• 제목/요약/키워드: 하드터닝

검색결과 12건 처리시간 0.027초

SKD11의 하드터닝 가공 열처리 시편의 표면잔류응력 측정에 관한 연구 (Residual Stress Measurement in Hard Turned Workpiece)

  • 김종혁;이태홍;장동영;한동철
    • 한국정밀공학회지
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    • 제20권5호
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    • pp.148-155
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    • 2003
  • Most manufacturing processes such as welding, cutting and molding generate residual stresses on the surface of manufactured parts. Between compressive and tensile residual stresses, the tensile residual stress is harmful to the surface integrity, which results in reduced fatigue life and causes other structural failures when the service stresses are superimposed on the residual stresses. In the research, the residual stresses in the hardened tool steel (SKD11) were measured using hole-drilling method. The specimens were prepared through hard turning. Most of residual stresses in the machined surface were compressive.

하드터닝에서 CBN 공구홀더의 열변형이 가공정밀도에 미치는 영향 (Analysis of Thermal Displacement of PCBN Tool Holder for Machining Accuracy in Hard Turning)

  • 노승국;이찬홍;하재용
    • 한국정밀공학회:학술대회논문집
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    • 한국정밀공학회 2003년도 춘계학술대회 논문집
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    • pp.363-366
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    • 2003
  • The hard turning is a turning operation performed in high strength alloy steels (HRC>30) in order to reach surface roughness close to those obtained in grinding. This is possible because of availability of improved tool materials (polycrystalline cubic boron nitride. PCBN), ad more rigid machine tools. According to many previous work of hard turning mechanism, the maximum temperature of cutting can be raised up to 100$0^{\circ}C$. As the heat generation rate is very high, the thermal displacement of tool holder cannot be negligible. Therefore, the aim of this paper is to analyze effects of high heat generation at CBN tool tip to the thermal displacement of a tool holder in hard turning and finally geometric accuracy. The thermal behavior of a CBN tool holder is investigated by numerical simulation and experiment, and the result shows thermal elongation of microns order is possible during hard turning process.

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절삭력에 의한 하드터닝의 표면조도 예측에 관한 연구 (Study on Prediction of Surface Roughness in Hard Turning by Cutting Force)

  • 이강재;양민양;하재용;이창호
    • 한국정밀공학회:학술대회논문집
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    • 한국정밀공학회 2003년도 춘계학술대회 논문집
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    • pp.1768-1771
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    • 2003
  • Hard turning replaces grinding for finishing process with expectations of higher productivity and demanded surface quality. Especially for the surface roughness as surface quality demanded in finishing process of hard turning, know-how of machining characteristics of hardened materials by cutting force analysis should be accumulated in company with achievement of precision of elements and high stiffness design technology in hard turning. Considering chip formation mechanism of hardened materials, adequate cutting conditions are selected for machining experiments and cutting forces are measured according to cutting conditions. Increase of cutting forces especially thrust force and increase of dynamic instability could occur in hard turning. Analysis of dynamic characteristics of the cutting forces is executed to investigate relation between dynamic instability and surface roughness in hard turning. Investigation on effects of relative motion of machining system generated by vibration due to dynamic instability shows that ultimate surface roughness could be predicted considering relative motion of machining system with geometrical surface roughness.

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고경도강(AISI 4140, HrC60)의 하드터닝에서 가공속도 및 윤활조건 변경에 따른 CBN 공구의 마모 특성 (Wear Characteristics of CBN Tools on Hard Turning of AISI 4140)

  • 양기동;박경희;이명규;이동윤
    • 한국정밀공학회지
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    • 제31권9호
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    • pp.799-804
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    • 2014
  • Hard turning is a machining process for hardened materials with high surface quality so that grinding process can be eliminated. Therefore, the hard turning is capable of reducing machining time and improving productivity. In this study, hardened AISI4140 (high-carbon chromium steel) that has excellent yield strength, toughness and wear resistance was finish turned using CBN tools. Wear characteristics of CBN tool was analyzed in dry and MQL mixed with nano-particle (Nano-MQL). The dominant fracture mechanism of CBN tool is diffusion and dissolution wear on the rake surface resulting in thinner cutting edge. Abrasive wear by hard inclusion in AISI4140 was dominant on the flank surface. Nano-MQL reduced tool wear comparing with the dry machining but chip evacuation should be considered. A cryogenically treated tool showed promising result in tool wear.

초경합금재의 하드터닝에서 공구재종에 따른 절삭성 (Hard Turning Machinability of V30 Cemented Carbide with PCD, cBN and PcBN Cutting Tool)

  • 허성중
    • 한국정밀공학회지
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    • 제25권12호
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    • pp.47-54
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    • 2008
  • Hard turning process can be defined as a single-point machining process carried out on "hard" materials. The process is intended to replace or limit traditional grinding operations that are expensive, environmentally unfriendly, and inflexible. The purpose of this study is to achieve a systematic understanding of machining characteristics and the effects of machining parameters on cutting force, tool wear shape and chip formation by the outer cutting of a kind of wear resistant tungsten carbide V30. Hard turning experiments were carried out on this alloy using the PCD (Poly Crystalline Diamond), cBN (cubic Boron Nitride) and PcBN (Polycrystalline cubic Boron Nitride) cutting tools. The PcBN and the usual cBN tools were used to be compare with the PCD tool and the dry turning was carried out. The PcBN is attractive as the tool material which replaces the PCD. The tool wear width and cutting force were measured, and the worn tool and chip were observed. The difference of the tool wear mechanism among the three tool materials was investigated.

