study on new ultra-precision plane magnetic...
TRANSCRIPT
博士学位論文
Study on new ultra-precision plane
magnetic abrasive finishing process using
alternating magnetic field
変動磁場を利用した新しい超精密平面磁気
研磨法に関する研究
平成 28年 1月
呉 金忠
Contents
I
Contents
Chapter 1. Introduction ........................................ 1
1.1 Research Significance ........................................................... 1
1.2 Research process of MAF process ........................................ 5
1.3 Research purpose.................................................................. 9
Chapter 2. Development of plane MAF process
using AC magnetic field .....................................10
2.1 Introduction ...................................................................... 10
2.2 Conventional plane MAF process .................................... 11
2.3 Finishing principle of plane MAF process using alternating
magnetic field ......................................................................... 13
2.4 Development of experimental setup ................................ 16
2.5 Conclusion ........................................................................ 18
Chapter 3. Investigation of magnetic field
distribution and finishing force .........................19
Contents
II
3.1 Introduction ...................................................................... 19
3.2 Investigation of magnetic field distribution .................... 20
3.2.1 Measuring conditions and method ............................. 20
3.2.2 Measuring results and discussion .............................. 24
3.3 Measurement and investigation of finishing force .......... 25
3.3.1 Effect of magnetic field on finishing force .................. 25
3.3.1.1Measuring method and conditions ......................... 25
3.3.1.2 Measuring results and discussion ........................ 27
3.3.2 Effect of finishing factors on finishing force ............... 30
3.3.2.1 Impact of cutting fluid ........................................... 30
3.3.2.2 Impact of rotational speed .................................... 33
3.3.2.3 Impact of frequency ............................................... 36
3.3.2.4 Impact of magnetic particle .................................. 39
3.3.2.5 Impact of current ................................................... 42
3.4 Conclusion ........................................................................ 46
Chapter 4. Finishing characteristics and
mechanism of MAF process using alternating
Contents
III
magnetic field .....................................................47
4.1 Introduction ...................................................................... 47
4.2 Finishing characteristics of plane MAF process using
alternating magnetic field ...................................................... 49
4.2.1 Experimental conditions and method ........................ 49
4.2.2 Experimental results and discussion ......................... 50
4.3 Effect of finishing factors on finishing characteristic ...... 59
4.3.1 Impact of cutting fluid ................................................ 60
4.3.1.1 Experimental conditions and method ................... 60
4.3.1.2 Experimental results and discussion .................... 62
4.3.2 Impact of rotational speed of magnetic pole .............. 67
4.3.3 Impact of current frequency ....................................... 73
4.4 Improvement of finishing efficiency ................................. 82
4.4.1 Experimental conditions ............................................. 82
4.4.2 Experimental results and discussion ......................... 83
4.5 Mechanism of plane MAF process using alternating
magnetic field ......................................................................... 86
4.6 Conclusion ........................................................................ 89
Contents
IV
Chapter 5. Plane MAF process using alternating
magnetic field in industry application ..............91
5.1 Introduction ...................................................................... 91
5.2 Precision finishing of POM resin plate ............................ 92
5.2.1Finishing importance of POM resin plate ................... 92
5.2.2 Experimental conditions ............................................. 92
5.2.3 Experimental results and discussion ......................... 94
5.3 Precision finishing of Brass C2680 .................................. 96
5.3.1Finishing importance of Brass C2680 ......................... 97
5.3.2 Experimental conditions ............................................. 97
5.3.3 Experimental results and discussion ......................... 98
5.4 Precision finishing of micro groove parts ...................... 103
5.4.1Introduce ................................................................... 103
5.4.2 Experimental conditions .......................................... 103
5.4.3 Experimental results and discussion ...................... 105
5.5 Conclusions .................................................................... 108
Chapter 6. Conclusions .................................. 109
Contents
V
Reference ........................................................ 114
Acknowledgement .......................................... 123
Contributed papers related to this study ...... 124
Chapter 1.Introduction
1
Chapter 1.Introduction
1.1 Research Significance
With the development of high technology industries, the higher
requirements of quality and diversifications for products are put forward.
Ultra-precision finishing technology has become a complicated systems
engineering, which is widely applied to industrial fields. It is demanded
that the parts used in manufacturing semiconductors, optical lenses, atomic
energy parts, medical instruments and aerospace components, have a very
high surface precision.
At presently, ultra-precision finishing is mainly can be classified into two
classes: traditional and advanced. Some simple shape of the parts automatic
processing production may be achieved by traditional methods such as
grinding, lapping and honing. However, extraordinary properties of
materials, the automatic processing of complicated micro curved surface is
difficult to be completed by CNC machine tool. This because the traditional
machining tools is difficult to enter the processing site. In order to realize
the precision finishing of complicated micro parts surface, a series of
advanced finishing process were developed in recent decades. The
advanced abrasive finishing processes can be divided into two groups
accord to their processing principles. First one includes Abrasive Flow
Finishing (AFF), Elastic Emission Machining (EMM), Chemical
Mechanical Polishing (CMP) where forces on the workpiece acting during
Chapter 1.Introduction
2
the finishing process are not possible to control externally. The second one
includes Magnetorheological Finishing (MRF), Magnetorheological
Abrasive Flow Finishing (MRAFF), Magnetic Float Polishing (MFP) and
MAF (MAF) [101]
. In these processes, the forces acting on the workpiece
can be controlled by changing magnetic field intensity.
MAF (MAF) is a very promising magnetic field-assisted finishing
technology, which utilizing the action at a distance between magnetic pole
and incompact magnetic abrasive to finish work piece by introducing the
magnetic and electric fields [102]
. This process is considered to be a
promising precision finishing technique for flat surfaces [103 - 104]
, complex
curve surface [105]
and inner surfaces of tube [106 - 107]
because polishing tools
(magnetic brush) composed of fine magnetic particles is flexible and easy
to closely follow the finished surface [108 - 109]
. The method can not only
finish ferromagnetic materials, but can also polish effectively
non-ferromagnetic materials such as stainless steel, plastic [11112]
, glass [113]
,
ceramic [114 - 115]
and brass [116]
. Moreover, the method has many attractive
advantages such as self-sharpening, high adaptability, controllability, and
can effectively connect to numerically controlled machine tools and robot,
easy to realize the automation of finishing. Nowadays, magnetic
field-assisted finishing processes are becoming developed for a wide
variety of applications including the manufacturing of medical components
[117 - 118], electronic components, optics parts
[113, 119], dies and molds, fluid
systems and micro-electromechanical systems [120]
.
Despite the MAF process has potential advantages, the process is
difficult to achieve effectively several nano-level finishing for flat and
micro complex surface. The key issues are as follows: In conventional
Chapter 1.Introduction
3
plane MAF process using magnetic brush, in order to obtain high surface
quality few microns magnetic particles need to be used in ultra-precision
finishing process. However, there are some problems that the fine magnetic
particles consist of magnetic brush are easy to agglomerate during finishing
process and magnetic brush is difficult to recover its original shape after
contact with workpiece surface, which hinder the realization of
ultra-precision finishing to some extent. Moreover, in finishing process,
non-uniform distribution of abrasives is also indirectly affecting the
uniformity of finished surface. On the other hand, magnetic brush itself is
still under static magnetic field, resulting abrasives cannot be adequately
transported over the magnetic brush in finishing process. Therefore, in
complicated micro-curved surface MAF, abrasives are difficult to polish
into all machined surfaces. Moreover, continuous use of the same abrasives
particles leading to dullness of the cutting edges of the abrasives particles,
decreasing finishing efficiency.
In order to overcome these problems, a new MAF process using low
frequency alternating magnetic field was proposed in this paper. Firstly, we
selected magnetic cluster instead of conventional magnetic brush. The
magnetic cluster is made of iron power, abrasive and grinding fluid, which
present a liquid state without the action of magnetic force. Magnetic cluster
is considered to more applicable to nanometer level surface finishing
because it is more flexible than conventional magnetic brush not easy to
cause to surface scratches. Secondly, we use of alternating current to
energize electromagnetic which makes the magnetic field fluctuating.
Therefore, the flexible magnetic cluster will generate a fluctuation of up
and down under the action of alternating magnetic field. The fluctuating
Chapter 1.Introduction
4
flexible magnetic cluster is not only promote to the scatter of micro
magnetic particles, but also prevent itself deformation after contact with
workpiece surface, achieving circulation and update to ensure the stability
of grinding tools. Moreover, with the fluctuation of magnetic cluster the
abrasive particles can be refreshed and mixed during finishing process
without recharging, which improve homogenous of finish surface and
enhance finishing efficiency compared to use of static magnetic cluster.
Chapter 1.Introduction
5
1.2 Research process of MAF process
MAF is essentially the manipulation of a homogeneous mixture of
magnetic particles and abrasive particles with a magnetic field to impart a
machining force on a workpiece. Relative motion between the particle
mixture and workpiece surface result in material removal. Since MAF does
not require direct contact with the tool, the particles can be introduced into
areas which are hard to reach by conventional techniques. Additionally
careful selection of magnetic particles and abrasive particles give rise to
surface texture and roughness control that was previously impossible
especially for hard to access areas [121 - 122]
.
Soviet Union initially developed as a machining process in the Soviet
Union in the 1930s and the first patent in the 1940s. Since then, Bulgaria,
Germany, US and Poland also began the research works of MAF. Research
and practical application of the paper in abrasive machining using magnetic
field was first published in 1960. The researchers of Japan started in-depth
study on MAF in 1980s. Shinmura first reported to MAF in Japan society
for precision engineering in 1983 [102]
, and then made the external surface
of cylinder, internal surface of blend pipe, flat and curved surface as
research object, conducted comprehensive research on processing
equipment, finishing characteristics, finishing mechanism and so on [123 -
124].
At present, the researches of MAF in Japan are mainly concentrated in
university, research institution and private enterprise. University research in
Utsnomiya University, Tokyo University, Tohoku University, Shinshu
University, Akita Prefectural University, Nippon Institute of Technology,
Chapter 1.Introduction
6
University of Yamanashi and so on. Research institution mainly includes
Riken Institute, Nagoya Municipal Industrial Research Institute, Industrial
Technology Center of Tochigi Prefecture, Industrial Technology Institute
and Kagawa Prefectural Industrial. Private enterprise mainly includes
Kyoei Denko, Kureha, Toyo Kenmazai Kogyo, Kumakura, Osamu Nakano.
In abroad, Many institutions engaged in research work of MAF such as
Oklahoma State University, Rochester University, Toledo University in
America, Indian Institute of Technology, Indian industrial university [125 -
126], Russia Petersburg state university of technology
[127], Korea Advanced
Institute of Science and Technology [128]
, Rumania Suceava University
Shanghai Jiao Tong University, Northeastern University, Zhejiang
University, Hunan University and Liaoning University of Science and
Technology in China.
In recent decades, some researches related to plane MAF process are
reported in this paper.
Shinmura et al. studied the basic processing principle and abrasive
characteristics of plane MAF and verified that the MAF have the ability to
achieve precision finishing of flat surface [121 - 122]
. They developed plane
MAF process using high rotary speed magnetic pole, spindle-finish type
MAF process and plane MAF experimental equipment of coil rotary style
and coil fixed style [129 - 131]
, improved surface precision of flat, spherical
surface and 3D free surface by use of MAF process.
