The Experts below are selected from a list of 228 Experts worldwide ranked by ideXlab platform
Muhammad P. Jahan - One of the best experts on this subject based on the ideXlab platform.
-
Sequential Micro-EDM
Micro-electrical Discharge Machining Processes, 2019Co-Authors: Md. Rashef Mahbub, Asma Perveen, Muhammad P. JahanAbstract:In this chapter, different sequential conventional and non-conventional Micromachining processes with Micro-EDM have been discussed elaborately with their applications in modern-day research and industrial fields. The necessity and advantages of sequential Micromachining Micromachining processes and their difference from hybrid Micromachining Micromachining have been carefully identified. Micro-EDM combined with Micro-grinding, Micro-Milling, Micro-turning, Micro-ECM, Micro-drilling, laser Micromachining Micromachining , LIGA Lithographie, Galvanoformung, Abformung (LIGA) have been discussed with their advantages over respective single processes. The common issues that generally stand in the way of pulling out sequential processes successfully or hamper their accuracy have also been addressed. The chapter also suggests some initiatives to solve those issues. While wrapping up, the chapter emphasizes on the fact that how sequential Micromachining Micromachining , if properly implied, can solve a lot of problems that currently available single processes are dealing with and widen the vast possibility of Micromachining Micromachining of 3D complex structure with high level of accuracy.
-
Sequential Micro-EDM
Materials Forming Machining and Tribology, 2018Co-Authors: Rashef Mahbub, Asma Perveen, Muhammad P. JahanAbstract:In this chapter, different sequential conventional and non-conventional Micromachining processes with Micro-EDM have been discussed elaborately with their applications in modern-day research and industrial fields. The necessity and advantages of sequential Micromachining processes and their difference from hybrid Micromachining have been carefully identified. Micro-EDM combined with Micro-grinding, Micro-Milling, Micro-turning, Micro-ECM, Micro-drilling, laser Micromachining, LIGA have been discussed with their advantages over respective single processes. The common issues that generally stand in the way of pulling out sequential processes successfully or hamper their accuracy have also been addressed. The chapter also suggests some initiatives to solve those issues. While wrapping up, the chapter emphasizes on the fact that how sequential Micromachining, if properly implied, can solve a lot of problems that currently available single processes are dealing with and widen the vast possibility of Micromachining of 3D complex structure with high level of accuracy.
-
A comparative study on the performance of sinking and Milling Micro-EDM for nanofinishing of tungsten carbide
International Journal of Nanomanufacturing, 2010Co-Authors: Muhammad P. Jahan, Yoke San Wong, Mustafizur RahmanAbstract:Micro-electrical discharge machining (Micro-EDM) is a flexible machining technique offering the possibility to produce freeform Microstructures and Micromoulds using hard-but-conductive materials like tungsten carbide (WC). It is desirable to obtain fine surface finish directly using Micro-EDM when Micromoulds and dies are machined, so that subsequent polishing can be avoided. This paper presents a comparative study between the performance of die-sinking and Milling Micro-EDM for the semi-finish and finish machining of WC. The comparison was conducted with respect to achieved material removal rate (MRR), relative electrode wear ratio (EWR), surface topography, average surface roughness (Ra) and peak-to-valley roughness (Rmax). It has been found that, Micro-EDM Milling is capable of generating smooth, shiny and defect-free surfaces with lower Ra and Rmax at comparatively higher MRR and lower EWR in the finish Micro-EDM of WC. Moreover, the MRR in Milling Micro-EDM can further be increased at semi-finishing regime with the sacrifice of surface finish and EWR by increasing the electrode scanning speed. Comparing all the performance parameters, Milling Micro-EDM has been found to be the better option for semi-finishing and finishing of WC than die-sinking.