Wavelet을 이용하여 하드터닝 공정에서 표면품위의 향상을 위한 채터 진단에 관한 연구 (Chatter Detection for Improving Surface Quality of Hard Turning Process with Wavelet Transformation)

  • 박영호;공정흥;양희남;김일해;장동영;한동철
    • 대한기계학회논문집A
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    • 제28권1호
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    • pp.70-78
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    • 2004
  • This paper presents study of efficiency of wavelet transformation for on-line chatter detection during hard fuming process. From comparison with other time series and statistical methods such as fast fourier transformation (FFT), Kurtosis and standard deviation (STD), wavelet transform is better than others in on-line chatter detection. With using wavelet function with pseudo frequency corresponding to chatter frequency, chatter could be detected more sensitively. And for both force signal from dynamometer and displacement signal from capacitance type cylindrical sensor (CCS), wavelet transform with DB2 function on level 4 could be well used for chatter detection in hard turning process.

베어링에 적용되는 장수명 표면 처리(Burnishing) 연구 (The Study on Long-Life Surface Treatment(Burnishing) in Bearing)

  • 심희찬;김태경
    • 한국표면공학회:학술대회논문집
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    • 한국표면공학회 2015년도 추계학술대회 논문집
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    • pp.283-283
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    • 2015
  • 현재 LAC 베어링에 적용되는 표면 처리는 일반적으로 하드터닝+슈퍼피니싱 가공이 적용되고 있고, 장수명을 위한 표면 처리 기술이 보다 더 요구되는 추세이다. Burnishing 기술은 매끄럽고 단단한 공구를 베어링 궤도면에 충분한 압력을 가하여 서로 문질러(rubbing) 마찰면을 소성 변형시켜 표면 거칠기 및 압축 잔류 응력 등을 향상 시키는 기술이며, 베어링과 같은 금속의 경우 버니싱 가공 적용 시 광택을 띠는 특성을 가지므로 외관 품질 향상에 기여하므로 슈퍼 피니싱 공정을 대신할 수 있다. 또한 표면 finishing, 표면 경도, 내마모성 및 피로/부식 저항성을 향상시킨다. 이에 본 연구에서는 슈퍼 피니싱 가공을 대신하기 위한 버니싱 가공의 물성을 검토하였고, 다른 공정과의 비교를 통한 버니싱 기술의 효과 확인하였다.

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볼스크류 가공용 선회형 스핀들의 발열 특성에 관한 연구 (Heat Generation Characteristics of Whirling Spindle for Ball Screw Machining)

  • 문홍만;김상원;정호인;이춘만
    • 한국기계가공학회지
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    • 제19권10호
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    • pp.44-51
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    • 2020
  • We studied the heating characteristics of a whirling spindle. This spindle is an important component of a whirling machine for turning a ball screw shaft. In the manufacturing process for a conventional ball screw shaft, a single tool is used to form a spiral in a lathe machine tool. Thereafter, a high-frequency heat treatment process is performed. Recently, a whirling-type cutting method has emerged. This method can perform hard turning in the rotating direction of the spiral portion of the ball screw shaft by rotating and mounting multiple tools. The whirling method can be applied to the heat-treated material. In this study, an experimental apparatus was constructed to analyze the whirling spindle. The experiment proceeded in four steps. The rotating speed of the whirling spindle was set to ISO random and sequential rising conditions. Cooling and non-cooling modes in the cooling jacket were tested. As a result of the above experiment, the heating characteristics of the whirling spindle were derived.

에어-오일 냉각방식에 의한 고경도재료의 선삭 (Turning of Hardened Materials Using the Air-oil Cooling System)

  • 정보구;고태조;김희술
    • 한국정밀공학회지
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    • 제14권8호
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    • pp.73-81
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    • 1997
  • The hard turning process defined as a single point turning of materials harder than $H_{R}$C 58 differs from conventional turning because of hardness of the work materials and cutting toos needed in the process. In hard turning, tool life is very short, of the order of a few minutes, during which the cutting tool is subjected to the extremes of stress and temperature. In this regard, it is well known that CBN tool is proper for this process in spite of expensive cost. In this research, we studied the feasibility of the use of the low cost cutting tool such as a aTiN coated tool. To this end, a new cooling system was designed with an air-oil method for reducing tool temperature, which is based on the principle of air vortex flow. That is, the outlet temperature of the air becomes aver 20 .deg. C lower than atmosphere temperature by entering pressurized air of 5kgf/c $m^{2}$ into the inlet. This cooled air ejected to the top of the cutting tool lowered tool temperature, which reduced the wear of a TiN coated tool by the 30% of CBN tool life with respect to the same cutting length.h.

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액화질소를 이용한 고정도 하드 터닝 (Precision Hard Turning with Cryogenic Cooling)

  • 박영우;김기수
    • 한국정밀공학회:학술대회논문집
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    • 한국정밀공학회 2001년도 춘계학술대회 논문집
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    • pp.1048-1051
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    • 2001
  • This paper presents an analytical and experimental study of a cryogenic machining for precision hard turning. A cryogenic circulation system is designed and mounted on the top of the tool insert. The machining process used is facing operation on a CNC turning center with dry and cryogenic conditions. The tool temperature and cutting forces are measured by the K-type thermocouple and by a three-component Kistler dynamometer, respectively. Both data are fed into the data acquisition program through an A/D card. Surface roughness and form accuracy of the machined surface are measured by WYKO NT2000. It is also found that surface roughness and form accuracy with cryogenic cooling are better than those with no coolant.

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