ArticlePDF Available

Abstract and Figures

Magnesium alloy is highly potential material for biodegradable implant application. Due to limitations in conventional machining methods, non-traditional machining method such as electrical discharge machining (EDM) die sinking process is proposed to produce intricate shape with tight tolerance on magnesium alloy. Nine EDM experiments with three levels and four parameters were conducted using Taguchi method on AZ31 magnesium alloy to explore the optimum machining parameters. It was found that pulse on-time was the most significant parameter affecting the surface roughness (Ra) of the machined surface. The optimum EDM condition obtained was 47 A peak current, 80V voltage, 16μs pulse on-time and 512μs pulse off-time. A confirmation test was conducted and the result shows 95.5% similarity with the predicted Ra. However, the formation of cracks and craters were found on the machined surface area. It is proposed to solve this problem by applying powder mixed EDM method in future research work.
Content may be subject to copyright.
Procedia Engineering 148 ( 2016 ) 916 922
1877-7058 © 2016 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license
Peer-review under responsibility of the organizing committee of ICPEAM 2016
doi: 10.1016/j.proeng.2016.06.501
Available online at
4th International Conference on Process Engineering and Advanced Materials
Electrical Discharge Machining on Biodegradable AZ31
Magnesium Alloy using Taguchi method
M.A. Razaka,c,
, A.M. Abdul-Rania, T.V.V.L.N. Raoa, S.R. Pedapatia, S. Kamalb
aMechanical Engineering Department, Universiti Teknologi PETRONAS, Bandar Seri Iskandar, 32610 Perak, Malaysia
bPetroleum Engineering Department, Universiti Teknologi PETRONAS, Bandar Seri Iskandar, 32610 Perak, Malaysia
cManufacturing Section, Universiti Kuala Lumpur Malaysian Spanish Institute, Kulim Hi-Tech Park, 09000 Kedah, Malaysia
Magnesium alloy is highly potential material for biodegradable implant application. Due to limitations in conventional machining
methods, non-traditional machining method such as electrical discharge machining (EDM) die sinking process is proposed to
produce intricate shape with tight tolerance on magnesium alloy. Nine EDM experiments with three levels and four parameters
were conducted using Taguchi method on AZ31 magnesium alloy to explore the optimum machining parameters. It was found
that pulse on-time was the most significant parameter affecting the surface roughness (Ra) of the machined surface. The optimum
EDM condition obtained was 47 A peak current, 80 V voltage, 16 μs pulse on-time and 512 μs pulse off-time. A confirmation
test was conducted and the result shows 95.5% similarity with the predicted Ra. However, the formation of cracks and craters
were found on the machined surface area. It is proposed to solve this problem by applying powder mixed EDM method in future
research work.
© 2016 The Authors. Published by Elsevier Ltd.
Peer-review under responsibility of the organizing committee of ICPEAM 2016.
Keywords: Biodegradable material; EDM; Magnesium alloy; Taguchi method
1. Introduction
Magnesium alloy is a biocompatible material that can be used as temporary biomedical implant with high
potential for in-vivo degradation [1]. Magnesium has the ability to dissolve in biological environment such as a
* Corresponding author. Tel.: +604-403-5199; fax: +604-403-5201.
E-mail address:
© 2016 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license
Peer-review under responsibility of the organizing committee of ICPEAM 2016
M.A. Razak et al. / Procedia Engineering 148 ( 2016 ) 916 – 922
human body and yet remain non-toxic [2-4]. In average, human body contain 35 g magnesium per 70 kg body
weight. Human has been established to require up to 375 mg of magnesium daily [5]. The density of magnesium is
1.738 g/cm3 while the density of magnesium alloys is between 1.75 g/cm3 and 1.85 g/cm3. They are very similar to
human cortical bone density which is 1.75 g/cm3 which made it ideal [6]. Magnesium alloy possess mechanical
tensile strength between 185 to 230 MPa and fracture toughness between 17.6 to 20.7 MPa·m1/2 suitable for bone
fixation device [7, 8]. Several magnesium alloys suitable for biomedical applications including magnesium-calcium
(Mg-Ca), magnesium-zinc (Mg-Zn) and magnesium-aluminum-zinc (AZ31 and AZ91) [9-12].
