Min- Yang

The prediction of cutting force in ball-end milling

Abstract Due to the development of CNC machining centers and automatic programming software, the ball-end milling have become the most widely used machining process for sculptured surfaces. In this study, the ball-end milling process has been analysed, and its cutting force model has been developed to predict the instantaneous cutting force on given machining conditions. The development of the model is based on the analysis of cutting geometry of the ball-end mill with plane rake faces. A cutting edge of the ball-end mill was considered as a series of infinitesimal elements, and the geometry of a cutting edge element was analysed to calculate the necessary parameters for its oblique cutting process assuming that each cutting edge was straight. The oblique cutting process in the small cutting edge element has been analysed as an orthogonal cutting process in the plane containing the cutting velocity and chip flow vectors. And with the orthogonal cutting data obtained from end turning tests on thin-walled tubes over wide range of cutting and tooling conditions, the cutting forces of ball-end milling could be predicted using the model. The predicted cutting forces have shown a fairly good agreement with test results in various machining modes.

The prediction of the cutting force in ball-end milling with a flexible cutter

Abstract In some situations, such as machining sculptured surfaces with long or slender ball-end mills, the cutter deflection in ball-end milling is a main factor affecting the machining accuracy. In this paper, a mechanistic cutting force prediction model of ball-end milling in consideration of cutter deflection is presented and its machining characteristics are discussed with experimental results. This model takes account of the changes in chip thickness by the deflection of a cutter and the cutter deflection is obtained by solving an equilibrium equation between cutting force and reaction force. The model was verified from the measurements of cutting forces for different machining conditions.

Roll-to-Roll Cohesive, Coated, Flexible, High-Efficiency Polymer Light-Emitting Diodes Utilizing ITO-Free Polymer Anodes

This paper reports solution-processed, high-efficiency polymer light-emitting diodes fabricated by a new type of roll-to-roll coating method under ambient air conditions. A noble roll-to-roll cohesive coating system utilizes only natural gravity and the surface tension of the solution to flow out from the capillary to the surface of the substrate. Because this mechanism uses a minimally cohesive solution, the roll-to-roll cohesive coating can effectively realize an ultra-thin film thickness for the electron injection layer. In addition, the roll-to-roll cohesive coating enables the fabrication of a thicker polymer anode film more than 250 nm at one time by modification of the surface energy and without wasting the solution. It is observed that the standard sheet resistance deviation of the polymer anode is only 2.32 Ω/□ over 50 000 bending cycles. The standard sheet resistance deviation of the polymer anode in the different bending angles (0 to 180°) is 0.313 Ω/□, but the case of the ITO-PET is 104.93 Ω/□. The average surface roughness of the polymer anode measured by atomic force microscopy is only 1.06 nm. Because the surface of the polymer anode has a better quality, the leakage current of the polymer light-emitting diodes (PLEDs) using the polymer anode is much lower than that using the ITO-PET substrate. The luminous power efficiency of the two devices is 4.13 lm/W for the polymer anode and 3.21 lm/W for the ITO-PET. Consequently, the PLEDs made by using the polymer anode exhibited 28% enhanced performance because the polymer anode represents not only a higher transparency than the ITO-PET in the wavelength of 560 nm but also greatly reduced roughness. The optimized the maximum current efficiency and power efficiency of the device show around 6.1 cd/A and 5.1 lm/W, respectively, which is comparable to the case of using the ITO-glass.

A Study on the Relationships Between Static/Dynamic Cutting Force Components and Tool Wear

The development of flexible automation in the manufacturing industry is concerned with production activities performed by unmanned machining systems. A major topic relevant to metal-cutting operations is monitoring tool wear, which affects process efficiency and product quality, and implementing automatic tool replacements. In this paper, the measurement of the cutting force components has been found to provide a method for an in-process detection of tool wear. Cutting force components are divided into static and dynamic components in this paper. The static components of cutting force have been used to detect flank wear and the dynamic components of cutting force have been analyzed to detect crater wear. To eliminate the influence of variations in cutting conditions, tools, and workpiece materials, the relationships between normalized cutting forces and cutting conditions are established. According to the proposed method, the static and dynamic force components could provide the effective means to detect flank and crater wear for varying cutting conditions in turning operation.

