• Journal of the Semiconductor & Display Technology
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• v.14 no.2
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• pp.47-52
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• 2015

In this paper, the performance of uncoated- and Titanium nitride aluminium TiAlN-PVD coated- carbide twist drills were investigated when drilling aluminium alloy, Al 6061. This research focuses on the optimization of drilling parameters using the Taguchi technique to obtain minimum surface roughness and thrust force. A number of drilling experiments were conducted using the L9 orthogonal array on a CNC vertical machining center. The experiments were performed on Al 6061 material l blocks using uncoated and coated HSS twist drills under dry cutting conditions. Analysis of variance(ANOVA) was employed to determine the most significant control factors. The main objective is to find the important factors and combination of factors influence the machining process to achieve low surface roughness and low cutting thrust force. From the analysis of the Taguchi method indicates that among the all-significant parameters, feed rate are more significant influence on surface roughness and cutting thrust than spindle speed.

• Journal of Industrial Technology
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• v.15
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• pp.23-32
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• 1995

The methodology of automatic generation of tool path for rough cutting of a sculptured surface is proposed with the improved contouring method, unequal level line machining. Considering the surface shape and the diameter of the endmill, the distance between level lines is obtained. To improve MMR, initial rough cutting is processed with the large diameter endmill and the remained material is removed by the relatively small diameter endmill. Tool path is generated from the offset curve of respective level line and the interferences between the tool and workpiece are automatically avoided. After generating NC part program, the sculptured surface is machined at the vertical machining center. From the experimental results, total cutting length and machining time are reduced more effectively than conventional contouring methods.

• Transactions of the Korean Society of Automotive Engineers
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• v.24 no.1
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• pp.67-73
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• 2016

The application of titanium has been gradually rising because the utilizing ranges for low weight and high strength are rapidly increased by the need for improving the fuel economy in production industries such as the aviation and automotive in recent. The purpose in this study is to investigate the appropriate cutting conditions on the life of flat and round end mills by measuring the maximum cutting temperature relative to the machining time, and calculating the wear rates of cutting tool with the spindle speed and feed rate of vertical machining center as a parameter in the titanium roughing cut machining which is widely used in critical parts of aircraft, cars, etc. When the wetted roughing cut machining of titanium with a soluble cutting oil is conducted by the flat and round end mills, the maximum cutting temperatures for a variety of spindle speed and feed rate are measured at ten-minute intervals during 60 minutes by an infrared thermometer, and the wear rates of cutting tool are calculated by the weight ratios based on tool wear before and after the experiment. It is found that the maximum cutting temperature and the wear rates of cutting tool are raised as the cutting amount per tool edge is increased with the rise of feed rate, in this experimental range, and as the frictional area due to the rise of contacting friction numbers between tool and specimen is increased with the rises of cutting time and spindle speed. In addition, the increasing rate of maximum cutting temperature in the flat and round end mills are the highest for the cutting time from 50 to 60 minutes, and the wear rate of cutting tool in the flat end mill is 1.14 to 1.55 times higher than that in the round end mill for all experimental conditions.

• International Journal of Precision Engineering and Manufacturing
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• v.8 no.1
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• pp.11-15
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• 2007

Composite materials are widely used to make all kinds of machine parts, internal and structural materials of cars, aerospace components, building structures, ship materials, sporting goods and others, It is worth while to use composite space substitute material in various applications when compared with others. But the use of composite material is limited in the field of the mechanical processing because of the difficulties in processing. Thus, it is proved that the surface is rough at the in and out sections of the hole processing when the GFRP is machined with HSS drill in the vertical machining center. And it is observed that the more it is processed, the more the fluid type long chip is changed into the powdered chip.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 1996.10a
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• pp.40-45
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• 1996

this paper presents a dynamic analysis of the high-speed spindle system for vertical machining center using finite element techniques. The computed natural frequencies are compared with the measured frequencies obtained from experimental modal analysis. The results show that the bending and twisting deformations of the spindle housign dominated in the lowest modes owing to low dynmic stiffness of the housing structure. The design parameters used in the analysis are:(a) panel thickness of the housing (b) height of the housing and (c) spindle-to-column distance of the housing. Through sensitivity analysis and optimizing simulation considering design constraints an optimal design of the spindle system has been obtained.