However, machining magnesium alloys using conventional methods such as milling, turning and drilling cause
formation of cracks, built-up edge and chatter. The most important precaution need to bear in mind while machining
magnesium alloy is that the formation of fine chips and the dust is highly flammable [13]. Melting point of
magnesium is 650°C and this metal is only stable below its melting point. Therefore, non-traditional machining such
as EDM die sinker and EDM wire cut are preferable especially to produce intricate shapes with tight tolerance. This
paper aims at establishing the optimum parameters for EDM process on magnesium alloy. In this research, design of
experiment and result is analyzed using Taguchi method.
2. Literature review
EDM process uses spark erosion principle for material removal from the workpiece as shown in Fig. 1. The
sparks occur across a small gap between electrode and workpiece surface which takes place in a dielectric fluid
which pumped through the gap at a pressure of 2 kg/cm2 or less [14]. A suitable gap between 0.01 to 0.5 mm known
as spark gap is maintained between the electrode and the workpiece by a servomotor. The dielectric fluid becomes
ionized in the gap to create a path for each discharge. Kerosene oil is the most widely used dielectric fluid.
Alternatively, paraffin and mineral oil can also be used. The dielectric fluid in EDM process functioned as spark
conductor, flushing medium and also to remove particles of eroded metal [15].
Basic rule in the EDM process is that the electrode and the workpiece materials must be electrically conductive.
The current may vary from 0.5 to 400 A and the pulse duration can be varied from 2 to 2000 μ sec. A spark
generator performs the important functions of supplying sufficient voltage to maintain the discharge. The direct
current used for getting rapidly recurring discharges. The voltage of pulse generator is between 40 to 300 V and the
sparks frequency can be achieved up to 10,000 sparks per second [16]. The energy in the form of local heat released
during repetitive sparks. High temperature up to 20,000°C reached at the spot hit causes some metal melted and
eroded. A true replica of the electrode shape is produced on the workpiece surface in the process. A sudden
temperature reduction occurs when approximately 20,000 to 30,000 Hz of pulsating direct current is turned off and
the plasma channel breaks down. This allows the circulation of the dielectric fluid at the pole surfaces and flushes
away the molten material [17].
Fig. 1. Spark occurs between electrode and workpiece [18].
918 M.A. Razak et al. / Procedia Engineering 148 ( 2016 ) 916 – 922
3. Methodology
Taguchi method involves reducing the variation in a process through robust design of experiments. This method
uses orthogonal arrays to organize the parameters affecting the process and the levels at which they should be
varied. Only necessary data collected to determine which factors are most affecting the result with minimum number
of experiment, thus saving time and resources. New parameter values to optimize the performance characteristic can
be obtained by analyzing data using Taguchi approach [19, 20]. In general, Taguchi method involves steps as
x Determine the process objective and parameters affecting the process.
x Create orthogonal arrays for the parameter design.
x Conduct the experiments.
x Complete data analysis to determine the effect of the different parameters on the performance measure.
x Predict the optimum parameters and conduct a confirmation test.
There were nine EDM experiments conducted with three levels and four parameters as indicated in Table 1. The
orthogonal array for the experiment is shown in Table 2. Parameter values as suggested in machine user manual
were used in the experiments. Each experiment was repeated diligently three times to ensure data accuracy.
Workpiece material used in this research was biocompatible AZ31 magnesium alloy which was suitable for
temporary implant application while copper was chosen as EDM electrode. A constant cutting depth of 2 mm
maintained through-out the experiment. Surface roughness, Ra, was measured and analyzed using Mitutoyo SV3000
Surface Roughness Tester at three different locations on each specimen. Optimum EDM parameters for smoothest
surface were obtained using Taguchi approach and validated via confirmation test.
Table 1. Variable process parameters.
Level 1
Level 2
Level 3
Peak current
38 A
47 A
55 A
80 V
220 V
320 V
Pulse on-time
16 µs
32 µs
64 µs
Pulse off-time
128 µs
256 µs
512 µs
Table 2. Orthogonal array for EDM experiment.
