Milling Depth Research Articles

Experimental and numerical investigations of machining depth for glass material in electrochemical discharge milling

Electrochemical discharge milling (ECDM) is one of the best alternatives for microchannel fabrication in non-conducting materials. The ECDM is a complex process which makes difficult the prediction of the material removal rate (MRR). The prediction of the machining depth in the microchannel fabricated with electrochemical discharge milling (ECD milling) was an interesting research subject. This study attempts to present a thermal model based on the finite element method (FEM) to predict the machining depth in ECD milling. The input parameters of the FEM model were calculated based on different machining conditions such as machining voltages and electrolyte concentrations. The model is validated by conducting experiments in the same ECD milling conditions. In the FEM model, the different criteria for the material removal temperature (Teq) were applied and the machining depths were calculated. The comparisons of the results show that there is good agreement between FEM models and experimental results when the Teq were selected between 600 to 850°C. It seems that the softening Littleton point of 720°C is a good suggestion as a criterion for the material removal temperature in ECD milling.

An improved fix-length compensation method for electrical discharge milling using tubular tools

Abstract Due to inevitable wear of electrodes in micro electrical discharge machining (μEDM), compensation of tools is of great importance to maintain machining accuracy. Among all of the compensation strategies, fix-length compensation method is one of the most efficient ways for cavity milling because large single layer thickness can be achieved. However, previous studies have shown that slots with triangle-shape cross section are formed, and extra processing has to be performed to remove the surface fluctuations, which degrade machining accuracy and lower total efficiency. To improve the traditional fix-length compensation method, in this work, the cylindrical tool is replaced by the tubular tool, and a truncated conic tool end is observed in experiments. An analytical model is then developed relating the truncated conic shape to fix-length compensation parameters. This analytical model is then used to determine the machining parameters, which correspond to a preset milling depth. The effects of key parameters on plane machining are predicted by the analytical model and verified through double slots machining experiments, which show high machining accuracy can be reached under any overlapping ratios and target depths. Finally, the presented machining method is further validated by machining a rectangular cavity and a cavity with a circular pattern. Machining results prove the depth accuracy of the proposed method can be controlled within 4 μm.

Investigation on critical cutting depth in milling of wave-transmitting Si3N4 ceramics

Wave-transmitting Si3N4 ceramics exhibits high levels of brittleness, and the milling surface inevitably exists defects. Critical cutting depth is an important reference parameter to improve the surface quality and processing efficiency in milling. A theoretical mathematical model has been proposed to predict the critical cutting depth in the study. The contact relationship between the tool cutting edge and the ceramics surface is analyzed, and the non-uniform bearing crack system is established. The micro cracks propagation critical condition has been put as the criterion of critical cutting depth. Through the model calculation, the critical cutting depth is 0.38 mm, and it is confirmed the critical cutting depth is between 0.3 and 0.4 mm with experimental results. The model predictions are consistent well with the experimental results. In addition, the theoretical model shows that the critical cutting depth decreases exponentially with the increase of the material hardness, while the increase of fracture toughness, tool helix angle and side edge rear angle, leads to critical cutting depth rising. The theoretical model can be applied to evaluate the critical cutting depth of brittle ceramics in milling.

Reducing curtaining effects in FIB/SEM applications by a goniometer stage and an image processing method

