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This work presents a novel fabrication method for submicron to micro size textures on flat surfaces using the backside patterned texturing (BPT). The proposed method utilizes the pre-fabricated macro-features on the backside of work material, and thereafter the front side is face turned with a single point diamond tool to generate textured surfaces. Different from existing texturing methods, BPT produces textured surfaces from submicron to micro scale without any external gadgets such as vibration assisted machining or synchronized tool-spindle motion. The miniature feature arises on the diamond turned surface due to the induced residual stresses when the specimen is unleashed from the machine. To demonstrate the efficacy of the method, a series of machining experiments were conducted to fabricate various types of freeform surface textures like water-drop freeform, cylindrical freeform surfaces, etc. The fabrication methodology of different sizes of bumps with precisely controlled surface quality is illustrated. The texture profiles comprising the deformation height from hundreds of nanometer to few micrometers with mirror surface quality were successfully fabricated on the diamond machined surface. The experimental results suggest that the pre-fabricated pattern, workpiece thickness and machining condition play a critical role to determine the final shape and geometry of generated textures. ASTAR (Agency for Sci., Tech. and Research, S’pore) Accepted version

The dynamics of machine tools are greatly dependent on joints, since they add flexibility and damping to structures. In this study, the linear stiffness and damping of a joint in the transverse direction are obtained using two different methods: the inverse receptance coupling method and the new analytical joint identification (AJI) approach. The former approach finds the joint frequency response function by determining the difference between the response of the assembled structure and those of the substructures. However, the only required data for the AJI method are modal parameters of the assembled structure, which can be measured using experimental modal analysis. The accuracy of these methods is first investigated using numerical simulations. Experiments are then conducted on a structure consisting of two beams attached to one another in a lap joint. The proposed methods are utilized to experimentally extract the joint parameters in the transverse direction. Finally, the effects of varying the joint conditions, including surface roughness and the addition of interfacial materials, are investigated.

This article proposes a time domain model for predicting an end milling stability considering process damping caused by a variety of cross edge radiuses and flank profiles. The time domain model of calculating indentation areas, as well as regenerative dynamic uncut chips, is formulated for the prediction of the stabilizing effect induced by interference areas between the edge profiles and undulation left on a workpiece. The interference area generates forces against the vibration motion, which acts as a damping effect. In the model, the present and previous angular position of cross radiuses and flank edge profiles are located to calculate the dynamic uncut chip as well as indentation area based on a time history of the dynamic cutter center position. The phenomenon that chatter is damped according to cross edge radiuses and flank edge profiles is successfully simulated with the proposed dynamic model and validated through the extensive experimental tests.

A nano-texturing method in single point diamond turning using backside patterned workpiece is presented. The back side of the workpiece is pre-machined to first create a pattern. The front side is then diamond turned on an ultra-precision lathe. After machining down to a certain thickness, periodic bumps and valleys that mirror the back side pattern start to appear on the front diamond machined surface. The periodic wavy/bumpy surfaces have nanometer depths, and possess mirror finish. The results suggest that this technique provides an alternative method to create optical features that are conventionally developed using tool-spindle synchronized cutting motions.

Recently, vibration assistance has been mainly applied to feed and cross-feed directions for milling processes. This paper investigates the effect of ultrasonic vibration assistance in tooling’s axial direction for improvement of machined surface with reduction of chatter marks. With the designed ultrasonic vibration assisted milling process with 39.7 kHz and a few micro-meter amplitudes, workpiece vibrates along tooling’s axial direction while various cutting speeds and feed rates are applied. In addition to a cutter rotation motion, the axial directional vibration assistance acts as additional cutting motion which further reduces the leftover surface error. Experimental results validate that surface roughness can be improved with the reduced chatter marks through the axial directional vibration assistance for the tested conditions. Finally, process simulation demonstrates that milling stability can be enhanced with the tooling’s ultrasonic vibration assistance, which explains the experimental phenomenon of the chatter marks reduction of the mesoscale milling processes.

