• Proceedings of the Korean Society of Precision Engineering Conference
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• 1995.10a
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• pp.720-723
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• 1995

As a part of the configuration design expert system of machine tools, inference mechanisms are constructed in this paper. In addition to procedural inference, the method of multivariable inference is considered as an efficient approach to deal with the cases of highly coupled condition. We propose a generalized multivariable inference procedure. The procedure is applied to the type selection module of the configuration design expert system of machine tools in order to demonstrate the efficiency and validity.

• Journal of the Korean Society for Precision Engineering
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• v.13 no.7
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• pp.24-28
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• 1996

In this paper, a new measurement system has been developed for measuring servo errors of CNC machine tools. Unlike the ball link bar method using circular path, the developed system uses two orthogonal straight paths for measurement of errors, giving relatively short test length. For position measurment, linear displacement sensor and steel cube have been designed, and the software for relevant data sampling and error evaluation has been implemented.

• Journal of the Korean Society for Precision Engineering
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• v.25 no.5
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• pp.52-59
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• 2008

The accuracy of the machine tools is degraded because of thermal error of structure due to thermal variation. To improve the accuracy of a machine tools, measurement and prediction of thermal error is very important. The main part of thermal source is spindle due to high speed with friction. The thermal error of spindle is very important because it is over 10% in total thermals errors. In this paper, the suitable thermal error prediction technology for machine tools with open architecture controller is developed and implemented to machine tools. Two thermal error prediction technologies, neural network and multi-linear regression, are investigated in several methods. The multi-linear regression method is more effective for implementation to CNC. The developed thermal error prediction technology is implemented on the internal function of CNC.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2001.04a
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• pp.377-380
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• 2001

A recent trend in flexible manufacturing systems(FMS) is to compose of the identical versatile-machines and to use dynamic tool allocation strategy, sharing tools between machines with fast tool delivery system. Unlike a conventional FMS where parts are fed to the machines with the required tools, tools are acquired from other machines using a tool delivery system and parts can be finished on the same machine in these FMS. Therefore it is more important problem to plan tool flow using tool delivery system in these FMS rather than part flow in conventional FMS. According to existing study, in FMS 20~30 percent of the total management cost is the cost related with tools and it is possible to reduce the tool inventory by 40 percent using efficient tool allocation. In this study, in FMS under dynamic tool allocation strategy, a new method of part release considering tool flow at the stage of part release is proposed. In order to prove the efficiency of the proposed part release it is compared with other part release through simulation experiments. Performance measures in these experiments are the throughput and the number of tardy parts.

• Journal of Power System Engineering
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• v.14 no.2
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• pp.34-39
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• 2010

Recently, technical trend for machine tools is focused on enhancement of speed and accuracy. High speedy processing causes thermal and structural deformation of objects from the machine tools. Water cooler has to be applied to machine tools to reduce the thermal negative influence with accurate temperature controlling system. Existing On-Off control type can't control temperature accurately because compressor is operated and stopped repeatedly and causes increment of power consumption and decrement of the expected life of compressor. The goal of this study is to minimize temperature error in steady state. In addition, control period of an electronic expansion valve were considered to increment of lifetime of the machine tools and quality of product with a water cooler. PI controller is designed using type of hot-gas bypass for precise control of temperature. Gain of PI is decided easily by method of critical oscillation response, excellent performance of control is shown with 4.24% overshoot and ${\pm}0.2^{\circ}C$error of steady state. Also, error range of temperature is controlled within $0.2^{\circ}C$although disturbance occurs.

• Journal of the Korean Society for Precision Engineering
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• v.16 no.1 s.94
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• pp.265-271
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• 1999

In the feed drive systems or the spindle systems of machine tools that consist of many mechanical components, a torsional vibration is often generated because of its elastic elements in torque transmission-Generally, the accuracy of motion control system is strongly influenced by the dynamic behavior of coupled transmission components Especially, a torsional vibration caused by the elasticity of mechanical elements might deteriorate the quick movement of system and lead to shorten the life time of the mechanical transmission elements. So, it is necessary to analyze the electromechanical system mathematically to optimize the dynamic characteristics of the feed m1d spindle system. In this paper, based on the DC motor model, a model of electro-drive system with motor has been developed and an optimal criterion for tuning the gain of speed controller is discussed. The frequency bandwidth of the system and the damping ratio in time domain are optimal design specifications for the gain adjustment speed controller. The gains of PI speed controller are then derived from the bandwidth and damping ratio, and those relationships have been classified.

