• Steel and Composite Structures
• /
• v.34 no.5
• /
• pp.681-698
• /
• 2020

The paper addresses contribution to the modeling and optimization of major machinability parameters (cutting force, surface roughness, and tool wear) in finish dry hard turning (FDHT) for machinability evaluation of hardened AISI grade die steel D₃ with PVD-TiN coated (Al₂O₃-TiCN) mixed ceramic tool insert. The turning trials are performed based on Taguchi's L₁₈ orthogonal array design of experiments for the development of regression model as well as adequate model prediction by considering tool approach angle, nose radius, cutting speed, feed rate, and depth of cut as major machining parameters. The models or correlations are developed by employing multiple regression analysis (MRA). In addition, statistical technique (response surface methodology) followed by computational approaches (genetic algorithm and particle swarm optimization) have been employed for multiple response optimization. Thereafter, the effectiveness of proposed three (RSM, GA, PSO) optimization techniques are evaluated by confirmation test and subsequently the best optimization results have been used for estimation of energy consumption which includes savings of carbon footprint towards green machining and for tool life estimation followed by cost analysis to justify the economic feasibility of PVD-TiN coated Al₂O₃+TiCN mixed ceramic tool in FDHT operation. Finally, estimation of energy savings, economic analysis, and sustainability assessment are performed by employing carbon footprint analysis, Gilbert approach, and Pugh matrix, respectively. Novelty aspects, the present work: (i) contributes to practical industrial application of finish hard turning for the shaft and die makers to select the optimum cutting conditions in a range of hardness of 45-60 HRC, (ii) demonstrates the replacement of expensive, time-consuming conventional cylindrical grinding process and proposes the alternative of costlier CBN tool by utilizing ceramic tool in hard turning processes considering technological, economical and ecological aspects, which are helpful and efficient from industrial point of view, (iii) provides environment friendliness, cleaner production for machining of hardened steels, (iv) helps to improve the desirable machinability characteristics, and (v) serves as a knowledge for the development of a common language for sustainable manufacturing in both research field and industrial practice.

• Journal of the Korean Society of Manufacturing Technology Engineers
• /
• v.7 no.6
• /
• pp.80-89
• /
• 1998

Back rake angle of tool is one of the fundamental effects to the cutting ability. In this paper, for several back rake angle of lathe tool (-5$^{\circ}$ , 0$^{\circ}$ , 5$^{\circ}$ , 10$^{\circ}$ , 15$^{\circ}$ ), we experimentally examine cutting forces via orthogonal cutting. Using measured cutting forces, a formula for specific cutting resistance is derived according to the variation of tool angle. Also, the measured cutting forces are analyzed in both time and frequency domain. Cutting parameters are obtained by measuring the thickness of chip, and the effect of the back rake angle of tool is manifested. This study maintains the predicted cutting model with improved accuracy.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 1995.10a
• /
• pp.271-275
• /
• 1995

Chip control is a major problem in automatic machining process, especially in finish operation. Chip breaker is one of the important factors to be determined for the scheme of chip control. As unbroken chips are grown, there deteriorate quality of the surface roughness and process automation can be carried out. In this study, to get rid of chip curling problem while turning internal hole, optimal chip breaker is selected form the experiment. The experiment is planned with Taguchi's method that is based on the orthogonal arrary of design factor. From the respose table, cutting speed, feedrate, depth of cut, and tool geometry are major factors affecting chip formation. Then, optmal chip breaker is selected and this is verified good enough for chip control from the experiment.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.11 no.1
• /
• pp.74-81
• /
• 1987

The orthogonal cutting method of the nodular graphite cast iron in the lathe turning, whose structure were formulated under two kinds of annealing conditions, has been experimentally studied and the results investigated. The various characteristics of machinabilities of the nodular cast iron, depending upon its structure, have been obtained from the results as follows. (1) As depth of cut increases, the shearing strain decreases and tend gradually to increase with increase of ferrite matrix. (2) As depth of cut increases, the shearing stress slightly decreases for P$_{1}$, but it tends to increase for both of P$_{2}$ and P$_{3}$ under the same condition. The annealing effect in the process of light cutting was found to be greater than heavy cutting. (3) The cutting energy slightly decreases with the increassing of the depth of cut, and the effect of decreasing the cutting energy by the annealing is higer the light cutting than the heavy cutting. (4) The cutting equations as follow. P$_{1}$ : 2.phi.+1.58(.betha.-alpha.)=92 deg. P$_{2}$ : 2.phi.+1.40(.betha.-alpha.)=84 deg. P$_{3}$ : 2.phi.+1.37(.betha.-alpha.)=82 deg. (5) The machining constants for P$_{1}$, P$_{2}$ and P$_{3}$ which are the test-pieces in this study and classified according to the containing quantity of ferrite matrix given respectively in 78deg., 70 deg., and 68 deg. From these it can be known that the machining constants slightly decreases with increasing of the quantity of ferrite matrix contained in the nodular graphite cast iron.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.10 no.6
• /
• pp.807-813
• /
• 1986

The orthogonal cutting method of the nodular graphite cast iron in the lathe turning, whose matrix were formulated under two kinds of annealing conditions, has been experimentally studied and the results investigated. The various characteristics of machinabilities of the nodular cast iron, depending upon its matrix, have been obtained from the results as follows. (1) As depth of cut increases, the cutting ratio and the shear angles tend to slightly increase, and as the containing quantity of ferrite matrix increases, they slightly decrease. (2) As depth of cut increases, the cutting force increases in an approximate straight line, and as the containing quantity of ferrite matrix increases, they decreases and the decreasing rate is about 20-30%. (3) As the containing quantity of ferrite matrix increases, the friction force acting on the tool face decreases and the decreasing rate is about 34-40% in case of the lower depth of cut, but in case of the higher depth of cut the decreasing rate is very small. (4) Both shearing force and vertical force show a lineal increases, and according as ferrite matrix increases there is a decrease by 25% in shearing force and a 12-25% decrease in vertical force. (5) Shearing speed and chip flow speed keep almost a constant value irrespective of matrix.