Voltage (V)
Pulse on-time (µs)
Pulse off-time (µs)
M.A. Razak et al. / Procedia Engineering 148 ( 2016 ) 916 – 922
4. Result and Discussion
Data taken from three repeated experiments were re-arranged into lower average, medium average and higher
average as shown in Table 3. Average Ra of all three repetitions is indicated in most right column. Experiment eight
with parameters combination of 55 A peak current, 220 V voltage, 16 μs pulse on-time and 512 μs pulse off-time
obtained the lowest Ra value with 5.926 µm. On the other hand, experiment five with parameters combination of 47
A peak current, 220 V voltage, 64 μs pulse on-time and 128 μs pulse off-time obtained the highest Ra value with
13.149 µm.
Table 3. Average Ra of EDM experiment.
Lower Ra (µ m)
Medium Ra (µm)
Higher Ra (µm)
Average Ra (µm)
Fig. 2. Main effects plot (data means) for means.
Graph for main effects of data means is shown in Fig. 2 and the response of mean is shown in Table 4. The most
significant parameter is pulse on-time and followed by pulse off-time. Among four parameters, voltage is less
significant compared to others. Optimum condition for smaller-is-better was selected from lowest mean value from
each parameter which is A2, B1, C1 and D3. Predicted optimum Ra by mean was computed with equation (1) and
the result obtained was 5.322 µm. The signal to noise ratios for smaller-is-better were derived from Taguchi loss
function as shown in equation (2). Main effect plot for signal to noise ratios is shown in Fig. 3 and the response for
signal to noise is shown in Table 5. The maximum value from each parameter in the plot was selected to calculate
prediction value by signal to noise ratios. The predicted optimum value by signal to noise ratios computed with
equation (3) is -14.8818.
920 M.A. Razak et al. / Procedia Engineering 148 ( 2016 ) 916 – 922
Table 4. Response of mean.
Voltage (V)
On-time (µs)
Off-time (µs)
Fig. 3. Main effects plot (data means) for signal to noise ratios.
Table 5. Response of signal to noise ratios for smaller-is-better.
Voltage (V)
On-time (µs)
Off-time (µs)
A confirmation test has been conducted and Ra of 5.561 µm was obtained with 95.5% similarity to the predicted
value. However, one of the drawbacks found from the machined surface area was the formation of cracks and craters
in consequences of electrical sparks as shown in Fig. 4. The size of cracks and craters increase when the energy
content per pulse increased. They can cause disruption of surface oxide layer and expedites the corrosion process
M.A. Razak et al. / Procedia Engineering 148 ( 2016 ) 916 – 922
[21, 22]. This phenomenon is not good for biomedical implant application due to direct contact and reaction with
body fluid such as water, proteins and amino acids. In-vitro study reported by Wong et al. shows that uncoated
magnesium alloy corrodes 12 mg per two months [23]. Even though magnesium alloy is suggested for
biodegradable implant, high corrosion rate of the implant causes degrade whilst the defect has yet to recuperate.
Further investigation is needed to avoid or reduce the formation of cracks and craters during EDM process.
Fig. 4. Scanning electron microscope image of machined surface.
5. Conclusion
As a conclusion, there are three important points can be drawn. Firstly, among four EDM parameters, the most
significant effect to the Ra was pulse on-time and followed by pulse off-time. Secondly, the optimum EDM
parameters to machine AZ31 magnesium alloy are 47 A peak current, 80 V voltage, 16 μs pulse on-time and 512 μs
pulse off-time. Finally, even though EDM is excellent in machining intricate shapes with tight tolerance and burr-
free, the undesirable cracks and craters were found on the machined surface area. It is proposed to have further
investigation to solve this problem. In recent years, new exploratory research works have been initiated to improve
the efficiency of EDM process using powder mixed EDM method which also known as PMEDM. This method has
potential to reduce or omit the formation of cracks and craters during EDM process.
We would like to express our gratitude to all academic and support staff from Mechanical Engineering
Department and Research and Innovation Office, Universiti Teknologi PETRONAS for the assistance provided
during conducting this research.
[1] P.R. Cha, H.S. Han, G.F. Yang, Y.C. Kim, K.H. Hong, S.C. Lee, et al., "Biodegradability engineering of biodegradable Mg alloys: Tailoring
the electrochemical properties and microstructure of constituent phases," Scientific reports, vol. 3, pp. 1-6, 2013.