In the last two decades, focused ion beam (FIB) systems have been used for sample preparation. For example, the edges of a sample can be polished for analytical measurements or continuous cross-sections can be milled for three-dimensional (3D) tomography and reconstruction. One major challenge in both procedures is the so-called curtaining effect, i.e., increasing surface roughness in the direction of the milling depth. The roughness of the cut can influence the result of the measurement and the segmentation process. In the present study, the authors report on two different methods to reduce the curtaining effect, namely, a hardware- and a software-based solution. For instance, Tescan implemented the so-called “rocking stage” in its plasma FIB. However, this is not available for other FIB systems. Therefore, for our FEI gallium FIB, an inhouse-developed goniometer stage is installed, which can be adapted as necessary. With this relatively inexpensive solution, the sample can be rotated around an additional axis and tilted by ±8°. Different sample heights are adjustable, and the sample's edge can be polished and imaged without stage movement. However, for automated milling and imaging procedures such as 3D tomography, such a tilting stage is not feasible. Therefore, as a second option, an image processing method is proposed that can be applied after the milling procedure on a whole image stack. A novel variation of this method for mathematical image processing is developed to reduce milling artifacts. Besides the curtaining effect, additional artifacts such as discontinuities caused by redeposition of previously removed materials or charging effects can be removed. The method is applied to the entire 3D dataset, and distortions are reduced by using information of their particular structure and directional dependence. The resulting new image stack can then be used to compose a 3D volume reconstruction. As an example, the geometries of silicon carbide particles reinforcing an aluminum matrix can be measured with nearly no milling artifacts.

Optimization of process parameters for minimum energy consumption based on cutting specific energy consumption

In order to reduce the energy consumption of machine tool, the process parameters were optimized by the optimization model with the cutting specific energy consumption (CSEC) and the processing time. Based on the energy consumption characteristics of the numerical control (NC) machine tool, the energy consumption module of NC machine tool was analyzed. The power composition of machining process which was based on energy consumption module was proposed, and then CSEC was given with the cutting process parameters. The optimization model to minimum cutting specific energy consumption and minimum processing time was established with the process parameters under the actual constraint conditions in the manufacturing process. The multi-objective optimization model was transformed into the single objective optimization model by introducing the subjective and objective comprehensive weights and solved by the quantum genetic algorithm. When the optimization goal was to trade off processing time and CSEC to reduce the energy consumption, the selecting of the milling parameters should consider the complex effect if the constraints could be met with, large feed speed and large milling depth could benefit if the constrains of milling process were met with. The processing energy consumption of optimized process parameters decreased 27.21% compared with that of preferred process parameters while CSEC was reduced 32.07% and the processing time was reduced 34.11%. The proposed approach in this paper provided an efficient solution to reduce the impact of the environment caused by energy consumption and to realize the sustainable manufacturing.

Investigation of processing parameters for three-dimensional laser ablation based on Taguchi method

Laser ablation is a high-efficiency, high-precision, and very flexible process for removal material which has been widely used in many industrial applications, such as semiconductor, electronic, aerospace, and other fields. With the development of modern manufacturing industry, the application of laser ablation technology needs to be expanded to meet the growing demand of three-dimensional processing. A method named laser ablation by projective galvanometer scanning (LPAGS) can effectively apply laser ablation technology to three-dimensional processing field. For three-dimensional processing, the machining results are strongly affected by the processing parameters. Optimal selection of process parameters is highly critical for successful material removal and achieving high surface quality. In this paper, the effects of processing parameters including laser incident angle, scan speed, laser power, and fill spacing on ablation depth and surface roughness were studied in detail. An orthogonal experiment based on Taguchi method was used to determine the optimal processing direction for minimizing the surface roughness and maximizing the milling depth. The typical structural patterns were fabricated on surface of aluminum by using a LPAGS processing system. Signal/noise ratio (S/N ratio) and analysis of variance (ANOVA) were employed to investigate the optimal levels of processing parameters. The analysis results indicated that laser incident angle and laser power have significant effect on the ablation depth with 48.02 and 39.67% contribution, and laser incident angle, laser power, and scan speed are most significant parameters with 40.88, 24.66, and 30.16% contribution on surface roughness.