So far, the industrial application of ultrasonic vibration assistance has been successful in continuous machining process such as turning process where ultrasonic vibration velocity is much higher than cutting velocity. Recently, vibration assistance has been experimentally investigated to the intermittent milling process mainly for feed and cross- feed directions. This paper focuses on the effect of ultrasonic vibration assistance in spindle axial direction for improvement of machined surface. With the designed ultrasonic vibration assisted milling process with 39.7 kHz and a few micro-meter amplitudes, workpiece vibrates along spindle axial direction while different RPMs and feed rates are applied. The axial directional vibration assistance acts as additional cutting motion which further reduces the leftover surface error. Experimental results validate that surface roughness can be improved from 20 % to 65 % for the tested conditions. Apparently chatter marks of the milling process are reduced with the help of the axial ultrasonic vibration assistance.

In the conventional use of vibration assisted machining, vibratory motion is mostly applied to the continuous machining processes such as turning where the cutting speed is much lower than the vibration speed. Even the recent articles on vibration assisted milling processes are also quite limited to low spindle speed less than 3k RPM. This study investigates vibration assistance that is applied to the workpiece in a high speed micro/meso-scale intermittent milling system where the cutting speed is much higher than the vibration speed. In addition to this, the vibration effect is analyzed considering feed and cross-feed directional application separately, which gives an idea of a right vibration assistance direction for surface quality improvement. To validate this, a one-directional ultrasonic vibration assisted milling system with ultrasonic frequency at 40 kHz and with amplitudes of a few microns is designed and its effect on the machined surface quality is investigated at high spindle RPMs over 15k. As a result, cusp heights are found to be reduced with ultrasonic vibratory motion of cutting edge in high cutting speed. Furthermore, the machined surface quality clearly tells that feed directional vibration assistance is able to generate better surface quality with reduced wavy burrs than cross-feed directional vibration assistance.

One-directional ultrasonic vibration assisted milling system is designed and its performance is investigated in terms of machined surface quality under 135,000 rpm. The ultrasonic vibration generator excites the workpiece with a frequency around 40 kHz and amplitude of a few micro meters. The milling tool’s cutting speed is controlled by an air-bearing spindle system. Both feed-directional and cross-feed directional ultrasonic vibration assistance are considered in order to understand the mechanism of ultrasonic vibration assistance for surface roughness generation. A comparison is done on a milled surface which is generated with and without ultrasonic vibration assistance. The experimental results show that ultrasonic vibration assistance can improve the machined surface quality which depended on the cutting edge radius and the feed per tooth.

Chatter has been a problem in CNC machining process especially during pocket milling process using an end mill with low stiffness. Since an iterative time-domain chatter solution consumes a computing time along tool paths, a fast chatter prediction algorithm for pocket milling process is required by machine shop-floor for detecting chatter prior to real machining process. This paper proposes the systematic solution based on integration of a stability law in frequency domain with geometric information of material removal for a given set of tool paths. The change of immersion angle and spindle speed determines the variation of the stable cutting depth along cornering cut path. This proposed solution transforms the milling stability theory toward the practical methodology for the stability prediction over the NC pocket milling.

Plunge milling operations are used to remove excess material rapidly in roughing operations. The cutter is fed in the direction of spindle axis which has the highest structural rigidity. This paper presents time domain modeling of mechanics and dynamics of plunge milling process. The cutter is assumed to be flexible in lateral, axial, and torsional directions. The rigid body feed motion of the cutter and structural vibrations of the tool are combined to evaluate time varying dynamic chip load distribution along the cutting edge. The cutting forces in lateral and axial directions and torque are predicted by considering the feed, radial engagement, tool geometry, spindle speed, and the regeneration of the chip load due to vibrations. The mathematical model is experimentally validated by comparing simulated forces and vibrations against measurements collected from plunge milling tests. The study shows that the lateral forces and vibrations exist only if the inserts are not symmetric, and the primary source of chatter is the torsional–axial vibrations of the plunge mill. The chatter vibrations can be reduced by increasing the torsional stiffness with strengthened flute cavities.