• Journal of the Korean Society for Precision Engineering
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• v.16 no.10
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• pp.172-181
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• 1999

The objective of this research is to develop a measurement error model for sculptured surfaces in On-Machine Measurement (OMM) process based on a closed-loop configuration. The geometric error model of each axis of a vertical CNC Machining center is derived using a 4${\times}$4 homogeneous transformation matrix. The ideal locations of a touch-type probe for the scupltured surface measurement are calculated from the parametric surface representation and X-, Y- directional geometric errors of the machine. Also, the actual coordinates of the probe are calculated by considering the pre-travel variation of a probe and Z-directional geometric errors. Then, the step-by-step measurement error analysis method is suggested based on a closed-loop configuration of the machining center including workpiece and probe errors. The simulation study shows the simplicity and effectiveness of the proposed error modeling strategy.

• International Journal of Precision Engineering and Manufacturing
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• v.9 no.1
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• pp.19-24
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• 2008

We propose a new miniature air-bearing stage with a moving-magnet slotless linear motor. This stage was developed to achieve the precise positioning required for submicron-level machining and miniaturization by introducing air bearings and a linear motor sufficient for mesoscale precision machine tools. The linear motor contained two permanent magnets and was designed to generate a preload force for the vertical air bearings and a thrust force for the stage movement. The characteristics of the air bearings, which used porous pads, were analyzed with numerical methods, and a magnetic circuit model was derived for the linear motor to calculate the required preload and thrust forces. A prototype of a single-axis miniature stage with dimensions of $120\;(W)\;{\times}\;120\;(L)\;{\times}\;50\;(H)\;mm$ was designed and fabricated, and its performance was examined, including its vertical stiffness, load capacity, thrust force, and positioning resolution.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.9 no.2
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• pp.102-111
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• 2000

Methodology of volumetric error identification and compensation is presented to improve the accuracy of NC machine tools by using a reference artifact and a touch trigger probe. Homogeneous transformation matrix and kinematic chain are used for modeling the geo-metric and thermal errors of a three-axis vertical machining center. The reference artifact is designed and fabricated to identify the model parameters by machine tool metrology. Parameters in the error model are able to be identified and updated by direct measurement of the reference artifact on the machine tool under the actual conditions which include the thermal interactions of error sources. A volumetric error compensation system based on IBM/PC is linked with a FANUC CNC controller to compensate for the identified volumetric error in machining workspace.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1993.10a
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• pp.321-327
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• 1993

In order to maintain the cutting force at a desired level during peripheral end milling processes in spite of variation of the depth of cut and other machining conditions, a feedrate override. Apaptive Control Constraint (ACC) system are developed. Feedrate override was accomplished by a developed MMC board and PMC interface techniques. Nonlinear model of the cutting process was linearized as an adaptive model with time varying paramrters. Integral type estimators were introduced for on-line identification of cutting and control parameters in peripheral and milling processes. Zero Order Jold (ZOH) type degital control methodology which uses pole-placement concepts was applied for the ACC system. Performance of the developed ACC system was confirmed on the vertical machining center equipped with FANUC OMC for a large amount of experiment

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1993.10a
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• pp.411-416
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• 1993

In order to achieve computer-oriented control and automation of manufacturing processec, a distributed NC (DNC_) system was developed for FMS under the Windows environment. The DNC system consists of conventional DNC, PMC interface and tool management modules. Real-time system conditon monitoring and control fuctions required for machine tools and machining processes were accomplished by developing a PMC interface module called MMC board. Tool condition monitoring and management was performed by the developed tool management module composed of a tool setting probe and softwares. Performance of the DNC system was confirmed on the horizontal and the vertical type machining center equipped with FANUC OMC for the large amount of experiments.