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Experiments and simulations of micro-hole manufacturing by electrophoresis-assisted micro-ultrasonic machining
Accepted Manuscript Title: Experiments and Simulations of Micro-hole manufacturing by Electrophoresis-assisted Micro-ultrasonic Machining Authors: J.F. He, Z.N. Guo, H.S. Lian, J.W. Liu, Y. Zhen, Y. Deng PII: DOI: Reference:
S0924-0136(18)30388-1 https://doi.org/10.1016/j.jmatprotec.2018.08.046 PROTEC 15911
To appear in:
Journal of Materials Processing Technology
Received date: Revised date: Accepted date:
7-4-2018 18-7-2018 30-8-2018
Please cite this article as: He JF, Guo ZN, Lian HS, Liu JW, Zhen Y, Deng Y, Experiments and Simulations of Micro-hole manufacturing by Electrophoresisassisted Micro-ultrasonic Machining, Journal of Materials Processing Tech. (2018), https://doi.org/10.1016/j.jmatprotec.2018.08.046 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Experiments and Simulations of Micro-hole Manufacturing by Electrophoresisassisted Micro-ultrasonic Machining J.F. Hea,b, Z.N. Guoa,b, H.S. Lianc, J.W. Liua,b, Y. Zhena,b, Y. Denga,b,* a
School of Electromechanical Engineering, Guangdong University of Technology, Guangzhou 510016,
P.R. China b
Guangzhou Key Laboratory of Nontraditional Machining and Equipment, Guangzhou 510006,
c
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P.R. China
School of Electromechanical Engineering, Lingnan Normal University, Zhanjiang 524048, P.R. China
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*Corresponding author: Y. Deng.
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Tel: 86-20-39322412; Fax: 86-20-39322412; Email: [email protected]
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ABSTRACT
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Electrophoresis-assisted micro-ultrasonic machining (EPAMUSM) is an effective method for
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solving the problem of using traditional micro-ultrasonic machining (MUSM) to fabricate microholes in materials that are hard and brittle, namely the low utilization ratio of abrasive particles.
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EPAMUSM uses an electric field to attract the abrasive particles to the processing area during processing, which is useful for improving both the utilization ratio of abrasive particles and the
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processing quality. Numerical simulations of the concentration distributions of abrasive particles in MUSM and EPAMUSM show that the abrasive concentration on the tool surface is much higher in
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EPAMUSM. The concentration increases rapidly from 1 mol/m3 to 4.68 mol/m3 after 10 s in EPAMUSM. Comparative experiments show that EPAMUSM has advantages over MUSM under the same processing conditions: the EPAMUSM edge chipping rate (0.03) is much less than the
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MUSM one (0.22) and the EPAMUSM material removal rate (1.916×10−4 mm3/min) is marginally better than the MUSM one (1.718×10−4 mm3/min). Single-factor experiments are used to study how varying certain parameters (namely DC voltage, ultrasonic power, and spindle speed) affects EPAMUSM manufacturing quality and efficiency. Finally, the processing parameters are optimized by means of response-surface experiments, and the optimum EPAMUSM processing parameters are determined (namely an applied voltage of 7.5 V, an ultrasonic power of 22.5 W, a spindle speed of 1
300 rpm, and a mass fraction of 10%).
Keywords: Hard-brittle material; Ultrafine abrasive particles; Electrophoresis-assisted machining; Micro-ultrasonic machining.
1. Introduction
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With the increasing industrial demand for micro-products, advanced manufacturing technologies are being developed continuously (Rajurkar et al., 2006). The use of precision parts in
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the manufacturing of micro-products has created new micro-manufacturing process requirements,
such as those in terms of the microstructure (Zhao et al., 2008). Hard and brittle materials are commonly used in microstructure manufacturing, but their physical characteristics can make them
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difficult to process; in particular, edge chipping (EC) is inevitable during processing. Micro-
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ultrasonic machining (MUSM) is an effective way to process microstructures made of hard-brittle
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materials (Hu et al., 2006; Kandaa et al., 2006). Kumar and Singh. (2018) used rotary ultrasonic machining (RUM) to drill holes in BK-7 optical glass and then scrutinized the spindle speed, feed
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rate, and ultrasonic power to evaluate the machining proficiency in terms of the surface roughness
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and the material removal rate (MRR). Wang et al. (2018) used RUM combined with diamond grinding with small-amplitude tool vibration to improve the machining of hard and brittle materials. This technique was applied successfully to the machining of a number of brittle materials, including
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optical glasses, advanced ceramics, and ceramic matrix composites. However, traditional ultrasonic machining has some inherent limitations (Tateishi et al., 2009),
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one being the low utilization ratio of abrasive particles (Tateishi et al., 2009). MUSM results from the comprehensive mechanical impact and polishing effect of the abrasive particles under the actions of ultrasonic vibration and cavitation, the main factor being the impact of the free abrasive particles.
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Under the impact of a large number of free abrasive particles, the surface of workpiece starts to form microstructure. The impacting effect of the free abrasive particles is shown schematically in Fig. 1.
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Fig. 1. Impacting effect of free abrasive particles.
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Agarwal (2015) investigated the mechanism of the MRR for glass when using ultrasonic
machining. That analysis showed that material is removed mainly by micro-brittle fracture on the
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workpiece surface. For this fracture mode, a relationship with abrasive particles and manufacturing
quality was established for the MRR based on simple fracture mechanics and considering the abrasive grains impacting the workpiece directly. Tateishi et al. (2009) discovered that ultrasonic
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vibration of the micro-tool or workpiece and rotation of the micro-tool expelled abrasive particles from the machining region, leaving none therein in the worst case. This increases the likelihood of
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the tool touching the workpiece directly, leading to unwanted EC and low MRR.
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Simulation modeling is an effective method for studying particle motion. The motion of
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abrasive particles in electrophoresis-assisted ultrasonic machining is yet to be reported, but some scholars have studied particle tracking in other area. Zheng et al. (2018) studied the electrical
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characteristics of particle transport by considering the electrohydrodynamics and the effect of particle space charge through numerical simulation. The influence of particle space charge is
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considered in particle motion and is thus worthy of reference in practical application. Guha et al. (2007) used non-invasive computer-automated radioactive particle tracking to study the solids flow
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field in dense solid–liquid suspensions. That method provides a Lagrangian description of the solids flow field, which is then used to obtain time-averaged velocity fields and turbulent quantities. Because of the electrophoretic characteristics of the ultrafine abrasive particles,
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electrophoresis-assisted micro-ultrasonic machining (EPAMUSM) can attract the abrasive particles to the processing area by means of an electric field during processing. Herein, the manufacture of high-quality micro-holes by EPAMUSM during micron-level processing is studied. The trajectories of the abrasive particles are predicted by modeling and simulation. The proposed technique raises the MRR and lowers the edge chipping rate (ECR) significantly in micro-hole manufacturing. The effects of the EPAMUSM parameters on the machining quality based on the electrophoretic features 3
of the ultrafine particles are studied, whereupon the parameters are optimized to make high-quality micro-holes in silicon.
2. Method and materials 2.1. Mechanism of EPAMUSM EPAMUSM is proposed to address the problem of low utilization ratios of abrasive particles
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and also to reduce EC and improve the MRR. In electrophoresis, charged particles move toward
their opposite polarities in an electric field (Cai, 2008; Feng et al., 2009). In addition to wetting,
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spreading, and adsorption, the ultrafine abrasive particles (which are in contact with the working
solution as a solid gel core in solution) often exhibit electrification (Peng et al., 1999). When ions are adsorbed on the surface of an abrasive particle, the particle becomes charged. Oppositely
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charged ions then diffuse to the vicinity of the gel core, and a special electric double-layer structure
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appears at the solid–liquid interface of the gel core. Because of the stronger attraction of the gel core
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to the adsorbed layer than to the diffusion layer, the gel core splits from the diffusion layer under the action of an external electric field, which is the phenomenon of electrophoresis. Charged
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particles move toward the poles, resulting in directional migration of the ultrafine abrasive particles
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in solution. In EPAMUSM, by controlling the electric field, the abrasive particles can overcome the vibration and centrifugal force during processing. This ensures that there are always enough particles in the processing area, thereby improving the abrasive-particle utilization ratio (Lian et al.,
2014).
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2016), processing quality (Zarepour and Yeo, 2012), and processing efficiency (Anupam et al.,
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As shown in Fig. 2, EPAMUSM is a new type of hybrid manufacturing process in which an
adjustable DC power supply and an electrophoresis auxiliary electrode are integrated into MUSM technology. Consequently, a constant electric field is formed between the auxiliary electrode and
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the micro-tool so that the particles in the working fluid are charged and attracted to the machining tool. This guarantees the concentration of particles in the processing area.
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Fig. 2. Schematic of electrophoresis-assisted micro-ultrasonic machining (EPAMUSM).
The machining experiment was performed on a self-developed micro-machining system, as shown in Fig. 3. Its main components are an electrophoresis-assisted system, an ultrasonic-vibration
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spindle system, a control system, and data acquisition. The electrophoresis-assisted system
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comprises an auxiliary electrode for electrophoresis, a DC power supply, a solution containing
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particles, and a tank for the working fluid. The ultrasonic-vibration spindle system comprises a spindle, an ultrasonic transducer, and a power supply. The spindle rotation speed is adjustable in the
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range 0-1,500 rpm. The spindle is attached to a sliding table and fixed to vertical column of the multifunctional system and supplies the rotational motion of the micro-tool. With a diameter of
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roughly 100 μm, the micro-tool was prepared by block-electrode discharge. The control system and data acquisition comprise mainly a dynamometer, an analog-to-digital converter, an amplifier, and
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a three-dimensional motion platform (M-L03K008; Physik Instrumente, Germany). The platform’s motion is controllable with a resolution of 0.1 μm. The working-fluid tank is installed on the moving
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platform.
