• Title/Summary/Keyword: Down Cut

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Effects of the Tool Path on the Geometric Characteristics of Milled Surface (가공경로가 밀링가공면의 기하학적 특성에 미치는 영향)

  • Park, Moon-Jin;Kim, Kang
    • Journal of the Korean Society for Precision Engineering
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    • v.15 no.6
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    • pp.58-63
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    • 1998
  • There are lots of factors that are related to the geometric characteristics of machined surface. Among them, the tool path and milling mode (up cut milling or down cut milling) are the easiest controllable machining conditions. Thus, the first objective of this research is to study the effects of them on the milled surface that is generated by an end milling tool. To get precision parts, not only the machining process but also the measurement of geometric tolerance is important. But, this measurement requires a lot of time, because the infinite surface points must be measured in the ideal case. So, the second objective is to propose a simple flatness measurement method that can be available instead of the 3-D geometric tolerance measurement method, using a scale factor and characterized points. Finally, it is also shown that the possibility of flatness improvement by shifting the consecutive fine cutting tool path as compared with the last rough cutting tool path.

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Effects of Cutting Speed and Feed Rate on Axial Shape in Side Walls Generated by Flat End-milling Process (평엔드밀링 공정에서 절삭속도 및 이송속도가 측벽의 축방향 형상에 미치는 영향)

  • Kim, Kang
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.41 no.5
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    • pp.391-399
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    • 2017
  • This paper presents the effects of the cutting speed and feed rate on the axial shape of flat end-milled down cut side walls. Experiments were performed using the cutting speed, tool diameter, and feed per tooth as variables, and the thrust force and axial shape were measured as the experimental results. The results of this study confirmed that a smaller feed per tooth, which is proportional to the value obtained by dividing the feed rate by the cutting speed, results in a higher axial shape accuracy. In addition, the axial shape can be simplified to a form in which two straight lines having different slopes meet at a singular point. Therefore, it was concluded that the shape accuracy could easily be estimated during the operation and improved by adjusting the feed per tooth.

Improvement of the Accuracy in Machining Deep Pocket by Up Milling (상향절삭에 의한 깊은 홈 가공시 정밀도 향상에 대한 연구)

  • Lee, Sang-Kyu;Ko, Sung-Lim
    • Journal of the Korean Society for Precision Engineering
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    • v.16 no.4
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    • pp.220-228
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    • 1999
  • The machining accuracy has been improved with the development of NC machine tools and cutting tools. However, it is difficult to obtain a high degree of accuracy when machining deep pocket with long end mill, since machining accuracy is mainly dependant on the stiffness of the cutting tool. To improve surface accuracy in machining deep pocket using end mill, the performance by down cut and up cut is compared theoretically and experimentally. To verify usefulness of up milling, various experiments were carried out. As a result, it is found that up milling produce more accurate surface than down milling in machining deep pocket. For effective application of up milling, various values in helix angle, number of teeth, radial depth of cut and axial depth of cut are applied in experiment.

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A Fundamental Study on High Efficient Grinding with General Grinding Machine (범용 연삭기의 고능률 가공에 관한 기초적 연구)

  • Kim, Nam-Kyung;Song, Ji-Bok
    • Journal of the Korean Society for Precision Engineering
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    • v.7 no.4
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    • pp.65-72
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    • 1990
  • After observing grinding characteristics according to variable grinding condition in order to raise the grinding effect without making worse the grinding quality by using general grinding machine, main conclusions of this study are as follows; 1) When grinding quality is constant, grinding effect is changed according to the speed of the workpiece. But the rapidly increasing critical speed of table is($V_w{\leq}4m/min$). 2) As grinding effect is equal, the lower the speed of the workpiece becomes, the lower the grinding force and surface roughness obtains good results. 3) In terms of grinding method, the down cut grinding method produces good grinding surface royghness in case of little grinding depth;otherwise, the up cut method in case of more grinding depth.

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Cutting Performance of a Developed Small-angle Spindle Tool (소형 앵글 스핀들 공구의 절삭성능에 관한 연구)

  • Kim, Jin Su;Kim, Yohng Jo
    • Journal of the Korean Society of Manufacturing Process Engineers
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    • v.15 no.2
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    • pp.111-117
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    • 2016
  • The cutting performance of a developed small-angle spindle tool was investigated with Al6061 using a TiAlN coated high-speed steel end mill. Up-cut and down-cut processes in a milling machine were carried out at the range of 1000-4000 rpm for spindle speed and 50-300 mm/min for feed rate. As a result, the highest cutting force in the Fx direction was obtained from the up-cut process when the spindle speed was 1000 rpm and the feed rate was 100 mm/min. In the Fy direction, the highest cutting force appeared in the up-cut process at a feed rate of 250 mm/min at the same spindle speed. Conversely, the lowest cutting force came out in the up-cut process at a spindle speed of 4000 rpm and a feed rate of 50 mm/min. As for surface finish, the finest surface roughness was obtained as Ra 0.7642 um at a spindle speed of 4000 rpm and a feed rate of 50 mm/min. Consequently, given the cutting performance of the developed small-angle spindle tool, we conclude that its use in industrial practice is feasible.