-
Migration of Materials during Finishing Micro-EDM of Tungsten Carbide
Key Engineering Materials, 2010Co-Authors: Muhammad P. Jahan, Mustafizur Rahman, Yoke San WongAbstract:Present study aims to investigate the migration of materials onto the surface of workpiece and electrode during fine-finish die-sinking and Milling Micro-EDM of tungsten carbide using pure tungsten electrode. The effect of materials transfer on the machined surface characteristics is also presented. The machined surfaces have been examined under scanning electron Microscope (SEM) and energy dispersive X-ray (EDX) in order to investigate the changes in chemical composition due to the migration of materials. It has been observed that materials from both workpiece and electrode transfer to each other depending on machining conditions and discharge energy. A significant amount of carbon migrates to both electrode and workpiece surface due to the decomposition of dielectric hydrocarbon during breakdown. The migration occurs more frequently at lower gap voltages during finish die-sinking Micro-EDM due to low spark gap and stationary tool electrode. Milling Micro-EDM suffers from lower amount of carbon migration and fewer surface defects which improve the overall surface finish and reduce surface roughness significantly.
Y. S. Wong - One of the best experts on this subject based on the ideXlab platform.
-
Study of the Diffusion of Carbon, Its Sources, and Effect on Finishing Micro-EDM Performance of Cemented Carbide
Journal of Materials Engineering and Performance, 2012Co-Authors: M. P. Jahan, M. Rahman, Y. S. WongAbstract:Apart from the necessity of surface modification based on different applications, in most of the cases, diffusion of carbon or foreign particles on the workpiece surface during Micro-electrodischarge machining (Micro-EDM) is avoidable, especially in finishing Micro-EDM. This study aims to investigate different sources of materials that migrate to the machined surface during fine-finishing of Micro-EDM of cemented tungsten carbide (WC-Co). The machined surfaces have been examined under scanning electron Microscope and energy dispersive x-ray to investigate the changes in chemical composition. It has been observed that during finishing of Micro-EDM, the major source of materials' transfer to both the workpiece and electrode is the diffusion of carbon that comes from the decomposition of the hydrocarbon dielectric. In addition, materials from both workpiece and electrode transfer to each other based on machining conditions and discharge energy. The migration occurs more frequently at lower gap voltages during die-sinking with Micro-EDM because of low spark gap and stationary tool electrode. Milling Micro-EDM results in lower amount of carbon migration and fewer surface defects that improve the overall surface finish significantly.
-
Soft Computing Applications in Industry - Noise-Robust Tool Condition Monitoring in Micro-Milling with Hidden Markov Models
Soft Computing Applications in Industry, 1Co-Authors: K. P. Zhu, Y. S. Wong, Geok Soon HongAbstract:Tool condition monitoring is crucial to the efficient operation of machining process where the cutting tool is subject to continuous wear. In particular, in Micro machining, the tolerances, depth of cut, and even workpiece sizes are in Micro scale. Micromachining can overcome the shortcomings of Micro fabrication techniques (such as lithography and etching) with limitation of work materials (mostly on silicon) and geometric forms (2 or 2.5 dimensions) (Byrne et al. 2003; Liu et al. 2004). One very versatile Micro-machining process is Micro-Milling. Micro-Milling has advantages over other Micro-machining techniques with respect to the types of workable materials and the free-form 3D Micro structures with high aspect ratios and high geometric complexity. However, in Micro-Milling, with the miniaturisation of the cutting tool ( 10,000 rpm), the tool wears quickly. It is critical to monitor the tool wear in Micro-machining due to the high precision required. Compared to conventional machining, the noise component in the signal for monitoring Micro-machining is usually very high and difficult to separate (Tansel et al 1998; Zhu et al. 2007). This phenomenon makes it difficult to apply TCM in Micro-machining.
Thomas Becker - One of the best experts on this subject based on the ideXlab platform.
-
From native malt to pure starch – Development and characterization of a purification procedure for modified starch
Food Hydrocolloids, 2016Co-Authors: Michael Rittenauer, L. Kolesnik, Martina Gastl, Thomas BeckerAbstract:Abstract Starch characteristics influence the gelatinization process, which is an important prerequisite for the saccharification required in many industrial processes. In order to determine these characteristics in barley malt, an adapted purification procedure allowing to preserve the native starch composition and simultaneously segregating the amylolytic enzymes which were formed during the germination is indispensable. Therefore, this research aimed to develop a method based on a combination of dry Milling, Micro-sieving and density gradient centrifugation. The impact on the starch characteristics was evaluated for three germinated barley varieties. The purified starches showed starch contents greater than 90% and proteins contents less than 0.4%. Yields ranged from 40.3 to 48.6%, depending on the variety. Considering the starch properties, the amylose/amylopectin ratio was not modified during the purification. The circularity of the granules as well as the ratio of A- and B-type granules remained constant. The particle size distribution of A-granules was not shifted, B-granules with a specific diameter of 5–10 μm were slightly reduced in dependency of the native granule composition. The highest impact could be observed on the amylolytic enzymes, which were completely segregated regardless of their initial value. The standard deviation of repeatability was less than 5%, except for the determination of B-type particle size distribution (7%). The newly developed procedure supplements existing isolation methods of unmalted grains by enabling the purification of germinated barley in a reproducible manner, without altering the native starch properties and by providing pure starch free of amylolytic activity.
