by comparing them with the experimental results of previous papers.

Study on magnetic polishing of free-form surfaces

Magnetic polishing technology applicable to free-form surfaces such as the die/mold manufacturing field, has been studied using two types of magnetic polishing tool. Finishing efficiency and final surface roughness can be satisfactorily achieved at the same time by magnetic polishing using two types of magnetic polishing tool. One is an abrasive wheel type and the other is a magnetic brush type. The possibility of free-form surface polishing has been confirmed by use of the magnetic polishing technology because it has flexibility of profiling and does not need any complex tool-path control, with respect to workpiece surfaces. Magnetic force was estimated and measured. A two-stage magnetic polishing experiment has been executed using the magnetic polishing tools and mini CNC milling machine without tool-path control. A realization of efficient polishing of curved surfaces is possible using the two-stage magnetic polishing method, and it was also confirmed that automation of free-form surface polishing is possible by this method.

Development and finite element analysis of the finishing system using rotating magnetic field

A polishing system using rotating magnetic field has been developed for the internal finishing of tubes, especially curved tubes which are very difficult to finish by typical finishing methods. The mechanism and characteristics of the developed system are summarized. Finite element method was used to analyze the magnetic flux distribution and flux density in the working zone for two driving modes, from which the desirable mode for efficient polishing was determined.

A study on the optimization of the cylindrical lapping process for engineering fine-ceramics (Al2O3) by the statistical design method

A cylindrical fine-ceramics, Al2O3, component was lapped on its outer surface by the use of a vibrational lapping unit manufactured in the laboratory. It is necessary that the cylindrical lapping of fine-ceramics be characterized and optimized because the process, as with other finishing methods, is time-consuming and thus inefficient, and because it is a very complicated and random process affected by numerous factors both in itself and in its environment. In this study, an efficient experimental approach, the experimental design method, was used to analyze the characteristics of the cylindrical lapping of fine-ceramics. Al2O3, and response surface methodology (RSM) was used to determine the optimal combination of variables for the maximum improvement of the surface roughness Ra. From the final surface-roughness point of view, for given lapping conditions, a stationary point or optimal lapping conditions, as well as the possible maximum improvement of the surface roughness Ra, has been predicted.

Simulation of an internal finishing process of rectangular tube using a magnetic field

Abstract An internal finishing system for rectangular tube is simulated mathematically. The finishing pressure on the workpiece is produced by applying a magnetic field to the air-gap between the finishing tool and the magnetic poles, and the tool driving force by moving the magnetic pole. The finishing process is controllable because the finishing pressure is controlled by the input current to the winding coil of the electromagnet and the tool driving force by the movement of the magnetic pole. Thus, the finishing force and the tool driving force are simulated from the simplified magnetic circuit model for the finishing system. From the simulation some important aspects of the internal finishing process of a rectangular tube are considered.