Suzuki et al. developed metal short fiber mixed magnetic grains and
proposed MAF process using centrifugal force [132]
. It is used in processing
for ceramics, optical glass, stainless steal and brass. Anzai et al. developed
magnetic abrasive equipment of five-axis linkage robot, and it was
Chapter 1.Introduction
7
confirmed that automation of free-form surface polishing is possible by this
method [133]
. Kim et al. proposed magnetic polishing of free form surface
using two types of magnetic polishing tool. One is an abrasive wheel type
(in rough machining stage) and the other is a magnetic brush type (final
finishing stage) [134]
. It realized efficient polishing of curved surfaces.
Jain et al. have studied the MAF process on non-magnetic stainless steel
workpiece and concluded that the working gap and circumferential speed
are the parameters which significantly influence the surface roughness
value, proved forces and change in surface roughness (△Ra) increase with
increase in current to the electromagnet and decrease in the working gap
[135 - 137]. Joshi et al. analysis of MAF of plane surfaces and concluded that
the surface finishing may improve significantly with an increase in the
grain size, feed rate and current [138]
.
Yin et al. developed three modes (horizontal vibration, vertical vibration
and compound vibration) of vibration-assisted MAF process for polished
flat surface and 3D micro-curved surface. It is observed that the
combination of the vibrations leaded to a higher polishing efficiency as
well as a smoother surface [105, 139]
. Pandey et al. have studied the
mechanism of surface finishing in UAMAF (Ultrasonic-Assisted Magnetic
Abrasive Finishing) process and verified that the polishing effectiveness of
MAF can be improved significant by add ultrasonic vibrations [140 - 141]
.
Zou et al. proposed a plane MAF process using a constant-pressure
magnetic brush [142]
, studied on plane magnetic abrasive trajectory [143]
and
elevated the surface precision and homogeneity [144]
.
The previous researchers have concluded the main parameters affecting
the performance of MAF process and find out the methods improving
Chapter 1.Introduction
8
significantly efficiency of MAF. However, to processing quality, the MAF
process is still considered to be difficult to obtain effectively few
nanometer finish surface, especially in finishing on flat and micro complex
surface workpiece made of hard materials.
Chapter 1.Introduction
9
1.3 Research purpose
Section 1.1 and section 1.2 stated that the conventional MAF process is
difficult to realize the ultra-precision finishing of flat and complex micro
surface. In this paper, we proposed a new ultra-precision plane magnetic
abrasive finishing process using alternating magnetic field. This process
can produce a fluctuating finishing force under the action of alternating
magnetic field, which not only may prevent magnetic cluster deformation,
but also promotes the abrasives into all finished surface, achieving
circulation and update to ensure the stability of grinding tool. In this study,
we fabricated a set of experimental setup, investigated the magnetic field
distribution and studied the effects of fluctuating magnetic cluster on
finishing force and abrasive behavior. Moreover, we analysis of finishing
mechanism, investigated the finishing characteristics and discussed its
application in industry.
The final aims of this study is to realize the ultra-precision finishing of
flat and complicated micro surface and hope this process may contribute to
the development of semiconductor and optical high technology industry.
Chapter.2 Development of plane MAF process using AC magnetic
field
10
Chapter 2.Development of plane
MAF process using AC magnetic
field
2.1 Introduction
MAF refers to using 1 µm - 2 µm iron particles mixed with an abrasive
to apply the machining force through manipulation of the particles with a
magnetic field. The magnetic particles and abrasives mixture is commonly
referred to the "magnetic brush" because it appears and behaves similar to a
wire brush. In traditional plane MAF process using magnetic brush, there
are some problems that the fine magnetic particles consist of magnetic
brush are easy to agglomerate during finishing process and magnetic brush
is difficult to recover its original shape after contact with workpiece surface,
which hinder the realization of ultra-precision finishing to some extent.
Moreover, in finishing process, non-uniform distribution of abrasives is
also indirectly affecting the uniformity of finished surface.
In this chapter, the author proposed a new ultra-precision plane MAF
process using alternating magnetic field to improve the surface precision of
flat and complicated curve surface. Analyzed and compared the plane MAF
process between traditional direct magnetic field and new alternating
magnetic field in finishing principle. Moreover, we developed a set of
experimental setup for finishing flat surface.
Chapter.2 Development of plane MAF process using AC magnetic
field
11
2.2 Conventional plane MAF process
Fig.2.1 shows schematic of processing principle in conventional plane
MAF process using static magnetic field. Magnetic abrasives of unbonded
type (a mixture of magnetic particles, abrasives and cutting fluid) are
supplied between the magnetic pole and workpiece. The distance between
the workpiece and the magnetic pole is a few millimeters. The mixed type
magnetic abrasives form a magnetic brush along the magnetic flux. The
finishing of workpiece surface is realized under the high rotation speed of
magnetic pole (the rotation of magnetic brush) and the movement of
workpiece in direction X and Y [201]
.
In conventional plane MAF process using magnetic brush, in order to
obtain high surface quality several microns magnetic particles need to be
used in ultra-precision finishing process. However, there are some
problems that the fine magnetic particles consist of magnetic brush are easy
to agglomerate during finishing process and magnetic brush is difficult to
recover its original shape after contact with workpiece surface, which
hinder the realization of ultra-precision finishing to some extent. Moreover,
in finishing process, non-uniform distribution of abrasives is also indirectly
affecting the uniformity of finished surface.
On the other hand, the conventional plane MAF process is simply
applied to the polish of flat surface and difficult to realize the finishing of
complicated micro curved surface. Magnetic brush itself is still under static
magnetic field, resulting abrasives cannot be adequately transported over
the magnetic brush in finishing process. Therefore, in finishing of
complicated curved surface, abrasives are difficult to polish into all
Chapter.2 Development of plane MAF process using AC magnetic
field
12
machined surfaces and not sufficiently combined corner and groove surface.
Moreover, under the high speed rotating of magnetic brush, the edge side of
micro-curved surface worn in processing leads to the damage of the
workpiece shape.
Fig.2.1 Schematic of processing principle in conventional plane MAF
process using static magnetic field
Chapter.2 Development of plane MAF process using AC magnetic
field
13
2.3 Finishing principle of plane MAF process
using alternating magnetic field
Fig.2.2 Force analysis of magnetic particles in alternating magnetic field
Fig.2.2 shows the force analysis of magnetic particles in alternating
magnetic field. A magnetic particle along magnetic equipotential line
Chapter.2 Development of plane MAF process using AC magnetic
field
14
direction generates a force Fx and along magnetic force line direction
generates a force Fy, it is calculated by the following formula (2.1) [202]
:
𝐹𝑥 = Vχ𝜇0𝐻 (𝜕𝐻
𝜕𝑥) 𝐹𝑦 = Vχ𝜇0𝐻 (
𝜕𝐻
𝜕𝑦) (2.1)
Where V is the volume of magnetic particle, χ is susceptibility of
abrasive particles, μ0 is permeability of vacuum, H is the magnetic field
intensity, ∂H / ∂x and ∂H / ∂y are gradients of magnetic field intensity
in x and y directions, respectively.
Due to the size and direction of alternating current present a cyclical
variation over time, the direction of magnetic force Fy is changing under
alternating magnetic field. Therefore, when the alternating current is
supplied to the electromagnet, the magnetic cluster will generate a
fluctuation of up and down with the change of magnetic field direction.
Fig.2.3 shows a schematic of the plane MAF process using alternating
magnetic field. The tray contains the compound magnetic finishing fluid
(grinding fluid, iron powders and abrasives), the lower is the magnetic pole
and the upper is the workpiece. After electromagnetic coil entering
alternating current, the iron particles are attracted towards each other along
the magnetic force lines and abrasive particles are mixed between the iron
particles. The compound magnetic finishing fluid is transformed into
magnetic cluster in between the tray and workpiece. With the rotation and
movement of magnetic pole, a relative friction is produced between the
workpiece surface and magnetic cluster. The friction is combined with
fluctuating magnetic force produced by magnetic cluster, thereby realizing
effectively the material removal.
Chapter.2 Development of plane MAF process using AC magnetic
field
15
Fig.2.3 Schematic of processing principle in plane MAF process using
alternating magnetic field
Chapter.2 Development of plane MAF process using AC magnetic
field
16
2.4 Development of experimental setup
Fig.2.4 External view of the experimental setup and processing region
expanding photos
The external view of the experimental setup is shown in Fig.2.4. The
selected workpiece size is 80mm×90mm×1mm. The tray containing
compound magnetic cutting fluid (a mixture of magnetic particles,
abrasives and cutting fluid) is under the workpiece. Fix the tray on the
Chapter.2 Development of plane MAF process using AC magnetic
field
17
magnetic pole and the tray self-rotation can be achieved by connecting the
magnetic pole to motorⅠ. Electromagnetic coil with the wire diameter of
1mm and 2000turns has been selected to install on the mobile stage. After
the operation of motorⅡ, the mobile stage will drive the coil to achieve
movement in all directions. Furthermore, connect the electromagnetic coil
to alternating current power device, and then we may freely select the
voltage and current frequency in the range of 1v-300v and 1Hz-999Hz
according to experimental needs.
Chapter.2 Development of plane MAF process using AC magnetic
field
18
2.5 Conclusion
In this chapter, the main research results can be summarized as follows:
(1) We introduced the processing principle of plane MAF process using
magnetic brush and described the existent issues of the conventional
finishing process.
(2) We proposed a new ultra-precision plane MAF process using
alternating magnetic field. This process can produce a fluctuating finishing
force under the action of alternating magnetic field, which not only may
prevent magnetic cluster deformation, but also promotes the abrasives into
all finished surface, achieving circulation and update to ensure the stability
of grinding tool.
(3) A set of experimental devices have been designed for finishing flat
surface.
Chapter 3. Investigation of magnetic field distribution and
finishing force
19
Chapter 3.Investigation of
magnetic field distribution and
finishing force
3.1 Introduction
In the previous chapter, we described the processing principle of plane
MAF process using alternating magnetic field and developed a set of
experimental setup for finishing flat surface.
In this chapter, firstly, we measured magnetic flux density and
investigated magnetic field distribution in processing region. Secondly, we
measured finishing force and discussed the effect of alternating magnetic
field on finishing force wave in detail. Moreover, we investigated the
effects of finishing parameters such as cutting fluid, rotational speed of
magnetic pole, diameter of magnetic particles, current frequency and
current on finishing force.
Chapter 3. Investigation of magnetic field distribution and
finishing force
20
3.2 Investigation of magnetic field
distribution
3.2.1 Measuring conditions and method
The magnetic field distribution in processing region controls the
finishing force distribution of the magnetic particles, which has an
important effect on finishing characteristics. Therefore, it is necessary to
understand the magnetic field distribution in processing region. The peak
value of magnetic flux density Bp can be estimated by the following
formula (3.1) [301]
:
𝐵𝑝 = 𝜇0𝑛𝐼 (3.1)
Where 𝜇0 is the magnetic permeability in vacuum, n is the number of
turns in the coil and I is the excitation current. The peak value in the
magnetic flux density Bp increases with the increasing of excitation current
I.