[2] F. Witte, J. Fischer, J. Nellesen, H.A. Crostack, V. Kaese, A. Pisch, et al., "In vitro and in vivo corrosion measurements of magnesium
alloys," Biomaterials, vol. 27, pp. 1013-1018, 2006.
[3] F. Klocke, M. Schwade, A. Klink, and A. Kopp, "EDM machining capabilities of Magnesium (Mg) alloy WE43 for medical applications,"
Procedia Engineering, vol. 19, pp. 190-195, 2011.
[4] M.T. Andani, N.S. Moghaddam, C. Haberland, D. Dean, M.J. Miller, and M. Elahinia, "Metals for bone implants. Part 1. Powder metallurgy
and implant rendering," Acta biomaterialia, vol. 10, pp. 4058-4070, 2014.
[5] G. Song and S.Z. Song, "A possible biodegradable magnesium implant material," Advanced Engineering Materials, vol. 9, pp. 298-302,
[6] L. Li, J. Gao, and Y. Wang, "Evaluation of cyto-toxicity and corrosion behavior of alkali-heat-treated magnesium in simulated body fluid,"
Surface and Coatings Technology, vol. 185, pp. 92-98, 2004.
[7] NADCA, "Alloy Data," in Product Specification Standard for Die Castings, ed: North American Die Casting Association, 2009.
[8] H. Somekawa and T. Mukai, "Fracture toughness in a rolled AZ31 magnesium alloy," Journal of alloys and compounds, vol. 417, pp. 209-
213, 2006.
[9] J.Z. Ilich and J.E. Kerstetter, "Nutrition in bone health revisited: a story beyond calcium," Journal of the American College of Nutrition, vol.
19, pp. 715-737, 2000.
922 M.A. Razak et al. / Procedia Engineering 148 ( 2016 ) 916 – 922
[10] X. Gu, X. Li, W. Zhou, Y. Cheng, and Y. Zheng, "Microstructure, biocorrosion and cytotoxicity evaluations of rapid solidified Mg3Ca alloy
ribbons as a biodegradable material," Biomedical materials, vol. 5, p. 035013, 2010.
[11] S. Zhang, X. Zhang, C. Zhao, J. Li, Y. Song, C. Xie, et al., "Research on an MgZn alloy as a degradable biomaterial," Acta Biomaterialia,
vol. 6, pp. 626-640, 2010.
[12] F. Witte, V. Kaese, H. Haferkamp, E. Switzer, A. Meyer-Lindenberg, C. Wirth, et al., "In vivo corrosion of four magnesium alloys and the
associated bone response," Biomaterials, vol. 26, pp. 3557-3563, 2005.
[13] M. Elektron, "Machining Magnesium," Datasheet 254 ed, 2012, pp. 1 -15.
[14] M.P. Groover, Fundamentals of Modern Manufacturing: Materials, Processes, and Systems: John Wiley & Sons, 2010.
[15] M.A. Razak, A.M. Abdul-Rani, and A.M. Nanimina, "Improving EDM Efficiency with Silicon Carbide Powder-Mixed Dielectric Fluid,"
International Journal of Materials, Mechanics and Manufacturing, vol. 3, pp. 40-43, 2015.
[16] K. Ho and S. Newman, "State of the art electrical discharge machining (EDM)," International Journal of Machine Tools and Manufacture,
vol. 43, pp. 1287-1300, 2003.
[17] R.K. Jain, Production Technology, 17 ed. New Delhi: Khanna Publishers, 2001.
[18] D. Singh, Fundamentals of manufacturing engineering: CRC Press, 2008.
[19] R.K. Roy, Design of experiments using the Taguchi approach: 16 steps to product and process improvement: John Wiley & Sons, 2001.
[20] R.H. Myers, D.C. Montgomery, and C.M. Anderson-Cook, Response surface methodology: process and product optimization using designed
experiments vol. 705: John Wiley & Sons, 2009.
[21] K. Ponappa, S. Aravindan, P. Rao, J. Ramkumar, and M. Gupta, "The effect of process parameters on machining of magnesium nano alumina
composites through EDM," The International Journal of Advanced Manufacturing Technology, vol. 46, pp. 1035-1042, 2010.
