• 한국공작기계학회논문집
• /
• 제17권2호
• /
• pp.58-64
• /
• 2008

The cutting process of materials is accompanied with the elastic and plastic deformation due to chucking forces in the boring process of thin holes on the turning. Upon removal of chucking forces at the end of process, the original shape is remained in the plastic deformation; on the other hand, it is modified in the elastic deformation due to spring back. Fixing materials by chucks on the turning has influence on roundness because the process is conducted with unbalanced distribution load induced from the fixing of three jaws. Moreover, the amount of spring back depends on the magnitude of fixing forces. We studied the change of roundness according to fixing forces as well as the method to reduce the influence of chucking forces.

• 한국생산제조학회지
• /
• 제19권3호
• /
• pp.381-387
• /
• 2010

This paper presents a study of the influence of fixed pressure in turning. The effect of roundness error and diameter deformation were studied with respect to the fixed pressure applied inside the cylindrical work piece made by boring tool in CNC lathe. The boring tool used in this study is a tungsten carbide coated. The material of workpiece is SM45C and the machining method is dry cutting. Cutting conditions as cutting speed, feed rate and depth of cut are constant. Finally, the change of fixed pressure had influence on the roundness error and diameter deformation.

• 한국정밀공학회:학술대회논문집
• /
• 한국정밀공학회 2010년도 춘계학술대회 논문집
• /
• pp.123-124
• /
• 2010

• 한국생산제조학회지
• /
• 제22권3호
• /
• pp.349-355
• /
• 2013

Recently, there is an increasing need to produce more precise products with small deviations from defined target values. Machine capability is the ability of a machine tool to produce parts within a tolerance interval. Capability indices are a statistical way of describing how well a product is machined compared to defined target values and tolerances. Today, there is no standardized way to acquire a machine capability value. This paper describes a method for evaluating machine capability indices in machining centers. After the machining of specimens, the straightness, roundness, and positioning accuracy were measured by using CMM (coordinate measuring machine). These measured values and defined tolerances were used to evaluate the machine capability indices. It will be useful for the industry to have standardized ways to choose and calculate machine capability indices.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2005년도 추계학술대회논문집
• /
• pp.112-118
• /
• 2005

Ball bearings which were fitted between housing and shaft play an important role in rotating shaft system smoothly, Therefore bearing's running accuracy has significant influence on that of rotating machinery. Manufacturing accuracy of bearings as well as that of shaft and housing is main factor to affect bearing running accuracy In this paper, bearing's vibration and fatigue life considering raceway roundness of ball bearing before and after being fitted into housing are theoretically estimated. To perform analysis, a simple three degrees of freedom model was proposed and then these analysis was conducted utilizing the Newton-Raphson iterative method. The results show that vibration magnitude of ball bearing fitted into housing is considerably larger than before assembly, and bearing's theoretical L$_{10}$ fatigue life that ninety percent of the bearing population will endure decreased in about fifty percent.

• 한국기계가공학회지
• /
• 제15권1호
• /
• pp.20-25
• /
• 2016

Recently, the requirements for high precision and efficiency machining are gradually increased to raise international competitiveness at the industrial fields of automotive and gears. This trend had made effects on the industrial fields in Korea and which needs further studying of high accuracy and efficiency machining. This study is to investigate the effects of Jig type chuck for roundness improvement in CNC turning machining of high stage speed gear. After hobbing machining, Dimensional change before and after heat treatment was very largely generated. In order to solve this problem was to develop a jig type chuck. After the heat treatment, the operation of the chuck which was the most distinguished equipment among Jig type chuck(0.006mm), Scroll type chuck(0.05mm) and Bolt type chuck(0.04mm). Therefore, Jig type chuck was satisfied the requirement from the actual field(0.02mm).

• 한국공작기계학회논문집
• /
• 제10권4호
• /
• pp.55-64
• /
• 2001

In this study, hemisphere and cylindrical shapes were machined for different tool paths and machining conditions with ball endmill cutters. Tool deflection, cutting forces and shape accuracy were measured according to the inclination position of the sculptured surface. As the decreasing of inclination position angle, the tool deflection was increased due to the decreased cutting speed when the cutting edge is approaching toward the center. Tool deflection when upward cutting is obtained less than that of downward cutting and down-milling in upward cutting showed the least tool deflection for the sculptured surface. Roundness values were found in least roundness error when down-milling in upward cutting. It is obtained the very little difference between 90。and 45。 of inclination position angle. The best surface roughness value was obtained in upward up-milling and showed different tendency with tool deflection and cutting force. For down-milling, the cutting resistance of the side wall direction is larger than that of feed direction. Therefore, this phenomenon which is received over cutting resistance can be caused of chatter.

• 한국정밀공학회지
• /
• 제12권11호
• /
• pp.45-51
• /
• 1995

In order to suggest the proper cutting conditons of the CNC milling machining for the free-form surface, some experments were carried out. In the experiments, the influence of cutting conditions on a inclined spherical surface were examined by geometrical analysis. In this study, the roundness and cutting force were measured to know the effect of several cutting conditions on the machined surface and the cutting characteristics were carefully investigated. The results obtained in this study are aw follows. 1) If the tool ha s enough rigidity, we can get better dimensional accuracy in up-ward cutting than down- ward cutting. 2) A great roundness error is appeared on the surface declined under 30 degress to the horizontal plane in circular machining by a bal end mill. 3) If the thrust force is increased, the stability of tool is decreased. And the phenomenon is apperared in great in down-ward cutting than up-ward cutting.

• 대한기계학회논문집A
• /
• 제23권6호
• /
• pp.881-894
• /
• 1999

Cylindrical plunge grinding is widely used for final machining process of precision parts such as automobile, aircraft, measurement units. But in order to make parts which have high precision accuracy and high surface integrity, it is necessary to consider grinding characteristics due to accumulation phenomena of grinding wheel in plunge grinding process. In this study, in order to examine closely plunge grinding process, grinding power, grinding force, real depth of cut are monitored in transient state, steady state and spark out state. As the result, it is shown that grinding power and force are affected by dressing condition, depth of cut and speed ratio and that there exist threshold grinding force and it also affected by dressing condition. Also considered effects of grinding conditions on surface roughness and roundness of workpiece

• 대한기계학회논문집
• /
• 제16권6호
• /
• pp.1056-1063
• /
• 1992

본 연구에서는 평면변형이론을 적용하여, 진원형 튜브의 경우 주로 Durban의 과정에 따르고, 몇 가지의 타원형 모델들에 대하여 상용 유한 요소프로그램인 Solvia 를 이용하여 각기 해석하고, 파열압력에 대한 예측값을 구하였으며 각기 해석하고, 파열압력에 대한 예측값을 구하였으며 결함의 영향을 파악하였다.또 반경 대 두께 비가 다른 2가지 시편에 대한 파열시험을 수행하여 해석결과와 비교하였다.