Kuang-Hua Fuh

A residual-stress model for the milling of aluminum alloy (2014-T6)

Abstract One of the important problems encountered in the milling processes is the elastic deformation of the workpiece; thus, how to select the cutting parameters to reduce the residual stress is especially crucial. A mathematical model is presented for predicting the residual stresses of alloy 2014-T6 caused by end-milling. Factors such as the cutting conditions (cutting speed, feed, and cutting depth) and the tool geometries (tool nose radius and flank wear) are considered in this paper. To reduce the number of experiments required and to build the mathematical model for these variables, Response Surface Methodology (RSM) with the Takushi method are used. In addition, variance analysis and an experimental check are conducted to determine the prominent parameters and the adequacy of the model. According to the above processes, it is shown that the cutting speed, feed, tool nose radius and flank wear have the most significant effect on the residual stresses and there is an interaction between the cutting speed and flank wear. The affect on the residual stress of the cutting conditions and tool geometries can be explained in terms of the cutting force, the rise in temperature and the microstructure variation. Therefore, this model, offering good correlation between the experimental and predicted results, is useful in selecting suitable cutting parameters for the machining of alloy 2014-T6.

The prediction of cutting forces in the ball-end milling process

Abstract This paper presents the development and verification of a predictive model for the force system in ball-end milling. The force model is essentially derived from metal cutting theory and for the geometric relations of the ball-end milling process. A concise method for characterizing the complex geometry of a ball-end mill is first determined. This method of generation not only simplifies the description of the geometry of the cutting edge, but also provides the basis for the determination of all geometric parameters to an accuracy commensurate with that needed for the oblique cutting process. The force model developed in able to deal with many of the process variables, including changes in the axial and radial depths of cut and in the feed-rate, as well as the eccentricity (run-out) inevitably found in practice. As a result, the predicted cutting forces show a fairly good agreement with the values from the verification experiments.

Force modeling and forecasting in creep feed grinding using improved bp neural network

The object of this study is to model and forecast the grinding force for the creep feed grinding process, using back propagation (BP) neural network. The BP neural network is improved by integrating an error distribution function (EDF), a process that proves to be useful in overcoming local minimum problems effectively, so as to find the global minimum solution, and greatly accelerate the convergence speed. Compared with the theoretical force model, the force model implemented by the improved BP neural network is found to be accurate and to predict the grinding force satisfactorily.

A predictive force model in ball-end milling including eccentricity effects

Abstract In this study, a new predictive force model in ball-end milling has been derived from a metal cutting theory and for the geometric relations of the ball-end milling process. It was necessary initially to define the cutting edge shape and then to determine the tool geometry of each cutting edge element by simple geometric procedures. The cutting edge on a ball-end mill can be considered as the curve of an intersection of a spherical surface with a skew plane. The advantage of this method is that the effects of the various parameters concerning the oblique cutting process can be readily calculated. The force model developed considers many of the process variables as well as the eccentricity (run-out) inevitably found in practice. The predicted and experimental results show good correlation and highlight the importance of the eccentricity on the forces and their fluctuations.

Model for cutting forces prediction in ball-end milling

Abstract This paper presents the development and verification of a predictive model for the force system in ball-end milling. The force model is essentially derived from metal cutting theory and for the geometric relations of the ball-end milling process. A concise method for characterizing the complex geometry of a ball-end mill is first determined. This method of generation not only simplifies the description of the geometry of the cutting edge, but also provides the basis for the determination of all geometric parameters to an accuracy commensurate with that needed for the oblique cutting process. The force model developed is able to deal with many of the process variables, including changes in the axial and radial depths of cut and in the feedrate, as well as the eccentricity (runout) inevitably found in practice. As a result, the predicted cutting forces show a fairly good agreement with the values from the verification experiments.

A predicted milling force model for high-speed end milling operation

In this study, a predicted milling force model for the end milling operation is proposed. The speed of spindle rotation, feed per tooth, and axial and radial depth of cut are considered as the affecting factors. An orthogonal rotatable central composite design and the response surface methodology are used to construct this model. The milling force per spindle revolution period obtained from each treatment is equally divided into suitable sections. The extreme value of the milling force in each section is selected to build the predicted model so as to predict the extreme force in each section for any cutting conditions within the specified range of the design database, including the speed of spindle rotation, feed per tooth, and axial and radial depth of cut. Moreover, the predicted extreme force in each section is applied to reconstruct the milling force waveform by means of the expansion of the Fourier series. The predicted model presented in this paper is adequate for a 95% confidence interval, and shows good correlation between experimental and predicted results.

Temperature rise in twist drills with a finite element approach

Abstract The finite element method is presented to predict the temperature responses of a full scale conventional twist drill. The effects of the penetration depth, the cutting speed, the web thickness, and the helix angle on the drill temperature responses have been investigated. The temperature contours are also presented for the flank surface, the cross section, and the three-dimensional drill body. The transient numerical results compare favorably with experimental data from literature. The motivation is to develop an optimum working condition from the view point of the thermal analysis.

Design optimization of a split-point drill by force analysis

Abstract A modified force model incorporating the splitting parameters for predicting the thrust forces and torque of a split-point drill has been developed. The effect of the notch angle on the thrust forces and torque has been deduced, also from the proposed force model. Experiments were conducted to evaluate the thrust forces and torque, the calculated thrust forces and torque being shown to compare favorably with those obtained from drilling tests on a JIS S45C steel. The optimization of the drill-point geometry was obtained by minimizing the thrust forces and torque, as well as by using the finite-element method to compute the displacement and stress distributions of the drill point. According to the experimental results for both thrust forces and torque, and the calculated values of the maximum displacement and maximum stress at the drill point, the optimal value of the notch angle was about 57.7°.

Prediction of the cutting forces for chamfered main cutting edge tools

A new cutting model of various tool geometries for tools with a chamfered main cutting edge has been built. Theoretical values of cutting forces were calculated and compared with the experimental results; the forces predicted by this model were consistent with the experimental values. Special tool holders were designed and manufactured to obtain various tool geometries. Cutting experiments were conducted on a carbon steel to examine the mechanism of secondary chip formation; the relationship between the shapes of secondary chips and tool geometries was observed.

Design and implementation for maximum metal removal-rate control of a constant turning-force system

Abstract Operational parameters such as cutting depth, feed, and spindle speed, are regulated to satisfactory values by an adaptive controller with constraints (ACC) in order to bring the machine tool to its maximum productivity during the cutting process. When the cutting force is maintained by a constant turning force (CTF) controller, the spindle speed can be determined easily by specifying a cutting condition such as that of metal removal rate (MRR). In this paper, an auxiliary maximum MRR (MRR max ) controller on the CTF system, with a variable structure system (VSS) controller, can automatically manipulate the spindle speed to maintain the MRR at the specified suitable maximum-value. The design and implementation method are presented, and a series of simulations and experimental results, illustrating the reliable improvement over the CTF system, are given.