Young-Moon Lee

Analysis of cutting properties with reference to amount of coolant used in an environment-conscious turning process

In the recent years, environmentally conscious design and manufacturing technologies have attracted considerable attention. The coolants, lubricants, solvents, metallic chips and discarded tools from manufacturing operations will harm our environment and the earth’s ecosystem. In the present work, the Tukey method of multiple comparisons is used to select the minimum level of coolant required in a turning process. The amount of coolant is varied in 270 designed experiments and the parameters cutting temperature, surface roughness, and specific cutting energy are carefully evaluated. The effects of coolant mix ratio as well as the amount of coolant on the turning process are studied in the present work. The cutting temperature and surface roughness for different quantity of coolant are investigated by analysis of variance (ANOVA)-test and a multiple comparison method. ANOVA-test results signify that the average tool temperature and surface roughness depend on the amount of coolant. Based on Tukey’s Honestly Significant Difference (HSD) method, one of the multiple comparison methods, the minimum level of coolant is 1.0 L/min with 2% mix ratio in the aspect of controlling tool temperature. F-test concludes that the amount of coolant used does not have any significant effect on specific cutting energy. Finally, Tukey method ascertains that 0.5 L/min with 6% mix ratio is the minimum level of coolant required in turning process without any serious degradation of the surface finish. Considering all aspects of cutting, the minimum coolant required is 1.0 L/min with 6% mix ratio. It is merely half the coolant currently used i.e. 2.0 L/min with 10% mix ratio. Minimal use of coolant not only economically desirable for reducing manufacturing cost but also it imparts fewer hazards to human health. Also, sparing use of coolant will eventually transform the turning process into a more environment-conscious manufacturing process.

Cutting force signal pattern recognition using hybrid neural network in end milling

Abstract Under certain cutting conditions in end milling, the signs of cutting forces change from positive to negative during a revolution of the tool. The change of force direction causes the cutting dynamics to be unstable which results in chatter vibration. Therefore, cutting force signal monitoring and classification are needed to determine the optimal cutting conditions and to improve the efficiency of cut. Artificial neural networks are powerful tools for solving highly complex and nonlinear problems. It can be divided into supervised and unsupervised learning machines based on the availability of a teacher. Hybrid neural network was introduced with both of functions of multilayer perceptron (MLP) trained with the back-propagation algorithm for monitoring and detecting abnormal state, and self organizing feature map (SOFM) for treating huge datum such as image processing and pattern recognition, for predicting and classifying cutting force signal patterns simultaneously. The validity of the results is verified with cutting experiments and simulation tests.

CUTTING FORCES ANALYSIS IN WHIRLING PROCESS

Whirling is a cutting process in which a series of cutting edges remove material by turning over the rotating workpiece. In this process, the whirling ring with a number of cutting teeth combined with the rotation and advancement of workpiece, produces pitches of worm. Mechanics of chip formation of the process, however, has not been fully estabilished. To estimate the cutting force during the process, the kinematics and the maximum undeformed chip thickness to be removed by each cutting edge should be thoroughly analyzed. In this study, using the recently developed model of undeformed chip thickness and the DEFORM software, cutting forces of the whirling process are estimated. The effects of cutting forces on tool are analyzed using the ADAMS software. The validity of the simulations has been verified with a series of cutting experiments.

Analysis of Worm Cutting Characteristics in Whirling Process

The improved geometrical accuracy and better surface finish of worms are required, especially in automobile industry. To meet this requirement, whirling process has been used in the manufacture of worm. Whirling process is a cutting process in which a series of cutting edges on the whirling ring remove material by turning over the rotating workpiece. In this study, cutting characteristics of the worm in whirling process has been analyzed. The undeformed chip models of front and side cutting edges were established. Using the undeformed chip models and DEFORM software, cutting force analyses are carried out. The calculated cutting force imposed on the tool is nearly the same as the sum of the forces calculated which are separately imposed on the front and side cutting edges.

Development of Machine Vision System and Dimensional Analysis of the Automobile Front-Chassis-Module

In the present research work, an automated machine vision system and a new algorithm to interpret the inspection data has been developed. In the past, the control of tolerance of front-chassis-module was done manually. In the present work a machine vision system and required algorithm was developed to carryout dimensional evaluation automatically. The present system is used to verify whether the automobile front-chassis-module is within the tolerance limit or not. The directional ability parameters related with front-chassis-module such as camber, caster, toe and king-pin angle are also determined using the present algorithm. The above mentioned parameters are evaluated by the pose of interlinks in the assembly of an automobile front-chassis-module. The location of ball-joint center is important factor to determine these parameters. A method to determine the location of ball-joint center using geometric features is also suggested in this paper. In the present work a 3-D best fitting method is used for determining the relationship between nominal design coordinate system and the corresponding feature coordinate system.