[22] R. Walter, M.B. Kannan, Y. He, and A. Sandham, "Effect of surface roughness on the in vitro degradation behaviour of a biodegradable
magnesium-based alloy," Applied Surface Science, vol. 279, pp. 343-348, 2013.
[23] H.M . Wong, K.W. Yeu ng, K.O. Lam, V. Tam, P.K. Chu, K.D. Luk, et al., "A biodegradable polymer-based coating to control the
performance of magnesium alloy orthopaedic implants," Biomaterials, vol. 31, pp. 2084-2096, 2010.
... A bio-implant is an artificial organ that can be used to treat a body part's faulty natural organ or tissue while causing no harm to other body parts [69]. These can be implanted into the body and allowed to develop naturally through the process of biological self-bone development to improve the quality of a person's life and longevity. ...
Full-text available
Surface modifications play a vital role in the performance of bio-implants. Powder mixed electric discharge machining (PM-EDM), a recently developed advanced machining method, can machine and coat the surface of conductive materials at the same time. Hydroxyapatite is a bio-ceramic with a bone-like composition and excellent biocompatibility. Several coating techniques are used to deposit a bio-ceramic layer on the implant surface; however, hydroxyapatite powder mixed-EDM (HAp-EDM) is an electro-thermal process that can be used for surface coating as well as machining of metallic biomaterials. In this review article, surface characteristics such as surface morphology/topography, micro-hardness, phase analysis, recast layer, elemental composition, corrosion/wear resistance, and biocompatibility of the coated surface of an implant after HAp-EDM have been meticulously reviewed. This review also looks at future research opportunities for the HAp-EDM process to meet the high standards required for biomedical materials and their applications in bio-implant manufacturing. ARTICLE HISTORY
... Hence, the pulse interval must be longer than the time it takes to deionise the dielectric. The pulse interval has an impact on MRR [59,74], EWR [23,38,59,64,79] and SR [59,66,75,80,81]. The same is summarised in Table 2. ...
Full-text available
With the implementation of ISO 14000 standards for environmental regulations, numerous manufacturing industries are implementing newer concepts like 6 R, i.e. Redesign, Remanufacturing, Recycle, Reuse, Reduce, and Recover. This paper focuses on understanding the various aspects of Electric Discharge Machining (EDM) that check its environmental friendliness and sustainability through a comprehensive literature review. This includes looking through the work related to bio-dielectrics as well as process parameters that compute energy consumption. The first section of this manuscript provides a succinct overview of using bio dielectric to make EDM more environmentally friendly. The review suggests that the problems of environmental pollution in the form of aerosol emission, unsustainability and cost of conventional EDM dielectric can be easily solved by using various bio-dielectrics. The second section focuses on reducing energy consumption by optimising electrical and non-electrical process parameters as well as by using various hybrid EDM. Recent scientific papers have been critically reviewed mentioning their significance and important contribution. EDM machining of some modern materials like hybrid Metal Matrix Composites (MMCs), ceramic and nanomaterial is also summarised. Finally, the conclusion and direction for future work have been proposed keeping in view the gaps identified in the existing literature.
Magnesium alloys are some of the recently developed biomaterials that have a number of beneficial properties including biocompatibility, biodegradability, and mechanical properties that are comparable to that of bone. The poor corrosion resistance of magnesium alloys is sometimes beneficial in terms to avoid the second surgery to remove the implant. This paper focuses on the machining characteristics of the wire EDM process for AZ-31 alloy. The input process parameters selected based on past literature are pulse-on duration, servo voltage, wire tension, and wire feed rate, whereas the output response is kerf width. The experiments are designed based on central composite design (CCD) of response surface methodology. To determine the critical process parameters, ANOVA analysis has also been conducted. Experimental results indicate that with the increase in pulse-on duration and servo voltage, kerf width of AZ-31 alloy always increases, whereas the kerf width for AZ-31 alloy always decreases with an increase in wire feed rate and wire tension.