Study of milling on Al2O3 ceramic/GFRP component using sintering diamond tools

Al2O3 ceramic/Glass fibre-reinforced plastics are difficult to cut materials. Milling technology on component made of them is studied in this paper. First, influence of feed force, spindle speed and milling depth on milling efficiency was studied; then, influence of feed speed, spindle speed and milling depth on milling force was analysed; single-factor tests were also carried out to study milling force empirical formula. The results show: (1) feed force is the most significant factor influencing the efficiency, and is positively related with it, but overlarge feed force also lowers milling efficiency; influencing order is feed force > milling depth > spindle speed; (2) high milling efficiency and better processing quality can be achieved under 2600 r/min in spindle speed, 5 mm in milling depth and 770 N in feed force; (3) feed speed is the most significant factor influencing milling force and influencing order is feed speed > milling depth > spindle speed; and (4) milling force decreases with the increase in spindle speed, and increases when milling depth and feed speed increase.

A Systematic Approach for Online Minimizing Volume Difference of Multiple Chambers in Machining Processes Based on High-Definition Metrology

The volume variation of multiple chambers of a workpiece is one of the most important factors that can directly influence the performance of the final product. This paper presents a novel systematic approach for online minimizing the volume difference of multiple chambers of a workpiece based on high-definition metrology (HDM). First, the datum of high-density points is transformed by a random sample consensus (RANSAC) algorithm due to its good robustness in fitting. Second, a procedure containing reconstruction of interior curved surfaces of chambers, boundary extraction, and projection is developed to calculate the accurate volumes of the multiple chambers. Third, a model for obtaining an optimized machining parameter for depth of chambers is explored to minimize the volume difference of any two ones of all the chambers. The model is formulated as a multi-objective optimization (MOO) problem, and a new procedure of multi-objective particle swarm optimization (MOPSO) algorithm is developed to solve this problem. Finally, a milling depth is output as the optimal milling parameter for controlling the volume variation of multiple chambers. The results of a case study show that the proposed approach can minimize the volume difference of four combustion chambers of a cylinder head and it can be well applied online in volume variation control of multiple chambers in machining processes.

Fabrication of high-aspect-ratio microgrooves using an electrochemical discharge micromilling process

In this study, we created high-aspect-ratio microgrooves in hard, brittle materials using an electrochemical discharge machining (ECDM) process by introducing microtextured machining tool. To enhance the electrical discharge activity, the morphology of the tool side surface was treated via micro-electrical discharge machining to produce fine microprotrusive patterns. The resulting microtextured surface morphology enhanced the electric field and played a key role in improving the step milling depth in the ECDM process. Using the FEM analysis, the evaluation of the field enhancement factor is also addressed. Our experimental investigation revealed microgrooves having an aspect ratio of 1:4, with high geometric accuracy and crack-free surfaces, using one-step ECDM.

Magnetic property (T ∼ 300 K) originated from InZnP:Ag nano-rods fabricated with noble metal Ag using ion milling method

Abstract The well aligned InZnP:Ag nano-rods doped with noble metal Ag were fabricated using ion milling method. Results for XPS coincide with results for AES, especially Ag 3d5. The uniformity, density, and height of InZnP:Ag nano-rods were well formed in TEM measurements. In order to clarify the formation of InZnP:Ag nano-rods, SEM was carried out due to the doping of Ag. XRD measurements were performed in order to support the above TEM results, it is confirmed that the lattice was well aligned without distortion and that the nano-rod was a single crystalline zinc blende structure. The variation of FWHM for TAD peaks demonstrates that noble metal Ag is incorporated into InZnP:Ag nano-rods. The trend of FWHM results coincides with the trend of TEM results according to ion milling depth. The clear opening of the ferromagnetic hysteresis loop indicates the formation of ferromagnetic spin coupling interaction in InP:Zn doped with Ag. The FC M-T curve clearly displays that the ferromagnetism of InZnP:Ag persists near 300 K.