In this study, the selected AC power input current is sinus waveform as
shown in Fig.3.1(a). Current peak value is 3A, average value is 1.9 A and
frequency is 3Hz. The size and direction of current is changed periodically,
resulting in a changing magnetic field. Fig.3.1(b) shows that variation of
magnetic flux density with time at some point. We may measure magnetic
flux density peak value Bp and valley value – Bp by measurement
instrument. Therefore, the value of magnetic flux density is changing
constantly within – Bp and Bp at this point.
Chapter 3. Investigation of magnetic field distribution and
finishing force
21
Fig.3.1. Alternating current wave and magnetic field wave
Chapter 3. Investigation of magnetic field distribution and
finishing force
22
The measuring conditions as shown in Table.3.1. The measurement
instrument (Fig.3.2) is made in Electron Magnetic Industry Company with
the model of GM-4002 and the type of measuring Probe is T-402. The
groove shaped magnetic pole (with four crossing grooves, width is 1mm,
depth is 1.5mm) was selected with the diameter of 15mm and the material
is SS400. The distance of workpiece and magnetic pole is 3mm. Fig.3.3
shows that the measurement method of magnetic flux density in processing
region. In order to measure distribution of magnetic flux density in
processing region, we made a plastic plate with the thickness of 3mm fix
on the pole and divided it into thirteen sections, namely every 2 mm from
the center to both sides to conduct magnetic flux density measurement.
Table 3.1 Measuring conditions
Measuring instrument
Measuring probe
Workpiece-Pole tip
clearance
Magnetic pole
Alternating current
Frequency
GM-4002 (made in EM/C)
T-402 (made in EM/C)
3mm
Material: SS400
Size: 15mm in diameter, with four
crossing grooves (width : 1mm, depth :
1.5mm)
1.9A (average value)
3Hz
Chapter 3. Investigation of magnetic field distribution and
finishing force
23
Fig.3.2 Photo of measuring equipment of magnetic flux density
Fig.3.3 Measured method of magnetic flux density
Chapter 3. Investigation of magnetic field distribution and
finishing force
24
3.2.2 Measuring results and discussion
The distribution of magnetic field in processing region is shown in
Fig.3.4. It can be seen that the peak value of magnetic flux density
decreases gradually from the outer diameter of magnetic pole (x=±6mm) to
the center of pole (x=±2mm), and produced a maxmium value at the pole
edge(x=±7.5mm). It is because the edge has intensive magnetic induction
line distribution in head face of cylindrical magnetic pole. Therefore, on the
edge of magnetic pole the workpiece should suffer the most powerful force
and the distribution of magnetic particles is the most intensive.
Fig.3.4 Magnetic field distribution in processing region
Chapter 3. Investigation of magnetic field distribution and
finishing force
25
3.3 Measurement and investigation of
finishing force
The finishing force is important to understand the mechanism of material
removal and it has a profound impact on finishing characteristics in
finishing process. In this paper, we designed a measuring device of
finishing force and investigated the effects of magnetic field (DC, AC),
cutting fluid (water-soluble cutting fluid, silicone fluid, neat cutting oil),
rotational speed of magnetic pole (0rpm, 250rpm, 350rpm, 450rpm),
current frequency (3Hz, 5Hz, 7Hz, 9Hz), magnetic particle (6μm, 30μm)
and current (1A, 2A, 3A, 4A) on finishing force, respectively.
3.3.1 Effect of magnetic field on finishing force
3.3.1.1Measuring method and conditions
Fig. 3.5 shows the schematic view of force measuring system. The
finishing force was measured by using two diamagnetism strain gauges
(KFN-2-350-C9-11) and a bridge case by sensor interface (PCD-300A)
(Kyowa Electronic Instrument Co. Ltd). The measurement value and waves
shape were analysed by the data record processor (PCD-30A). The external
view of measuring instrument is shown in Fig.3.6. In this measurement, we
investigated the effect of different magnetic fields on finishing force. The
measuring conditions are shown as Table 3.2.
Chapter 3. Investigation of magnetic field distribution and
finishing force
26
Fig.3.5. Schematic view of force measuring system
Fig.3.6 Photo of measuring instrument of finishing force
Chapter 3. Investigation of magnetic field distribution and
finishing force
27
Table 3.2 Measuring conditions
Measuring plate Brass plate C5210P, 115×33×0.6mm
Strain gauges KFN-2-350-C9-11
Work-Pole tip clearance 3mm
Magnetic particles Electrolytic iron powder , 30μm in mean
diameter: 1.2g
Abrasive WA 10000: 0.3g
Finishing fluid Neat cutting oil: 0.8ml
Magnetic pole Material: SS400
Size: 15mm in diameter, with four crossing
grooves (width : 1mm, depth : 1.5mm)
Rotation speed 0 rpm
Magnetic field Type 1: Direct magnetic field:
I = 1.9A, U = 16V
Type 2: Alternating magnetic field:
Ia = 1.9A, Ea = 16V (average)
Frequency: 3Hz
3.3.1.2 Measuring results and discussion
The measuring results of finishing force in different magnetic fields are
shown in Fig.3.7. In direct magnetic field, the size and direction of direct
current are not change over time. As shown in Fig.3.7 (a), the forced value
is 12N and this value-centric with a slight fluctuations. The workpiece was
forced under a single direct magnetic field and force waveform is
Chapter 3. Investigation of magnetic field distribution and
finishing force
28
correspond to direct current waveforms. Therefore, the force waveform can
be considered linear waveform and produced a fixed force value.
As shown in Fig.3.7 (b), in alternating magnetic field, owing to magnetic
field is changing, resulting pulsed finishing force is produced and the
finishing force value presents a cyclical variation. Therefore, magnetic
particles may produce the up and down movement under pulsed finishing
force and drive the abrasives to float to the magnetic cluster surface for the
polishing of workpiece. It can be seen that the finishing force in alternating
magnetic field is greater than that of direct magnetic field from
measurement results. According to Preston equation [302, 303]
, the high
finishing force can produce a large material removal in the same conditions.
Therefore, MAF using alternating magnetic field can produce a higher
finishing efficiency.
Chapter 3. Investigation of magnetic field distribution and
finishing force
29
Fig.3.7. Measured finishing force wave (magnetic field)
Chapter 3. Investigation of magnetic field distribution and
finishing force
30
3.3.2 Effect of finishing factors on finishing force
In this study, we investigated the effects of finishing factors such as
cutting fluid, rotational speed of magnetic pole, frequency, diameter of
magnetic particles and current on finishing force.
3.3.2.1 Impact of cutting fluid
Measuring conditions are shown in Table.3.3. The measuring
experiments investigated the effect of cutting fluid such as water-soluble
cutting fluid, silicone fluid and neat cutting oil on finishing force.
The measured finishing force waves are shown in Fig.3.8. The effect of
cutting fluid on finishing force is shown in Fig.3.9. It can be seen that in
the case of using neat cutting oil the average value of finishing force is
higher than that of silicone oily and water-soluble cutting fluid. From the
finishing force waves, we can know that when used the silicone oily and
water-soluble cutting fluid, the magnetic particles generated the irregular
fluctuation and the amplitude of fluctuation is smaller than that of neat
cutting oil. Therefore, the experimental results showed that under
alternating magnetic field MAF process using neat cutting oil can produce
a steady pulsed finishing force.
Chapter 3. Investigation of magnetic field distribution and
finishing force
31
Table.3.3 Measured conditions
Measuring plate Brass plate C5210P, 115×33×0.6mm
Strain gauges KFN-2-350-C9-11
Work-Pole tip
clearance
3mm
Magnetic pole Material: SS400
Size: 15mm in diameter, with four crossing
grooves (width : 1mm, depth : 1.5mm)
Magnetic particles Electrolytic iron powder, 30μm in mean
dia:1.2g
Abrasive WA 10000, 1μm in mean dia: 0.3g
Alternating current 1.9A (Average)
Current frequency 3Hz
Rotational speed of
magnetic pole
0 rpm
Cutting fluid Type 1: Water-soluble cutting fluid
(SCP-23): 0.8ml
Type 2: Silicone fluid
(KF-96-50CS): 0.8ml
Type 3: Neat cutting oil
(Honilo 988): 0.8ml
Chapter 3. Investigation of magnetic field distribution and
finishing force
32
Fig.3.8 Measured finishing force (cutting fluid)
Chapter 3. Investigation of magnetic field distribution and
finishing force
33
Fig.3.9 The effect of cutting fluid on finishing force
3.3.2.2 Impact of rotational speed
In finishing process, magnetic particles produce a fluctuating magnetic
force in a vertical aspect under the influence of alternating magnetic field.
Moreover, as a result of the relative movement of magnetic cluster against
workpiece surface, a frictional force in the horizontal direction produces.
Therefore, finishing force is considered as a resultant force of pulse
magnetic force and frictional force. In this experiment, we investigated the
effect of rotational speed of magnetic pole (0rpm, 200rpm, 300rpm,
400rpm) on finishing force. The measuring conditions are shown in
Table.3.4
Chapter 3. Investigation of magnetic field distribution and
finishing force
34
Table.3.4 Measuring conditions
Measuring plate Brass plate C5210P, 115×33×0.6mm
Strain gauges KFN-2-350-C9-11
Work-Pole tip
clearance
3mm
Magnetic pole Material: SS400
Size: 15mm in diameter, with four crossing
grooves (width : 1mm, depth : 1.5mm)
Magnetic particles Electrolytic iron powder, 30μm in mean
dia:1.2g
Cutting fluid Neat cutting oil (Honilo 988): 0.8ml
Abrasive WA 10000, 1μm in mean dia: 0.3g
Alternating current 1.9A (Average)
Current frequency 3Hz
Rotational speed of
magnetic pole
0 rpm, 250rpm, 350rpm, 450rpm
The measured finishing force waves are shown in Fig.3.10. The effect of
rotational speed of magnetic pole on finishing force is shown in Fig.3.11. It
can be seen that finishing force is increasing gradually with the increase of
rotational speed of magnetic pole. This is because the centrifugal force
acting on magnetic particles is increasing as the rotation speed increases. It
intensifies the collision of magnetic cluster against the workpiece, increases
frictional force. However, we observed that finishing force wave generated
the irregular fluctuation when the rotational speed is 450rpm. This is
Chapter 3. Investigation of magnetic field distribution and
finishing force
35
because excessive greater centrifugal force result to some of magnetic
particles and abrasive grains were thrown out of tray, breaked the original
pulsed finishing force.
Fig.3.10 Measured finishing force (rotational speed)
Chapter 3. Investigation of magnetic field distribution and
finishing force
36
Fig.3.11 The effect of rotational speed on finishing force
3.3.2.3 Impact of frequency
In this experiment, we investigated the effect of frequency (3Hz, 5Hz,
7Hz, 9Hz) on finishing force. The measuring conditions are shown in
Table.3.5.
The measured finishing force waves are shown in Fig.3.12. The effect of
current frequency on finishing force is shown in Fig.3.13. It can be seen
that the finishing force is increasing with the increase of current frequency.
This is because vibration angle of magnetic particles smaller and vibration
speed faster as frequency increases, which makes the magnetic cluster
become harder, improves finishing force. However, with the decrease of
Chapter 3. Investigation of magnetic field distribution and
finishing force
37
vibration angle of magnetic particles decrease the fluctuation amplitute of
finishing force.