Adaptive Fabrication of a Flexible Electrode by Optically Self-Selected Interfacial Adhesion and Its Application to Highly Transparent and Conductive Film

A novel adaptive electrode fabrication method using optically self-selected interfacial adhesion between a laser-processed metal layer and polymer film is introduced to fabricate cost-effectively a high-resolution arbitrary electrode with high conductivity. The quality is close to that from vacuum deposition on a highly heat sensitive polymer film, with active response to various design requirements. A highly conductive metal film (resistivity: 3.6 μΩ cm) below a 5 μm line width with a uniform stepwise profile and mirror surface quality (R(rms) : 5-6 nm) is fabricated on a cheap polymer film with a heat resistance limit of below 100 °C. Severe durability tests are successfully completed without using any adhesion promoters. Finally, a highly transparent and conductive electrode with a transparency above 95% and sheet resistance of less than 10 Ω sq⁻¹ is fabricated on a polymer film and on glass by using this method. These results can help realize a potential high-throughput, low-cost, solution-processable replacement for transparent conductive oxides.

In-process prediction of cutting depths in end milling

In geometric adaptive control systems for the end milling process, the surface error is usually predicted from the cutting force owing to the close relationship between them, and the easiness of its measurement. Knowledge of the cutting depth improves the effectiveness of this approach, since different cutting depths result in different surface errors even if the measured cutting forces are the same. This work suggests an algorithm for estimating the cutting depth based on the pattern of cutting force. The cutting force pattern, rather than its magnitude, better reflects the change of the cutting depth, because while the magnitude is influenced by several cutting parameters, the pattern is affected mainly by the cutting depth. The proposed algorithm can be applied to extensive cutting circumstances, such as presence of tool wear, change of work material hardness, etc.

A PC-NC milling machine with new simultaneous 3-axis control algorithm

Abstract Increasing demands on precision machining have necessitated that the tool move not only with a position error as small as possible, but also with smoothly varying feed rates. In this paper, a 3-axis PC–NC milling system, which is capable of synchronized simultaneous 3-dimensional (3D) machining, is developed. To achieve the synchronous 3D linear and circular motions, new interpolation algorithms based on the intersection criteria are presented. A real-time reference-pulse 3D linear and circular interpolator is developed using a PC to implement in the framework of the PC–NC milling machine reconfigured in this research. The performance test via computer simulation and actual machining have shown that the developed PC–NC milling system is useful for the machining of arbitrary lines and circles in 3D space.

Detection of cutting tool fracture by dual signal measurements

Abstract Fracture of a cutting tool is one of the most serious problems in machining systems. As a result, several methods have been proposed to detect cutting tool fracture. However, most of these have some problems from the viewpoint of practical application. In this study, the feasibility of using acoustic emission (AE) and cutting force signals for the detection of massive tool breakages as well as small fractures of the cutting tool were investigated. Turning experiments were performed using conventional carbide insert tools under realistic cutting conditions where S45C steel and the heat treated S45C steel were used as workpieces. The signal characteristics of the AE and cutting force components for the fracture of cutting tools were illustrated. The fracture of cutting tools was successfully detected through the analysis of these dual signals in the several types of tool fracture.

Enhanced Performance of a Polymer Solar Cell upon Addition of Free-Standing, Freshly Etched, Photoluminescent Silicon Nanocrystals

We demonstrate an organic–inorganic hybrid solar cell using poly(3-hexylthiophene) (P3HT)/[6,6]-phenyl-C61-butyric acid methyl ester (PCBM) and silicon nanocrystals (Si-NCs). To achieve an enhanced response in the hybrid layer, Si-NCs were freshly etched and blended with P3HT/PCBM. The incorporation of Si-NCs into the bulk heterojunction structure induced the coupling of optical excitation between the polymers and Si-NCs and led to an extended optical excitation response. A hybrid solar cell exhibited a 26% increase in JSC relative to an identical cell prepared without the Si-NCs. Consequently, improved power conversion efficiency is obtained by the addition of Si-NCs into polymers.

High-resolution and high-conductive electrode fabrication on a low thermal resistance flexible substrate

Processes based on the liquid-state pattern transfer, like inkjet printing, have critical limitations including low resolution and low electrical conductivity when fabricating electrodes on low thermal resistance flexible substrates such as polyethylene terephthalate (PET). Those are due to the nonlinear transfer mechanism and the limit of the sintering temperature. Although the laser direct curing (LDC) of metallic inks is an alternative process to improve the resolution, it is also associated with the disadvantages of causing thermal damage to the polymer substrate. This paper suggests the laser induced pattern adhesion transfer method to fabricate electrodes of both high electrical conductivity and high resolution on a PET substrate. First, solid patterns are cost-effectively created by the LDC of the organometallic silver ink on a glass that is optically and thermally stable. The solid patterns sintered on the glass are transferred to the PET substrate by the photo-thermally generated adhesion force of the substrate. Therefore, we achieved electrodes with a minimum line width of 10 ?m and a specific resistance of 3.6 ??cm on the PET substrate. The patterns also showed high mechanical reliability.