In-Vehicle Evaluation of Milled Rumble Strips in Pre– and Post–Chip Seal Maintenance Periods

Driver fatigue and drowsiness can have a profound impact on safety. Centerline and shoulder rumble strips are popular countermeasures designed to produce audible and tactile warning when vehicles deviate from the travel lane onto the rumble strips. These warnings reduce the risk of lane departure crashes. Studies show that the noise produced by rumble strips is a function of many variables. Rumble strip depth is known to have the greatest impact in alerting drivers. However, chip seal pavement maintenance operations tend to reduce the original rumble strip design depth, which may have an impact on the functional effectiveness of the rumble strips. The purpose of this study was to conduct a controlled experiment to understand the relationship between milled rumble strip depth and noise and vibration in the vehicle cab. In-vehicle noise and vibration levels were collected on rumble strips of five depths (⅛, ¼, ⅜, ½, and ⅝ in.) and three types (shoulder, single centerline, and double centerline) on three highways in the state of Nebraska by two vehicles traveling at speeds of 45, 55, and 65 mph. Rumble strip depths at ⅛-in. intervals were used to simulate the influence of a chip seal on rumble strip effectiveness. From the in-vehicle sound and vibration levels of all the tested rumble strip depths, it can be hypothesized that a ⅛-in. reduction in the current milled rumble strip design depth, as a result of chip sealing, would not cause a practical reduction in the effectiveness of rumble strips producing audible and tactile warnings to alert drivers.

A prediction-correction scheme for microchannel milling using femtosecond laser

In this paper, a prediction-correction scheme is proposed to online measure and regulate the milling depth of microchannel using an indicator of laser triggered plasma. Firstly, a prediction model, with respect to the laser fluence and feedrate, is established with several calibration tests using the least square fitting method. It is utilized to change the focal position of objective to track the depth evolution of newly generated surface. Meanwhile, a scanning path for every milling layer with an offset in Z-axis at the beginning and the end of the trajectory, is developed to drive the plasma brightness periodically changing. Then, the milling depth could be obtained when the brightness reaches to the maximum value. By doing so, an online measurement method is presented to estimate the milling depth using the trend of plasma brightness. Furthermore, a correction model is developed to iteratively adjust the feedrate with the online estimated depth. Therefore, the microchannel milling process could be monitored and controlled in a closed-loop manner, in order to accurately regulate the milling depth. Finally, an online measurement and closed-loop microchannel milling is carried out on the self-developed micro-machining center. The effectiveness and correctness of the proposed method are verified by comparing the estimated depth with the actually measured results.

ЭКСПЕРИМЕНТАЛЬНОЕ ИССЛЕДОВАНИЕ ПРОЦЕССА ФОРМИРОВАНИЯ ПОКАЗАТЕЛЕЙ КАЧЕСТВА ПРИ ФРЕЗЕРОВАНИИ СТЕКЛОПЛАСТИКА

Composite materials are widely used in mechanical engineering, but at edge cutting machining, in particular, during milling these materials a number of peculiarities arise which must be taken into account at the definition of cutting modes and design-geometrical parameters of cutters. Besides, new composite materials machining does not allow using effectively the recommendations developed earlier. In such a way, to solve such a problem it is necessary to carry out experimental investigations on the analysis of the influence of milling mode characteristics and design-geometrical of a tool upon values of roughness of a surface processed and tool wear. As a cutter for investigations there were taken hardmetal endmilling cutters of TC-8 (tungstencobalt) type, the experimental samples – pipes made of composite material with oblique longi-tudinal-transverse fiber winding (OLTFW). As varied parameters were adopted cutting modes: cutting speed V, m/min, feed S, mm/tooth and milling depth t, mm. During the experiments were controlled the following parameters: tool wear Δ, mkm, roughness of the surface Ra, mkm and a depth of a faulty layer h, mkm.
 To carry out the experiments there was offered an original design of an assembly milling cutter which allows defining in an experimental way optimum geo-metrical parameters of a tools to achieve output milling parameters specified. On the basis of experiments data there are obtained dependences allowing the estimate of parameter modes influence upon the period of cutter duration at the same time a temperature is affected mostly by a milling depth and a feed on a tooth affects the wear of an end flank.