Table.3.5 Measuring conditions
Measuring plate Brass plate C5210P, 115×33×0.6mm
Strain gauges KFN-2-350-C9-11
Work-Pole tip
clearance
3mm
Magnetic pole Material: SS400
Size: 15mm in diameter, with four crossing
grooves (width : 1mm, depth : 1.5mm)
Magnetic particles Electrolytic iron powder, 30μm in mean
dia:1.2g
Cutting fluid Neat cutting oil (Honilo 988): 0.8ml
Abrasive WA 10000, 1μm in mean dia: 0.3g
Alternating current 1.9A (Average)
Rotational speed of
magnetic pole
0 rpm
Current frequency 3Hz, 5Hz, 7Hz, 9Hz
Chapter 3. Investigation of magnetic field distribution and
finishing force
38
Fig.3.12 Measured finishing force (current frequency)
Chapter 3. Investigation of magnetic field distribution and
finishing force
39
Fig.3.13 Effect of current frequency on finishing force
3.3.2.4 Impact of magnetic particle
In this experiment, we investigated the effect of magnetic particle
(Carbonyl iron powder with the mean diameter of 6μm, Electrolytic iron
powder with the mean diameter of 30μm) on finishing force. Electrolytic
iron powder and carbonyl iron powder have superior magnetic properties as
soft magnetic material. The most outstanding characteristic is that they
have low coercive force, and the coercive force is decreasing gradually
with the smaller of iron particle size. Therefore, they can show the
excellent responsiveness to improve the fluctuation of magnetic cluster
under alternating magnetic field. The measuring conditions are shown in
Table.3.6.
Chapter 3. Investigation of magnetic field distribution and
finishing force
40
Table.3.6 Measuring conditions
Measuring plate Brass plate C5210P, 115×33×0.6mm
Strain gauges KFN-2-350-C9-11
Work-Pole tip
clearance
3mm
Magnetic pole Material: SS400
Size: 15mm in diameter, with four crossing
grooves (width : 1mm, depth : 1.5mm)
Cutting fluid Neat cutting oil (Honilo 988): 0.8ml
Abrasive WA 10000, 1μm in mean dia: 0.3g
Alternating current 1.9A (Average)
Rotational speed of
magnetic pole
0 rpm
Current frequency 3Hz
Magnetic particles Carbonyl iron powder, 6μm in mean
dia:1.2g (type1)
Electrolytic iron powder, 30μm in mean
dia:1.2g (type2)
The measured finishing force waves are shown in Fig.3.14. The effect of
magnetic particles on finishing force was shown in Fig.3.15. It may be seen
that the size and variation amplitude of force is gradually increasing with
the increase of magnetic particles diameter. This is because the greater
magnetic particle can produce longer magnetic cluster, result in increased
fluctuate of magnetic force.
Chapter 3. Investigation of magnetic field distribution and
finishing force
41
Fig.3.14 Measured finishing force wave (magnetic particle)
Chapter 3. Investigation of magnetic field distribution and
finishing force
42
Fig.3.15 The effect of magnetic particle on finishing force
3.3.2.5 Impact of current
In this experiment, we investigated the effect of current (1A, 2A, 3A, 4A)
on finishing force. The measuring conditions are shown in Table.3.7.
The measured finishing force waves are shown in Fig.3.16. The effect of
current frequency on finishing force is shown in Fig.3.17. It can be seen
that the finishing force is increasing with the increase of current. This is
because the magnetic field intensity increase with the increase of current,
which makes the magnetic cluster become harder, improves finishing force.
However, the fluctuation amplitute of finishing force changed almost
nothing.
Chapter 3. Investigation of magnetic field distribution and
finishing force
43
Table.3.7 Measuring conditions
Measuring plate Brass plate C5210P, 115×33×0.6mm
Strain gauges KFN-2-350-C9-11
Work-Pole tip
clearance
3mm
Magnetic pole Material: SS400
Size: 15mm in diameter, with four crossing
grooves (width : 1mm, depth : 1.5mm)
Cutting fluid Neat cutting oil (Honilo 988): 0.8ml
Abrasive WA 10000, 1μm in mean dia: 0.3g
Magnetic particles Electrolytic iron powder, 30μm in mean
dia:1.2g
Rotational speed of
magnetic pole
0 rpm
Current frequency 3Hz
Alternating current 1A, 2A, 3A, 4A (peak value)
Chapter 3. Investigation of magnetic field distribution and
finishing force
44
Fig.3.16 Measured finishing force wave (current)
Chapter 3. Investigation of magnetic field distribution and
finishing force
45
Fig.3.17 The effect of current on finishing force
Chapter 3. Investigation of magnetic field distribution and
finishing force
46
3.4 Conclusion
In this chapter, we investigated the magnetic field distribution in
processing region and finishing force of plane MAF process using
alternating magnetic field, the main research results can be summarized as
follows:
(1) The size and direction of alternating magnetic field change
periodically; in processing region, magnetic flux density decreases
gradually from the outer diameter of magnetic pole (x=±6mm) to the center
of pole (x=±2mm) and produced a maximum value at the pole
edge(x=±7.5mm).
(2) A fluctuating finishing force was obtained under alternating magnetic
field. The average value of finishing force is greater than that of direct
magnetic field.
(3) Under alternating magnetic field, neat cutting oil can obtain higher
finishing force compared with water-soluble cutting fluid and silicone neat
cutting oil. It can combine with magnetic particles and abrasives adequately,
promote the magnetic cluster to produce feasible pulse magnetic force.
(4) The finishing force is increasing gradually with the increase of
rotational speed of magnetic pole.
(5) The finishing force is increasing with the increase of current
frequency.
(6) The size and variation amplitude of force is gradually increasing with
the increase of magnetic particles diameter.
(7) The force is gradually increasing with the increase of current.
Chapter 4.Finishing characteristics and mechanism of MAF
process using alternating magnetic field
47
Chapter 4.Finishing
characteristics and mechanism of
MAF process using alternating
magnetic field
4.1 Introduction
In the previous chapter, we investigated the distribution of magnetic field
density in finishing region and discussed the finishing force of alternating
magnetic field in detail.
Austenite stainless steels are frequently used as the materials of precise
instruments mainly because of it anti corrosive properties and high strength.
SUS304 is a kind of the austenite stainless steel, there are some features: (1)
Good corrosion resistance and heat resistance. (2) Excellent low
temperature strength and mechanical properties. (3) The remarkable hot
workability on punching bending. (4) No heat treatment hardening
phenomenon and non-magnetic. It is mainly used in indoor pipeline, water
heater, boiler, bath crock, auto parts, medical instruments, building
materials, chemical, food industry, agriculture, parts of the ship, etc.
A series of researches on the machining of the SUS304 using MAF
process have been reported in recent years. Zou et al. studied on SUS304
stainless steel flat, bend pipes, micro tubes and thick walled pipe tube [401 -
405]. Yamaguchi et al. researched the restraint of the burr when cutting of
Chapter 4.Finishing characteristics and mechanism of MAF
process using alternating magnetic field
48
Austenite stainless steel by the application of MAF process [406 - 407]
.
However, the few nanometers finish surface is still difficult to be acquired
by traditional MAF process.
In this chapter, we investigated the finishing characteristics of MAF
process using alternating magnetic field for SUS304 stainless steel plate,
discussed the effects of finishing parameters such as cutting fluid,
rotational speed of magnetic pole, abrasive and current frequency on
finishing characteristics. The feasibility and finishing performances of
plane MAF process using alternating magnetic field were verified by
finishing experiments. Moreover, we analysis of the movement of magnetic
particles under alternating magnetic field and discussed the mechanism of
MAF process using alternating magnetic field.
Chapter 4.Finishing characteristics and mechanism of MAF
process using alternating magnetic field
49
4.2 Finishing characteristics of plane MAF
process using alternating magnetic field
4.2.1 Experimental conditions and method
In this study, we conducted the comparison experiments, finishing the
SUS304 stainless steel plate in alternating magnetic field and direct
magnetic field, respectively.
The experimental conditions are shown in Table 4.1. The experiments
are divided into two stages. In order to improve the finishing efficiency,
electrolytic iron powder with the mean diameter of 30μm and WA#10000
abrasive were selected in the first stage. In case realize the ultra-precision
finishing, the magnetic particle diameter is limited in sevaral microns in
general. Carbonyl iron powder with the diameter of 6μm and diamond
powder with the mean diameter of 1μm were selected in second stage. Each
stage of the finishing time is 60 minutes. In order to understand the
variation of material removal and surface roughness, we measured the
workpiece every ten minutes. The selected surface roughness measurement
device is non-contact optical surface profiling with the type of WYKO
NT1100M. We used the 20X objective with a multiple magnification
detector of 1X, the field of view was 0.3mm.
Chapter 4.Finishing characteristics and mechanism of MAF
process using alternating magnetic field
50
Table 4.1 Experimental conditions
Parameters First stage Second stage
Finishing time 60min 60min
Magnetic particles Electrolytic iron
powder,30μm in
mean dia: 1.2g
Carbonyl iron
powder,6μm in mean
dia: 1.2g
Abrasives WA 10000, 1μm
in mean dia: 0.3g
diamond powder, 1μm in
mean dia: 0.3g
Finishing fluid Neat cutting oil (Honilo 988): 0.8ml
Feed speed of
mobile stage
260mm/min
Rotation speed of
magnetic pole
350 rpm
Workpiece SUS304 stainless steel plate with the size of
80mm×90mm×1mm
Magnetic field Type 1:Direct magnetic field:
I = 1.9A, U = 16V
Type 2:Alternating magnetic field:
Ia = 1.9A, Ea = 16V (average)
Current frequency :3Hz
4.2.2 Experimental results and discussion
Fig.4.1 shows the shape of magnetic cluster before and after finishing.
The compound magnetic finishing fluid become magnetic cluster under the
Chapter 4.Finishing characteristics and mechanism of MAF
process using alternating magnetic field
51
acting force of direct magnetic field, a mass of abrasives and finishing fluid
still remain to the tray and not be used sufficiently, and the magnetic cluster
produce serious deformation after finishing. On the other hand, it can be
seen that the magnetic particles, abrasive, cutting fluid is combined
sufficiently under the effect of alternating magnetic field. The abrasives
float the surface of magnetic cluster and the magnetic cluster is little
suffered deformation after finishing. This is because magnetic particles
themselves could produce the up and down movement under the acting of
electromagnetic force, which promote the scatter of magnetic particles and
improve the roll of abrasive particles. Moreover, as a result of the active
scatter of magnetic particles, the shape of magnetic cluster in alternating
magnetic field is larger than that of direct magnetic field. Therefore, plane
MAF process using alternating magnetic field is not only improved the
finishing efficiency but also increase the processing range.
Fig.4.2 shows the state of compound magnetic finishing fluid on surface
after 10 minutes finishing. It can be seen that a mass of abrasives is adhered
to finished surface under alternating magnetic field. In contrast, in direct
magnetic field, the compound magnetic finishing fluid on the workpiece
surface is nearly consumed, which indicated the abrasive in the top of
magnetic cluster not be renovated and difficult to realize the effective and
stable finishing.