Fig. 3. Experimental setup of EPAMUSM. 5
2.2. Materials The micro-tool was used to fabricate holes in workpieces with both EPAMUSM and MUSM. The workpiece material was monocrystalline silicon (workpiece size: 20 mm × 10 mm × 0.6 mm) that was provided by Lijing Materials Co., Ltd. The micro-tool was made of WC-Co that was provided by Hongming Carbide Co., Ltd., and its length and nominal diameter were 30 mm and 100 μm, respectively. The abrasive particles were made of diamond that was provided by the
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Fangyuan Diamond Co., Ltd., with nominal diameters of 0.1 μm. The auxiliary electrode for electrophoresis had a nominal diameter of 30 mm and was made of brass that was provided by
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Yonghao Metal.
The surface morphology and EC were analyzed using a confocal laser scanning microscope (OLY4000; Olympus, Japan), a white-light interferometer (Contour GT-X; Bruker, USA), and a
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scanning electron microscope (S-3400N; Hitachi, Japan).
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2.3. Numerical simulation
In this study, EPAMUSM was modeled and simulated using COMSOL Multiphysics 4.4. The
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particle tracking model is an important part of COMSOL Multiphysics and can be coupled to other
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physical fields such as flow fields and electric fields. The particle tracking model has three modes: charged particle tracking, fluid particle tracking, and mathematical particle tracking. Particle–field interaction can be realized by accessing the particle tracking model through the interface which built
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into the COMSOL physics field, thereby achieving multi-physics coupling. Charged particle tracking is commonly used to study the trajectories of electrons and ions in
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an electric field, such as in magnetic lenses, electron guns, and mass spectrometers. At the same time, phase trajectories and Poincaré maps can be extracted easily to draw particle trajectories. Fluid particle tracking uses a precise physics field to track particle trajectories in a fluid system.
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Predefined tensions, gravity, and other forces are easily loaded into the model if required. In other words, physical particle trajectories can be studied, such as those in electrophoresis, dielectrophoresis, and magnetophoresis. Mathematical particle tracking provides sufficient flexibility and freedom for particle-tracking equations of motion by specifying equations for particle motion by using equations such as Lagrangian or Hamiltonian mechanics. Particle tracking describes the problem in terms of Lagrange’s equation and uses Newton’s 6
Second Law of Motion is used to cast the problem as an ordinary differential equation. In threedimensional space, the position of a particle is determined by three-dimensional coordinates, thereby requiring three equations to determine the three coordinates. In the particle tracking model, an ordinary differential equation described by Lagrang e’s equation is used to solve for each coordinate. Simplifying the model into two dimensions means that two ordinary differential equations are needed to determine the position of each particle. Because the particle tracking model
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uses a general computational method to calculate particle trajectories, it can be applied equally to
the motions of (i) charged particles in the electromagnetic fields of large planets and galaxies and
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(ii) particles in laminar, turbulent, and multiphase flow systems. In the present study, the charged and fluid particle tracking models were used to model the movement of abrasive particles.
During EPAMUSM, the abrasive particles can be considered to be affected by both the flow
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field and the electric field. The location of a particle can be simplified as
(1)
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𝐺(𝐿, 𝐹) = 𝐿 + 𝐹
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where 𝐹 describes the motion of a particle in a fluid based on Newton’s Second Law, and 𝐿 represents the equation of motion of a charged particle in an electric field and is derived from
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Lagrange’s equation:
𝐯
(2)
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𝐿 = −𝑚𝑝 𝑐 2√1 − 𝐯 · 𝑐 2 + 𝑞𝐀 · 𝐯 – 𝑞𝑉
where 𝑚𝑝 is the particle mass, 𝑐 is the speed of light, 𝐯 is the particle velocity, 𝑞 is the particle
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charge, 𝐀 is the magnetic vector potential, and 𝑉 is the scalar potential. However, because the particles move far slower than light, 𝐿 can be simplified as follows by neglecting electrodynamic
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effects:
𝑑
𝐿(𝑚, 𝐯, 𝑉) = 𝑑𝑡 (𝑚𝑝 v) =
𝑚𝑝 v2 2
– 𝑞𝑉
(3)
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Assuming that the particles experience a fluid drag force when they move in the solution, then 1
𝒇𝑫 = ( ) 𝑚𝑝 (𝐮 − 𝐯) 𝜏p
(4)
where 𝜏p is the response time of the particles and 𝐮 is the fluid velocity. The force of gravity on the particles in solution is assumed to be 𝒇 𝒈 = 𝑚𝑝 𝐠
(𝜌p −𝜌z )) 𝜌p
(5)
where 𝜌p is the particle density, 𝜌z is the density of the surrounding fluid, and 𝐠 is the 7
gravitational acceleration vector. If an electric field is applied to the solution, the associated force can be expressed as 𝒇𝒆𝒙𝒕 = e𝒁𝑬
(6)
where e is the elementary charge, 𝒁 is the electric charge, and 𝑬 is the electric field intensity. Accordingly, the equation of motion of a particle in the fluid can be expressed as 𝑑 𝑑𝑡
(𝑚𝑝 v) = 𝒇𝑫 + 𝒇𝒈 + 𝒇𝒆𝒙𝒕
(7)
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𝐹(𝑓𝑫 , 𝑓𝒈 , 𝑓𝒆𝒙𝒕 ) =
The motion of an EPAMUSM abrasive particle is affected primarily by the drag force, ultrasonic vibration, electric force, and solution viscosity. Therefore, the model shown in Fig. 4
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includes only the main micro-ultrasonic tool, the electrophoresis auxiliary electrode, and the working fluid containing charged abrasive particles.
According to the requirements of the experimental equipment, a geometric model is established.
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The gap between the electrophoresis auxiliary electrode and the micro-tool is 30 mm, the diameter
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of the micro-tool is 100 μm, and the height of the solution domain is 10 mm. A free mesh is used to
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divide the particles, which are distributed uniformly with an initial concentration of 1 mol/m3 and a
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particle diameter of 0.1 μm. The particles are released either singly or continuously. The tool voltage is set to 5 V and the auxiliary electrode voltage to 0 V. Each abrasive grain is given unit charge. The
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model abrasive particles are spherical, and the abrasive solution is treated as an incompressible fluid.
Fig. 4. Simplified model of EPAMUSM.
Next, the effects of material properties, laminar flow, fluid particle tracing, current, grid
movement, and other parameters are incorporated into the multi-physical field model (flow field and electric field). These field models are added simultaneously with actual processing. The relevant properties are listed in detail in Tables 1 and 2. A transient finite-element solver was used to calculate the simulation model.
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Table 1. Material properties Value
Unit −3
Dynamic viscosity Solution density Specific heat rate Electric conductivity Atmospheric heat capacity Thermal conductivity
1.01×10 1,000 1.0 5.5×10−6 4.18 0.60
Pa·s kg/m3 J/(kg·K) S/m kJ/(kg·K) W/(m·K)
Table 2. Simulation parameters Value
Unit
Amplitude Vibration frequency Applied voltage (DC) Initial concentration of abrasive Rotation speed
3 60 5 1 500
μm kHz V mol/m3 rpm
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Name
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Property
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A constant voltage is utilized between the electrophoretic auxiliary electrode and the tool, thereby generating an electrophoretic auxiliary electric field between them. According to the
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principle of potential distribution, the potential is highest at the tool surface and decreases gradually
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along the direction of the electrophoresis auxiliary electrode. The electric field lines point toward
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the auxiliary electrode, and negatively charged particles gather near the tool.
2.4. Experimental procedure
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Three experimental investigations were performed related to the ECR and MRR. The first compared the manufacturing quality between MUSM and EPAMUSM, the second investigated the
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effects of electrophoretic voltage, spindle speed, and ultrasonic power on the ECR and MRR in EPAMUSM by means of single-factor experiments, and the third optimized the processing
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parameters by means of response-surface experiments. The ECR can be calculated as
𝐸𝐶𝑅 =
𝛷−𝐷 𝐷
(8)
where 𝛷 is the EC diameter and D is the diameter of the machined micro-hole. The MRR can be calculated as
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𝑀𝑅𝑅 =
𝐷 2
𝜋·( )2 ·𝑑
(9)
𝑇
where 𝑑 is the depth of the micro-hole and 𝑇 is the time taken to machine it. For the experiments to compare MUSM and EPAMUSM, the common machining parameters are listed in Table 3.
Value
Mass fraction Spindle speed Feed speed Feed depth Abrasive particle size Ultrasonic power Applied voltage (EPAMUSM only)
5% 500 rpm 0.5 μm/s 100 μm 0.1 μm 20 W 5 V (DC)
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Parameter
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Table 3. Common machining parameters for comparison of MUSM and EPAMUSM
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Single-factor experiments were conducted to study parametric effects on the ECR and MRR in micro-hole manufacturing. The parameters specific to EPAMUSM are listed in Table 4.
