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박기범(Ki Beom Park),정원지(Won Jee Chung),이춘만(Choon Man Lee) 한국생산제조학회 2009 한국생산제조학회지 Vol.18 No.1
In general, the radial error motion of a machine tool spindle system is effected on the accuracy of the parts to be made. This paper presents in milling process an investigation into spindle rotational accuracy effects on surface roughness of processing parts. We experimented the effects on spindle rotational accuracy in milling process by cutting AL 7075 workpiece at various rotational speed. In order to analyze the effects of rotational accuracy on surface roughness, we proposed the method using iSIGHT's RBF Approximation. The proposed method can be used for anticipating the surface roughness when some spindle rotational accuracy experiments could be done in milling process.
고정밀 회전체의 불평형 변동에 따른 회전정밀도 영향에 관한 연구
김상화(Sang-Hwa Kim),김병하(Byung-Ha Kim),진용규(Yong-Gyoo Jin) 한국기계가공학회 2012 한국기계가공학회지 Vol.11 No.3
The spindle unit is a core part in high precision machine tool. Rotation accuracy of spindle unit is needed for high dignity cutting and improving the performance of machine tool. However, there are many factors to effect to rotational error motion(rotation accuracy). This study studied how rotational error motion is variation when unbalance amount is variation. Rotation accuracy of initial spindle unit is decided depending on parts and assembly such as bearing. When it is rotation, vibration and noise is appeared depending on volume of unbalance amount, so it works to decrease unbalance amount. The purpose of the study tests that unbalance amount how much effects to initial rotation condition. The result of the study shows that accuracy of parts and assembly is highly necessary to reach high rotation accuracy and unbalance amount hardly effects to initial rotation accuracy. However, it shorten spindle"s life because vibration and noise is increasing by increasing unbalance amount and we can expect situation that rotation accuracy is falling by long time operation.
롤러베어링 구조형 주축 회전체의 언밸런스 변동과 절삭표면상태 연관성에 관한 연구
하정웅(Jeong-ung Ha),박동희(Dong-hui Park),박황기(Hwang-gi Park),전승민(Seung-min Jeon),홍진표(Jin-pyo Hong),윤상환(Sang-hwan Yoon),박종규(Jong-kyu Park) 한국기계가공학회 2020 한국기계가공학회지 Vol.19 No.9
The rotation accuracy of the main spindle that determines the accuracy of CNC machine tools is closely related to the quality of production because it directly affects the shape error and surface roughness of the workpiece. Therefore, the main spindle requires high rotation accuracy, rigidity, and rotation technology. This rotation accuracy is greatly affected by the bearing, center alignment between rotating parts, assembly tolerance, and unbalance of the rotation mass. In this study, the effects of the unbalance of the rotation mass of the main spindle on the rotation accuracy were investigated experimentally. In particular, we tried to study the technical reasons for improving the unbalance of the main spindle and maintaining the rotation accuracy as we verified the correlation between the vibration characteristics of CNC machine tools due to the specifically set unbalance amount and the surface roughness of the workpiece.
김종관,이중기 한국소음진동공학회 1995 소음 진동 Vol.5 No.4
For evaluation of rotational accuracy performance of high speed machine tool spindle system, the characteristics of main spindle and tool motion behavior are presented by means of three point accuracy testing method. The results of experiments and analyses are as follows: (1) The high speed spindle rotational accuracy can be evaluated by the combination of the spindle and tool motion behavior. (2) The spindle motion behavior increases up to more that 4 times the tool motion behavior. (3) For the influence of oil viscosity on spindle and tool taper application, 32 cSt of oil viscosity showed the most satisfactory result for rotational accuracy. (4) In order to improve the rotational accuracy of high speed machine tool spindle system, it is needed to reduce the combination error. This can be achieved by improving the working accuracy and supplying the proper lubrication with contact area at the spindle and tool.
황주호(Jooho Hwang),박천홍(Chun-Hong Park) Korean Society for Precision Engineering 2010 한국정밀공학회지 Vol.27 No.7
This paper describes the design and evaluation procedure of an ultra-precision rotary table for freeform generating machined tools. Design of the thrust and journal hydrostatic bearings and experimental evaluation of the table were performed. To get the compact size and less lost motion direct drive servomotor with ultra precision encoder. From the considered design, following performance were confirmed by experiment. The total stiffness of the prototype rotary table was 483.6 N/㎛ and 97.6 N/㎛ for axial and radial direction, respectively. Rotational accuracy of the table was investigated by capacitive sensor and reversal measurement technique, and 0.10 ㎛ radial direction and 0.05 ㎛ axial direction of the rotational accuracy were confirmed. The micro resolution of the table was also investigated with displacement of capacitive sensor, and 0.5/10000° of micro resolution was confirmed. Index accuracy of the table was evaluated by the autocollimator and polygon mirror, and the ±0.39 arcsec accuracy and ±0.16 arcsec repeatability of the table were confirmed. Those are under the general requirements of ultra precision rotary tables for freeform generating machined tools.