Chapter 4.Finishing characteristics and mechanism of MAF
process using alternating magnetic field
52
(a) The first finishing stage
Chapter 4.Finishing characteristics and mechanism of MAF
process using alternating magnetic field
53
(b) The second finishing stage
Fig.4.1 Movement change of magnetic cluster before and after finishing
Chapter 4.Finishing characteristics and mechanism of MAF
process using alternating magnetic field
54
Fig.4.2 Comparison of compound magnetic finishing fluid on finished
surface
Fig.4.3 shows the variation of surface roughness (Ra) and material
removal (M) with the finishing time in alternating magnetic field and direct
magnetic field. In direct magnetic field, the material removals are 4.7mg
and 8.92mg in two stages finishing, respectively. In alternating magnetic
field, the material removals are 10.95mg and 15.02mg, respectively. It can
be seen that under alternating magnetic field material removal is
approximately twice as large compared with the direct magnetic field. In
alternating magnetic field, pulsed finishing force is produced. The effects
of pulsed vibration finishing hindered deformation of the magnetic cluster
and improved utilization rate of the abrasives.
On the other hand, in direct magnetic field, initial surface of 239.25nm
Ra pre-finishing was improved to 82.86 nm Ra after the first stage finishing,
and to 22.09nm Ra after the second stage finishing. In alternating magnetic
field, it was improved from 236.37nm Ra to 36.23nm Ra after the first
stage finishing, and then became 4.66nm Ra after the second stage
finishing. It can be seen that the surface roughness is decreasing gradually
Chapter 4.Finishing characteristics and mechanism of MAF
process using alternating magnetic field
55
over finishing time either in alternating magnetic field or direct magnetic
field. However, the improvement rate in the case of using alternating
magnetic field is higher than that of the direct magnetic field. Fig.4.4 shows
3D photographs of polished surfaces before and after finishing. Fig.4.5
shows photographs of polished surfaces before and after finishing. The
experimental results show that plane MAF process using alternating
magnetic field may realize nano-level finishing of plane, and may produce
a better finish. In alternating magnetic field, the continuous up and down
movement changes of the magnetic cluster improve the uniform
distribution of the abrasives, therefore, obtaining a smoother and more
uniform finished surface. Moreover, abrasives cutting edges scratching the
material in many directions have increased the finishing efficiency.
Chapter 4.Finishing characteristics and mechanism of MAF
process using alternating magnetic field
56
Fig.4.3 Variation of surface roughness and material removal with the
finishing time
Chapter 4.Finishing characteristics and mechanism of MAF
process using alternating magnetic field
57
Fig.4.4 3D photographs of polished surfaces before and after finishing
Chapter 4.Finishing characteristics and mechanism of MAF
process using alternating magnetic field
58
Fig.4.5 Photographs of finished surface of SUS304 stainless steel
Chapter 4.Finishing characteristics and mechanism of MAF
process using alternating magnetic field
59
4.3 Effect of finishing factors on finishing
characteristic
In this study, the experiment was divided into two stages to investigate
the effect of cutting fluid, rotational speed of magnetic pole and current
frequency on finishing characteristics. The finishing time of the first stage
was 60 minutes and the second finishing stage was 70 minutes. In order to
improve the finishing efficiency, electrolytic iron powder with the mean
diameter of 30μm and WA#10000 abrasive was selected in the first stage.
To realize the nano-level finishing, the diameter of magnetic particle is
within several microns in general. Therefore, in the second stage the
carbonyl iron powder with the diameter of 6μm and diamond powder with
the mean diameter of 1μm were selected.
In order to understand the variation of material removal and finish
surface over the time, we measured the workpiece every ten minutes. The
selected surface roughness measurement device is non-contact optical
surface profiling with the type of WYKO NT1100M.
Chapter 4.Finishing characteristics and mechanism of MAF
process using alternating magnetic field
60
4.3.1 Impact of cutting fluid
4.3.1.1 Experimental conditions and method
Cutting fluid is an important component of compound magnetic finishing
fluid, which is the carrier of magnetic particles, affecting the distribution of
abrasives and playing a role in lubrication and cooling in process.
Therefore, cutting fluid properties is the basis of ensuring the finishing
quality and efficiency. We selected water-soluble cutting fluid, silicone
fluid, and neat cutting oil based on the composition of cutting fluid for
experiments. The experimental conditions are shown in Table. 4.2.
Chapter 4.Finishing characteristics and mechanism of MAF
process using alternating magnetic field
61
Table.4.2 Experimental conditions
Parameters First stage Second stage
Finishing time 60min 70min
Magnetic particles Electrolytic iron
powder, 30μm
in mean dia:1.2g
Carbonyl iron
powder, 6μm in
mean dia:1.2g
Abrasive WA 10000,
1μm in mean
dia: 0.3g
Diamond
powder,1μm in
mean dia: 0.3g
Workpiece SUS304 stainless steel plate with the
size of 80mm×90mm×1mm
Alternating current 1.9A (Average)
Feed speed of mobile
stage
260 mm/min
Rotational speed of
magnetic pole
200rpm
Current frequency 3Hz
Cutting fluid Type 1: Water-soluble cutting fluid
(SCP-23): 0.8ml
Type 2: Silicone fluid
(KF-96-50CS): 0.8ml
Type 3: Neat cutting oil
(Honilo 988): 0.8ml
Chapter 4.Finishing characteristics and mechanism of MAF
process using alternating magnetic field
62
4.3.1.2 Experimental results and discussion
Fig.4.6 shows the effect of three different kinds of cutting fluid on the
finish surface and material removal. Fig.4.7 shows 3D photographs of
polished surfaces before and after finishing. It can be seen that the higher
surface roughness improvement and material removal can be obtained
using neat cutting oil. In contrast, when we use water-soluble cutting fluid
or silicone fluid, it is difficult to obtain the few nanometers finished
surface.
Why is the finish performance so different using different grinding fluids?
This is because grinding fluid has a great impact on the state of magnetic
cluster. Fig.4.8 shows the changes of magnetic cluster shape before and
after finishing in the conditions of using three different kinds of cutting
fluids. As shown in Fig. 4.8 (a), we can see that magnetic cluster produced
serious distortion using water-soluble cutting fluid. The magnetic particles
(black grains) generate fault after contacted with workpiece, and abrasives
(white powder) cannot disperse uniformly under the alternating magnetic
force. Silicone fluid can exhibit an excellent dispersion stability to prevent
the agglomeration of magnetic particles. However, magnetic particles
themselves cannot produce movement changes to promote the roll of
abrasive particles under the influence of alternating magnetic field.
Therefore, it is difficult to improve finishing efficiency and precision. Fig.
4.8 (c) shows that the neat cutting oil mixes with magnetic particles and
abrasives adequately and the magnetic cluster suffered little deformation
after finishing. This is because magnetic cluster itself can produce the up
and down movement in alternating magnetic field, which not only
Chapter 4.Finishing characteristics and mechanism of MAF
process using alternating magnetic field
63
promotes the dispersion of magnetic particles but also drives the abrasive to
float to the magnetic cluster surface for the polishing of workpiece.
(a) The first finishing stage
Chapter 4.Finishing characteristics and mechanism of MAF
process using alternating magnetic field
64
(b) The second finishing stage
Fig.4.6 Effect of cutting fluid on the surface roughness and material
removal
Chapter 4.Finishing characteristics and mechanism of MAF
process using alternating magnetic field
65
Fig.4.7 3D photographs of polished surfaces before and after finishing
(Cutting fluid)
Chapter 4.Finishing characteristics and mechanism of MAF
process using alternating magnetic field
66
Fig.4.8 Effect of cutting fluid on the shape of magnetic cluster
Chapter 4.Finishing characteristics and mechanism of MAF
process using alternating magnetic field
67
4.3.2 Impact of rotational speed of magnetic pole
In this experiment, we investigated the effect of rotational speed
(200rpm, 250rpm, 300rpm, 350rpm, 400rpm, 450rpm) on finish surface
and material removal. Some of magnetic particles and abrasive grains were
thrown out of tray when the rotational speed of magnetic pole is higher
than 450rpm. Therefore, rotational speed of magnetic pole is controlled
within 450rpm. The experimental conditions are shown in Table. 4.3.
Fig.4.9 shows the effect of rotational speed of magnetic pole on the
surface roughness and material removal. Fig.4.10 shows 3D photographs of
polished surfaces before and after finishing. It can be seen that the material
removal is increasing gradually with the increase of rotation speed. The
friction is increasing with the increase of relative speed between workpiece
and magnetic cluster, which is combined with pulse finishing force
produced by the up and down movement of magnetic particles, causing that
stock removal increases rapidly.
On the other hand, it is observed that the effect of rotation speed on
surface roughness improvement is different in different finishing stages.
Fig.4.9 (a) showed that in the first finishing stage, the improvement of
surface roughness is the best in the condition that rotation speed is 400rpm.
Fig.4.9 (b) showed that in the second finishing stage, the improvement of
surface roughness is the best when rotation speed is 350rpm. From the
experimental results, we may infer that when surface roughness of the
SUS304 stainless steel plate is greater than 90 nm, the highest finishing
efficiency will be obtained in the case that the rotational speed of magnetic
pole is 450rpm. When surface roughness is between 40nm and 90nm,
Chapter 4.Finishing characteristics and mechanism of MAF
process using alternating magnetic field
68
400rpm is considered to be the best experimental condition. When surface
roughness is lower than 40nm, the best finish surface will be obtained in
the condition of 350rpm, the surface roughness of SUS304 stainless steel
plate is improved from Ra 236.37nm to Ra 4.66nm in final.
Table.4.3 Experimental conditions
Parameters First stage Second stage
Finishing time 60min 70min
Magnetic particles Electrolytic iron
powder, 30μm in
mean dia:1.2g
Carbonyl iron
powder, 6μm in
mean dia:1.2g
Abrasive WA 10000, 1μm
in mean dia: 0.3g
Diamond
powder,1μm in
mean dia: 0.3g
Workpiece SUS304 stainless steel plate with the
size of 80mm×90mm×1mm
Alternating current 1.9A (Average)
Feed speed of mobile
stage
260 mm/min
Cutting fluid Neat cutting oil (Honilo 988): 0.8ml
Current frequency 3Hz
Rotational speed of
magnetic pole
200rpm, 250rpm, 300rpm
350rpm, 400rpm, 450rpm
Chapter 4.Finishing characteristics and mechanism of MAF
process using alternating magnetic field
69
Chapter 4.Finishing characteristics and mechanism of MAF
process using alternating magnetic field
70
Fig.4.9 Effect of rotational speed of magnetic pole on the surface roughness
and material removal
Chapter 4.Finishing characteristics and mechanism of MAF
process using alternating magnetic field
71
Chapter 4.Finishing characteristics and mechanism of MAF
process using alternating magnetic field
72
Fig.4.10 3D photographs of polished surfaces before and after finishing
(rotational speed of magnetic pole)
Chapter 4.Finishing characteristics and mechanism of MAF
process using alternating magnetic field
73
4.3.3 Impact of current frequency
In this experiment, we investigated the effect of current frequency (1Hz,
3Hz, 5Hz, 7Hz, 9Hz) on the movement of magnetic particles, finish surface
and material removal. The experimental conditions are shown in Table. 4.5.
