• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.10a
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• pp.3-6
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• 2002

This paper presents the cutting simulation system for prediction and regulation of cutting force in CNC machining. The cutting simulation system includes geometric model, cutting force model, and off-line fred rate scheduling model. ME Z-map(Moving Edge node Z-map) is constructed for cutting configuration calculation. The cutting force models using cutting-condition-independent coefficients are developed for flat-end milling and ball-end milling. The off-line feed rate scheduling model is derived from the developed cutting force model. The scheduled feed rates are automatically added to a given set of NC code, which regulates the maximum resultant cutting force to the reference force preset by an operator. The cutting simulation system can be used as an effective tool for improvement of productivity in CNC machining.

• Transactions of the Korean Society of Mechanical Engineers
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• v.15 no.1
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• pp.78-89
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• 1991

This Paper presents an application example of the Adaptive Robust Servocontrol (ARSC) scheme, which is an explicit (or indirect) pole-assignment adaptive algorithm with the property of "robustness". The ARSC scheme is applied to an end-milling process for cutting force regulation. It is shown that the federate of an end-milling process can be maximized by the adaptive regulation of the peak cutting force through the ARSC scheme. The results of simulation study and real cutting experiment are presented. It has been verified that asymptotic regulation can be achieved with robustness against the slowly time-varying perturbations to the process model parameters, which are caused by nonlinear cutting dynamics. dynamics.

• Journal of the Korean Society for Precision Engineering
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• v.16 no.3 s.96
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• pp.38-46
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• 1999

Spindle motor current is used to estimate the cutting force indirectly and control the feed rate for the cutting force regulation. The proposed algorithm is implemented to a DSP board based hardware for the industrial application. The software to make POP terminal communicate with the DSP board and POP server is coded under Windows 95 environment. Experiments under varying cutting conditions show that the DSP board recognizes the information of installed cutting tool and cutting conditions delivered from the POP server to use them for the proper control of the feed rate. The cutting force is regulated well during machining of tapered or stepped workpiece and circular shaped workpiece as well.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.1
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• pp.113-120
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• 1994

The dynamic characteristics of turning processes are complex, non-linear and time-varying. Consequently, the conventional techniques based on crisp mathematical model may not guarantee cutting force regulation. This paper presents a fuzzy controller which can regulate cutting force in turning process under varying cutting conditions. The fuzzy control rules are extablished from operator experience and expert knowledge about the process dynamics. Regulation which increases productivity and tool life is achieved by adjusting feedrate according to the variation of cutting conditions. The performance of the proposed controller is evaluated by cutting experiments in the converted conventional lathe. The results of experiments show that the proposed fuzzy controller has a good cutting force regulation capability in spite of the variation of cutting conditions.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.8
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• pp.1173-1182
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• 2001

Recent noticeable advances of CNC machine tools have considerably improved productivity and precision in manufacturing processes. However, in the respect of productivity some defects still remain because selection of machining conditions entirely depends on the experiences of programmers. Usually, machining conditions such as feed rate and spindle speed have been selected conservatively by considering the worst cases, and it has brought the loss of machining efficiency. Thus, the improvement of cutting force controller has been done to regulate cutting force constantly and to maximize feedrate simultaneously in case that machining conditions change variously. In this study, sliding mode control with boundary layer is applied to milling process for cutting force regulation and in a commercial CNC machining center data transfer between PC and PMC (programmable machine controller) of CNC machine is done using a standard interface method. And in the cutting force measurement, an indirect cutting force measuring system using current signal of AC servo is adopted in order not to use high-priced equipment like tool dynamometer. The purpose of this study is to maximize the productivity in milling process, thus its results can be applied to cases such as rough cutting process.

• Journal of the Korean Society for Precision Engineering
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• v.14 no.10
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• pp.15-27
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• 1997

Quasti-static cutting force variations in milling process are measured indirectly using spindle motor current. Quasi-static sensitivity of the spindle motor current is higher than that of the feed motor current. Magnitude of the spindle motor current is independent of cutting direction. The linear relationship between the cutting force and the spimdle motor RMS current at various spindle rotational speed is obtained. Frequency/ Voltage(F/V) converter voltage is measured to identify the spindle speed and to determine the cutting force at various spindle speeds. Overload on the tool during milling process can be detected using the proposed indirect cutting force measurement. Based on these measurements, cutting force is regulated at a constant level by feedrate control.

• 제어로봇시스템학회:학술대회논문집
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• 1996.10b
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• pp.840-843
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• 1996

This paper presents an adaptive cutting force controller for milling process, which can be attached to most commercial CNC machining centers in a practical way. The cutting forces of X,Y and Z axes measured indirectly from the use of currents drawn by AC feed-drive servo motors. A typical model for the feed-drive control system of a horizontal machining center is developed to analyze cutting force measurement from the drive motor. The pulsating milling forces can be measured indirectly within the bandwidth of the current feedback control loop of the feed-drive system. It is shown that indirectly measured cutting force signals can be used in the adaptive controller for cutting force regulation. The robust controller structure is adopted in the whole adaptive control scheme. The conditions under which the whole scheme is globally convergent and stable are presented. The suggested control scheme has been implemented into a commercial machining center, and a series of cutting experiments on end milling and face milling processes are performed. The adaptive controller reveals reliable cutting force regulating capability under various cutting conditions.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1996.11a
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• pp.605-609
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• 1996

Continuous sliding mode control is applied to turning process for cutting force regulation. The highest feedrate compatible with the allowable cutting force is applied in rough cutting process such that maximum productivity is ensured and tool breakage is avoided. The programmed feedrate is overridden after the control algorithm is carried out. However, most CNC lathe manufacturers offer limited number of data bits far feedrate override, thus resulting in nonlinear behavior of the machine tools. Such nonlinearity brings “quantized” effect, and the optimal faedrate is rounded off before being fed into the CNC system. To compensate for this problem, continuous sliding mode control is applied. Conventional switching control law at a sliding surface is replaced by a smooth control interpolation in a selected boundary layer to avoid the excitation of high-frequency dynamics. Simulation results are presented in comparison with those obtained by applying adaptive control.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.3 no.4
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• pp.20-29
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• 2004

A Tool wear monitoring system is indispensable for better machining productivity with guarantee of machining safety by informing the tool changing time in automated and unmanned CNC machining. Different from monitoring using other signals, the monitoring of spindle current has been used without requiring additional sensors on machine tools. For the reliable tool wear monitoring, current signal only of tool wear should be extracted from other parameters to avoid exhaustive analyses on signals in which all parameters are fused. In this paper, influences of force components of parameters on measured spindle current are investigated and a hybrid approach to cutting force regulation is employed for tool wear signal extraction in the spindle current. Finally, wear levels are verified with experimental results by means of real-time feedrate aspects changed to regulate the force component of tool wear.

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.1
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• pp.69-77
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• 1993

Adaptive Control is applied to regulate cutting force in turning operation under varying cutting conditions. Regulation is achieved primarily by adjusting feedrate. Such control leads to better machine utilization and increased tool life. The modeling of adaptive control system in turning operation is presented. The experimental results show that the adaptive PI controller is stable and performs more effective force control over wide range of cutting conditions as compared with the fixed gain PI controller.