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Parameter
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Table 4. EPAMUSM machining parameters
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Abrasive particle size Feed speed Feed depth Ultrasonic power Applied voltage (DC) Spindle speed Mass fraction
Value 0.1 μm 0.5 μm/s 100 μm 20–70 W 3–15 V 300–700 rpm 5%
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In EPAMUSM, improving machining efficiency is as important as improving machining quality. Generally, with micro-holes, the MRR is used to evaluate machining efficiency and the ECR is used to evaluate machining quality. Several factors affect the machining efficiency, such as ultrasonic power, spindle speed, particle mass fraction, and applied voltage. The machining
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parameters were optimized through response-surface experiments and the processing parameters by studying the interactions among them; the experimental parameters and levels are listed in Table 5. Each test was repeated three times and the results were averaged. Table 5. Machining parameters and levels. Index
Parameter
Level
A:
Applied voltage (V)
5–10
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B: C: D:
Spindle speed (rpm) Ultrasonic power (W) Mass fraction (%)
100–500 10–35 5–15
3. Results and discussion 3.1. Numerical simulations
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The distributions and trajectories of abrasive particles with and without electrophoresis were compared. With an electrophoresis time of 10 s, a tool radius of 100 µm, an auxiliary voltage of 5 V, a vibration frequency of 60 kHz, and rotation speed of 500 rpm, the concentration of particles on
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the tool surface varies with time as shown in Fig. 5. Fig. 5(a) shows the results for zero
interelectrode voltage (i.e., without electrophoresis). The rotation and vibration expel the abrasive particles near the tool from the processing area. Those abrasive particles in the traditional MUSM
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processing area are expelled and the ratio of particle utilization is low. In contrast, Fig. 5(b) shows
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that the electrophoretic electric field causes the abrasive particles to gather around the tool; the
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electric field influences the movement of the abrasive particles appreciably and improves their utilization ratio. As shown in Fig. 5(c), electrophoresis assists abrasive particles to concentrate near
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the tool. After 10 s, the maximum particle concentration in the processing area is 4.68 mol/m3, and
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the concentration decreases gradually with distance from the tool surface.
Fig. 5. Abrasive particle trajectories under various physical conditions: (a) no electric field; (b) electric field; (c) contours of abrasive-particle concentration near tool. 11
The abrasive concentration in the processing area is determined by the combined effects of electric force, centrifugal force, drag force, ultrasonic vibration, and viscous resistance. Fig. 6 shows how the particles are distributed at different times. The charged particles clearly move toward the tool electrode under the action of the electric field, and the abrasive concentration near the tool electrode increases with time. Specifically, the electrophoretic auxiliary voltage influences the particle aggregation was analyzed. The results fully indicate that the electric field improves the
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abrasive-particle concentration.
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Fig. 6. Distribution of abrasive particles at various times: (a) 0 s; (b) 3 s; (c) 6 s; (d) 10 s. Next, Fig. 7 shows how various parameters affect the particle concentration. Particles were
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released continuously, and the solving time was 100 s. Clearly, the larger the applied voltage, the easier the ultrafine abrasive particles are adsorbed on the tool surface. For a fixed quantity of charge,
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the greater the electrophoresis voltage, the greater the force on the ultrafine abrasive particles propelling them toward the tool electrode. Therefore, when the average particle size is relatively large, increasing the electrophoretic voltage allows the abrasive particles to overcome the resistance
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toward the tool electrode and ensure their sufficient presence in the processing area. Fig. 7 shows that the concentration index of the abrasive particles decreases with both the
rotation speed and the ultrasonic power. This is because the viscosity of the liquid ensures that the solution near the processing area is rotated accordingly and when the rotation speed and ultrasonic power are increased, the abrasive particles in the solution are affected more by the centrifugal force and the ultrasonic vibration, whereby an outward force is generated. This expels abrasive particles 12
from the processing area, thereby decreasing their utilization rate. Such an explanation is consistent
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with the results presented herein.
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Fig. 7. Influences of different parameters on abrasive-particle concentration.
A set of experiments was conducted to analyze the motion of abrasive particles in the electrophoretic field and verify the simulation results. The applied voltage was 5 V, the power was
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20 W, and the spindle speed was 500 rpm. The effects of abrasive-particle aggregation on the tool
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are shown in Fig. 8. There is clearly no abrasive aggregation or surface adhesion without an electric
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field, even though the tool is soaked in abrasive solution. This can be interpreted as there being no
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electric field between the auxiliary electrode for electrophoresis and the micro-tool, meaning that abrasive particles cannot aggregate in the processing area. Fig. 8(b) shows the tool after
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electrophoretic assistance. After 30 s, a thin layer of abrasive particles is attracted onto the surface of tool as the external diameter of the tool increases. Fig. 8(c) and (d) show scanning electron
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microscopy (SEM) surface images with and without electrophoresis, respectively, and energy-
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dispersive X-ray (EDX) spectra.
Fig. 8. Abrasive-particle morphologies on electrophoresis-assisted tool: (a) surface without 13
electrophoresis; (b) surface with electrophoresis; EDX spectra and SEM images (c) with and (d) without electrophoresis. The EDX spectra and SEM images of the tool surfaces indicate that no diamond particles were found on the surface of the tool without electrophoresis, for which the EDX spectra show that the main components were W and Co. In contrast, Fig. 8(d) shows that 92.822% of the material on the surface processed with the assistance of electrophoresis was carbon, meaning that abrasive particles
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are attracted to the tool surface via electrophoresis.
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3.2. Experimental study of rates of edge chipping and material removal by EPAMUSM 3.2.1. Comparison of MUSM and EPAMUSM
To show the superiority of EPAMUSM over MUSM, a comparative experiment was conducted
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to highlight the advantages of EPAMUSM over MUSM regarding the ECR and MRR. Fig. 9(a) and
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(b) show the differences in ECR and MRR between MUSM and EPAMUSM. As shown in Fig. 9(a), because of the electrophoresis assistance, the EPAMUSM ECR (0.03) is much less than the MUSM
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one (0.22), and in Fig. 9(b) the EPAMUSM MRR (1.916×10−4 mm3/min) is marginally better than
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the MUSM one (1.718×10−4 mm3/min). This is because EPAMUSM guarantees that the abrasive particles are used at a certain rate, thereby enhancing the mechanical impact of particles on the
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workpiece. When the voltage is increased, the MRR also increases, thereby enhancing the MRR of the workpiece. Fig. 9(c) shows a micro-hole processed with traditional MUSM, the quality of which
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is poor because of edge issues. Fig. 9(d) shows a corresponding micro-hole fabricated by EPAMUSM, for which there are far fewer edge issues. When electrophoresis is applied at 5 V DC,
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the concentration of particles in the processing area increases. The particles are attracted to the processing area, thereby preventing the tool from hammering the workpiece directly. These consequences are confirmed through the SEM images that are shown in Fig. 9(c) and (d).
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The SEM images illustrate the bottom surfaces of micro-holes that are manufactured by MUSM and EPAMUSM, respectively. There are clearly more particles embedded in the bottom of the EPAMUSM hole, whereas there are few such particles in the MUSM one. This shows that the particles are cleared away from the processing area in MUSM, with the consequence that the microtool grinds the workpiece directly. This also verified that in EPAMUSM, more abrasive particles are involved in the processing, indicating that the electrophoresis-assisted technology can effectively 14
improve the utilization of abrasive particles in ultrasonic processing. Moreover, it can be seen from the results that increasing the utilization rate of abrasive grains has a certain influence on processing quality and processing efficiency. The superiority of electrophoresis-assisted ultrasonic machining is proven. Increasing the MRR and decreasing the ECR as much as possible would improve the processing efficiency, so it is necessary to study the effects of the EPAMUSM parameters on quality and
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efficiency.
Fig. 9. The quality and efficiency of micro-holes fabricated with micro-ultrasonic machining
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(MUSM) and EPAMUSM: (a) edge chipping rate (ECR); (b) material removal rate (MRR); (c) MUSM images; (d) EPAMUSM images (5 V).
3.2.2. Effect of excessive applied electrophoresis voltage
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The electrophoresis voltage clearly has an appreciable impact on the micro-hole machining
quality. In Fig. 10(a), increasing the applied voltage above 10 V worsens the EC. When the applied voltage is 5 V, 8 V, and 15 V, the ECR is 0.03, 0.06, and 0.15, respectively. The initial effect of increasing the applied voltage is to increase the concentration of particles in the machining area, thereby avoiding direct hammering between the workpiece and the tool. However, too many particles in the machining gap can block the removal of machining debris and weaken the vibrations, 15
which has a negative effect on the machining quality. When the applied voltage is less than 10 V, the ECR is less than 0.07. When the voltage is less than 5V, the ECR rises slightly. This shows that when the voltage is low, the attraction of the electric field to the abrasive particles is insufficient to overcome the ultrasonic vibration and repulsion generated by the tool rotation. At this time, the concentration of the abrasive particles is insufficient. This causes the ECR to rise. Fig. 10(a) shows how the MRR varies with applied voltage. When the applied voltage is
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increased from 3 to 15 V, The MRR first increases and then decreases. This is because the electric
field leads to there being ever more particles in the machining area. The higher the voltage, the more
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particles are driven into the machining area, thereby increasing the MRR from 1.81 to 2.29×10−4 mm3/min (the voltage increased from 3 to 8 V). However, with more particles in the
machining gap, a particle layer accumulates and covers the micro-hole and the tool. This blocks the
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removal of machining debris and weakens the vibrations, thereby decreasing the MRR once the
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voltage exceeds 8 V. The quality of micro-holes is shown in Fig. 10(b) and (c); the ECR and size of
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the micro-hole are both clearly somewhat larger for the higher voltage.
Fig. 10. (a) Variations of ECR and MRR of EPAMUSM micro-holes produced with applied
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voltage. (b) and (c) EPAMUSM micro-holes produced with applied voltages of (b) 5 V and (c) 15 V.
