• Title, Summary, Keyword: machining tolerance

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A Development of the Tolerance Modeler for Feature-based CAPP (특징형상에 기반한 공정설계를 위한 공차 모델러 개발)

  • 김재관;노형민;이수홍
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • pp.267-271
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    • 2000
  • A part definition must not only provide shape information of a nominal part but also contain non-shape information such as tolerances, surface roughness and material attributes. Although machining features are useful for suitable shape information for process reasoning in the CAPP, they need to be integrated with tolerance information for effective process planning. We develop the tolerance modeler that efficiently integrates machining features with tolerance information for feature-based CAPP It is based on the association of machining features, tolerance features. and tolerances Tolerance features, where tolerances are assigned, are classified into two types; one is the face that is a topological entity on a solid model and the other is the functional geometry that is not referenced to topological entities. The functional geometry is represented by using machining features All the data for representing tolerance information with machining features are stored completely and unambiguously in the independent tolerance structure. The developed tolerance modeler is implemented as a module of a comprehensive feature-based CAPP system.

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Concurrent Optimization of Design and Machining Tolerances with Accumulated Scrap Cost Model(ASCM) (누적 재가공 비용 모델을 이용한 설계 및 가공 공차의 동시 최적화)

  • Choe, Min-Seok;Lee, Du-Yong
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.25 no.3
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    • pp.452-460
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    • 2001
  • Most of researches of tolerance optimization have used a simple sum of tolerance-cost functions with several constraint equations as an optimization model. However, if there is a machining sequence with more than one processes to complete a part, and machining failure, i.e., out-of-tolerance occurs at one of the intermediate processes, the tolerance-cost of this process should be added by the machining cost of all the previous processes already completed on the part. In this study, an accumulated scrap cost model(ASCM) is proposed considering the scrapped machining cost, and applied to a simple assembly example. The result of tolerance optimization using ASCM is compared with that of using a traditional optimization model to confirm its effectiveness.

A Study on the Tolerance Modeler for Feature-based CAPP (특징형상에 기반한 자동공정설계용 공차 모델러 연구)

  • Kim, Jae-Gwan;No, Hyeong-Min;Lee, Su-Hong
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.26 no.1
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    • pp.48-54
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    • 2002
  • A part definition must not only provide shape information of a nominal part but also contain non-shape information such as tolerances, surface roughness and material specifications. Although machining features are useful for suitable shape information fur process reasoning in CAPP, they need to be integrated with tolerance information for effective process planning. We develop a tolerance modeler that efficiently integrates the machining features with the tolerance information fur feature-based CAPP. It is based on the association of machining features, tolerance features, and tolerances. The tolerance features in this study, where tolerances are assigned, are classified into two types; one type is a face that is a topological entity on a solid model and the other type is a functional geometry that is not referenced to topological entities. The (unctional geometry is represented by using machining features. All the data fur representing the tolerance information are stored completely and unambiguously in an independent tolerance data structure. The developed tolerance modeler is implemented as a module of a comprehensive feature-based CAPP system.

An Evaluation on Cutting Characteristics in Milling Process with Different Helix Angle Endmills (밀링가공에서 부등각 엔드밀의 절삭특성 평가)

  • 이상복;김원일;왕덕현;김실경
    • Transactions of the Korean Society of Machine Tool Engineers
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    • v.12 no.6
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    • pp.1-7
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    • 2003
  • The experimental research was conducted to find an end mill with an ideal helix angle, which has a superior anti-vibration effect and a low machining tolerance. A conventional endmill which all low blades are $30^{\circ}$ helix angles and a different helix angle endmill which the opposite two blades are $30^{\circ}$ and the other opposites are different helix angles were studied. The cutting farce, machining tolerance and surface roughness were obtained. The AE signals appeared to have low values in up-milling rather than in down-milling. These are also appeared to have low values at low spindle revolutions rates. The cutting force values of Fxy and Fxyz were found to be increased according to the value of helix angle. In up-milling, it was difficult to find a definite tendency in machining tolerance, but in down-milling machining tolerance of the different helix angle end mill was found to be lower than that of the convention end mill. There is a definite tendency that the surface roughness gets better as the RPM increases. In down-milling, Type A($25^{\circ}$$30^{\circ}$) appeared to bring the most satisfactory result.