Plunge milling operations are used to remove excess material rapidly in roughing operations. The cutter is fed in the direction of the spindle axis which has the highest structural rigidity. This paper presents a comprehensive model of plunge milling process by considering rigid body motion of the cutter, and three translational and torsional vibrations of the structure. The time domain simulation model allows prediction of cutting forces, torque, and vibrations while considering tool setting errors and time varying process parameters. The stability law is formulated as a four-dimensional eigenvalue problem, and the stability lobes are predicted directly with analytical solution in frequency domain. Time domain prediction of cutting forces and vibrations, as well as the frequency domain and chatter stability solution are verified with a series of plunge milling experiments.

Plunge milling operations are used to remove excess material in boring cylinders, roughing pockets, dies and mold cavities. This paper presents a frequency domain, chatter stability prediction theory for plunge milling. The regenerative chip thickness is modeled as a function of lateral, axial and torsional vibrations. The stability of the plunge milling is formulated as a fourth order eigenvalue problem by relating the regenerative chip thickness, cutting forces and torque, and the structural modes of the cutter. The stability lobes are predicted analytically from the eigenvalue solution. The stability lobes are experimentally proven by conducting over one hundred plunge milling tests.

Application of a ball-end milling process model to a CAD/CAM or CAPP system requires a generalized methodology to determine the cutting force coefficients for different cutting conditions. In this paper, we propose a mechanistic cutting force model for 3D ball-end milling using instantaneous cutting force coefficients that are independent of the cutting conditions. The uncut chip thickness model for three-dimensional machining considers cutter deflection and runout. An in-depth analysis of the characteristics of these cutting force coefficients, which can be determined from only a few test cuts, is provided. For more accurate cutting force predictions, the size effect is also modeled using the cutter edge length of the ball-end mill and is incorporated into the cutting force model. This method of estimating the 3D ball-end milling force coefficients has been tested experimentally for various cutting conditions.

This paper presents an analytical model of off-line feed rate scheduling to determine desired feed rates for 3D ball-end milling. Off-line feed rate scheduling is presented as the advanced technology to regulate cutting forces through change of feed per tooth, which directly affects variation of uncut chip thickness. In this paper, the uncut chip thickness is calculated by following the movement of the position of the cutter center, which is determined by runout and cutter deflection. Also, since the developed cutting force model uses the cutting-condition-independent coefficients, off-line feed rate scheduling can be effectively performed regardless of continuous change of cutting conditions. Transverse rupture strength of the tool is used to determine the reference cutting force at which resultant cutting forces are regulated through feed rate scheduling. Experiments validated that the presented feed rate scheduling model reduced machining time drastically and regulated cutting forces at the reference cutting force.

This paper presents a systematic and practical method for determining cutting-condition-independent coefficients in ball-end milling. An approach for estimating the runout offset and its location angle is also described based on a single cutting force measurement. An in-depth analysis of the characteristics of these cutting coefficients, which can be determined from only a few test cuts, is provided. The size effect is also modelled, including the characteristics of the ball-end mill geometry, and incorporated into the cutting force model. This method of estimating the 3D ball-end milling force coefficients was tested experimentally for various cutting conditions and gave excellent cutting force predictions. Also, the estimated values of the runout offset agreed well with the measurements.

This paper presents an advanced technology to automatically determine optimum feed rates for 2 1 2 axis CNC machining, without requiring the expertise of a machinist or the information contained in a machining data handbook. Present CAM technology does not consider important physical properties such as cutting forces and machined surface errors. However, the virtual machining system developed in this study can simulate real machining for a given set of NC codes. An analytical model for off-line feed rate scheduling is formulated to improve productivity and machining accuracy. Using this model, it is possible to regulate the cutting force, which drastically improves the overall form accuracy of the machined surface.

In this three-part paper, components of a virtual machining system for evaluating and optimizing cutting performance in 2 1 2 -axis NC machining are presented. Part 1 describes a new method of calculating cutting-condition-independent coefficient and its application to the prediction of cutting forces over a wide range of cutting conditions. The prediction of the surface form error and transient cutting simulations, described in Parts 2 and 3, respectively, can be effectively performed based on the cutting force model with the improved size effect model that is presented in Part 1. The relationship between the instantaneous uncut chip thickness and the cutting coefficients is calculated by following the movement of the center position of the cutter, which varies with nominal feed, cutter deflection and runout. The salient feature of the presented method is that it determines the cutting-condition-independent coefficients using experimental data processed for one cutting condition. The direct application of instantaneous cutting coefficient with size effects provides more accurate predictions of the cutting forces. A systematic comparison of the predicted and measured cutting forces over a wide range of cutting conditions confirms the validity of the proposed mechanistic cutting force and size effect models.