CNC 공작기계 장착형 고속스핀들을 이용한 고속가공 실용화 기술
이용철(Yong-Chul Lee),곽태수(Tae-Soo Kwak),김경년(Gyung-Nyun Kim),이종열(Jong-Ryul Lee) 한국기계가공학회 2012 한국기계가공학회지 Vol.11 No.2
A newly developed attachment type high-speed spindle can be easily attached to the conventional CNC machining center to allow high-speed machining with low investment costs. This study has focused on the application of a conventional CNC machining center equipped with an attachment type high-speed spindle. A specimen of plastic mold material has been machined to compare the cutting effectiveness of the high-speed machining center and the conventional machining center with the attachment type high-speed spindle respectively. The rotational accuracy of the spindles are measured by a transmission optic measurement system and the surface roughness of the workpiece in accordance with revolution speed(rpm) of the spindle are investigated respectively. As the experimental results, it was shown that the surface roughness of the machined workpiece was 3.42㎛Rmax, 0.46㎛Ra in the case of attachment type spindle and 1.81 ㎛Rmax, 0.275㎛Ra in the case of the high-speed machining center. Moreover, the mean rotational accuracy was 7.57㎛ in the case of the attachment type spindle and 7.39㎛ in the case of the high-speed machining center.
황주호(Jooho Hwang),심종엽(Jong Youp Shim),홍성욱(Seong-Wook Hong),이득우(Deug-Woo Lee) Korean Society for Precision Engineering 2011 한국정밀공학회지 Vol.28 No.3
The error motion of a machine tool spindle directly affects the surface errors of machined parts. The error motions of the spindle are not desired errors in the three linear direction motions and two rotating motions. Those are usually due to the imperfect of bearings, stiffness of spindle, assembly errors, external force or unbalance of rotors. The error motions of the spindle have been needed to be decreased to desired goal of spindle’s performance. The level of error motion is needed to be estimated during the design and assembly process of the spindle. In this paper, the estimation method for the five degree of freedom (5 D.O.F) error motions of the spindle is suggested. To estimate the error motions of the spindle, waviness of shaft and bearings, external force model was used as input data. And, the estimation models are considering geometric relationship and force equilibrium of the five degree of the freedom. To calculate error motions of the spindle, not only imperfection of the shaft, bearings, such as rolling element bearing, hydrostatic bearing, and aerostatic bearing, but also driving elements such as worm, pulley, and direct driving motor systems, were considered.
Estimation of Rotational Motion Accuracy for Rotary Units
황주호(Jooho Hwang),심종엽(Jongyoup Shim),박천홍(Chun-Hong Park) Korean Society for Precision Engineering 2015 한국정밀공학회지 Vol.32 No.2
The error motion of a machine tool spindle directly affects the surface errors of machined parts. Those are usually due to the imperfectness of bearings, stiffness of spindle, assembly errors, external force or unbalance of rotors. The error motions of the spindle have been needed to be decreased to desired goal of spindles performance. The level of error motion is needed to be estimated during the design and assembly process of the spindle. In this paper, the estimation method for the five degree of freedom (5 D.O.F) error motions for rotary units such as a spindle and rotary table are suggested. To estimate the error motions of the rotary unit, waviness of bearings and external force model were used as input data. The estimation model considers geometric relationship and force equilibrium of the five degree of the freedom motions.
박천홍(Chun Hong Park),황주호(Joo Ho Hwang),조순주(Soon Joo Cho),조창래(Chang Rae Cho) Korean Society for Precision Engineering 2005 한국정밀공학회지 Vol.22 No.11
Design and performance evaluation of a spindle system which was composed of a grinding spindle and a regulating spindle for the centerless grinding of ferrule were performed in this paper. Layout and details of spindle system were designed and hydrostatic bearings for spindles were also designed. Prototype of spindle system was developed and its availabilities to machine the ferrule were discussed using the experimental results on the spindle stiffness of each spindle, loop stiffness, rotational accuracy and thermal characteristics. Loop stiffness of the spindle system was 130 N/㎛, which was enough to machine the ferrule. Rotational accuracies of each spindle were about 0.2 urn at the primary speed of 2,300 rpm(grinding spindle) and 300 rpm (regulating spindle). Temperature rises at the same speed were about 4.4 ~ 4.7 ℃ in the case of grinding spindle and 1.8 ℃ in the case of regulating spindle, which agreed well with the designed value. From these results, it was estimated that the prototype of spindle system had enough performances for the centerless grinding machine to machine the ferrule.