Table.4.5 Experimental conditions
Parameters First stage Second stage
Finishing time 60min 70min
Magnetic particles Electrolytic iron
powder, 30μm in
mean dia:1.2g
Carbonyl iron
powder, 6μm in
mean dia:1.2g
Abrasive WA 10000,
0.5μm in mean
dia: 0.3g
Diamond
powder,1μm in
mean dia: 0.3g
Workpiece SUS304 stainless steel plate with the
size of 80mm×90mm×1mm
Alternating current 1.9A (Average)
Feed speed of mobile stage 260 mm/min
Cutting fluid Neat cutting oil (Honilo 988): 0.8ml
Rotational speed of
magnetic pole
350rpm
Current frequency 1Hz, 3Hz, 5Hz, 7Hz, 9Hz
Chapter 4.Finishing characteristics and mechanism of MAF
process using alternating magnetic field
74
Fig.4.11. Movement change of magnetic particles under alternating
magnetic field
Fig.4.11 shows the movement change of magnetic particles under
alternating magnetic field. Owing to that the force direction of Fy is
changing with the magnetic field direction, magnetic particles can produce
the up and down movement change. The change speed and angle θ are
closely related to current frequency. Table.4.6 shows angle variation of
magnetic particles in different frequency. It can be seen that the angle
variation θ is decreasing with the increase of current frequency. The greater
the angle of magnetic particles change, magnetic cluster is more flexible.
Therefore, we can obtain the most flexible magnetic cluster in the condition
of 1Hz.
Chapter 4.Finishing characteristics and mechanism of MAF
process using alternating magnetic field
75
Table.4.6 Effect of current frequency on angle variation
Angle variation θ Current frequency
30°~ 45° 1Hz
15°~ 30° 3Hz
5°~ 15°
5°~ 10°
5Hz ,
7Hz
0°~ 5° 9Hz
Fig.4.12 shows the effects of current frequency on the surface roughness
and material removal. Fig.4.13 shows 3D photographs of polished surfaces
before and after finishing. In the first finishing stage, when frequency was
smaller than 7Hz, the surface roughness improvement and material removal
rate were increasing gradually with the increase of frequency. This is
because the finishing force is increasing with the increase of frequency.
However, in the second finishing stage, the highest surface roughness
improvement was obtained in the case of 1Hz, in contrast, the finish
surface was difficult to be improved to 10nm when current frequency was
greater than 5Hz. This is because the increase of frequency had few effects
on finishing force in the second stage, but the increase of magnetic cluster
angle variation may promote the roll of abrasive particles more effectively
and improve the cross-cutting effects of abrasives.
Chapter 4.Finishing characteristics and mechanism of MAF
process using alternating magnetic field
76
(a) The first finishing stage
Chapter 4.Finishing characteristics and mechanism of MAF
process using alternating magnetic field
77
(b) The second finishing stage
Fig.4.12 Effect of current frequency on the surface roughness and material
removal
Chapter 4.Finishing characteristics and mechanism of MAF
process using alternating magnetic field
78
Fig.4.13 3D photographs of polished surfaces before and after finishing
(Current frequency)
Chapter 4.Finishing characteristics and mechanism of MAF
process using alternating magnetic field
79
Fig.4.14 and Fig.4.15 shows the 3D profile and SEM image of the
finished surface in the condition that neat cutting oil, rotational speed of
magnetic pole is 350r/min and current frequency is 1Hz. The surface
roughness of SUS304 stainless steel plate is improved from 240.24nm to
4.37nm. Moreover, photographs of before and after finishing surface are
shown in Fig.4.16. It can be seen that a smooth surface with less scratches
is obtained. From these results, it has been understood that the nano-level
finishing of SUS304 stainless steel plate can be realized by MAF process
using low frequency alternating magnetic field.
Fig.4.14 3D photographs of polished surfaces before and after finishing
Chapter 4.Finishing characteristics and mechanism of MAF
process using alternating magnetic field
80
Fig.4.15 SEM image of before and after finishing surface
Chapter 4.Finishing characteristics and mechanism of MAF
process using alternating magnetic field
81
Fig.4.16 Photographs of before and after finishing surface
Chapter 4.Finishing characteristics and mechanism of MAF
process using alternating magnetic field
82
4.4 Improvement of finishing efficiency
4.4.1 Experimental conditions
Table.4.7 Experimental conditions
Parameters First stage Second stage
Finishing time 20min 20min
Magnetic particles Electrolytic iron
powder,30μm in
mean dia: 1.2g
Carbonyl iron
powder,6μm in mean dia:
1.2g
Frequency 7Hz 3Hz
Rotation speed of
magnetic pole
450 rpm 350 rpm
Workpiece SUS304 plate with the size of
80mm×90mm×1mm
Feed speed of
mobile stage
260mm/min
Finishing fluid Neat cutting oil (Honilo 988): 0.8ml
Abrasives diamond powder, 1μm in mean dia: 0.3g
Alternating current 3A
In preceding sections, we understood the effect of finishing factors on
finishing characteristic. In order to improve finishing efficiency, we
changed experimental conditions to finish the SUS304 stainless steel plate.
Chapter 4.Finishing characteristics and mechanism of MAF
process using alternating magnetic field
83
Table 4.7 show that the experimental conditions, the size of SUS304
stainless plate is 80mm×90mm×1mm. The size reduction of the magnetic
particles to less than 10μm was expected to promote few nanometers
finishing. With the point considered, a two-stages finishing process was
introduced to improve the surface roughness. Experiments were performed
using 30μm iron particles, 7Hz magnetic field frequency and 450rpm
rotation speed of magnetic pole in the first phase. In the second stage, the
mean diameter of electrolytic iron powder is 6μm, rotation speed of
magnetic pole is 350rpm and magnetic field frequency is 3Hz. Each stage
of the finishing time is 20 minutes.
4.4.2 Experimental results and discussion
Fig.4.17 Changes in surface roughness and material removal with the
finishing time
Fig.4.17 shows the changes in the surface roughness and material removal
Chapter 4.Finishing characteristics and mechanism of MAF
process using alternating magnetic field
84
with finishing time. The improvement of surface roughness and material
removal is higher than that of the second finishing stage. This is because in
the first stage, the diameter of iron particles, magnetic field frequency and
rotational speed were greater than that of the second finishing stage. Initial
surface of 128.19nm Ra pre-finishing was improved to 6.2nm Ra after the
two stages finishing, and the roughness surface of 1.2μm Rz pre-finishing
was improved to 67.36nm. Fig.4.18 shows surface roughness profiles of
unfinished and finished. The experimental results show that the acquisition
of few nanometers finishing surface of SUS304 stainless steel is possible
by MAF using alternating magnetic field.
Chapter 4.Finishing characteristics and mechanism of MAF
process using alternating magnetic field
85
Fig.4.18 3D photographs of polished surfaces before and after finishing of
SUS304
Chapter 4.Finishing characteristics and mechanism of MAF
process using alternating magnetic field
86
4.5 Mechanism of plane MAF process using
alternating magnetic field
Fig.4.19 shows that schematic of relative motion between magnetic
abrasives and workpiece. The MAF process using alternating magnetic
field exist three kinds of movement, including feed movement, rotational
motion and the up and down fluctuation of magnetic brush.
Fig.4.19 Schematic of relative motion between magnetic abrasives and
workpiece
The effect of alternating magnetic field on magnetic brush was shown in
Fig.4.20. It mainly include: (1).Blending deformation of magnetic brush.
(2).Compression between abrasive particles. (3).The rotational motion and
slide of the abrasive particle itself. (4).The mutual movement between
abrasive particles.
Chapter 4.Finishing characteristics and mechanism of MAF
process using alternating magnetic field
87
Fig.4.20 The movement of magnetic abrasives in alternating magnetic field
Under the action of alternating magnetic field, the flexible magnetic
cluster consisted by micro iron powders can generate a higher finishing
force against finished surface, and may closely follow the finished surface.
Utilizing this characteristic, we may conduct to ultra-precision finishing on
flat surface and micro complex surface. The continued fluctuation of
flexible magnetic cluster promotes the abrasives into all finished surface,
combine effectively corner and groove surface. Moreover, with the
fluctuation of magnetic cluster the abrasive particles can be refreshed and
mixed during finishing process without recharging, which improve
homogenous of finish surface and enhance finishing efficiency. Fig.4.21
shows the characteristic behavior of magnetic cluster in process. When the
direction of magnetic field is forced down, the abrasives may adequately
Chapter 4.Finishing characteristics and mechanism of MAF
process using alternating magnetic field
88
mix together with magnetic particles. When the direction of magnetic field
is forced up, magnetic particles may drive the abrasives to float to the
magnetic cluster surface to polish the workpiece. The continued up and
down movement change of the magnetic clusters achieve circulation and
update to ensure the stability of grinding tools.
Fig.4.21 Movement change of magnetic cluster under alternating magnetic
field
Chapter 4.Finishing characteristics and mechanism of MAF
process using alternating magnetic field
89
4.6 Conclusion
In this chapter, we investigated the finishing characteristics of plane
MAF process using alternating magnetic field and discussed the
mechanism, the main research results can be summarized as follows:
(1) Neat cutting oil is more applicable to MAF process using alternating
magnetic field. It can combine with magnetic particles and abrasives
adequately, promote the magnetic cluster to produce feasible pulse
magnetic force. In MAF process using alternating magnetic field, neat
cutting oil not only can obtain higher material removal, but also get a
smoother finished surface compared with water-soluble cutting fluid and
silicone neat cutting oil.
(2) The material removal is increasing gradually with the increase of
rotational speed of magnetic pole. The effect of rotational speed of
magnetic pole on surface roughness improvement rate is different in
different finishing stages. When surface roughness of the SUS304 stainless
steel plate is greater than 90 nm, the highest finishing efficiency is obtained
in the case of 450rpm. When surface roughness is between 40nm and 90nm,
400rpm is considered to be the best experimental condition. When surface
roughness is lower than 40nm, the best finish surface is obtained in the
condition of 350 rpm.
(3) The angle variation of magnetic particles is decreasing with the
increase of current frequency. The increase of angle variation can promote
the roll of abrasive particles more effectively and improve the utilization
rate of the abrasive.
(4) In the first finishing stage, when current frequency is smaller than
Chapter 4.Finishing characteristics and mechanism of MAF
process using alternating magnetic field
90
7Hz the surface roughness improvement and material removal rate is
increasing gradually with the increase of frequency. In the several
nano-level finishing stage, the best finish surface is obtained in the case of
1Hz. The experimental results showed that in the case finish surface is
lower than 30nm, MAF process using low frequency alternating magnetic
field can realize the several nano-level finishing more effectively.
(5) The plane MAF process using alternating magnetic field may obtain a
better finish surface compared of using direct magnetic field. This process
can realize the nano-level finish surface of plane.
(6) The effect of alternating magnetic field on magnetic brush mainly
include: (1).Blending deformation of magnetic brush. (2).Compression
between abrasive particles. (3).The rotational motion and slide of the
abrasive particle itself. (4).The mutual movement between abrasive
particles.
Under the action of alternating magnetic field, the flexible magnetic
cluster can generate a higher finishing force against finished surface, and
may closely follow the finished surface. Utilizing this characteristic, we
may conduct to ultra-precision finishing on flat surface and micro complex
surface. The continued fluctuation of flexible magnetic cluster promotes
the abrasives into all finished surface, combine effectively corner and
groove surface. Moreover, with the fluctuation of magnetic cluster the
abrasive particles can be refreshed and mixed during finishing process
without recharging, which improve homogenous of finish surface and
enhance finishing efficiency.