In this study, AZ61/15wt.%TiB2 and AZ61/15wt.%TiB2-0.5wt.%GNPs composites were manufactured by hot pressing, and the machinability of the produced samples was carried out by powder mixed electrical discharge machining (PMEDM). The influence of PMEDM parameters, namely pulse on time, current and materials, were studied by surface roughness (SR) and material removal rate (MRR) using the Taguchi design. The microstructure and surface quality of the machined surfaces and cross-sections were investigated using 3D microscopy, scanning electron microscopy (SEM), energy dispersive spectrometry (EDS) and X-ray diffraction (XRD). Results showed that PMEDM produced a melting, white layer and transition zone direct proportionally to the processing parameters. The white layer did not differ from the metal integrity of the transition zone. Additionally, volcanic craters, holes, cracks, debris covered with molten metal, and reinforcement particles were observed at the machined surface and cross-section. A high amount of oxygen was detected on the machined surface as a result of the interaction between kerosene and generated heat changing proportionally to the amount of the EDM parameters. The analysis of variance (ANOVA) showed that the pulse on time and materials, with 65.46% and 40.86%, were the most significant parameters on the SR and MRR, respectively. For regression models, the determination coefficient (R2) for the prediction of SR and MRR was noted to be 0.98 and 0.85, respectively. Keywords: AZ61 alloy, Mg matrix composites, TiB2, GNPs, PMEDMJournal Pre-proof
In this paper, the surface morphology of micro-hole produced in magnesium alloy AZ91D was investigated. The micro-hole was fabricated through a nanopowder mixed micro-electric discharge drilling (PM-μEDD) process. The tool electrode made of tungsten carbide (WC) having 0.97 mm in diameter was used to perform the experiments. The experiments were conducted considering four input variables namely (a) tool rotation, (b) feed rate, (c) voltage, and (d) powder concentration. The other parameters such as capacitance (100 μF), depth of cut (0.25 mm), and pulse on time (10 μs) were kept constant during the PM-μEDD process. FESEM images of the fabricated micro-holes were taken at a different magnification to investigate the characteristics of the machined surface. EDS analysis of the machined surface was also performed to study the elemental composition.
The present work is an extension of the work carried out by the authors previously. In the present study, the optimization of input parameters for wire-EDM cutting of a 2.5 mm thick Ti6Al4V alloy sheet was carried out to have desired cut quality and cutting speed. The experiments were statistically designed using an L8 orthogonal array. Voltage, current, capacitance, duty cycle, frequency, wire tension, and wire feed, were chosen as the input parameters. Kerf width, taper angle, surface roughness, and cutting speed were considered as the outputs. A newly developed, nature-inspired algorithm, called the Mayfly optimization algorithm, was used to minimize the kerf width, taper angle, and surface roughness, along with maximization of cutting speed. The minimum value of current, duty cycle, and frequency were found to be favorable to predict the desired output due to lower spark-energy generation. At the same time, the maximum value of voltage, wire feed, and wire tension were formulated by the algorithm for obtaining desired output. Upon confirmation test using the optimized process parameters, satisfactory experimental results were found for the predicted results within acceptable error.
Conference Paper
In this study, the Die Sink electric discharge machining (EDM) of titanium alloys Ti6Al4V and Ti5553 with copper electrode material were conducted to find the optimum process parameters and to compare machinability of these alloys on sink EDM for same input design. The design of experiments was conducted using Taguchi method to find the optimum machining parameters such as current (I), Pulse on time (Ton) and Pulse off time (Toff) for various response parameters such as Material removal rate (MRR), Surface roughness (Ra) and Radial over cut (ROC). Mean effect plots and S/N ratios have been used to optimize the machining parameters of Die sink EDM on Ti6Al4V and Ti5553 using the Taguchi method. ANOVA is performed to find the percentage contribution of each input parameter on each output variable. The experimental results reveal that Ti5553 material machinability on sink EDM w.r.t metal MRR, Ra and ROC is better compared to Ti6Al4V material, this signifies the factor that Die sink EDM is best suited for harder materials.