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3.2.3. Effect of excessive ultrasonic power The ultrasonic power also has considerable influence on the ECR and MRR of micro-hole
manufacturing. Fig. 11(a) shows how the ECR and MRR vary with ultrasonic power. The lowest ECR (0.06) was recorded for a power of 20 W (the corresponding hole is shown in Fig. 11(b)), and the MRR was 2.03×10−4 mm3/min. However, when the ultrasonic power was increased to 35 W, some defects began to appear around the micro-hole, leading to an ECR of 0.17. Increasing the ultrasonic power further to 70 W led to a potentially unacceptable ECR of 0.27 (the corresponding 16
hole is shown in Fig. 11(c)). With sufficient ultrasonic power, the abrasive particles can overcome the electrical attraction and escape from the machining gap. This leads to more direct hammering between the tool and the workpiece, leading to EC. The MRR is affected appreciably by the ultrasonic power. Fig. 11(a) shows the MRR clearly decreases as the ultrasonic power is increased from 20 to 35 W and then increases as the power is increased from 35 to 70 W. The latter effect is due to increased ultrasonic vibration energy during
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processing. Although this leads to a direct increase in MRR, it also drives the abrasive particles out of the machining area, thereby reducing their concentration in the processing area. Considering the
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ECR curve in Fig. 11(a), this effect clearly also increases the ECR. The quality of micro-holes
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produced with ultrasonic powers of 20 and 70 W is shown in Fig. 11(b) and (c), respectively.
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Fig. 11. (a) Variations of ECR and MRR of EPAMUSM micro-holes with ultrasonic power. (b) and (c) EPAMUSM micro-holes produced with ultrasonic powers of (b) 20 W and (c) 70 W. 3.2.4. Effect of excessive spindle speed
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Fig. 12(a) shows the effect of spindle speed. The impact of spindle speed on the ECR and MRR is demonstrated in Fig. 12 (a). As shown in Fig. 12(b), a spindle speed of 300 rpm leads to a high-
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quality micro-hole with an ECR of 0.03 and an MRR of 2.02×10−4 mm3/min. However, as the spindle speed increases, edge cracks become more severe; as shown in Fig. 12(c), a spindle speed of 700 rpm results in an ECR of 0.12. The tool rotation causes the surrounding working fluid to
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rotate because of its viscosity, meaning that the abrasive particles also rotate. A higher spindle speed means a greater centrifugal force acting on the particles; this helps the particles to escape from the machining gap, thereby reducing the concentration of abrasive particles. Again, because higher spindle speed means greater centrifugal force on the solution, some abrasive particles in the solution are expelled from the processing area as the spindle speed increases. This reduction in the number of free abrasive particles reduces the mechanical impact on the 17
workpiece, thereby decreasing the MRR. The quality of micro-holes produced with spindle speeds
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lower and higher than this value is shown in Fig. 12(b) and (c), respectively.
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Fig. 12. (a) Variations of ECR and MRR of EPAMUSM micro-holes with spindle speed. (b) and (c) EPAMUSM micro-holes produced with spindle speeds of (b) 300 rpm and (c) 700 rpm.
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3.3. Response-surface experiments on MRR and ECR
Based on the results of the single-factor experiments discussed in the previous subsection,
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some parameter values were selected that are appropriate for response-surface experiments. Fig. 13
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shows the interaction with MRR [Fig. 13(a)] and ECR [Fig. 13(b)] of each factor (ultrasonic power,
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spindle speed, particle mass fraction, and applied voltage). Analyzing the interactions among the
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different factors leads to the optimum EPAMUSM processing parameters.
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(a) MRR response surfaces
(b) ECR response surfaces Fig. 13. Effects of EPAMUSM processing parameters on MRR and ECR.
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From the above results, the optimal parameters for EPAMUSM machining quality and efficiency are an applied voltage of 7.5 V, an ultrasonic power of 22.5 W, a spindle speed of 300 rpm, and a mass fraction of 10%. High-quality micro-holes were manufactured by using those parameters (MRR: 2.08×10−4 mm3/min; ECR: 0.03).
4. Conclusions
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In this paper, based on the electrophoretic features of the particles in the solution, EPAMUSM technology can be used to solve the problems related to ECR and MRR in traditional MUSM. The
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present results show that the microscopic abrasive particles are attracted around the tool in
EPAMUSM, thereby reducing appreciably the EC caused by direct hammering between the tool and the workpiece, and also increasing the MRR somewhat. EPAMUSM has certain advantages over
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MUSM. Based on the present results from simulations and experiments, the following conclusions
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can be drawn.
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The simulation results indicate that electrophoresis greatly improves the concentration of abrasive particles near the tool. From the adsorption experiment, the SEM images and EDX spectra
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of tool surfaces show that abrasive particles are attached to the tool surface in EPAMUSM, thereby
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improving their utilization rate in the processing area. The comparative experiments show that EPAMUSM has advantages over MUSM. Under the same processing conditions, EPAMUSM improves the ECR considerably (down to 0.03 from 0.22)
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and also increases the MRR somewhat (up to 1.916×10−4 mm3/min from 1.718×10−4 mm3/min). More abrasive particles were discovered embedded in the bottom of the EPAMUSM micro-holes,
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showing that more abrasive particles were involved in the processing. Through single-factor experiments and response-surface experiments, by analyzing the
interactions among different factors, the optimum EPAMUSM processing parameters were obtained,
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namely an applied voltage of 7.5 V, an ultrasonic power of 22.5 W, a spindle speed of 300 rpm, and a mass fraction of 10%. The high-quality micro-holes were manufactured by using those parameters (MRR: 2.08×10−4 mm3/min; ECR: 0.03). Acknowledgments This research was supported by the National Natural Science Foundation of China (grant no. 20
51575113), the National Natural Science Foundation of China and Guangdong Province (grant no. U1601201), the Foshan Municipal Science and Technology Bureau project (grant no. 2015IT100162), the Science and Technology Planning Project of Guangdong Province (2016A010102017), the special support plan of Guangdong Province (grant no. 2014TQ01X542), the Fundamental Research Funds for the Central Universities (grant no. 2015ZZ080), and the
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National Natural Science Foundation of China (grant no. 51705228). References
Int. J. Machine Tools Manufac. 96, 1–14.
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Agarwal., S., 2015. On the mechanism and mechanics of material removal in ultrasonic machining.
Anupam, V., Tao, L., Yogesh, G., 2014. High resolution micro ultrasonic machining for trimming 3D microstructures. J. Micromech. Microeng. 24, 494–497.
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Cai., P., 2008. The advancement and application on electrophoretic technique. Life Sci. Instrum. 8,
N
3–7.
A
Feng, H., Jing, Z., Fang, Y., Mo., S., 2009. Two-dimensional electrophoresis and its application.
M
Biotechnol. Bull. 1, 59–63.
Guha, D., Ramachandran, P.A., Dudukovic, M.P., 2007. Flow field of suspended solids in a stirred
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tank reactor by Lagrangian tracking. Chem. Eng. Sci. 62, 6143–6154. Hu, X., Yu, Z., Rajurkar, K.P., 2006. State-of-the-art review of micro ultrasonic machining.
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International Conference on Manufacturing Science and Engineering, 2006, 1017–1024. Kandaa, T., Makinoa, A., Onoa, T., Suzumoria, K., Moritab, T., Kurosawa, M.K., 2006. A micro
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ultrasonic motor using a micro-machined cylindrical bulk PZT transducer. Sensors and Actuators A: Physical 127, 131–138.
Kumar, V., Singh, H., 2018. Machining optimization in rotary ultrasonic drilling of BK-7 through
A
response surface methodology using desirability approach. J. Brazilian Soc. Mech. Sci. Eng. 40, 83–97.
Lian, H.S., Guo, Z.N., Liu, J.W., Huang, Z.G., He., J.F., 2016. “Experimental study of electrophoretically assisted micro-ultrasonic machining,” International Journal of Advanced Manufacturing Technology, 85, 2115-2124. Peng, W., Xu, X., He, X., Chen, Z., 1999. An electrophoresis grinding process and its application. 21
China Mech. Eng. 10, 85–88. Rajurkar, K.P., Levy, G., Malshe, A., Sundaram, M.M., Mcgeough, J., Hu, X., Resnick, R., DeSilva, A., 2006. Micro and nano machining by electro-physical and chemical processes. CIRP Annals: Manufac. Technol. 55, 643–666. Tateishi, T., Shimada, K., Yoshihara, N., Yan, J.W., Kuriyagawa, T., 2009. Control of the behavior of abrasive grains by the effect of electrorheological fluid assistance-study on
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electrorheological fluid-assisted micro ultrasonic machining. Adv. Mater. Res. 76, 696–701.
Tateishi, T., Shimada, K., Yoshihara, N., Yan, J.W., Kuriyagawa, T., 2009. Effect of
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electrorheological fluid assistance on micro ultrasonic machining. Adv. Mater. Res. 69, 148– 152.
Tateishi, T., Yoshihara, N., Yan, J., Kuriyagawa, T., 2009. Study on electrorheological fluid-assisted
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micro-ultrasonic machining. Int. J. Abrasive Technol. 2, 70–82.
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Wang, J., Zhang, J., Fenga, P., Guo., P., 2018. Damage formation and suppression in rotary
A
ultrasonic machining of hard and brittle materials: a critical review. Ceramics Int. 44, 1227– 1239.
M
Zarepour, H., Yeo., S.H., 2012. Predictive modeling of material removal modes in micro-ultrasonic
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machining. Int. J. Machine Tools Manufac. 62, 13–23. Zhao, W.S., Gu, L., Kang, X., Jiang, Y., Li, L., Wang, D., Duan, J.Y., 2008. Latest advances of
14.
