• Journal of the Korean Society for Precision Engineering
• /
• v.14 no.2
• /
• pp.33-40
• /
• 1997

Recently, there are an increasing needs for high speed rotating spindle which is an important mechanical ele- ment for a high efficiency machine tool in order to shorten machining time and cut production costs. The heat gen- eration is the most important problem in the motor integrated spindle. In this study, the effects of temperature distribution and thermal behavior according to the oil-air lubrication and cooling conditions are investigate theo- retically and experimentally on the motor-integrated spindle under unloading condition. The experimental spin- dle system is composed with the angular contact steel ball bearings, oil-air lubrication, air or oil jacket cooling system. To analyze the thermal behavior and cooling characteristics for the motor integrated spindle, the analysis using the finite element method is carried out. The analytical results are compared with the experimental results.

• Transactions of the Korean Society of Machine Tool Engineers
• /
• v.12 no.3
• /
• pp.68-74
• /
• 2003

Any one of the high precision spindle systems and guide way systems, the high stiffness of structure, the error compensation during assembly, high accuracy control system is inevitable technology for development of high precision machine tools. Especially, among these, design of spindle system is one of the most important technologies leading high precision of machine tool and high quality of manufactured products. A high speed and high precision spindle system, which will be used for final machining of ferrule, is designed considering the effect of heat cutting torque, cutting fore, and work-piece materials. The detailed design and analysis process are presented.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.26 no.10
• /
• pp.1997-2007
• /
• 2002

Composite air spindles are appropriate for the high-speed and the high-precision machining as small hole drilling of printed circuit board (PCB) or wafer cutting for manufacturing semiconductors because of the low rotational inertia, the high damping ratio and the high fundamental natural frequency of composite shaft. The axial load and stiffness of composite air spindles fur drilling operation are determined by the thrust ben ring composed of the air supply part mounted on the housing and the rotating part mounted on the rotating shaft. At high-speed rotation, the rotating part of the thrust bearing should be designed considering the stresses induced by centrifugal force as well as the axial stiffness and the natural frequency of the rotating shaft to void the shaft from failure due to the centrifugal force and resonant vibration. In this work, the air supply part of the thrust bearing was designed considering the bending stiffness of the bearing and the applied load. The rotating part of the thrust bearing was designed through finite element analysis considering the cutting forces during manufacturing as well as the static and dynamic characteristics under both the axial and con trifugal forces during high-speed rotation.

• Transactions of the Korean Society of Machine Tool Engineers
• /
• v.16 no.1
• /
• pp.80-85
• /
• 2007

High speed cutting is a machining process which cuts materials with the fast movement and rotation of a spindle in a machine tool. High speed cutting leaves a plastically deformed layer on the machined surface. This deformed layer affects in various forms to the surface roughness of machined parts such as the dimensional instability, the micro crack. The surface roughness is called surface integrity which is very important in precision cutting. This paper aims to study on the machined surfaces characteristics of aluminum alloy and brass by AFM(Atomic force microscope) measurement. The objective is contribution to ultra- precision cutting by exhibit foundation data of surface roughness and tool wear when parts are cutting with diamond tool at the factory.

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.6 no.4
• /
• pp.57-64
• /
• 2007

In the recent years, development of machine tool with high speed feeding system have brought a rapid increase in productivity. Practically, thermal deformation problem due to high speed is, however, become a large obstacle to realize high precision machining. In this study, therefore, the construction of automatic error compensation system to control thermal deformation in high speed feeding system with real time is proposed. To attain this purpose, high speed feeding system with feeding speed 60mm/min is developed and experimental equation for relationship between thermal deformation and temperature of ball screw shaft using multiple regression analysis is established. Furthermore, in order to analyze thermal deformation error, compensation coefficient is determined and thermal deformation experiments is carried out. From obtained results, it is confirmed that automatic error compensation system constructed in this study is able to control thermal deformation error within $15{\sim}20{\mu}m$.