Magnesium represents a very attractive material for biodegradable orthopedic implants because of its capability to resolve the problem of stress shielding, osteocompatibility in addition to its biodegradability. Yet, pure Mg does not have adequate strength when exposed to body fluids as it starts degrading at a higher rate. The aim of this research is to study the effect of wire electric discharge machining on Mg-based alloy ZM21 to increase its effectiveness by surface grain refinement as a tool to limit the initial corrosion rate in body fluids (modulus of elasticity remains unchanged). Comparison of microstructural, mechanical, and in-vitro corrosion changes along with biocompatibility of the polished and wire EDM machined samples of ZM21 Magnesium alloy were performed in this study. The alloy experiences a change in grain size inthe recast layer formed on the machined surface which retards the initial degradation rate due to the occurrence of less number of high energy grain boundaries. Also ensures the production of corrosion resistive Mn2O3 and Mn3O4 compounds on the newly formed surface with MgO2 as the base.KeywordsZM21 Mg alloyBiodegradabilityOrthopedic implantWEDMCorrosion rateSBF
Magnesium alloys are one of the lightweight materials with exceptional mechanical characteristics that possess high strength to weight ratio and it is primarily used for various engineering applications. Due the better resistance to corrosion, these materials are primary choice for aerospace applications such as fuselages. However, the conventional machining process fails to achieve better machining performance with these alloys. Wire-Electro Discharge Machining (WEDM) is one of the contemporary machining methods mainly adopted for generating intricate shapes in any kind of hard materials. In the current study, Magnesium alloy is used as work material and input process parameters such as pulse on time (Pon), pulse off time (Poff), peak current (Ip) was selected. Material removal rate (MRR) and surface roughness (SR) are deemed as output parameters. Taguchi’s single aspect optimization method has been engaged for determining the best suitable combination to achieve better machining performance. The experimentation outcome affirm that the technique suggested in this investigation adequately enhances the machining performances of the Wire cut EDM process.
Wire Electrical Discharge Machining (WEDM) is one of the innovative approaches for removal material from the work piece that is the variant of Electrical Discharge Machining method. This method is prominently engaged for machining harder materials with intricate shapes. AA 7050 is an aluminium alloy is most generally used as a superior material for numerous engineering applications such as aircraft applications. Due to the exceptional behavior of AA 7050, these materials are primary choice for numerous engineering applications. In this present investigational analysis, an endeavor is taken to ascertain the impact of the chosen input variables (‘Ton’, ‘Toff’ and peak current) on the desired output measures namely material removal rate and surface roughness. Taguchi’s concept of design method is adopted for planning the combination of experiments. Interaction analysis has been done for unveiling the interaction effect of various input process variables on performance measures.
Full-text available
Besides high geometrical accuracy medical devices strongly require a good surface integrity of the produced parts. Surfaces should be optimized to reduce friction or to increase cell adhesion for optimal fitting, mechanical stability and biocompatibility to reduce the risk of inflammatory reactions. Therefore surfaces should posses tailored roughness, a closed structure without pores and cracks and should not contain any toxic substances as a result of the machining process. New biomaterials like magnesium alloys for biodegradable orthopaedic implants are very difficult to machine with conventional processes especially for complex and filigree 3D-structures. Therefore, alternative manufacturing technologies are desired and need to be developed. This paper analyzes the capabilities of state-of-the-art EDM process technologies regarding achievable surface integrity.
Full-text available
Crystalline Mg-based alloys with a distinct reduction in hydrogen evolution were prepared through both electrochemical and microstructural engineering of the constituent phases. The addition of Zn to Mg-Ca alloy modified the corrosion potentials of two constituent phases (Mg + Mg2Ca), which prevented the formation of a galvanic circuit and achieved a comparable corrosion rate to high purity Mg. Furthermore, effective grain refinement induced by the extrusion allowed the achievement of much lower corrosion rate than high purity Mg. Animal studies confirmed the large reduction in hydrogen evolution and revealed good tissue compatibility with increased bone deposition around the newly developed Mg alloy implants. Thus, high strength Mg-Ca-Zn alloys with medically acceptable corrosion rate were developed and showed great potential for use in a new generation of biodegradable implants.
The aim of the paper is to describe the activity of the 8th annual Session of the Russian Academy of Sciences on the problems of the purchasing productions in mechanical engineering (ME). The plenary meeting was devoted to the progressive technologies in ME. The problems of automation of assembly processes were discussed during the first day of the session. The long-term power-saving technologies in the purchasing production of ME were the subject of discussion in the second day of the Session.