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nontraditional machining technology-review of ISEM-XV. Electromachining & Mould, 1, 4–
Zheng, C.H., Zhang, X.F., Yang, Z.D., Liang, C.S., Guo, Y.S., Wang, Y., Gao., X., 2018. Numerical
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simulation of corona discharge and particle transport behaviour with the particle spacecharge
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effect. J. Aerosol Sci. 118, 22–33.
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S0924-0136(18)30388-1 https://doi.org/10.1016/j.jmatprotec.2018.08.046 PROTEC 15911
To appear in:
Journal of Materials Processing Technology
Received date: Revised date: Accepted date:
7-4-2018 18-7-2018 30-8-2018
Please cite this article as: He JF, Guo ZN, Lian HS, Liu JW, Zhen Y, Deng Y, Experiments and Simulations of Micro-hole manufacturing by Electrophoresisassisted Micro-ultrasonic Machining, Journal of Materials Processing Tech. (2018), https://doi.org/10.1016/j.jmatprotec.2018.08.046 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Experiments and Simulations of Micro-hole Manufacturing by Electrophoresisassisted Micro-ultrasonic Machining J.F. Hea,b, Z.N. Guoa,b, H.S. Lianc, J.W. Liua,b, Y. Zhena,b, Y. Denga,b,* a
School of Electromechanical Engineering, Guangdong University of Technology, Guangzhou 510016,
P.R. China b
Guangzhou Key Laboratory of Nontraditional Machining and Equipment, Guangzhou 510006,
c
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P.R. China
School of Electromechanical Engineering, Lingnan Normal University, Zhanjiang 524048, P.R. China
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*Corresponding author: Y. Deng.
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Tel: 86-20-39322412; Fax: 86-20-39322412; Email: [email protected]
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ABSTRACT
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Electrophoresis-assisted micro-ultrasonic machining (EPAMUSM) is an effective method for
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solving the problem of using traditional micro-ultrasonic machining (MUSM) to fabricate microholes in materials that are hard and brittle, namely the low utilization ratio of abrasive particles.
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EPAMUSM uses an electric field to attract the abrasive particles to the processing area during processing, which is useful for improving both the utilization ratio of abrasive particles and the
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processing quality. Numerical simulations of the concentration distributions of abrasive particles in MUSM and EPAMUSM show that the abrasive concentration on the tool surface is much higher in
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EPAMUSM. The concentration increases rapidly from 1 mol/m3 to 4.68 mol/m3 after 10 s in EPAMUSM. Comparative experiments show that EPAMUSM has advantages over MUSM under the same processing conditions: the EPAMUSM edge chipping rate (0.03) is much less than the
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MUSM one (0.22) and the EPAMUSM material removal rate (1.916×10−4 mm3/min) is marginally better than the MUSM one (1.718×10−4 mm3/min). Single-factor experiments are used to study how varying certain parameters (namely DC voltage, ultrasonic power, and spindle speed) affects EPAMUSM manufacturing quality and efficiency. Finally, the processing parameters are optimized by means of response-surface experiments, and the optimum EPAMUSM processing parameters are determined (namely an applied voltage of 7.5 V, an ultrasonic power of 22.5 W, a spindle speed of 1
300 rpm, and a mass fraction of 10%).
Keywords: Hard-brittle material; Ultrafine abrasive particles; Electrophoresis-assisted machining; Micro-ultrasonic machining.
1. Introduction
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With the increasing industrial demand for micro-products, advanced manufacturing technologies are being developed continuously (Rajurkar et al., 2006). The use of precision parts in
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the manufacturing of micro-products has created new micro-manufacturing process requirements,
such as those in terms of the microstructure (Zhao et al., 2008). Hard and brittle materials are commonly used in microstructure manufacturing, but their physical characteristics can make them
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difficult to process; in particular, edge chipping (EC) is inevitable during processing. Micro-
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ultrasonic machining (MUSM) is an effective way to process microstructures made of hard-brittle
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materials (Hu et al., 2006; Kandaa et al., 2006). Kumar and Singh. (2018) used rotary ultrasonic machining (RUM) to drill holes in BK-7 optical glass and then scrutinized the spindle speed, feed
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rate, and ultrasonic power to evaluate the machining proficiency in terms of the surface roughness
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and the material removal rate (MRR). Wang et al. (2018) used RUM combined with diamond grinding with small-amplitude tool vibration to improve the machining of hard and brittle materials. This technique was applied successfully to the machining of a number of brittle materials, including
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optical glasses, advanced ceramics, and ceramic matrix composites. However, traditional ultrasonic machining has some inherent limitations (Tateishi et al., 2009),
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one being the low utilization ratio of abrasive particles (Tateishi et al., 2009). MUSM results from the comprehensive mechanical impact and polishing effect of the abrasive particles under the actions of ultrasonic vibration and cavitation, the main factor being the impact of the free abrasive particles.
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Under the impact of a large number of free abrasive particles, the surface of workpiece starts to form microstructure. The impacting effect of the free abrasive particles is shown schematically in Fig. 1.
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Fig. 1. Impacting effect of free abrasive particles.
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Agarwal (2015) investigated the mechanism of the MRR for glass when using ultrasonic
machining. That analysis showed that material is removed mainly by micro-brittle fracture on the
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workpiece surface. For this fracture mode, a relationship with abrasive particles and manufacturing
quality was established for the MRR based on simple fracture mechanics and considering the abrasive grains impacting the workpiece directly. Tateishi et al. (2009) discovered that ultrasonic
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vibration of the micro-tool or workpiece and rotation of the micro-tool expelled abrasive particles from the machining region, leaving none therein in the worst case. This increases the likelihood of
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the tool touching the workpiece directly, leading to unwanted EC and low MRR.
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Simulation modeling is an effective method for studying particle motion. The motion of
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abrasive particles in electrophoresis-assisted ultrasonic machining is yet to be reported, but some scholars have studied particle tracking in other area. Zheng et al. (2018) studied the electrical
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characteristics of particle transport by considering the electrohydrodynamics and the effect of particle space charge through numerical simulation. The influence of particle space charge is
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considered in particle motion and is thus worthy of reference in practical application. Guha et al. (2007) used non-invasive computer-automated radioactive particle tracking to study the solids flow
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field in dense solid–liquid suspensions. That method provides a Lagrangian description of the solids flow field, which is then used to obtain time-averaged velocity fields and turbulent quantities. Because of the electrophoretic characteristics of the ultrafine abrasive particles,
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electrophoresis-assisted micro-ultrasonic machining (EPAMUSM) can attract the abrasive particles to the processing area by means of an electric field during processing. Herein, the manufacture of high-quality micro-holes by EPAMUSM during micron-level processing is studied. The trajectories of the abrasive particles are predicted by modeling and simulation. The proposed technique raises the MRR and lowers the edge chipping rate (ECR) significantly in micro-hole manufacturing. The effects of the EPAMUSM parameters on the machining quality based on the electrophoretic features 3
of the ultrafine particles are studied, whereupon the parameters are optimized to make high-quality micro-holes in silicon.
2. Method and materials 2.1. Mechanism of EPAMUSM EPAMUSM is proposed to address the problem of low utilization ratios of abrasive particles
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and also to reduce EC and improve the MRR. In electrophoresis, charged particles move toward
their opposite polarities in an electric field (Cai, 2008; Feng et al., 2009). In addition to wetting,
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spreading, and adsorption, the ultrafine abrasive particles (which are in contact with the working
solution as a solid gel core in solution) often exhibit electrification (Peng et al., 1999). When ions are adsorbed on the surface of an abrasive particle, the particle becomes charged. Oppositely
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charged ions then diffuse to the vicinity of the gel core, and a special electric double-layer structure
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appears at the solid–liquid interface of the gel core. Because of the stronger attraction of the gel core
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to the adsorbed layer than to the diffusion layer, the gel core splits from the diffusion layer under the action of an external electric field, which is the phenomenon of electrophoresis. Charged
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particles move toward the poles, resulting in directional migration of the ultrafine abrasive particles
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in solution. In EPAMUSM, by controlling the electric field, the abrasive particles can overcome the vibration and centrifugal force during processing. This ensures that there are always enough particles in the processing area, thereby improving the abrasive-particle utilization ratio (Lian et al.,
2014).
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2016), processing quality (Zarepour and Yeo, 2012), and processing efficiency (Anupam et al.,
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As shown in Fig. 2, EPAMUSM is a new type of hybrid manufacturing process in which an
adjustable DC power supply and an electrophoresis auxiliary electrode are integrated into MUSM technology. Consequently, a constant electric field is formed between the auxiliary electrode and
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the micro-tool so that the particles in the working fluid are charged and attracted to the machining tool. This guarantees the concentration of particles in the processing area.
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Fig. 2. Schematic of electrophoresis-assisted micro-ultrasonic machining (EPAMUSM).
The machining experiment was performed on a self-developed micro-machining system, as shown in Fig. 3. Its main components are an electrophoresis-assisted system, an ultrasonic-vibration
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spindle system, a control system, and data acquisition. The electrophoresis-assisted system
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comprises an auxiliary electrode for electrophoresis, a DC power supply, a solution containing
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particles, and a tank for the working fluid. The ultrasonic-vibration spindle system comprises a spindle, an ultrasonic transducer, and a power supply. The spindle rotation speed is adjustable in the
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range 0-1,500 rpm. The spindle is attached to a sliding table and fixed to vertical column of the multifunctional system and supplies the rotational motion of the micro-tool. With a diameter of
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roughly 100 μm, the micro-tool was prepared by block-electrode discharge. The control system and data acquisition comprise mainly a dynamometer, an analog-to-digital converter, an amplifier, and
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a three-dimensional motion platform (M-L03K008; Physik Instrumente, Germany). The platform’s motion is controllable with a resolution of 0.1 μm. The working-fluid tank is installed on the moving
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platform.