• Journal of the Korean Society for Precision Engineering
• /
• v.31 no.5
• /
• pp.389-394
• /
• 2014

In this paper, we report a new manufacturing method for friction reduction using micro-AAJ (abrasive air-jet) machining. AAJ machining employs compressed air to accelerate a jet of high-speed particles to mechanically machine features, including micro-channels and micro-holes, into glass, metal, or polymer substrates for use in microfluidics, MEMS (micro electromechanical systems). And we introduce the micro-AAJ machining system, which consists of a micro-AAJ nozzle and a five-axis positioning system. Various micro-AAJ nozzles can be used, depending on the required surface structure, and three-dimensional machining is possible. We machined samples under six different conditions and describe machining results obtained while using it. We also measured the coefficient of friction of micro-textured surfaces. We report the coefficient of friction of micro-textured surfaces patterned using micro-AAJ machining for engine piston ring.

• Journal of the Korean Society for Precision Engineering
• /
• v.15 no.10
• /
• pp.203-208
• /
• 1998

Carbon fiber epoxy composite materials are widely used in the structures of aircrafts, robots and other machines because of their high specific strength, high specific stiffness and high damping. In order for the composite materials to be used in the aircraft structures or machine elements, accurate surfaces for bearing mounting or joints must be provided, which require precise machining. In this paper, the machinability characterisitcs of the drilling operation of the carbon fiber epoxy composite materials was experimentally investigated. The experimental results are as follows 1.The entrance of hole is very good manufacturing existing, but exit come to occur sever surface exfoliation. 2. The cutting force in drilling of the carbon fiber epoxy composite materials is decreased as the drilling speed increased. 3.The hole of the carbon fiber epoxy composite materials is not good manufacturing by use of the standard twist, therefore, the new drill designed in order to accurate hole.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.22 no.7
• /
• pp.642-649
• /
• 2012

This paper deals with a copper die casting induction motor which has several advantages of motor performance. The developed motor is used as spindle motor in machining center. The dynamic characteristic analysis of rotor is dealt with for precision machining. The critical speed of rotor considering rotation and gyroscopic effect should be above operating speed, 18,000 rpm, and have a 201 % sufficient separation margin. Also, the 3-D unbalance vibration response analysis is performed and enabled the prediction of the expected vibration amplitude by unbalance in high speed. The unbalance vibration responses of each position on the rotor are satisfied with allowable vibration displacement of API 611 standard according to balancing G grade(G 0.4, G 2.5, G 6.3). Copper die casting high speed induction motor is successfully developed and verified by experiment.

• Journal of the Korean Society for Precision Engineering
• /
• v.19 no.4
• /
• pp.154-160
• /
• 2002

Powder metallurgy(P/M) process has been used for the production of high performance high-speed steels. P/M high speed steel has more uniform and fine microstructure than those of conventional wrought products. Therefore, it offers distinct advantages over conventional tool steels. The superior uniformity of composition and fine microstrucure lead to excellent toughness and less distortion during heat treatment, which in turn can reduce total grinding costs and provides other benefits, such as uniform hardness and increased tool life. From these reasons, milling, hole machining, broaching, and gear manufacturing tools are major applications of P/M high-speed steels. In this research, we evaluated tool wear of flat endmill which is made of P/M high-speed steel from the view point of cutting tool performance.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2004.10a
• /
• pp.977-980
• /
• 2004

Metalworking fluids (MWFs) are fluids used during machining and grinding to prolong the life of the tool, carry away debris, and protect the surfaces of work pieces. These fluids reduce friction between the cutting tool and the work surface, reduce wear and galling, protect surface characteristics, reduce surface adhesion or welding and carry away generated heat. Workers can be exposed to MWFs by inhaling aerosols (mists) and by skin contact with the fluid. Skin contact occurs by dipping the hands into the fluid, splashes, or handling workpieces coated with the fluids. The amount of mist generated (and the resulting level of exposure) depends on many factors. To reduce the environmental pollution wastes and the potential health risks associated with occupational exposures to MWFs, it is required to establish optimum MWFs supply method and condition with minimum quantity in all over the mechanical machining field including high-speed type heavy cutting process.