In part 2 of this three-part paper, a newly developed method that predicts the three-dimensional machined surface errors generated during the peripheral end milling process is presented. From the cutting force prediction system of Part 1, since the uncut chip thickness is calculated by tracing the movement of the cutter, the positions at which the cutting edges pass over the workpiece surface can readily be obtained. In this part of the paper these positions are used to construct surface error maps. In addition, by using the estimated locations of the peak and valley values of the cutting force component normal to the machined surface, a quantitative analysis of the machined surface error is given and followed by theoretical explanations. A series of machining tests on aluminum workpieces were conducted to validate the effectiveness of the model. The predicted cutting forces and surface errors were found in good agreement with their measured counterparts.

In Parts 1 and 2 of this three-part paper, a mechanistic cutting force model was developed and machined surface errors for steady cuts under fixed cutting conditions were predicted. The virtual machining system aims to simulate and analyze the machining and the machined states in a general flat end-milling process. This frequently involves transient as well as steady cuts. Therefore, a method for simulating the cutting process of transient cuts needs to be developed to realize the virtual machining system concept. For this purpose, this paper presents a moving edge-node (ME) Z-map model for the cutting configuration calculation. The simulation results of four representative transient cuts in two-dimensional pocket milling and an application of off-line feed-rate scheduling are also given. In transient cuts, the cutting configurations that are used to predict the cutting force vary during the machining operation. The cutting force model (Part 1) and surface error prediction method (Part 2) were developed for steady cuts; these are extended to transient situations using the ME Z-map model to calculate the varying cutting configurations efficiently. The cutting force and surface errors are then predicted. To validate the feasibility of the proposed scheme, the measured and predicted cutting forces for transient test cuts were compared. The predicted surface error maps for transient cuts were constructed using a computer simulation. Also, off-line feed-rate scheduling is shown to be more accurately performed by applying the instantaneous cutting coefficients that were defined in Part I.

A clock and data recovery circuit with a phase-locked loop for 10 Gb/s optical transmission system was realized in a hybrid IC form. The quadri-correlation architecture is used for frequency- and phase-locked loop. A NRZ-to-PRZ converter and a 360 degree analogue phase shifter are included in the circuit. The jitter characteristics satisfy the recommendations of ITU –T. The capture range of 150 MHz and input voltage sensitivity of 100 mVp-p were showed. The temperature compensation characteristics were tested for the operating temperature from –10 to 60 o C and showed no increase of error. This circuit was adopted for the 10 Gb/s transmission system through a normal single-mode fiber with the length of 400 km and operated successfully.

A SDH overhead terminator chip set has been designed for 10 Gbit/s optical transmission system. The chip set built on 0.6 /spl mu/m CMOS technology and 0.6 /spl mu/m H-GaAs III MESFET technology successfully realizes the functions needed for regenerator section termination and multiplex section termination with alarm detection and generation, and performance monitoring. This paper introduces a novel multiplexing structure for parallel processing of the STM-64 frame signal and describes the architecture of the chip set.

This article introduces a time domain model of side and plunge milling stability by considering cutting edge radius as well as dynamic motion of cutter center. Dynamic uncut chip thickness generated by side, plunge and ultrasonic milling can be simulated by tracking the cutter center positions at the present and previous vibrations with phase difference. Finally, the dynamic uncut chip thickness models as well as the mechanistic cutting force coefficients considering cutting edge radius are integrated into the time domain model. Especially, cross edge radius varies due to tool wear which affects cutting force coefficients and dynamics as well. Finally, the machining stability and vibrations are estimated using an identified transfer function and predicted cutting forces through the time domain solution. Experimental tests are compared against predicted results for validation of the proposed model.