Stability analysis in milling of the thin walled part considering multiple variables of manufacturing systems

In order to improve the precision of the milling stability analysis, the more exact milling dynamic model considering multiple variables of manufacturing systems is proposed, and in order to reduce the calculation time for the stability analysis of the milling dynamic model, the fast calculation of the stability analysis is proposed. Firstly, the contact region of the milling cutter and the thin walled part is discretized into many small intervals, the milling dynamic model considering helix angle of the milling cutter, two degrees of freedom of the thin-walled part, and coupling dynamic characteristic of the tool–spindle system is established in a discrete small interval. The dynamic model in the small discrete interval considering multiple variables is transformed into equation of states, and the equation of states is integrated in the range of the milling depth to establish the milling dynamic model considering multiple variables of manufacturing systems. Secondly, in order to enhance the calculation speed of the stability analysis for the established dynamic model considering multiple variables, and to avoid the loss of information, the sampling rule of the delay term is defined based on the sampling rule of Shannon sampling theorem, and the delayed term is reconstructed in the discrete interval by using the Shannon interpolation function, and the validity of the fast calculation of the stability analysis is verified by two degrees of the freedom milling dynamic model. Finally, the validity of the established milling dynamic model considering multiple variables is verified by milling experiment, and the results show that the established dynamic model is effective.

An approach for using iterative learning for controlling the jet penetration depth in abrasive waterjet milling

This paper presents a new methodology for controlling the jet penetration in abrasive waterjet milling. The generation of milled parts by means of abrasive waterjet is traditionally done by trial and error, relying mainly on the operator's expertise. An Iterative Learning Control (ILC) based approach is proposed to improve the prediction and correction of depth of the generated jet footprints in a systematic way every time the same part is milled. This approach utilizes a P-type (proportional) ILC algorithm to control the milling process, and uses a geometrical model based on non-linear partial differential equations for predictions of footprints to provide a fast convergence to the process input and reducing errors. The experimental validations of this approach were carried out using a Titanium alloy (Ti6Al4V) workpiece where a slope-varying profile was generated using 220 mesh grit-size abrasives with 0.04kg/min mass flow rate and 1380bar pressure. The results show that the achieved depth accuracy is indeed improved by more than 50% after four iterations when using this approach; providing basis for generating precision freeform surfaces using abrasive waterjet machines in a controlled manner.

Experimental Study of Thin Wall Milling Chatter Stability Nonlinear Criterion

The nonlinear dynamic behavior of milling process has been accompanied by the entire cutting process. In order to accurately determine and predict chatter stability of machining process, this article studied at both ends of the fixed thin part nonlinear criterion of milling chatter stability with experimental method. The experiment takes the vibration signal of thin part as the study object. And it analyses the vibration signal of different processing parameters based on the phase plane method, Poincare method and spectral analysis. Then, the relationship between the maximum Lyapunov exponent and the spindle speed and milling depth changes is discussed. Finally, taking the largest Lyapunov exponent as the criterion, the study determines the chatter stability domain of milling by using contour method. The comparative analysis is based on the milling chatter stability domain which obtained from the full discrete method. The experiments obtained the nonlinear stability criterion of aviation aluminium alloy 7075-T6 thin part.

Experimental Study on Cutting Forces at Ti6Al4V Milling

In this paper is presented an experiment whose aim is to determine the cutting forces that appear when machining Ti6Al4V titanium alloy, in order to optimize its working rate and productivity. This experiment uses carbide coated milling tools for milling titanium alloy. It has studied the influence that milling parameters have upon the three dimensional cutting forces. The equipment which was used included stationary dynamometer for measuring cutting forces, with piezoelectric transducers. The cutting force model is developed in terms of cutting speed, feed rate, axial depth and length of milling (radial depth), with values established according to response surface methodology in intervals from the specialised literature. Titanium alloys are a continuous challenge. This paper is important because is getting relevant results for improving manufacturing efficiency.

