• 한국정밀공학회지
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• 제32권2호
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• pp.127-133
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• 2015

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 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 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.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2000년도 춘계학술대회 논문집
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• pp.663-667
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• 2000

The spindle unit is core parts in high precision machine tools. Diverse static and dynamic charateristics of spindle unit are needed for special purpose of machine tools. Specially, high damping ability may be very useful to high precision and high speed spindle unit. But commercial bearing system has very low damping value and high stiffness. In this paper, the combined bearing system with ball-hydrostatic bearing is suggested for high damping spindle unit. The suggested bearing system has 30% damping ability more than general ball bearing's. The average rotational accuracy of spindle with combined bearing in working speed is 24% better than with ball bearing. The unbalance rotating experiment in spindle show that rotating error with combined bearing is only half value of with ball bearing.

• 한국정밀공학회지
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• 제13권1호
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• pp.45-52
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• 1996

It is one of the important causes that the precision of the thread grinder decide the machining errors of the ball screw. The approach described in this study demonstrates how the dominant causes of the inaccuracies in thread grinding system can be determined. To evaluate the machining error of thread grinder, rotary encoder is allocated to spindle shaft and master screw for measuring the rotational transfer error between spindle shaft and master screw and the laser measuring system is used for checking the movement error.

• 한국기계가공학회지
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• 제11권3호
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• pp.174-181
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• 2012

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.

• 한국정밀공학회지
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• 제12권2호
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• pp.59-68
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• 1995

In this study, the effects of the power transmission units on the rotational accuracy are investigated experimentally in a hydrostatic spindle. The effects of warm up time, unbalancing and the position of measuring sensor are pre-examined for the determination of measuring conditions. The misalignment of the power transmission units and the vibration excited by the fluctuation of belt are considered as the dominant parameters of error motion. The variation and scatter of run out at the range of 0 to 3,000rpm in rotational speed are appropriated for the camparison of availabilities of the transmission units to precision spin- dles.

• 한국기계가공학회지
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• 제13권1호
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• pp.78-84
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• 2014

The rotation of a spindle unit must be accurate for high-quality machining and to improve the quality of the machine tools.Therefore, the proper measurement of the rotation accuracy and ensuring a proper analysis are very important. Separate processes are necessary because spindle errors and roundness errors associated with the test balls can both factor into the measured rotation error values. We used three methods to discern test ball errors and analyzed which could be deemed as the most proper technique in a test of the rotation accuracy of the main spindle of a machine tool.

• 대한기계학회논문집
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• 제17권11호
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• pp.2723-2729
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• 1993

Moire principles are applied to the measurement of the spindle radial error motion. As opposed to conventional techniques, no master cylinder or ball is needed in the measurement so that the offset and out-of-roundness errors of the master can be inherently eliminated. Two periodic circular gratings are used, one is made on the spindle and the other is held stationary on the reference frame. When the two gratings are seen superimposed during spindle rotation, an interference fringe pattern is observed from which the information on the eccentricity between the two gratings can be extracted with high precision. The optical design and fringe analysis techniques of a prototype measurement system are described in detail with exemplary measurement results.

• 한국정밀공학회지
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• 제28권3호
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• pp.285-291
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• 2011

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.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1997년도 추계학술대회 논문집
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• pp.52-55
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• 1997

In this paper, the case study of reducing rotational errors is done for a grinding spindle with an active magnetic bearing system. The rotational errors acting on the magnetic bearing spindle are due to mass unbalance of rotor, runout, grinding excitation and unmodeled nonlinear dynamics of electromagnets. For the most case, the electrical runout of sensor target is big even in well-finished surface; this runout can cause a rotation error amplified by feedback control system. The adaptive feedforward method based on LMS algorithm is discussed to compensate this kind of runout effects, and investigated its effectiveness by numerical simulation and experimental analysis. The rotor orbit size in both bearings is reduced about to 5 pin due to lX rejection by feedforward control up to 50, 000 rpm.

• 한국정밀공학회지
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• 제32권2호
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• pp.135-140
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• 2015

It is an important thing for a designer to simulate and predict the performance of a spindle and a rotary table. In addition to the general performance such as static stiffness, the error motion performance information is beneficial to the designer in many cases. However for an aerostatic bearing the fluid film physical status should be calculated in order to simulate those performances and the calculation time is another obstacle for a simple performance simulation. In this paper the investigation on experiment and simulation is performed in order to find a more effective simulation method for the rotational error motion.