Mustafizur Rahman - One of the best experts on this subject based on the ideXlab platform.
-
Study on the nano-powder-mixed sinking and Milling Micro-EDM of WC-Co
The International Journal of Advanced Manufacturing Technology, 2011Co-Authors: Muhammad Pervej Jahan, Mustafizur Rahman, Yoke San WongAbstract:Present study investigates the feasibility of improving surface characteristics in the Micro-electric discharge machining (EDM) of cemented tungsten carbide (WC–Co), a widely used die and mould material, using graphite nano-powder-mixed dielectric. In this context, a comparative analysis has been carried out on the performance of powder-mixed sinking and Milling Micro-EDM with view of obtaining smooth and defect-free surfaces. The surface characteristics of the machined carbide were studied in terms of surface topography, crater characteristics, average surface roughness ( R _a) and peak-to-valley roughness ( R _max). The effect of graphite powder concentration on the spark gap, material removal rate (MRR) and electrode wear ratio (EWR) were also discussed for both die-sinking and Milling Micro-EDM of WC–Co. It has been observed that the presence of semi-conductive graphite nano-powders in the dielectric can significantly improve the surface finish, enhance the MRR and reduce the EWR. Both the surface topography and crater distribution were improved due to the increased spark gap and uniform discharging in powder-mixed Micro-EDM. The added nano-powder can lower the breakdown strength and facilitate the ignition process thus improving the MRR. However, for a fixed powder material and particle size, all the performance parameters were found to vary significantly with powder concentration. Among the two processes, powder-mixed Milling Micro-EDM was found to provide smoother and defect-free surface compared to sinking Micro-EDM. The lowest value of R _a (38 nm) and R _max (0.17 μm) was achieved in powder-mixed Milling Micro-EDM at optimum concentration of 0.2 g/L and electrical setting of 60 V and stray capacitance.
-
Special Issue on Micro/Nano Machining – Processes, Systems and Control
International Journal of Automation Technology, 2011Co-Authors: Mustafizur RahmanAbstract:In recent years, the trend in miniaturization of products is pervasive in areas such as information technology, biotechnology, environmental and medical industries. Micro-machining is the key supporting technology that has to be developed to meet the challenges posed by the requirements of product miniaturization and industrial realization of nanotechnology. Micro-machining techniques can be carried out by techniques based on energy beams (beam-based Micro-machining) or solid cutting tools (tool-based Micro-machining). Beambased Micro-machining have some limitations due to poor control of 3D structures, low material removal rate and low aspect ratio. Moreover, these processes require special facilities and the maximum achievable thickness is relatively small. Some of these limitations can be overcome by tool-based Micro-machining techniques using ultra precision machine tools and solid tools used as cutting elements to produce the Micro-features with well controlled shape and tolerances. Tool-based Micro-machining techniques essentially include precision machining processes as turning, Milling, grinding and electrical discharge machining (EDM), whereby material removal is done at the Micron level. The advantages of such processes are that almost every material such as metals, plastics and semiconductors can be machined with no limitation in machining shapes. Recently, combinations of conventional material removal processes, such as turning and Milling, have been hybridized with non-conventional machining processes like EDM and EDG to fabricate Micro-structures with high dimensional accuracy. In order to achieve meaningful implementation of compound Micro-machining techniques three important areas are required to be addressed. These are: development of machine tools capable of performing compound Micro-machining (i.e. Micro turning, Micro Milling, Micro EDM, etc. on the same machine and setup), understanding of process physics to provide relevant background for modeling,measurement, identification of control parameters and application of feedback control in order to control compound and hybrid manufacturing processes and development of compound and hybrid processes. An integrated effort in these areas is needed for successful implementation of tool-based Micro-machining. An attempt has been made in this special issue to highlight latest articles on these areas. I would like to express my sincere appreciation to the authors, reviewers and editors for their invaluable contributions for this issue.