The linear inverse problem in energy beam processing with an application to abrasive waterjet machining

The linear inverse problem for energy beam processing, in which a desired etched profile is known and a trajectory of the beam that will create it must be found, is studied in this paper. As an example, abrasive waterjet machining (AWJM) is considered here supported by extensive experimental investigations. The behaviour of this process can be described using a linear model when the angle between the jet and the surface is approximately constant during the process, as occurs for shallow etched profiles. The inverse problem is usually solved by simply controlling dwell time in proportion to the required depth of milling, without considering whether the target surface can actually be etched. To address this, a Fourier analysis Is used to show that high frequency components in the target surface cannot be etched due to the geometry of the jet and the dynamics of the machine. In this paper, this frequency domain analysis is used to improve the choice of the target profile in such a way that it can be etched. The dynamics of the machine also have a large influence on the actual movement of the jet. It is very difficult to describe this effect because the controller of the machine is usually unknown. A simple approximation is used for the choice of the slope of a step profile. The tracking error between the desired trajectory and the real one is reduced and the etched profile is improved. Several experimental tests are presented to show the usefulness of this approach. Finally, the limitations of the linear model are studied.

Surface finish and affected layer in milling of fine crystal grained stainless steel

When the removal depth in micro milling is downsized, the effect of the crystal grain in material becomes relatively large. The crystal grain in materials, therefore, should be downsized to achieve high qualities and high reliabilities of the micro devices. The study discusses the effect of the crystal grain size on the surface finish, burr formation and the affected layer in micro milling of stainless steel. The crystal grains are reduced to an average size of 1.5μm by repetition of material forming and phase transformation. The milling tests were performed to measure the cutting forces, the surface finishes, the burr shapes and the thicknesses of the affected layers. The force component ratio of the fine grained steel is higher than that of the standard steel. The shearing force decreases in cutting of the fine grained steel; meanwhile, the friction and/or the indentation forces increase. Burr formation is reduced when the crystal grain size is small. In cutting of the standard steel, X component in the cutting force suddenly drops near the end of the groove and a large burr is formed on the edge of the groove. The affected layer largely depends on the crystal grain size. The thickness of the affected layer remarkable decreases in milling of the fine grained steel.

English

Metal cutting is one of the most significant manufacturing processes in the area of material removal. Black defined metal cutting as the removal of metal chips from a work piece in order to obtain a finished product with desired attributes of size, shape, and surface roughness. The imperative objective of the science of metal cutting is the solution of practical problems associated with the efficient and precise removal of metal from work piece. It has been recognized that the reliable quantitative predictions of the various technological performance measures, preferably in the form of equations, are essential to develop optimization strategies for selecting cutting conditions in process planning. In this thesis experiments will be conducted to improve the surface finish quality of a nickel alloy Inconel 625 work piece by using carbide tips. The type is bull nose tip. A series of experiments will be done by varying the milling parameters spindle speed, feed rate and depth of cut. The spindle speeds are 3000rpm, 2500rpm and 2000rpm. The feed rates are 200mm/min, 300mm/min and 400mm/min. Depth of cut is 0.2mm and 0.3mm. Structural analysis will be also done to verify the strength. Modeling will be done in Pro/Engineer and analysis will be done in Ansys. Taguchi method is used to study the effect of process parameters and establish correlation among the cutting speed, feed and depth of cut with respect to the major machinability factor, surface finish. Validations of the modeled equations are proved to be well within the agreement with the experimental data. I. LITERATURE SURVEY In the paper by Dražen Bajic, etal [1] , examines the influence of three cutting parameters on surface roughness, tool wear and cutting force components in face milling as part of the off-line process control. The experiments were carried out in order to define a model for process planning. Cutting speed, feed per tooth and depth of cut were taken as influential factors. In the paper by K. Adarsh Kumar, etal [2] , Surface finish is