• The Journal of Korea Robotics Society
• /
• v.18 no.3
• /
• pp.251-259
• /
• 2023

In the path traveling of differential-drive robots, the steering controller plays an important role in determining the path-following performance. When a robot with a pure-pursuit algorithm is used to continuously drive a right-angled driving path in an unstructured environment without turning in place, the robot cannot accurately follow the right-angled path and stops driving due to the ground and motor load caused by turning. In the case of pure-pursuit, only the current robot position and the steering angle to the current target path point are generated, and the steering component does not reflect the speed plan, which requires improvement for precise path following. In this study, we propose a driving algorithm for differentially driven robots that enables precise path following by planning the driving speed using the radius of curvature and fusing the planned speed with the steering angle of the existing pure-pursuit controller, similar to the Model Predict Control control that reflects speed planning. When speed planning is applied, the robot slows down before entering a right-angle path and returns to the input speed when leaving the right-angle path. The pure-pursuit controller then fuses the steering angle calculated at each path point with the accelerated and decelerated velocity to achieve more precise following of the orthogonal path.

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.19 no.6
• /
• pp.73-79
• /
• 2020

Although engineering plastics that are light-weight and have excellent mechanical performance have been widely applied in various industries in place of steel structures to reduce the burden of cost and time, there have been few studies related to their surface roughness. This study aims to evaluate the optimal effects of feed rate, cutting speed, and depth of cut as cutting parameters as well as nose angle on the surface characteristics of MC nylon in CNC lathe machining. To determine the best conditions under different nose radii, the experiments were performed based on the Taguchi L9(34) orthogonal array method, in which the resulting data was analyzed using the S/N ratio and ANOVA. Results indicate that the most significant contribution was feed rate followed by nose angle and cutting speed, whereas the depth of cut did not influence the performance. This study demonstrates that the suggested method for improving the surface finishing of MC nylon is efficient compared with results obtained from experimentation and prediction.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.27 no.6
• /
• pp.1007-1013
• /
• 2003

As environmental restriction kas continuously become more strict, machining technology has emphasized on development of environment-friendly technology. In cutting technology, it has been well recognized that cutting fluids might have undesirable effects on workers health and working environment. In this study, compressed cold air was used as a replacement for conventional cutting fluids. The cooling effect on cutting tool was analyzed using the finite element method and the computational fluid dynamics. This study focused on the temperature simulation of cutting tool by real flow analysis of cold air. The maximum flow rate and the minimum temperature of compressed cold air are 300ι/min and -30$^{\circ}C$ respectively. To compare the simulation and experimental results, inner temperature of the cutting tool was measured with the thermocouple embedded in the insert. The results show that the analysis of cutting temperature using FEM and CFD is resonable, and the replacement of cutting fluid with cold air is available.

• ETRI Journal
• /
• v.28 no.3
• /
• pp.282-290
• /
• 2006

In vertically overlaid cellular systems, a temporary traffic concentration can occur in a hot-spot area, and this adversely affects overall system capacity. In this paper, we develop an adaptive hot-spot operating scheme (AHOS) to mitigate the negative effects from the nonuniform distribution of user location and the variation in the mixture of QoS requirements in orthogonal frequency division multiple access downlink systems. Here, the base station in a macrocell can control the operation of picocells within the cell, and turns them on or off according to the system overload estimation function. In order to determine whether the set of picocells is turned on or off, we define an AHOS gain index that describes the number of subcarriers saved to the macrocell by turning a specific picocell on. For initiating the picocell OFF procedure, we utilize the changes in traffic concentration and co-channel interference to the neighboring cells. According to computer simulation, the AHOS has been proved to have maximize system throughput while maintaining a very low QoS outage probability under various system scenarios in both a single-cell and multi-cell environments.

• Journal of Ocean Engineering and Technology
• /
• v.28 no.2
• /
• pp.152-159
• /
• 2014

KRISO(Korea Research Institute of Ships & Ocean Engineering) designed and manufactured a pilot mining robot called "MineRo" in 2012. MineRo is composed of four track modules. In general, much time and money are needed for deep-sea tests. Therefore, a numerical analysis to predict the dynamic behaviors has to be performed before a deep-sea test. In the numerical analysis, the information about the mining robot and soil properties are the most important factors to analyze the driving performance and dynamic response of MineRo. A terra-mechanics model of extremely cohesive soft soil is implemented in the form of the relationships between the normal pressure and sinkage, and between the shear stress and shear displacement. It is possible to acquire information about MineRo from the CAD model in the design phase. The Wong model is applied to the terra-mechanics model. This model is necessary to acquire many soil coefficients for a numerical analysis. However, in soil testing, the amount of soil property data obtained is limited. Moreover, it is difficult to analyze all of the cases for the many soil coefficients. In this paper, the dynamic behaviors of MineRo are analyzed according to the driving velocity, steering ratio, and variable extremely cohesive soft soil properties using a table of orthogonal arrays. The dynamic responses of MineRo are the turning radius, sinkage, and slip ratio. The relationships between the dynamic responses and variable soil properties are derived for MineRo.