-
A comparative study on the performance of sinking and Milling Micro-EDM for nanofinishing of tungsten carbide
International Journal of Nanomanufacturing, 2010Co-Authors: Muhammad P. Jahan, Yoke San Wong, Mustafizur RahmanAbstract:Micro-electrical discharge machining (Micro-EDM) is a flexible machining technique offering the possibility to produce freeform Microstructures and Micromoulds using hard-but-conductive materials like tungsten carbide (WC). It is desirable to obtain fine surface finish directly using Micro-EDM when Micromoulds and dies are machined, so that subsequent polishing can be avoided. This paper presents a comparative study between the performance of die-sinking and Milling Micro-EDM for the semi-finish and finish machining of WC. The comparison was conducted with respect to achieved material removal rate (MRR), relative electrode wear ratio (EWR), surface topography, average surface roughness (Ra) and peak-to-valley roughness (Rmax). It has been found that, Micro-EDM Milling is capable of generating smooth, shiny and defect-free surfaces with lower Ra and Rmax at comparatively higher MRR and lower EWR in the finish Micro-EDM of WC. Moreover, the MRR in Milling Micro-EDM can further be increased at semi-finishing regime with the sacrifice of surface finish and EWR by increasing the electrode scanning speed. Comparing all the performance parameters, Milling Micro-EDM has been found to be the better option for semi-finishing and finishing of WC than die-sinking.
-
Migration of Materials during Finishing Micro-EDM of Tungsten Carbide
Key Engineering Materials, 2010Co-Authors: Muhammad P. Jahan, Mustafizur Rahman, Yoke San WongAbstract:Present study aims to investigate the migration of materials onto the surface of workpiece and electrode during fine-finish die-sinking and Milling Micro-EDM of tungsten carbide using pure tungsten electrode. The effect of materials transfer on the machined surface characteristics is also presented. The machined surfaces have been examined under scanning electron Microscope (SEM) and energy dispersive X-ray (EDX) in order to investigate the changes in chemical composition due to the migration of materials. It has been observed that materials from both workpiece and electrode transfer to each other depending on machining conditions and discharge energy. A significant amount of carbon migrates to both electrode and workpiece surface due to the decomposition of dielectric hydrocarbon during breakdown. The migration occurs more frequently at lower gap voltages during finish die-sinking Micro-EDM due to low spark gap and stationary tool electrode. Milling Micro-EDM suffers from lower amount of carbon migration and fewer surface defects which improve the overall surface finish and reduce surface roughness significantly.
Michael Rittenauer - One of the best experts on this subject based on the ideXlab platform.
-
From native malt to pure starch – Development and characterization of a purification procedure for modified starch
Food Hydrocolloids, 2016Co-Authors: Michael Rittenauer, L. Kolesnik, Martina Gastl, Thomas BeckerAbstract:Abstract Starch characteristics influence the gelatinization process, which is an important prerequisite for the saccharification required in many industrial processes. In order to determine these characteristics in barley malt, an adapted purification procedure allowing to preserve the native starch composition and simultaneously segregating the amylolytic enzymes which were formed during the germination is indispensable. Therefore, this research aimed to develop a method based on a combination of dry Milling, Micro-sieving and density gradient centrifugation. The impact on the starch characteristics was evaluated for three germinated barley varieties. The purified starches showed starch contents greater than 90% and proteins contents less than 0.4%. Yields ranged from 40.3 to 48.6%, depending on the variety. Considering the starch properties, the amylose/amylopectin ratio was not modified during the purification. The circularity of the granules as well as the ratio of A- and B-type granules remained constant. The particle size distribution of A-granules was not shifted, B-granules with a specific diameter of 5–10 μm were slightly reduced in dependency of the native granule composition. The highest impact could be observed on the amylolytic enzymes, which were completely segregated regardless of their initial value. The standard deviation of repeatability was less than 5%, except for the determination of B-type particle size distribution (7%). The newly developed procedure supplements existing isolation methods of unmalted grains by enabling the purification of germinated barley in a reproducible manner, without altering the native starch properties and by providing pure starch free of amylolytic activity.