Relationship Between Flat End-mill Shape and Geometrical Characteristics in Side Walls Generated by End-milling Process (엔드밀링 공정에 의하여 생성된 측벽의 기하학적 특성과 평엔드밀 형상 사이의 관계)

  • Kim, Kang
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.39 no.1
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    • pp.95-103
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    • 2015
  • This paper presents the effects of the tool shape on the geometrical characteristics of flat end-milled side walls. A tool shape is characterized by such parameters as helix angle, number of cutting edges, and diameter. The geometrical characteristics of the side walls are represented by the surface profiles in the feed and axial directions, which are orthogonal to each other. The geometrical defects in each direction are estimated based on the instantaneous apparent cutting areas, which are represented by the interference area between the tool and workpiece and that between the cutting edge and workpiece. It is confirmed that a geometrical defect in the feed direction is formed when the tool leaves the workpiece and the curvature of the tool path changes. Defects in the axial direction are also found in the side walls, except for the defect zone in the feed direction. An up-cut using an end-mill with a steeper helix angle, a greater number of cutting edges, and a smaller diameter are thus found to improve the geometrical accuracy of end-milled side walls.

Effects of Cutting Area on Straightness Characteristics in Side Walls Caused by Form Generation Mechanism in End-Milling Process (엔드밀링 공정의 형상창성기구에 의하여 절삭면적이 측벽 진직도 특성에 미치는 영향)

  • Kim, Kang
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.37 no.10
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    • pp.1269-1278
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    • 2013
  • The cutting area changes periodically in the end-milling process because of its form generation mechanism. In this study, the effects of the cutting area on end-milled side walls are studied by developing a cutting area model that simulates the area formed by engagement between a workpiece and a cutting edge of the end mill. To do this, the straightness profile of the side wall in the axial direction is investigated. Models for estimating the cutting area and the transition point, where the slope of the straightness profile changes suddenly, are verified from real end-milling experiments under various radial and axial depth of cut conditions. Through this study, it is confirmed that the final end-milled side wall is generated in the regions where cutting areas are constant and decreasing in the down-cut. Similarly, in stable up-cut, it is also generated in the regions where cutting areas are increasing and constant. It is found that the transition point appears when the region changes.

The Usefulness of Cephalic Vein Cut-Down for Totally Implantable Central Venous Port in Children (소아에서 완전 이식형 중심정맥포트를 위한 두정맥 절개술의 유용성)

  • Jung, Kyu-Whan;Moon, Suk-Bae;Jung, Sung-Eun;Lee, Seong-Cheol;Park, Kwi-Won
    • Advances in pediatric surgery
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    • v.14 no.1
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    • pp.67-74
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    • 2008
  • The usefulness of totally implantable central venous port for long-term intravenous infusion is widely accepted in children. Usually the catheters are placed through the internal or external jugular vein. In case of jugular vein cut-down, two separate incisions are needed for catheter and port respectively. Patients also feel uncomfortable as the catheter run through the neck. However these disadvantages can be overcome by using the cephalic vein (CV). We reviewed our experiences on CV cut-down for totally implantable central venous port in children. From January 2002 to December 2006, 201 patients (M:F=127:74) underwent 218 central venous port insertions. Mean age at operation was 5.9 years (2 months - 19 years). Indications included chemotherapy (N=167), long-term intravenous antibiotics infusion (N=36), and total parenteral nutrition (N=15). CV was selected preferentially. The incision includes the deltopectoral triangle laterally, and both the CV cut-down and port insertion were achieved with a single incision. The number of insertion through external, internal jugular vein, and CV was 77, 66 and 75, respectively. The median age, height and body weight were higher in CV cut-down group. The youngest age for CV cut-down was 8 months, the shortest height was 69 cm and the smallest body weight was 5.9 kg. Of 118 trials of CV cut-down, cut-down was successful in 75 cases (63.6 %). CV was absent in 10 cases(8.4 %) and CV was sacrificed after catheter tip malposition in 10 cases (8.4 %). There was only one complication, in which the catheter was inserted into the minute branch of subclavian artery. The CV cut-down method for totally implantable central venous port was safe and feasible in selected groups of patients in children. In addition, preservation of jugular vein and a more favorable cosmetic effect are other benefits of CV cut-down.

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