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금형가공센터 고속 이송체의 성능 안정화를 위한 설계개선 사례
최영휴,홍진현,최응영,이재윤,김태형,최원선 한국공작기계학회 2004 한국공작기계학회 춘계학술대회논문집 Vol.2004 No.-
Heavy-weight head slides may cause excessive inertia impact & moment on the machine tool structure when they move or stop abruptly during operation. Consequently these inertia impact and unbalanced moment bring transient vibrations and rough sliding motions on the machine structure. Machine tool engineers have tried many kind of feed-slide designs in order to solve this problem; for example, the design optimization of the moving structure for minimum weight and maximum stiffness, box-in-box type slide design, and so on. In this article, force and moment equilibrium equations regarding to the inertia force & moment were derived for each one of a mold M/C's head slides. Furthermore, five different design configurations of head slide assembly were reviewed for its design improvement regarding to force & moment calculations and finite element structural analysis results.
가변 벌점함수 유전알고리즘을 이용한 금형가공센터 고속이송체 구조물의 최적설계
최영휴,차상민,김태형,박보선,최원선 한국공작기계학회 2003 한국공작기계학회 춘계학술대회논문집 Vol.2003 No.-
In this paper, a multi-step optimization using a G.A.(Genetic Algorithm) with variable penalty function is introduced to the structural design optimization of a high speed machining center. The design problem, in this case, is to find out the best cross-section shapes and dimensions of structural members which minimize the static compliance, the dynamic compliance, and the weight of the machine structure simultaneously. The first step is the cross-section shape optimization, in which only the section members are selected to survive whose cross-section area have above a critical value. The second step is a static design optimization, in which the static compliance and the weight of the machine structure are minimized under some dimensional constraints and deflection limits. The third step is a dynamic design optimization, where the dynamic compliance and the structure weight are minimized under the same constraints as those of the second step. The proposed design optimization method was successful applied to the machining center structural design optimization. As a result, static and dynamic compliances were reduced to 16% and 53% respectively from the initial design, while the weight of the structure are also reduced slightly.
Linear Motor 이송계의 진동 최소화를 위한 이송속도 최적화
최영휴,홍진현,최응영,김태형,최원선 한국공작기계학회 2004 한국공작기계학회 추계학술대회논문집 Vol.2004 No.-
Linear motor feed drive systems have been broadly used in machine tools or precision automatic feed systems. Recently, modern machine tools require high speed and high precision feed drive system to achieve high productivity. Unfortunately, a feed drive system, even though it was optimum designed, may experience severe transient vibrations during high-speed operation if its feed rate control is unsuitable. A rough feed rate curve having discontinuity in its acceleration profile causes a serious vibration problem in the feed slides system. This paper presents a feed rate optimization of a machine tool feed slide system, which is driven by a linear motor, for its minimum vibrations. Firstly, a 4-degree-of-freedom lumped parameter model is proposed for the vibration analysis of a linear motor driven machine tool feed drive system. Next, a feed rate optimization of the feed slide is carried out for minimum vibrations. The feed rate curve optimization strategy is to find out the most appropriate acceleration profile with jerk continuity. Of course, the optimized feed rate should approximate to the desired one as possible. A genetic algorithm with variable penalty function was used in this feed rate optimization.
초고속 공작기계용 Hybrid Poymer Concrete bed의 설계와 제작
서정도,임태성,이대길,김태형,박보선,최원선 한국공작기계학회 2004 한국공작기계학회 춘계학술대회논문집 Vol.2004 No.-
To maximize the productivity in machining molds and dies, machine tools should operate at high speeds. During the high speed operation of moving frames or spindles, vibration problems are apt to occur if the machine tool structures are made of conventional steel materials with inferior damping characteristics. However, self-excited vibration or chatter is bound to occur during high speed machining when cutting speed exceeds the stability limit of machine tool. Chatter is undesirable because of its adverse effect on surface finish, machining accuracy, and tool life. Furthermore, chatter is a major cause of reducing production rate because, if no remedy can be found, metal removal rates have to be lowered until vibration-free performances is obtained. Also, the resonant vibration of machine tools frequently occurs when operating frequency approaches one of their natural frequencies because machine tools have several natural frequencies due to their many continuous structural elements. However, these vibration problems are closely related to damping characteristics of machine tool structures. The polymer concrete has high potential for machine tool bed due to its good damping characteristics with moderate stiffness. This paper presents the use of polymer concrete and sandwich structures to overcome vibration problems. Also, co-cure bonding method for functional part mounting was exhibited experimentally, by which manufacturing time and cost for polymer concrete bed will be remarkably reduced.