Earticle

공작기계의 주축은 황삭 가공에서 부터 정삭가공에 이르는 다양한 작업들이 가능해야 하고, 정속운동 또는 회전 위치결정의 기능을 수행해야 되므로 주축설계에 고려해야 할 변수들이 많다. 주축이동식자동선반은 고정식자동선반에 비해 샤프트가 가늘고 긴 핀 들을 작업할 때 좋은 선반이다. 고정식 자동선반에 비해 외경가공의 정밀도가 매우 높다. 주축 이송 형 선반은 주로 소형 제품을 정밀가공 할 경우에 사용되므로 가공 정밀도가 높아야 한다. 최대 외경 가공 한계 치수는 Ø32, 내경가공 한계 치수는 Ø6까지 가공이 가능하게 제작되어야 한다. 본 연구에서는 주축이동식 자동선반에 사용되는 SCM440 소재의 정·동적특성을 이동식 선반에 적용하여 분석하였다. 주축의 정,동적 특성에 영향을 미치는 인자들을 고려하여 고속 화 및 고정밀도를 갖는 최적설계기술이 확보하기 위하여 수치해석을 이용하여 분석하였다.

In the machine tool spindle, various tasks ranging from roughing to finishing must be possible, and the functions of constant speed movement or rotation positioning must be performed. Therefore, there are many variables to be considered in the spindle design. The Swiss Turn Type spindle automatic lathe is a good machine tool for working pins with thinner shafts than a fixed automatic lathe. The Swiss Turn Type spindle is mainly used for precision machining of small products, so the machining precision should be high. The maximum outer diameter limit shall be Ø32 and the inner diameter limit shall be Ø6. In this study, the static and dynamic characteristics of the SCM440 material used in the spindle type automatic lathe were analyzed by applying it to the Swiss turn type spindle automatic lathe. Numerical analysis was used to obtain optimal design technique with high speed and high accuracy considering the factors affecting the static and dynamic characteristics of the spindle.

The positioning system for an ultra precision machine tool must be accurate to the order of a nanometer. Various feed drive devices have been proposed to achieve this resolution; currently, most attention is directed towards hydrostatic lead screws and friction drives. It has been reported that a positioning resolution accurate to an angstrom can be achieved using a twist-roller friction drive. Therefore, we manufactured an ultra precision positioning system driven by a twist-roller friction drive and assessed its performance when defining problems and finding solutions. Our study showed that the twist-roller friction drive is mechanically suitable for ultra precision positioning, but some considerations are required to obtain a higher resolution.

The main goal of this development is the PC-based controller setup on the CM2 tool grinding machine. Concerned cutting parameters with know-hows can be transferred to a useful program and then embedded in the PC-based controller. By automatic positioning of probes the automatic procedure can be achieved. An automatic and intelligent PC-based grinding machine for regrinding has been developed in this investigation. With the new machine and automatic procedure, regrinding process will be distinctly simplified. Based on a manual grinding machine CM2, a PC-based controller is integrated in the machine. The know-hows of the regrinding technology have been integrated with a self-developed program. For automatic dimensional inspection a contact probe is utilized as inspection sensor. By the programming and automatic dimensional inspection, the functions of tool regrinding machine have been enhanced greatly.

Reliability refers to the ability of a part, device or system to conduct an intended function in a given condition for a certain period of time. A mechanical system or structure such as a machine tool exercises the capacity of the entire system with regard to the various constituent parts that are connected to each other; as such, the reliability of the parts constituting the system determines the reliability of the entire system. A tool post is a device designed to efficiently provide the tools necessary for the processing of a turning machine: the parts used in a hard turning machine which requires higher stiffness must provide greater reliability. For the purposes of this study, the reliability of a tool post, which has the highest failure rate of a turning machine system, was assessed. In order to conduct a reliability assessment of a given tool post, reliability prediction using a failure rate database, weak point analysis, the manufacture of a reliability tester and the calculation of reliability testing and quantitative reliability criteria were also carried out. By so doing, the failure rate, the MTBF (Mean time between failures) and other factors could be calculated. Furthermore, the results can also be applied to other parts of the turning machine or to a reliability assessment of a subsystem by using the suggested assessment method.