Fig. 3. Experimental setup of EPAMUSM. 5
2.2. Materials The micro-tool was used to fabricate holes in workpieces with both EPAMUSM and MUSM. The workpiece material was monocrystalline silicon (workpiece size: 20 mm × 10 mm × 0.6 mm) that was provided by Lijing Materials Co., Ltd. The micro-tool was made of WC-Co that was provided by Hongming Carbide Co., Ltd., and its length and nominal diameter were 30 mm and 100 μm, respectively. The abrasive particles were made of diamond that was provided by the
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Fangyuan Diamond Co., Ltd., with nominal diameters of 0.1 μm. The auxiliary electrode for electrophoresis had a nominal diameter of 30 mm and was made of brass that was provided by
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Yonghao Metal.
The surface morphology and EC were analyzed using a confocal laser scanning microscope (OLY4000; Olympus, Japan), a white-light interferometer (Contour GT-X; Bruker, USA), and a
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scanning electron microscope (S-3400N; Hitachi, Japan).
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2.3. Numerical simulation
In this study, EPAMUSM was modeled and simulated using COMSOL Multiphysics 4.4. The
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particle tracking model is an important part of COMSOL Multiphysics and can be coupled to other
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physical fields such as flow fields and electric fields. The particle tracking model has three modes: charged particle tracking, fluid particle tracking, and mathematical particle tracking. Particle–field interaction can be realized by accessing the particle tracking model through the interface which built
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into the COMSOL physics field, thereby achieving multi-physics coupling. Charged particle tracking is commonly used to study the trajectories of electrons and ions in
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an electric field, such as in magnetic lenses, electron guns, and mass spectrometers. At the same time, phase trajectories and Poincaré maps can be extracted easily to draw particle trajectories. Fluid particle tracking uses a precise physics field to track particle trajectories in a fluid system.
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Predefined tensions, gravity, and other forces are easily loaded into the model if required. In other words, physical particle trajectories can be studied, such as those in electrophoresis, dielectrophoresis, and magnetophoresis. Mathematical particle tracking provides sufficient flexibility and freedom for particle-tracking equations of motion by specifying equations for particle motion by using equations such as Lagrangian or Hamiltonian mechanics. Particle tracking describes the problem in terms of Lagrange’s equation and uses Newton’s 6
Second Law of Motion is used to cast the problem as an ordinary differential equation. In threedimensional space, the position of a particle is determined by three-dimensional coordinates, thereby requiring three equations to determine the three coordinates. In the particle tracking model, an ordinary differential equation described by Lagrang e’s equation is used to solve for each coordinate. Simplifying the model into two dimensions means that two ordinary differential equations are needed to determine the position of each particle. Because the particle tracking model
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uses a general computational method to calculate particle trajectories, it can be applied equally to
the motions of (i) charged particles in the electromagnetic fields of large planets and galaxies and
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(ii) particles in laminar, turbulent, and multiphase flow systems. In the present study, the charged and fluid particle tracking models were used to model the movement of abrasive particles.
During EPAMUSM, the abrasive particles can be considered to be affected by both the flow
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field and the electric field. The location of a particle can be simplified as
(1)
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𝐺(𝐿, 𝐹) = 𝐿 + 𝐹
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where 𝐹 describes the motion of a particle in a fluid based on Newton’s Second Law, and 𝐿 represents the equation of motion of a charged particle in an electric field and is derived from
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Lagrange’s equation:
𝐯
(2)
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𝐿 = −𝑚𝑝 𝑐 2√1 − 𝐯 · 𝑐 2 + 𝑞𝐀 · 𝐯 – 𝑞𝑉
where 𝑚𝑝 is the particle mass, 𝑐 is the speed of light, 𝐯 is the particle velocity, 𝑞 is the particle
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charge, 𝐀 is the magnetic vector potential, and 𝑉 is the scalar potential. However, because the particles move far slower than light, 𝐿 can be simplified as follows by neglecting electrodynamic
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effects:
𝑑
𝐿(𝑚, 𝐯, 𝑉) = 𝑑𝑡 (𝑚𝑝 v) =
𝑚𝑝 v2 2
– 𝑞𝑉
(3)
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Assuming that the particles experience a fluid drag force when they move in the solution, then 1
𝒇𝑫 = ( ) 𝑚𝑝 (𝐮 − 𝐯) 𝜏p
(4)
where 𝜏p is the response time of the particles and 𝐮 is the fluid velocity. The force of gravity on the particles in solution is assumed to be 𝒇 𝒈 = 𝑚𝑝 𝐠
(𝜌p −𝜌z )) 𝜌p
(5)
where 𝜌p is the particle density, 𝜌z is the density of the surrounding fluid, and 𝐠 is the 7
gravitational acceleration vector. If an electric field is applied to the solution, the associated force can be expressed as 𝒇𝒆𝒙𝒕 = e𝒁𝑬
(6)
where e is the elementary charge, 𝒁 is the electric charge, and 𝑬 is the electric field intensity. Accordingly, the equation of motion of a particle in the fluid can be expressed as 𝑑 𝑑𝑡
(𝑚𝑝 v) = 𝒇𝑫 + 𝒇𝒈 + 𝒇𝒆𝒙𝒕
(7)
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𝐹(𝑓𝑫 , 𝑓𝒈 , 𝑓𝒆𝒙𝒕 ) =
The motion of an EPAMUSM abrasive particle is affected primarily by the drag force, ultrasonic vibration, electric force, and solution viscosity. Therefore, the model shown in Fig. 4
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includes only the main micro-ultrasonic tool, the electrophoresis auxiliary electrode, and the working fluid containing charged abrasive particles.
According to the requirements of the experimental equipment, a geometric model is established.
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The gap between the electrophoresis auxiliary electrode and the micro-tool is 30 mm, the diameter
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of the micro-tool is 100 μm, and the height of the solution domain is 10 mm. A free mesh is used to
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divide the particles, which are distributed uniformly with an initial concentration of 1 mol/m3 and a
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particle diameter of 0.1 μm. The particles are released either singly or continuously. The tool voltage is set to 5 V and the auxiliary electrode voltage to 0 V. Each abrasive grain is given unit charge. The
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model abrasive particles are spherical, and the abrasive solution is treated as an incompressible fluid.
Fig. 4. Simplified model of EPAMUSM.
Next, the effects of material properties, laminar flow, fluid particle tracing, current, grid
movement, and other parameters are incorporated into the multi-physical field model (flow field and electric field). These field models are added simultaneously with actual processing. The relevant properties are listed in detail in Tables 1 and 2. A transient finite-element solver was used to calculate the simulation model.
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Table 1. Material properties Value
Unit −3
Dynamic viscosity Solution density Specific heat rate Electric conductivity Atmospheric heat capacity Thermal conductivity
1.01×10 1,000 1.0 5.5×10−6 4.18 0.60
Pa·s kg/m3 J/(kg·K) S/m kJ/(kg·K) W/(m·K)
Table 2. Simulation parameters Value
Unit
Amplitude Vibration frequency Applied voltage (DC) Initial concentration of abrasive Rotation speed
3 60 5 1 500
μm kHz V mol/m3 rpm
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Name
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Property
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A constant voltage is utilized between the electrophoretic auxiliary electrode and the tool, thereby generating an electrophoretic auxiliary electric field between them. According to the
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principle of potential distribution, the potential is highest at the tool surface and decreases gradually
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along the direction of the electrophoresis auxiliary electrode. The electric field lines point toward
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the auxiliary electrode, and negatively charged particles gather near the tool.
2.4. Experimental procedure
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Three experimental investigations were performed related to the ECR and MRR. The first compared the manufacturing quality between MUSM and EPAMUSM, the second investigated the
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effects of electrophoretic voltage, spindle speed, and ultrasonic power on the ECR and MRR in EPAMUSM by means of single-factor experiments, and the third optimized the processing
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parameters by means of response-surface experiments. The ECR can be calculated as
𝐸𝐶𝑅 =
𝛷−𝐷 𝐷
(8)
where 𝛷 is the EC diameter and D is the diameter of the machined micro-hole. The MRR can be calculated as
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𝑀𝑅𝑅 =
𝐷 2
𝜋·( )2 ·𝑑
(9)
𝑇
where 𝑑 is the depth of the micro-hole and 𝑇 is the time taken to machine it. For the experiments to compare MUSM and EPAMUSM, the common machining parameters are listed in Table 3.
Value
Mass fraction Spindle speed Feed speed Feed depth Abrasive particle size Ultrasonic power Applied voltage (EPAMUSM only)
5% 500 rpm 0.5 μm/s 100 μm 0.1 μm 20 W 5 V (DC)
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Parameter
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Table 3. Common machining parameters for comparison of MUSM and EPAMUSM
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Single-factor experiments were conducted to study parametric effects on the ECR and MRR in micro-hole manufacturing. The parameters specific to EPAMUSM are listed in Table 4.