Chapter 5. Plane MAF process using alternating magnetic field in
industry application
91
Chapter 5. Plane MAF process
using alternating magnetic field in
industry application
5.1 Introduction
In the chapter.4, we investigated the finishing characteristics and
mechanism of MAF process using alternating magnetic field. In this
chapter, we focus on researching plane MAF process using alternating
magnetic field in industry application. At first, we conducted flat finishing
experiments for POM and brass, respectively and understood processing
particularity of this process in different materials. Secondly, we made
silicon optical wafer with micro - channel as processed object, discussed
the application of MAF process using alternating magnetic field in
finishing of complicated micro-curved surface.
Chapter 5. Plane MAF process using alternating magnetic field in
industry application
92
5.2 Precision finishing of POM resin plate
5.2.1Finishing importance of POM resin plate
POM (Poly form aldehyde) is a kind of homopolymer, it has four
outstanding features: (1) It has high mechanical strength, which can resist
fatigue resistance of alternating force millions of times. (2) It has
outstanding resistance to chemical attack by a broad spectrum of organic
chemicals, inorganic chemicals and solvents. (3) It can resist the creep
resistance generated by high stress loading. (4) It can show the specific
lubricity and wear resistance in the process of power transmission and
conduction. The unique function of POM makes it play an irreplaceable
role in engineering materials. In 1960, the Du Pont developed the POM,
and then the POM is gradually applied to aviation, automobile, precision
instruments, electrical, medical and buildings etc. It is mainly used in the
manufacture of all kinds of drive mechanisms, such as precision parts,
gears and bearings, etc.
5.2.2 Experimental conditions
The experimental conditions are shown in Table 5.1. The experiments
are divided into two stages. In order to improve the finishing efficiency,
electrolytic iron powder with the mean diameter of 30μm, WA#10000
abrasive, 450rpm rotation speed of magnetic pole and 7Hz magnetic field
frequency were selected in the first stage. In case realize the ultra-precision
finishing, the magnetic particle diameter is limited in sevaral micrometers
Chapter 5. Plane MAF process using alternating magnetic field in
industry application
93
in general. Carbonyl iron powder with the diameter of 6μm, diamond
powder with the mean diameter of 1μm, 350rpm rotation speed of magnetic
pole and 7Hz magnetic field frequency were selected in the second stage.
Each stage of the finishing time is 20 minutes. In order to understand the
variation of material removal and surface roughness, we measured the
workpiece every ten minutes. The selected surface roughness measurement
device is non-contact optical surface profiling with the type of WYKO
NT1100M.
Table.5.1 Experimental conditions
Parameters First stage Second stage
Finishing time 20min 20min
Magnetic particles Electrolytic iron
powder,30μm in
mean dia: 1.2g
Carbonyl iron powder,6μm
in mean dia: 1.2g
Frequency 7Hz 3Hz
Rotation speed of
magnetic pole
450 rpm 350 rpm
Workpiece POM plate with the size of 80mm×90mm×1mm
Feed speed of
mobile stage
260mm/min
Cutting fluid Neat cutting oil (Honilo 988): 0.8ml
Abrasives diamond powder, 1μm in mean dia: 0.3g
Alternating current 3A
Chapter 5. Plane MAF process using alternating magnetic field in
industry application
94
5.2.3 Experimental results and discussion
Fig.5.1 Changes in surface roughness and material removal with the
finishing time
Fig.5.1 shows the variation of surface roughness (Ra) and material
removal (M) with the finishing time in two finishing stages. It can be seen
that initial surface of 340.02nm Ra pre-finishing was improved to 30.58nm
Ra after the two stages finishing, and the roughness surface of 3.58μm Rz
pre-finishing was improved to 340.59nm after finishing. Fig.5.2 and Fig.5.3
shows 3D photographs and SEM images of polished surfaces before and
after finishing. The experimental results show that MAF process using low
frequency alternating magnetic field may realize ultra-precision finishing
of POM plate.
Chapter 5. Plane MAF process using alternating magnetic field in
industry application
95
Fig.5.2 Photographs of finished surface of POM plate
Chapter 5. Plane MAF process using alternating magnetic field in
industry application
96
(a) Before finishing (b)After finishing
Fig.5.3 SEM image
Chapter 5. Plane MAF process using alternating magnetic field in
industry application
97
5.3 Precision finishing of Brass C2680
5.3.1Finishing importance of Brass C2680
Brass C2680 is the most widely used in ordinary brass varieties, which is
featured by good thermoplastic, high strength and high machining
performance. It can be easily welded and can overcome the general
corrosion. It is mainly applied to glasses accessories, rivet, battery core rod,
fasteners, springs, brazing and welding wire and the cutting line.
The cutting resistance of Brass C2680 is lower in metallic materials. This
makes it possible to realize rapid machining. However, to processing
quality, the conventional using numerically-controlled machine tool
process is considered to be difficult to obtain effectively few nanometer
finish surface. This is because that the hard cutting tool is easy to cause to
surface scratches thereby decrease surface precision. MAF process is
considered to more applicable to nanometer level surface finishing because
the magnetic cluster as machine tool is more flexible than conventional
cutter. Therefore, we try to realize the ultra-precision finishing of C2680 by
use of the magnetic abrasive finishing process.
5.3.2 Experimental conditions
The experimental conditions are shown in Table 5.2. The experiments
are divided into two stages. In the first stage, the mean diameter of
electrolytic iron powder is 30μm, rotation speed of magnetic pole is
450rpm and magnetic field frequency is 7Hz. In the second stage, the mean
Chapter 5. Plane MAF process using alternating magnetic field in
industry application
98
diameter of electrolytic iron powder is 6μm, rotation speed of magnetic
pole is 350rpm and magnetic field frequency is 3Hz. Each stage of the
finishing time is 20 minutes. In order to understand the variation of
material removal and surface roughness, we measured the workpiece every
ten minutes.
Table.5.2 Experimental conditions
Parameters First stage Second stage
Finishing time 20min 20min
Magnetic particles Electrolytic iron
powder,30μm in
mean dia: 1.2g
Carbonyl iron powder,6μm
in mean dia: 1.2g
Frequency 7Hz 3Hz
Rotation speed of
magnetic pole
450 rpm 350 rpm
Workpiece C2680 plate with the size of 80mm×90mm×1mm
Feed speed of
mobile stage
260mm/min
Finishing fluid Neat cutting oil (Honilo 988): 0.8ml
Abrasives Diamond powder, 1μm in mean dia: 0.3g
Alternating current 3A
5.3.3 Experimental results and discussion
Fig.5.4 shows the variation of surface roughness (Ra) and material
Chapter 5. Plane MAF process using alternating magnetic field in
industry application
99
removal (M) with the finishing time in two finishing stages. It can be seen
that initial surface of 440.36nm Ra pre-finishing was improved to 9.99nm
Ra after the two stages finishing, and the roughness surface of 4.13μm Rz
pre-finishing was improved to 97.34nm after finishing. Fig.5.5 and Fig.5.6
shows 3D photographs and SEM images of polished surfaces before and
after finishing. Moreover, photographs of before and after finishing surface
are shown in Fig.5.7 It can be seen that a smooth surface with less
scratches is obtained. The experimental results show that MAF process
using low frequency alternating magnetic field may realize few nanometers
finishing of C2680.
Fig.5.4 Changes in surface roughness and material removal with the
finishing time
Chapter 5. Plane MAF process using alternating magnetic field in
industry application
100
Fig.5.5 3D photographs of polished surfaces before and after finishing of
Brass C2680
Chapter 5. Plane MAF process using alternating magnetic field in
industry application
101
(a) Before finishing (b) After finishing
Fig.5.6 SEM image
Chapter 5. Plane MAF process using alternating magnetic field in
industry application
102
Fig.5.7 Photographs of finished surface of C2680 copper plate
Chapter 5. Plane MAF process using alternating magnetic field in
industry application
103
5.4 Precision finishing of micro groove parts
5.4.1Introduce
Nowadays, as consumer and industrial products increasingly head towards
miniaturisation, it is urged for a viable technology that can produce
efficiently micro-featured parts in a wide range of materials with high
precision. In this section, we selected silicon optical wafer with micro -
channel as the processing object. The silicon optical wafer has outstanding
features such as electrical insulation properties, arc resistance, chemical
stability and general corrosion capability. Therefore, it is widely applied for
the scope of optical, semiconductor, medical, aviation and scientific
instruments. Using the traditional processing technology, it not only spend
a lot of finishing time but also difficult to guarantee the uniformity of
processing. Moreover, due to silicon optical wafer have the nature of
fragile the sharp machining tools is easy to damage original channel shape.
In this study, we conducted the comparison experiments, finishing the
silicon optical wafer in alternating magnetic field and direct magnetic field,
respectively.
5.4.2 Experimental conditions
Experimental conditions as shown in Table 5.3. The diameter of silicon
optical wafer is 30mm. The size reduction of the magnetic particles to less
than 10μm was expected to promote few nanometers finishing. With the
point considered, a two-stages finishing process was introduced to improve
Chapter 5. Plane MAF process using alternating magnetic field in
industry application
104
the surface roughness. Experiments were performed using 30μm iron
particles, 7Hz magnetic field frequency and 450rpm rotation speed of
magnetic pole in the first phase. In the second stage, the mean diameter of
electrolytic iron powder is 6μm, rotation speed of magnetic pole is 350rpm
and magnetic field frequency is 3Hz. Each stage of the finishing time is 20
minutes.
Table.5.3 Experimental conditions
Parameters First stage Second stage
Finishing time 20min 20min
Magnetic particles Electrolytic iron
powder,30μm in
mean dia: 1.2g
Carbonyl iron powder,6μm
in mean dia: 1.2g
Rotation speed of
magnetic pole
450 rpm 350 rpm
Workpiece Material : silicon optical wafer
Size : 30mm in diameter, with 5 crossing grooves
(width:2μm,depth:1μm)
Feed speed of
mobile stage
260mm/min
Finishing fluid Neat cutting oil (Honilo 988): 0.8ml
Abrasives Diamond powder, 1μm in mean dia: 0.3g
Magnetic field Type 1:Direct magnetic field:
I = 1.9A, U = 16V
Type 2:Alternating magnetic field:
Ia = 1.9A, Ea = 16V (average)
frequency :7Hz (first finishing stage)
3Hz (second finishing stage)
Chapter 5. Plane MAF process using alternating magnetic field in
industry application
105
5.4.3 Experimental results and discussion
The measuring position is shown in Fig.5.8. In this study, we measured
surface roughness in point A, B, C and D, respectively and investigated the
change of groove and edge before and after finishing by use of SEM.
Fig.5.8 Measured method
Fig.5.9 shows the changes of the surface roughness in point A, B, C and D.
In direct magnetic field, the initial surface roughness of 123.38nm (A)
130.71nm (B), 136.08nm (C), 129.39nm (D) decreased to 63.66nm (A),
72.78nm (B), 71.18nm (C), 70.92nm (D) after 40 min. In alternating
magnetic field, it became to 55.18nm (A), 50.92nm (B), 55.62nm (C),
52.42nm (D) after finishing. It can be seen that the surface roughness is
decreasing gradually over finishing time either in alternating magnetic field
or direct magnetic field. However, the improvement rate in the case of
using alternating magnetic field is higher than that of the direct magnetic
field for the finishing of silicon optical wafer.