Machining cost for electro-discharge machining (EDM) is high due to longer machining time. EDM efficiency is hypothesize can be increased using powder-mixed dielectric fluid (PMEDM). PMEDM works gradually at low pulse energy and distributes evenly the powder in machining area. PMEDM may lead to improve machined part surface finish, improve material removal rate (MRR) and reduce tool wear rate (TWR). Further investigations on powder concentration and powder particles size for silicon carbide (SiC) PMEDM are proposed. Number of experiments to be conducted is based on Taguchi orthogonal array with three level and two factors. The outcomes are expected capable to increase MRR, improve surface finish, reduce TWR, reduce machining time and reduce machining cost.
New metal alloys and metal fabrication strategies are likely to benefit future skeletal implant strategies. These metals and fabrication strategies form the point of view of standard-of-care implants for the mandible were looked. These implants are used as part of the treatment for segmental resection due to oropharyngeal cancer, injury, or correction of deformity due to pathology or congenital defect. The aim of this two part paper is to review the issues associated with the failure of existing mandibular implants that are due to mismatched material properties. Also potential directions for future research was studied. To mitigate these issues the use of low-stiffness metallic alloys has been highlighted. To this end, development, processing and biocompatibility of superelastic NiTi as well as resorbable Magnesium-based alloys were discussed. Additionally, engineered porosity was reviewed as it can be an effective way of matching the stiffness with the tissue surrounding an implant. These porosities and the overall geometry of the implant can be optimized for strain transduction and with a tailored stiffness profile. Rendering patient-specific, site-specific, morphology-specific, and function-specific implants can now be achieved using these and other metals with bone-like material properties by additive manufacturing. The biocompatibility of implants prepared from superelastic and resorbable alloys was also reviewed.
In this study, the in vitro degradation behaviour of AZ91 magnesium alloy with two different surface finishes was investigated using electrochemical impedance spectroscopy (EIS) in simulated body fluid (SBF). The polarisation resistance (Rp) of the rough surface alloy immersed in SBF for 3 h was ~30% lower as compared to that of the smooth surface alloy. After 12 h immersion in SBF, the Rp values for both the surface finishes decreased and were also similar. However, localised degradation occurred sooner, and to a noticeably higher severity in the rough surface alloy as compared to the smooth surface alloy.
A study was conducted to develop and study the possibility of using magnesium as a degradable bio-compatible implants. A magnesium ingot was cut into 1-2 cm3 coupons which was used for corrosion tests and making electrodes. The Hank solution was used as a simulated body fluid (SBF) and its pH was adjusted with HCl to a slightly acidic level (pH~ 6) to avoid precipitation or formation of sediments in the solution. The coupons were polished with up to 1000 grit SiC paper and AC impedance spectra and polarization curves were analyzed. It was observed that magnesium is compatible with the human body and the direct corrosion product Mg2+ can be tolerated in the human body, while rapid accumulation of corrosion by-products such as hydrogen gas and hydroxides may exclude the possible application of magnesium vent in vascular system. Result shows that magnesium vents cannot be used vascular system due to hydrogen gas, but it can be used as implant for broken bones.
The effect of texture on fracture toughness was investigated for a wrought AZ31 magnesium alloy, which was a commercial rolled plate having strong basal texture. The value of plane-strain fracture toughness, KIC=17.6–20.7MPam1/2, was obtained from the stretched zone (SZ) analysis. The value of KIC varied with the distribution of basal texture; the sample having a pre-crack normal to rolled direction was the highest value of KIC in all present samples. The crack-tip having parallel to the rolled direction was easily able to propagate and/or proceed with applied load.
Electrical discharge machining (EDM) is a well-established machining option for manufacturing geometrically complex or hard material parts that are extremely difficult-to-machine by conventional machining processes. The non-contact machining technique has been continuously evolving from a mere tool and die making process to a micro-scale application machining alternative attracting a significant amount of research interests. In recent years, EDM researchers have explored a number of ways to improve the sparking efficiency including some unique experimental concepts that depart from the EDM traditional sparking phenomenon. Despite a range of different approaches, this new research shares the same objectives of achieving more efficient metal removal coupled with a reduction in tool wear and improved surface quality. This paper reviews the research work carried out from the inception to the development of die-sinking EDM within the past decade. It reports on the EDM research relating to improving performance measures, optimising the process variables, monitoring and control the sparking process, simplifying the electrode design and manufacture. A range of EDM applications are highlighted together with the development of hybrid machining processes. The final part of the paper discusses these developments and outlines the trends for future EDM research.