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Parameter
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Table 4. EPAMUSM machining parameters
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Abrasive particle size Feed speed Feed depth Ultrasonic power Applied voltage (DC) Spindle speed Mass fraction
Value 0.1 μm 0.5 μm/s 100 μm 20–70 W 3–15 V 300–700 rpm 5%
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In EPAMUSM, improving machining efficiency is as important as improving machining quality. Generally, with micro-holes, the MRR is used to evaluate machining efficiency and the ECR is used to evaluate machining quality. Several factors affect the machining efficiency, such as ultrasonic power, spindle speed, particle mass fraction, and applied voltage. The machining
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parameters were optimized through response-surface experiments and the processing parameters by studying the interactions among them; the experimental parameters and levels are listed in Table 5. Each test was repeated three times and the results were averaged. Table 5. Machining parameters and levels. Index
Parameter
Level
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Applied voltage (V)
5–10
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B: C: D:
Spindle speed (rpm) Ultrasonic power (W) Mass fraction (%)
100–500 10–35 5–15
3. Results and discussion 3.1. Numerical simulations
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The distributions and trajectories of abrasive particles with and without electrophoresis were compared. With an electrophoresis time of 10 s, a tool radius of 100 µm, an auxiliary voltage of 5 V, a vibration frequency of 60 kHz, and rotation speed of 500 rpm, the concentration of particles on
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the tool surface varies with time as shown in Fig. 5. Fig. 5(a) shows the results for zero
interelectrode voltage (i.e., without electrophoresis). The rotation and vibration expel the abrasive particles near the tool from the processing area. Those abrasive particles in the traditional MUSM
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processing area are expelled and the ratio of particle utilization is low. In contrast, Fig. 5(b) shows
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that the electrophoretic electric field causes the abrasive particles to gather around the tool; the
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electric field influences the movement of the abrasive particles appreciably and improves their utilization ratio. As shown in Fig. 5(c), electrophoresis assists abrasive particles to concentrate near
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the tool. After 10 s, the maximum particle concentration in the processing area is 4.68 mol/m3, and
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the concentration decreases gradually with distance from the tool surface.
Fig. 5. Abrasive particle trajectories under various physical conditions: (a) no electric field; (b) electric field; (c) contours of abrasive-particle concentration near tool. 11
The abrasive concentration in the processing area is determined by the combined effects of electric force, centrifugal force, drag force, ultrasonic vibration, and viscous resistance. Fig. 6 shows how the particles are distributed at different times. The charged particles clearly move toward the tool electrode under the action of the electric field, and the abrasive concentration near the tool electrode increases with time. Specifically, the electrophoretic auxiliary voltage influences the particle aggregation was analyzed. The results fully indicate that the electric field improves the
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abrasive-particle concentration.
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Fig. 6. Distribution of abrasive particles at various times: (a) 0 s; (b) 3 s; (c) 6 s; (d) 10 s. Next, Fig. 7 shows how various parameters affect the particle concentration. Particles were
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released continuously, and the solving time was 100 s. Clearly, the larger the applied voltage, the easier the ultrafine abrasive particles are adsorbed on the tool surface. For a fixed quantity of charge,
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the greater the electrophoresis voltage, the greater the force on the ultrafine abrasive particles propelling them toward the tool electrode. Therefore, when the average particle size is relatively large, increasing the electrophoretic voltage allows the abrasive particles to overcome the resistance
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toward the tool electrode and ensure their sufficient presence in the processing area. Fig. 7 shows that the concentration index of the abrasive particles decreases with both the
rotation speed and the ultrasonic power. This is because the viscosity of the liquid ensures that the solution near the processing area is rotated accordingly and when the rotation speed and ultrasonic power are increased, the abrasive particles in the solution are affected more by the centrifugal force and the ultrasonic vibration, whereby an outward force is generated. This expels abrasive particles 12
from the processing area, thereby decreasing their utilization rate. Such an explanation is consistent
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with the results presented herein.
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Fig. 7. Influences of different parameters on abrasive-particle concentration.
A set of experiments was conducted to analyze the motion of abrasive particles in the electrophoretic field and verify the simulation results. The applied voltage was 5 V, the power was
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20 W, and the spindle speed was 500 rpm. The effects of abrasive-particle aggregation on the tool
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are shown in Fig. 8. There is clearly no abrasive aggregation or surface adhesion without an electric
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field, even though the tool is soaked in abrasive solution. This can be interpreted as there being no
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electric field between the auxiliary electrode for electrophoresis and the micro-tool, meaning that abrasive particles cannot aggregate in the processing area. Fig. 8(b) shows the tool after
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electrophoretic assistance. After 30 s, a thin layer of abrasive particles is attracted onto the surface of tool as the external diameter of the tool increases. Fig. 8(c) and (d) show scanning electron
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microscopy (SEM) surface images with and without electrophoresis, respectively, and energy-
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dispersive X-ray (EDX) spectra.
Fig. 8. Abrasive-particle morphologies on electrophoresis-assisted tool: (a) surface without 13
electrophoresis; (b) surface with electrophoresis; EDX spectra and SEM images (c) with and (d) without electrophoresis. The EDX spectra and SEM images of the tool surfaces indicate that no diamond particles were found on the surface of the tool without electrophoresis, for which the EDX spectra show that the main components were W and Co. In contrast, Fig. 8(d) shows that 92.822% of the material on the surface processed with the assistance of electrophoresis was carbon, meaning that abrasive particles
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are attracted to the tool surface via electrophoresis.
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3.2. Experimental study of rates of edge chipping and material removal by EPAMUSM 3.2.1. Comparison of MUSM and EPAMUSM
To show the superiority of EPAMUSM over MUSM, a comparative experiment was conducted
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to highlight the advantages of EPAMUSM over MUSM regarding the ECR and MRR. Fig. 9(a) and
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(b) show the differences in ECR and MRR between MUSM and EPAMUSM. As shown in Fig. 9(a), because of the electrophoresis assistance, the EPAMUSM ECR (0.03) is much less than the MUSM
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one (0.22), and in Fig. 9(b) the EPAMUSM MRR (1.916×10−4 mm3/min) is marginally better than
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the MUSM one (1.718×10−4 mm3/min). This is because EPAMUSM guarantees that the abrasive particles are used at a certain rate, thereby enhancing the mechanical impact of particles on the
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workpiece. When the voltage is increased, the MRR also increases, thereby enhancing the MRR of the workpiece. Fig. 9(c) shows a micro-hole processed with traditional MUSM, the quality of which
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is poor because of edge issues. Fig. 9(d) shows a corresponding micro-hole fabricated by EPAMUSM, for which there are far fewer edge issues. When electrophoresis is applied at 5 V DC,
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the concentration of particles in the processing area increases. The particles are attracted to the processing area, thereby preventing the tool from hammering the workpiece directly. These consequences are confirmed through the SEM images that are shown in Fig. 9(c) and (d).
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The SEM images illustrate the bottom surfaces of micro-holes that are manufactured by MUSM and EPAMUSM, respectively. There are clearly more particles embedded in the bottom of the EPAMUSM hole, whereas there are few such particles in the MUSM one. This shows that the particles are cleared away from the processing area in MUSM, with the consequence that the microtool grinds the workpiece directly. This also verified that in EPAMUSM, more abrasive particles are involved in the processing, indicating that the electrophoresis-assisted technology can effectively 14
improve the utilization of abrasive particles in ultrasonic processing. Moreover, it can be seen from the results that increasing the utilization rate of abrasive grains has a certain influence on processing quality and processing efficiency. The superiority of electrophoresis-assisted ultrasonic machining is proven. Increasing the MRR and decreasing the ECR as much as possible would improve the processing efficiency, so it is necessary to study the effects of the EPAMUSM parameters on quality and
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efficiency.
Fig. 9. The quality and efficiency of micro-holes fabricated with micro-ultrasonic machining
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(MUSM) and EPAMUSM: (a) edge chipping rate (ECR); (b) material removal rate (MRR); (c) MUSM images; (d) EPAMUSM images (5 V).
3.2.2. Effect of excessive applied electrophoresis voltage
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The electrophoresis voltage clearly has an appreciable impact on the micro-hole machining
quality. In Fig. 10(a), increasing the applied voltage above 10 V worsens the EC. When the applied voltage is 5 V, 8 V, and 15 V, the ECR is 0.03, 0.06, and 0.15, respectively. The initial effect of increasing the applied voltage is to increase the concentration of particles in the machining area, thereby avoiding direct hammering between the workpiece and the tool. However, too many particles in the machining gap can block the removal of machining debris and weaken the vibrations, 15
which has a negative effect on the machining quality. When the applied voltage is less than 10 V, the ECR is less than 0.07. When the voltage is less than 5V, the ECR rises slightly. This shows that when the voltage is low, the attraction of the electric field to the abrasive particles is insufficient to overcome the ultrasonic vibration and repulsion generated by the tool rotation. At this time, the concentration of the abrasive particles is insufficient. This causes the ECR to rise. Fig. 10(a) shows how the MRR varies with applied voltage. When the applied voltage is
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increased from 3 to 15 V, The MRR first increases and then decreases. This is because the electric
field leads to there being ever more particles in the machining area. The higher the voltage, the more
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particles are driven into the machining area, thereby increasing the MRR from 1.81 to 2.29×10−4 mm3/min (the voltage increased from 3 to 8 V). However, with more particles in the
machining gap, a particle layer accumulates and covers the micro-hole and the tool. This blocks the
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removal of machining debris and weakens the vibrations, thereby decreasing the MRR once the
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voltage exceeds 8 V. The quality of micro-holes is shown in Fig. 10(b) and (c); the ECR and size of
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the micro-hole are both clearly somewhat larger for the higher voltage.
Fig. 10. (a) Variations of ECR and MRR of EPAMUSM micro-holes produced with applied
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voltage. (b) and (c) EPAMUSM micro-holes produced with applied voltages of (b) 5 V and (c) 15 V.