Chapter 5. Plane MAF process using alternating magnetic field in
industry application
106
Fig.5.9 Measured result of surface roughness
Fig. 5.10 shows SEM photographs of the groove and edge before and after
finishing under two different magnetic fields. We know that both in the
case of direct magnetic field or alternating magnetic field burr was
removed to some extent. However, we found that in the case of direct
magnetic field the edge side of micro-curved surface was worn in
processing leads to the damage of the original shape.
Chapter 5. Plane MAF process using alternating magnetic field in
industry application
107
Fig.5.10 SEM image of finished surface of silicon optical wafer
Chapter 5. Plane MAF process using alternating magnetic field in
industry application
108
5.5 Conclusions
In this chapter, we discussed the MAF process using alternating
magnetic field in industry application. The main research results can be
summarized as follows:
(1). We conducted flat finishing experiments for SUS304, brass and POM,
respectively and understood processing particularity of this process in
different materials. In the finishing of POM, initial surface of 340.02nm Ra,
3.58μm Rz pre-finishing was improved to 30.58nm Ra, 340.59nm Rz after
40min. In the finishing of C2680 brass, initial surface of 440.36nm Ra,
4.13μm Rz pre-finishing decreased to 9.99nm Ra, 97.34nm Rz after 40min
finishing.
(2). In this chapter, surface finishing and deburring characteristics of
silicon optical wafer are investigated. The finishing experiment results
demonstrate that realization of the efficient finishing of silicon optical
wafer is possible by MAF process using alternating magnetic field.
Moreover, we know that MAF process using alternating magnetic field not
only remove burr in micro groove of silicon optical wafer but also retain
the original shape of workpiece.
Chapter 6.Conclusions
109
Chapter 6.Conclusions
In order to realize the ultra-precision finishing of flat and complicated
micro surface components, we proposed a new ultra-precision plane
magnetic abrasive finishing process using alternating magnetic field in this
paper. This process can produce a fluctuating finishing force under the
action of alternating magnetic field, which not only may prevent magnetic
cluster deformation, but also promotes the abrasives into all finished
surface, achieving circulation and update to ensure the stability of grinding
tool. In this study, we fabricated a set of experimental setup, investigated
the magnetic field distribution and studied the effects of fluctuating
magnetic cluster on finishing force and abrasive behavior. Moreover, we
analysis of finishing mechanism, investigated the finishing characteristics
and discussed its application in industry. The main research contents in
each chapter are as follows:
In chapter 1, we introduced the characteristics of magnetic abrasive
finishing process, research background and research significance.
Moreover, we expounded the necessity of research and the aim of this
paper accord to analysis of research process of plane MAF process.
In chapter 2, the author proposed a new ultra-precision plane MAF
process using alternating magnetic field and developed a set of
experimental setup and investigated the magnetic field distribution. The
main research achievements are as following:
1. We compared to finishing principle in MAF process using static
Chapter 6.Conclusions
110
magnetic field and MAF process using alternating magnetic field. In static
magnetic field, the magnetic particles are easy to agglomerate, magnetic
cluster is difficult to recover to its original shape and abrasives cannot be
adequately transported over the magnetic cluster in finishing process. In
alternating magnetic field, we can obtain a fluctuating finishing force,
which not only may prevent magnetic cluster deformation, but also
promotes the abrasives into all finished surface, achieving circulation and
update to ensure the stability of grinding tool.
2. A set of experimental devices have been designed for finishing flat
surface.
In chapter 3, we investigated the magnetic field distribution in processing
region and finishing force of plane MAF process using alternating
magnetic field, the main research results can be summarized as follows:
1. The size and direction of alternating magnetic field change periodically;
in processing region, magnetic flux density decreases gradually from the
outer diameter of magnetic pole (x=±6mm) to the center of pole (x=±2mm)
and produced a maximum value at the pole edge(x=±7.5mm).
2. A fluctuating finishing force was obtained under alternating magnetic
field. The average value of finishing force is greater than that of direct
magnetic field.
3. Under alternating magnetic field, neat cutting oil can obtain higher
finishing force compared with water-soluble cutting fluid and silicone neat
cutting oil. It can combine with magnetic particles and abrasives adequately,
promote the magnetic cluster to produce feasible pulse magnetic force.
4. The finishing force is increasing gradually with the increase of
Chapter 6.Conclusions
111
rotational speed of magnetic pole.
5. The finishing force is increasing with the increase of current frequency.
6. The size and variation amplitude of force is gradually increasing with
the increase of magnetic particles diameter.
In chapter 4, we investigated the finishing characteristics and mechanism
of plane MAF process using alternating magnetic field, the main research
results can be summarized as follows:
1. Neat cutting oil is more applicable to MAF process using alternating
magnetic field. It can combine with magnetic particles and abrasives
adequately, promote the magnetic cluster to produce feasible pulse
magnetic force. In MAF process using alternating magnetic field, neat
cutting oil not only can obtain higher material removal, but also get a
smoother finished surface compared with water-soluble cutting fluid and
silicone neat cutting oil.
2. The material removal is increasing gradually with the increase of
rotational speed of magnetic pole. The effect of rotational speed of
magnetic pole on surface roughness improvement rate is different in
different finishing stages. When surface roughness of the SUS304 stainless
steel plate is greater than 90 nm, the highest finishing efficiency is obtained
in the case of 450rpm. When surface roughness is between 40nm and 90nm,
400rpm is considered to be the best experimental condition. When surface
roughness is lower than 40nm, the best finish surface is obtained in the
condition of 350 rpm.
3. The angle variation of magnetic particles is decreasing with the
increase of current frequency. The increase of angle variation can promote
the roll of abrasive particles more effectively and improve the utilization
Chapter 6.Conclusions
112
rate of the abrasive.
4. In the first finishing stage, when current frequency is smaller than 7Hz
the surface roughness improvement and material removal rate is increasing
gradually with the increase of frequency. In the several nano-level finishing
stage, the best finish surface is obtained in the case of 1Hz. The
experimental results showed that in the case finish surface is lower than
30nm, MAF process using low frequency alternating magnetic field can
realize the several nano-level finishing more effectively.
5. The plane MAF process using alternating magnetic field may obtain a
better finish surface compared of using direct magnetic field. This process
can realize the nano-level finish surface of plane.
6. The effect of alternating magnetic field on magnetic brush mainly
include: (1).Blending deformation of magnetic brush. (2).Compression
between abrasive particles. (3).The rotational motion and slide of the
abrasive particle itself. (4).The mutual movement between abrasive
particles.
Under the action of alternating magnetic field, the flexible magnetic
cluster can generate a higher finishing force against finished surface, and
may closely follow the finished surface. Utilizing this characteristic, we
may conduct to ultra-precision finishing on flat surface and micro complex
surface. The continued fluctuation of flexible magnetic cluster promotes
the abrasives into all finished surface, combine effectively corner and
groove surface. Moreover, with the fluctuation of magnetic cluster the
abrasive particles can be refreshed and mixed during finishing process
without recharging, which improve homogenous of finish surface and
enhance finishing efficiency.
Chapter 6.Conclusions
113
In chapter 5, we discussed the MAF process using alternating magnetic
field in industry application. The main research results can be summarized
as follows:
1. We conducted flat finishing experiments for SUS304, brass and POM,
respectively and understood processing particularity of this process in
different materials. In the finishing of POM, initial surface of 340.02nm Ra,
3.58μm Rz pre-finishing was improved to 30.58nm Ra, 340.59nm Rz after
40min. In the finishing of C2680 brass, initial surface of 440.36nm Ra,
4.13μm Rz pre-finishing decreased to 9.99nm Ra, 97.34nm Rz after 40min
finishing.
2. We investigated surface finishing and deburring characteristics of
silicon optical wafer. The finishing experiment results demonstrate that
realization of the efficient finishing of silicon optical wafer is possible by
MAF process using alternating magnetic field. Moreover, we know that
MAF process using alternating magnetic field not only remove burr in
micro groove of silicon optical wafer but also retain the original shape of
workpiece.
In chapter 6, we summarized the main research achievements in each
chapter.
Reference
114
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Acknowledgement
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Acknowledgement
I would like to express my profound sense of gratitude to my advisor,
Associate Professor Zou Yanhua whose guidance and constructional
advises were in valuable. Especially informative guidance and suggestions
from her for the period of four years are gratefully acknowledged.
I would also like to express sincere thank the committee members,
Professor Sugiyama Hitoshi, Professor Takayama Yoshimasa, Professor
Yokota Kazutaka and Professor Yoshida Katsutoshi for their valuable
suggestions.
This completion of the research has involved cooperations from
Utsunomiya University Machine Shop staff who has contributed their time
and workmanship for the machining parts produced to realize the finishing
machine in this research. A warm thankful to Utsunomiya University
Innovation Center for Research and Education due to the provided 3D
design software SolidWorks.
I would also like to thank the Rotary Yoneyama Memorial Foundation
for provide the scholarship to make me accomplish concentrative this study.
Gratitude is also extended to Utsunomiya University, creative Department
for Innovation (CDI) for their support in this research.
Special thanks are due to my wife Yang Renxue, my best friend Liu
Chunliang and Mr. Fukumoto Mitsuo whose sacrifice and encouragement
made this study complete.
Contributed papers related to this study
124
Contributed papers related to this
study
[1] Articles
(1) Study on an ultra-precision plane magnetic abrasive finishing process
by use of alternating magnetic field, Jinzhong Wu,Yanhua Zou, Applied
Mechanics and Materials, Vols. 395 - 396, pp. 985 - 989, (2013).
(2) Study on ultra-precision magnetic abrasive finishing process using
low frequency alternating magnetic field, Jinzhong Wu, Yanhua Zou,
Hitoshi Sugiyama, Journal of Magnetism and Magnetic Materials,
Vol.386 (15),pp.50 - 59, (2015).
(3) Study on finishing characteristics of magnetic abrasive finishing
process using low frequency alternating magnetic field, Jinzhong Wu,
Yanhua Zou, Hitoshi Sugiyama, The International Journal of Advanced
Manufacturing Technology, DOI 11007/s00170-015-7962-9, (2015).
Contributed papers related to this study
125
[2] Meetings
(1) Development of ultra-precision plane magnetic abrasive finishing
process by application of variable magnetic field, Yanhua Zou, Jinzhong
Wu,The Japan Society for Precision Engineering, Spring Meeting (14th
March 2013), pp.173 - 174.
(2) Development of Ultra-precision plane Magnetic Abrasive Finishing
Process using alternating magnetic field, Yanhua Zou, Jinzhong Wu,The
Japan Society for abrasive technology, Autumn Meeting (11th September
2014), pp.339 - 340.
(3) Study on ultra-precision plane magnetic abrasive finishing process
using alternating magnetic field - Effect of rotational speed of magnetic
pole on finishing characteristics -, Jinzhong Wu,Yanhua Zou, The Japan
Society for abrasive technology, Autumn Meeting (10th September 2015),
pp.318 - 319.