• Journal of the Korean Society for Precision Engineering
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• v.30 no.5
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• pp.480-485
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• 2013

Enhancing energy efficiency of machine tools causes substantial impacts on the manufacturing industries, to cope with the competitive introduction of the total energy management strategies. Real-time energy monitoring is essential to identify energy consumption patterns of the machine tools and correlate them with the energy management strategy. Integrated analysis of machine tool's operation status and the corresponding energy usage is most important to accurately evaluate the energy efficiency under the various machining process environments. This paper proposes a system architecture to realize the online energy monitoring system and the embedded energy monitoring approach interconnected with the CNC kernel. The shop-floor operation management system is presented to integrate the proposed online energy monitoring approach.

• Journal of Advanced Marine Engineering and Technology
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• v.33 no.7
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• pp.1003-1011
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• 2009

This study aims at precise control of oil outlet temperature in the oil cooler system of machine tools for enhancement of working speed and processing accuracy. PID control logic is adopted to obtain desired oil outlet temperature of the oil cooler system with hot-gas bypass method. We showed that the gains of PID controller could be easily determined by using gain tuning methods to get the gain of PID controller without any mathematical model. We also investigated various gain tuning methods to design the gains of PID and compared each control performance for selecting the optimal tuning method on the hot gas bypass method through experiments. Moreover, we confirmed excellent control performance with proposed PI controller gain even though disturbances were abruptly added to the experimental system.

• Journal of the Korean Society for Precision Engineering
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• v.16 no.2 s.95
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• pp.201-210
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• 1999

One of the major limitations of productivity and quality in metal cutting is the machining accuracy of machine tools. The machining accuracy is affected by geometric and thermal errors of the machine tools. Therefore, a key requirement for improving te machining accuracy and product quality is to reduce the geometric and thermal errors of machine tools. This study models geometric error for error analysis and develops on-machine measurement system by which the volumetric erors are measured. The geometric error is modeled using form shaping function(FSF) which is defined as the mathematical relationship between form shaping motion of machine tool and machined surface. The constant terms included in the error model are found from the measurement results of on-machine measurement system. The developed on-machine measurement system consists of the spherical ball artifact (SBA), the touch probe unit with a star type stylus, the thermal data logger and the personal computer. Experiments, performed with the developed measurement system, show that the system provides a high measuring accuracy, with repeatability of ${\pm}2{\mu}m$ in X, Y and Z directions.

• Journal of the Korean Society of Safety
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• v.29 no.6
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• pp.144-150
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• 2014

A man is a component of a large system how complex it may be so that human performance which can influence on the system safety should be included in system safety assessment. Meanwhile, human performance can vary over time due to lots of factors. Among them, stress is an indirect factor that may cause human error which can result in industrial accidents. To assess stress level of human workers, not a few assessment tools have been developed. However, it can be questionable to utilize them for human performance anticipation because they were mainly developed with the viewpoint of mental health, though stress assessment can be also required in the safety aspect. Therefore, this study aimed to survey the possibility of their application with safety purpose. About 10 kinds of work stress tools were collected and analyzed with reference to assessment items, assessment and analysis methods, and follow-up measures. The results showed that most tools focused their weights on Demands, Supports, and Relationships, in sequence. However, they, except only one tool developed by the Japanese researchers, merely advised to set up counterplans in PDCA cycle or risk management activities. In consequence, application of stress assessment tools mainly developed for mental health seemed impractical for safety purpose with respect to human performance anticipation so that it was concluded that development of a new assessment tools aimed to human performance variation and accident prevention would be inevitable.