Aa Evaluation on Cutting Characteristics in Milling process with Different Helix Angle Endmills (밀링가공에서 부등각 엔드밀의 절삭특성에 관한 고찰)

  • 이상복;김원일;왕덕현;김실경
    • Proceedings of the Korean Society of Machine Tool Engineers Conference
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    • pp.196-201
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    • 2003
  • The experimental research was conducted to find an end mill with an ideal helix angle, which has a superior anti-vibration effect and a low machining-tolerance. A conventional endmill which all four blades are $30^\circ$ helix angles and a different helix angle endmill which the opposite two blades are $30^\circ$ and the other opposites are different helix angles were studied. The cutting force, machining tolerance and surface roughness were obtained. The AE signals appeared to have low values in up-milling rather than in down-milling. These are also appeared to have low values at low spindle revolutions rates. The cutting force values of Fxy and Fxyz were found to be increased according to the value of helix angle. In up-milling, it was difficult to find a definite tendency in machining tolerance, but in down-milling, machining tolerance of the different helix angle end mill was found to be lower than that of the convention end mill. There is a definite tendency that the surface roughness gets better as the RPM increases. In down-milling, Type $A(25^\circ+30^\circ)$ appeared to bring the most satisfactory result.

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A study on the Methodology of Machining process of Features Using STEP AP224 (STEP AP224를 이용한 특징형상의 가공 방법에 관한 연구)

  • 김야일;강무진
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • pp.145-149
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    • 1997
  • STEP AP224 includes the information of machining feature and tolerances. Machining features are machined from raw material. Tolerance constrain feasible methods of manufacture, strongly influence the cost of manufacture. And tolerances influence the machining process. We need to decide the precedence between features .tool radius and tool direction for minimum tool changes. This paper deals with the method of decision of precedence between features and process parameters using feature information and tolerances in STEP AP224.

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A Study of Feedrate Optimization for Tolerance Error of NC Machining (NC가공에서 허용오차를 고려한 가공속도 최적화에 관한 연구)

  • Lee, Hee-Seung;Lee, Cheol-Soo;Kim, Jong-Min;Heo, Eun-Young
    • Journal of The Korean Society of Manufacturing Technology Engineers
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    • v.22 no.5
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    • pp.852-858
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    • 2013
  • In numerical control (NC) machining, a machining error in equipment generally occurs for a variety of reasons. If there is a change in direction in the NC code, the characteristics of the automatic acceleration or deceleration function cause an overlap of each axis of the acceleration and deceleration zones, which in turn causes a shift in the actual processing path. Many studies have been conducted for error calibration of the edge as caused by automatic acceleration or deceleration in NC machining. This paper describes a geometric interpretation of the shape and processing characteristics of the operating NC device. The paper then describes a way to determine a feedrate that achieves the desired tolerance by using linear and parabolic profiles. Experiments were conducted by the validate equations using a three-axis NC machine. The results show that the machining errors were smaller than the machine resolution. The results also clearly demonstrate that the NC machine with the developed system can successfully predict machining errors induced with a change in direction.

A Study on the 3-D Form Characteristics of Center Ground Parts (원통연삭 가공물의 3차원 형상특성에 관한 연구)

  • Cho, Jaeil;Kim, Kang
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • pp.95-99
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    • 1996
  • The form accuracy of parts has become an important parameter. Therefore dimensional tolerance and geometric tolerance are used in design to satisfy required quility and functions of parts. But the informations for machining conditions, which can satisfy the assigned geometric tolerance in design, are insufficient. The objectives of this research are to study the effects of the grinding parameters such as traverse speed, work speed, depth of cut, and dwell time on the after-ground workpiece shape, and to find out the major parameters among these parameters. Finally, a methodology is proposed for getting the optimal grinding condition for precision workpiece The results are as follows; The effects of work speed and depth of cut on workpiece shape are ignorable compared to the effect of traverse speed. These is the optimal dwell time depending on the traverse speed. The optimal dwell time is decreasing when the traverse speed is increased.

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A study on Rough machining path generation of sculptured surface by bisection method (이분법에 의한 자유곡면 황삭가공 경로산출에 관한 연구)

  • 신동혁;주종남
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • pp.157-163
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    • 1995
  • This paper presents an algorithm to deternine the tool path height for rough machining of sculptured surface. To minimize rough machining of sculptured surface, it is necessary to determine the tool path heights of contour planes. the proposed algorithm searches for the height at which maximum metal removal rate is obtained. This bisection method is accomplished until all shoulder heights are within roughing tolerance. The machining experiment demonstrates the superiority of the algorithm presented in this thesis.

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