Collapse characteristics of hydroformed tubes

Tube hydroforming technology (THF) has been extensively applied to auto-body structural members such as the engine cradle and side member in order to meet the urgent need for vehicle weight and cost reduction as well as high quality for collision accidents. In this paper, the mechanical properties for hydroformed tubes with various bulging strians under the plane strain mode are experimentally investigated. Axial compression tests for hydroformed tubes are performed to investigate the collapse load and collapse absorption capacity through the collapse load-displacement curves. Moreover, the collapse absorption capacities are compared and discussed among as-received, hydroformed, and press formed tubes. Results demonstrate that the hydroformed tubes show higher collapse absorption capability in comparison with the as-received tube and the press formed tube because of its high yield strength due to strain hardening.

EFFECTS OF THE MAXIMUM UNDEFORMED CHIP THICKNESS ON ROUGHNESS AND SPECIFIC ENERGY IN SURFACE GRINDING

In this study, effects of the maximum undeformed chip thickness on roughness of ground surface and specific grinding energy were investigated. The acoustic emission (AE) signals generated during grinding processes have been analyzed to find out the appropriate AE parameters for assessing the processes. SM45C steels were ground under conditions yielding volumetric removal rate per unit width of 100, 200, 300 and 400 mm3/min. From the experimental results, it is found that surface roughness (Ra) increases but grinding power (P), energy rate of AE signal (AErms2) and specific grinding energy(e) consumed decrease as the maximum undeformed chip thickness(g) increases.

Analytical and experimental study on the quality improvement of 2 cavity injection-molded LCD frame

The LCD frame is an important part which supports the BLU of medium/large sized TFT-LCD. To produce it efficiently, it is necessary to achieve the molding process improvement from 1 cavity to 2 cavity system. Because 2 cavity mold is compact and its hot-runner zone is broadened, it is difficult to control the temperature on the mold. In this study, injection molding analysis on the frame in 2 cavity process with FEA(Finite Element Analysis) software is carried out to estimate its quality. The calculated injection molding pressures and maximum deflection in 1 and 2 cavity processes are 41.13 MPa and 1.62 ㎜, 40.49 MPa and 1.66 ㎜ respectively. The measured maximum flexure load and surface roughness of the left and right frame of 2 cavities are 209 N and 0.08 ㎛, 193 N and 0.10 ㎛ while those in 1 cavity are 140 N and 0.13 ㎛. Thermal image shows that the maximum standard deviation of the temperature on left and right side of 2 cavity mold is 1.23 ℃ The simulation and measurement results show that the quality of the frame in 2 cavity injection molding process as a whole is not worse than that of 1 cavity system. But maximum flexure loads of the frame in 2 cavity process are far greater than that in 1 cavity process.

EXTRUSION SIMULATION FOR MANUFACTURING STABILIZATION OF EXPANDABLE POLYMER

This study investigates pressure and temperature changes in an extrusion die of expandable polymer according to resin flow. Depending on die design each three structural changes of the die neck width and lip height were assumed and the effects were analyzed. It is revealed that the maximum pressure decreases as the inlet width of die neck and outlet height of die lip increase. The mean temperature decreases as the inlet width increase, but it does not change with the outlet height.

Tribological Characteristics on the Helical Gear in Cold Forging Mold

The purpose of this study is to find out the tribological characteristics of the various lubricants in cold forging of helical gear, which is used in mobile auto-transmission. Five kinds of lubricant were used in this study, i.e. L1, L2, L3, L4 and L5. The pin-on-disk type of friction wear test system has been adopted here. The normal load of 20, 40, 60, 80 and 100N has been applied to the test specimen. The sliding velocities were 0.06, 0.10, 0.14, 0.18, 0.22, 0.26, 0.30 and 0.34m/s. Experimental results show that the friction coefficients of oils having higher kinematic viscosity such as L1, L2, L4 and L5 tend to increase gradually as the sliding velocity increases. The increasing rate of the friction coefficient is relatively high in lower sliding velocity range. However in case of L3 which has low kinematic viscosity the friction coefficient tends to decrease as the sliding velocity increases. The friction coefficients of Bondelube and Bondelite were 3 times higher than those of L1 and L5. The Stribeck curve indicates that L1, L2, L4 and L5 were in hydrodynamic lubrication condition and L3 was in boundary lubrication condition. SEM micrographs revealed that there were some scratch, adhesive wear, adhesion wear and scuffing on the worn surface.