The objectives of this research are (1) identifying duties of machine tool operators in small and medium enterprises; and (2) identifying tasks carried out by machine tool operators in small and medium enterprises. This research uses descriptive research method. The study participants were eight machine tool operators from five small and medium enterprises in Yogyakarta, Indonesia. Methods of data collection using document review, observation, questionnaires and focus group discussions. Data analysis using descriptive analysis. Results of research: (1) 5 duties done by machine tool operator are identified (maintain safe work environment, maintain the machine tools, analyze blueprint, perform machining operations, clean machine and workplace), and (2) 27 tasks executed by machine tool operator are identified; 22 knowledge and skills; 17 behaviours; and 18 machines, tools and equipment required by machine operators.

본 연구에서 공작기계 주축 시스템의 고강성을 위해서 주축 베어링의 최적 위치를 결정하기 위한 설계 가이 드라인을 개발하였다. 주축 시스템은 주로 축, 절삭 공구, 모터, 그리고 베어링으로 구성된다. 축을 지지하는 부품으로써 베어링의 위치는 주축의 동강성에 큰 영향을 미친다. 가이드라인은 다양한 베어링 위치에 따른 정강 성 및 진동수 유한요소해석의 분석 결과를 바탕으로 개발되었다. 절삭 공구를 위한 절점 질량 요소와 베어링 강성을 위한 스프링 요소와 같은 적절한 요소의 종류를 사용하여 정적 및 모달 해석 모두를 위해서 통합된 해 석 모델을 개발하였다. 이 설계 가이드라인은 최소의 시간과 노력으로 주축 시스템 설계의 근사 최적의 베어링 위치를 결정하는데 도움을 줄 것으로 기대한다.

This paper analyses the tool switching problem in the dynamic environment, where parts to be processed on a flexible machine arrive randomly. As the total number of tools required to Process a set of parts on the machine is generally larger than the available magazine storage capacity, tool switches between parts are usually necessary. We assume that tool switching must be made just before the processing of the parts. Since the time required for tool switches can be significant relative to processing time and cause the processing of parts to be delayed, it is desirable to minimize the number of tool switches. Therefore, we present one heuristic algorithm to minimize the total number of tool switches and the t)reposed heuristic is compared with the KTNS (Keep Tool Needed Soonest) policy on randomly generated problems.

This paper addresses the problem of placing tools in a tool magazine with random-select capability on a flexible machine. The tool placement problem could be a significant portion of the total processing time. It is assumed that the total number of tools required to process a set of parts exceeds the available magazine capacity, and so tool switches may occur between two adjacent parts in a given part sequence. Two heuristics are presented so as to minimize the total travel distance of the tool magazine before the completion of all parts.

In this paper, a simulation based estimation method of energy consumption of the spindle and feed drives for the NC machine tool during the cutting process is proposed. To predict energy consumption of the feed drive system, position, velocity, acceleration and jerk of the table are analyzed based on NC data and then the power and energy are calculated considering friction force and mass of the stages. Energy consumption of the spindle is estimated based on models from acceleration motion of rotating parts, friction torque and power loss of motors. Moreover, simulation models of cutting power and energy for the material removal along the NC tool paths are proposed.

A kinematically-hybrid 5-axis machine tool is analyzed from the perspective of machine tool design. Its kinematic characteristics are pointed out, which should be considered during the conceptual design process. A result of the structural analysis of the machine is presented, which is performed during the detailed design process. It is also presented how we improve the thermal characteristics of the machine tool by changing the installation position of the actuators.

In many optimal methods for the structural design, the structural analysis is performed with the given design parameters. Then the design sensitivity is calculated based on its structural anaysis results. There-after, the design parameters are changed iteratively. But genetic algorithm is a optimal searching technique which is not depend on design sensitivity. This method uses for many design para- meter groups which are generated by a designer. The generated design parameter groups are become initial population, and then the fitness of the all design parameters are calculated. According to the fitness of each parameter, the design parameters are optimized through the calculation of reproduction process, degradation and interchange, and mutation. Those are the basic operation of the genetic algorithm. The changing process of population is called a generation. The basic calculation process of genetic algorithm is repeatly accepted to every generation. Then the fitness value of the element of a generation becomes maximum. Therefore, the design parameters converge to the optimal. In this study, the optimal design pro- cess of a machine tool structure for static loading is presented to determine the optimal base supporting points and structure thickness using a genetic algorithm.