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3.2.3. Effect of excessive ultrasonic power The ultrasonic power also has considerable influence on the ECR and MRR of micro-hole
manufacturing. Fig. 11(a) shows how the ECR and MRR vary with ultrasonic power. The lowest ECR (0.06) was recorded for a power of 20 W (the corresponding hole is shown in Fig. 11(b)), and the MRR was 2.03×10−4 mm3/min. However, when the ultrasonic power was increased to 35 W, some defects began to appear around the micro-hole, leading to an ECR of 0.17. Increasing the ultrasonic power further to 70 W led to a potentially unacceptable ECR of 0.27 (the corresponding 16
hole is shown in Fig. 11(c)). With sufficient ultrasonic power, the abrasive particles can overcome the electrical attraction and escape from the machining gap. This leads to more direct hammering between the tool and the workpiece, leading to EC. The MRR is affected appreciably by the ultrasonic power. Fig. 11(a) shows the MRR clearly decreases as the ultrasonic power is increased from 20 to 35 W and then increases as the power is increased from 35 to 70 W. The latter effect is due to increased ultrasonic vibration energy during
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processing. Although this leads to a direct increase in MRR, it also drives the abrasive particles out of the machining area, thereby reducing their concentration in the processing area. Considering the
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ECR curve in Fig. 11(a), this effect clearly also increases the ECR. The quality of micro-holes
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produced with ultrasonic powers of 20 and 70 W is shown in Fig. 11(b) and (c), respectively.
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Fig. 11. (a) Variations of ECR and MRR of EPAMUSM micro-holes with ultrasonic power. (b) and (c) EPAMUSM micro-holes produced with ultrasonic powers of (b) 20 W and (c) 70 W. 3.2.4. Effect of excessive spindle speed
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Fig. 12(a) shows the effect of spindle speed. The impact of spindle speed on the ECR and MRR is demonstrated in Fig. 12 (a). As shown in Fig. 12(b), a spindle speed of 300 rpm leads to a high-
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quality micro-hole with an ECR of 0.03 and an MRR of 2.02×10−4 mm3/min. However, as the spindle speed increases, edge cracks become more severe; as shown in Fig. 12(c), a spindle speed of 700 rpm results in an ECR of 0.12. The tool rotation causes the surrounding working fluid to
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rotate because of its viscosity, meaning that the abrasive particles also rotate. A higher spindle speed means a greater centrifugal force acting on the particles; this helps the particles to escape from the machining gap, thereby reducing the concentration of abrasive particles. Again, because higher spindle speed means greater centrifugal force on the solution, some abrasive particles in the solution are expelled from the processing area as the spindle speed increases. This reduction in the number of free abrasive particles reduces the mechanical impact on the 17
workpiece, thereby decreasing the MRR. The quality of micro-holes produced with spindle speeds
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lower and higher than this value is shown in Fig. 12(b) and (c), respectively.
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Fig. 12. (a) Variations of ECR and MRR of EPAMUSM micro-holes with spindle speed. (b) and (c) EPAMUSM micro-holes produced with spindle speeds of (b) 300 rpm and (c) 700 rpm.
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3.3. Response-surface experiments on MRR and ECR
Based on the results of the single-factor experiments discussed in the previous subsection,
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some parameter values were selected that are appropriate for response-surface experiments. Fig. 13
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shows the interaction with MRR [Fig. 13(a)] and ECR [Fig. 13(b)] of each factor (ultrasonic power,
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spindle speed, particle mass fraction, and applied voltage). Analyzing the interactions among the
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different factors leads to the optimum EPAMUSM processing parameters.
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(a) MRR response surfaces
(b) ECR response surfaces Fig. 13. Effects of EPAMUSM processing parameters on MRR and ECR.
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From the above results, the optimal parameters for EPAMUSM machining quality and efficiency are an applied voltage of 7.5 V, an ultrasonic power of 22.5 W, a spindle speed of 300 rpm, and a mass fraction of 10%. High-quality micro-holes were manufactured by using those parameters (MRR: 2.08×10−4 mm3/min; ECR: 0.03).
4. Conclusions
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In this paper, based on the electrophoretic features of the particles in the solution, EPAMUSM technology can be used to solve the problems related to ECR and MRR in traditional MUSM. The
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present results show that the microscopic abrasive particles are attracted around the tool in
EPAMUSM, thereby reducing appreciably the EC caused by direct hammering between the tool and the workpiece, and also increasing the MRR somewhat. EPAMUSM has certain advantages over
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MUSM. Based on the present results from simulations and experiments, the following conclusions
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can be drawn.
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The simulation results indicate that electrophoresis greatly improves the concentration of abrasive particles near the tool. From the adsorption experiment, the SEM images and EDX spectra
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of tool surfaces show that abrasive particles are attached to the tool surface in EPAMUSM, thereby
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improving their utilization rate in the processing area. The comparative experiments show that EPAMUSM has advantages over MUSM. Under the same processing conditions, EPAMUSM improves the ECR considerably (down to 0.03 from 0.22)
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and also increases the MRR somewhat (up to 1.916×10−4 mm3/min from 1.718×10−4 mm3/min). More abrasive particles were discovered embedded in the bottom of the EPAMUSM micro-holes,
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showing that more abrasive particles were involved in the processing. Through single-factor experiments and response-surface experiments, by analyzing the
interactions among different factors, the optimum EPAMUSM processing parameters were obtained,
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namely an applied voltage of 7.5 V, an ultrasonic power of 22.5 W, a spindle speed of 300 rpm, and a mass fraction of 10%. The high-quality micro-holes were manufactured by using those parameters (MRR: 2.08×10−4 mm3/min; ECR: 0.03). Acknowledgments This research was supported by the National Natural Science Foundation of China (grant no. 20
51575113), the National Natural Science Foundation of China and Guangdong Province (grant no. U1601201), the Foshan Municipal Science and Technology Bureau project (grant no. 2015IT100162), the Science and Technology Planning Project of Guangdong Province (2016A010102017), the special support plan of Guangdong Province (grant no. 2014TQ01X542), the Fundamental Research Funds for the Central Universities (grant no. 2015ZZ080), and the
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National Natural Science Foundation of China (grant no. 51705228). References
Int. J. Machine Tools Manufac. 96, 1–14.
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Agarwal., S., 2015. On the mechanism and mechanics of material removal in ultrasonic machining.
Anupam, V., Tao, L., Yogesh, G., 2014. High resolution micro ultrasonic machining for trimming 3D microstructures. J. Micromech. Microeng. 24, 494–497.
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Cai., P., 2008. The advancement and application on electrophoretic technique. Life Sci. Instrum. 8,
N
3–7.
A
Feng, H., Jing, Z., Fang, Y., Mo., S., 2009. Two-dimensional electrophoresis and its application.
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Biotechnol. Bull. 1, 59–63.
Guha, D., Ramachandran, P.A., Dudukovic, M.P., 2007. Flow field of suspended solids in a stirred
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tank reactor by Lagrangian tracking. Chem. Eng. Sci. 62, 6143–6154. Hu, X., Yu, Z., Rajurkar, K.P., 2006. State-of-the-art review of micro ultrasonic machining.
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International Conference on Manufacturing Science and Engineering, 2006, 1017–1024. Kandaa, T., Makinoa, A., Onoa, T., Suzumoria, K., Moritab, T., Kurosawa, M.K., 2006. A micro
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ultrasonic motor using a micro-machined cylindrical bulk PZT transducer. Sensors and Actuators A: Physical 127, 131–138.
Kumar, V., Singh, H., 2018. Machining optimization in rotary ultrasonic drilling of BK-7 through
A
response surface methodology using desirability approach. J. Brazilian Soc. Mech. Sci. Eng. 40, 83–97.
Lian, H.S., Guo, Z.N., Liu, J.W., Huang, Z.G., He., J.F., 2016. “Experimental study of electrophoretically assisted micro-ultrasonic machining,” International Journal of Advanced Manufacturing Technology, 85, 2115-2124. Peng, W., Xu, X., He, X., Chen, Z., 1999. An electrophoresis grinding process and its application. 21
China Mech. Eng. 10, 85–88. Rajurkar, K.P., Levy, G., Malshe, A., Sundaram, M.M., Mcgeough, J., Hu, X., Resnick, R., DeSilva, A., 2006. Micro and nano machining by electro-physical and chemical processes. CIRP Annals: Manufac. Technol. 55, 643–666. Tateishi, T., Shimada, K., Yoshihara, N., Yan, J.W., Kuriyagawa, T., 2009. Control of the behavior of abrasive grains by the effect of electrorheological fluid assistance-study on
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electrorheological fluid-assisted micro ultrasonic machining. Adv. Mater. Res. 76, 696–701.
Tateishi, T., Shimada, K., Yoshihara, N., Yan, J.W., Kuriyagawa, T., 2009. Effect of
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electrorheological fluid assistance on micro ultrasonic machining. Adv. Mater. Res. 69, 148– 152.
Tateishi, T., Yoshihara, N., Yan, J., Kuriyagawa, T., 2009. Study on electrorheological fluid-assisted
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micro-ultrasonic machining. Int. J. Abrasive Technol. 2, 70–82.
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Wang, J., Zhang, J., Fenga, P., Guo., P., 2018. Damage formation and suppression in rotary
A
ultrasonic machining of hard and brittle materials: a critical review. Ceramics Int. 44, 1227– 1239.
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Zarepour, H., Yeo., S.H., 2012. Predictive modeling of material removal modes in micro-ultrasonic
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machining. Int. J. Machine Tools Manufac. 62, 13–23. Zhao, W.S., Gu, L., Kang, X., Jiang, Y., Li, L., Wang, D., Duan, J.Y., 2008. Latest advances of
14.
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nontraditional machining technology-review of ISEM-XV. Electromachining & Mould, 1, 4–
Zheng, C.H., Zhang, X.F., Yang, Z.D., Liang, C.S., Guo, Y.S., Wang, Y., Gao., X., 2018. Numerical
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simulation of corona discharge and particle transport behaviour with the particle spacecharge
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effect. J. Aerosol Sci. 118, 22–33.
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