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Dielectric (e.g., kerosene-based oil, deionized water, air) is an essential part of electrical discharge machining (EDM), insulating the workpiece and the electrode and removing the gaseous bubbles and debris. In this paper, ultrasonic vibration (USV) and mist are added to micro-EDM in nitrogen plasma jet (NPJ) to improve machining performance. Water contact angle on the workpiece surface becomes very small due to increased hydrophilicity of the NPJ-treated surface. Experimental results indicate that the discharge distance is about 3.5 times of that without adding mist. Compared to results in NPJ under the same conditions, the material removal rate (MRR) has increased by four when aided with mist and increased more than six times further when aided with USV. Meanwhile, the surface roughness increased. In addition, the tool electrode wear rate (TWR) in NPJ and mist significantly decreased, especially, aided by USV. 3D micro feature has been generated in Brass successfully by the proposed method, and the TWR (-0.04%) is near zero.

In micro EDM, the discharge is significantly influenced by the bubble behavior. The depth-dependent characteristics of bubble behavior play a key role on the dielectric exchange and debris exhaust. However, the difficulty of direct observation on the narrow gap area is a big obstacle in clarifying the bubble behavior in the gap area. In this paper, a method is put forward to both directly observe the behavior of bubble in the interelectrode gap area and the behavior of bubble escaping from the micro hole based on the self-designed SiC sandwich workpiece in the micro hole drilling with EDM. The aim is to comprehensively investigate the bubble behavior by combining the observation of bubbles in the interelectrode gap area with the bubbles escaping from the micro hole. The observation was performed by a high-speed camera at high frame rate. Depending on the proposed methods, the influence of bubble behavior on the micro hole drilling with EDM is comprehensively analyzed.

The quality of a via hole on a multilayer stack of Low Temperature Co-fired Ceramic (LTCC) tape is of utmost importance to its functionality. This paper investigates a substitute for the commonly used circular shape hole to a more complex one and its implications when different parameters such as sheet thickness, punch speed, travel distance and tool clearance are changed. Fabrication of the punch tools and the punching process is carried out at the same machine, ensuring alignment. Two types of non-circular shape are chosen to carry out the experiment. Pre-sintered complex shape hole measurements show that while punch conditions such as speed and tool gap have little effect on the size, sheet thickness and travel depth play a vital role in the overall dimension. Albeit having only a slight effect on the size, those parameters are significant in other aspects of hole quality. Post-sintering investigation is also observed and discussed.<

Micro punching process is suitable for mass production of micro parts. It is a challenge to fabricate micro punching mold with complex cross-sectional shape on-machine. The micro punching system’s structure design has to meet the requirement of large punching force. In this study, a micro punching system has been developed with a micro electrical discharge machining (EDM) module. A series of machining operations, from the fabrication of micro molds to punching, have been completed with no secondary clamping error. The micro die and reversed electrode are prepared using micro EDM milling. The micro punch is fabricated using reversed electrode. The punching clearance is around 11 μm. Complex shape punched holes and blanked parts have been successfully fabricated on copper, brass, 304 stainless steel, and 3J21 alloy. After punching, there was no damage on the edges of micro die and micro punch. The key dimensional error of blanked part varies by different materials, which is less than 2.5 μm.

As one of the micro-forming technologies, micro punching process produces workpieces in high efficiency and low cost. It has attracted the attention of researchers from all over the world in recent years. The current micro punching mold is prepared on-line by micro electrical discharge machining (EDM) with simple cross-sectional shape. During punching, the punching load is small due to the soft material and small circumference of workpiece. To form micro part with complex cross sectional shape using micro punching technology, three-dimensional micro-EDM milling and reversed micro EDM are used to generate micro die and punch on-line to provide a solution to alignment of die and punch on machine. In order to obtain high dimensional accuracy of micro punching mold, in this paper, dimensional errors including electrode, reversed electrode, micro die and micro punch caused during machining process are identified. The correlation between dimensional errors and the clearance of micro die and micro punch are analyzed. Based on preliminary experimental results and dimensional error control strategy, the final punching clearance of micro punch molds was machined within the required range.

Dielectric, such as kerosene-based oil, deionized water or air, is an essential part of electrical discharge machining (EDM). It directly influences machining performance of the EDM process. While there is large tool electrode wear during machining in liquid dielectric, micro EDM in gas dielectric exhibits almost no tool electrode wear. However, small discharge energy, low dynamic viscosity and low debris concentration of micro EDM in gas creates narrow discharge gap, causing frequent occurrence of abnormal discharge. In this paper, nitrogen plasma jet (NPJ) is used as a dielectric to increase the discharge gap of micro EDM in gas. The machining characteristics of micro EDM in NPJ are investigated and compared with those in other dielectrics. It was found that the discharge distance, machining efficiency and surface quality are significantly improved in NPJ, compared to those in gas under the same conditions. The coaxial high-velocity air jet is helpful to reduce short circuits. Experimental results reveal that NPJ is a viable dielectric in micro EDM.

The micro EDM is widely utilized to drill micro hole in many metallic materials regardless of its hardness such as the inkjet printer nozzle and diesel fuel injection nozzle. Although the drilling micro hole by micro EDM has been well developed and many methods have been put forward to improve the machining efficiency and accuracy, the problem of decrease in machining speed has not been solved completely. In most cases, the reason for the decrease of drilling speed was thought to be the accumulation of debris and bubble in the gap area. However, the assumption has not been confirmed directly so far. Hence, in this research, in order to find out the debris and bubble behavior and its influence in micro EDM, a high speed camera was utilized to observe the gap area during drilling micro-hole in SiC and stainless steel SUS304 sheet workpieces by using the sandwich workpiece. The diameter of micro tool was equal to the thickness of workpiece, which made it possible to directly observe the gap area through the glass plates. It was found that a bubble grows up alone or merges with other bubbles to become a big bubble with the increase of feed depth, then overflows out of gap area slowly. When a micro hole is drilled into a certain depth, debris is accumulated in the bottom of gap area and the occurrence of abnormal discharge becomes more frequent. Hence, the workpiece material is difficult to be removed and the machining speed decreases seriously.

This paper investigates the characteristics of micro electrical discharge machining (EDM) in cold plasma jet using transistor pulse generator. In order to improve the processing efficiency and quality in stable process conditions, oxygen-assisted nitrogen plasma jet, nitrogen-oxygen mixed plasma jet and external compressed air assisted nitrogen plasma jet are used in micro-EDM experiments. It was found that the material removal rate and surface roughness increases with the increase of oxygen flow rate in oxygen-assisted nitrogen plasma jet experiment. In addition, it was found that micro-EDM with a compressed air-assisted plasma jet is superior to oxygen-assisted nitrogen plasma jet in surface quality and edge quality. Nitrogen element is not found on the machined surface in micro-EDM based in NPJ or NJ. The content of oxygen element has an increasing trend when compressed air is used as an auxiliary gas.

In drilling with micro electrical discharge machining (EDM), gradual deterioration of the interelectrode environment with increasing drilling depth results in bad process control, low machining efficiency and poor shape accuracy. The reasons are attributed to three key factors: tool wear, bubble and debris. Tool wear changes the initial tool shape and results in poor machining accuracy. Bubble behavior affects dielectric exchange and debris evacuation by virtue of the bubble flushing effect. Debris plays the decisive role on the dielectric contamination. This paper reveals the characteristics of three factors at the micro level and elucidates how they affect the drilling process. First, the influence of tool wear on the material removal process is investigated by presenting the evolution of micro hole shape based on the in situ observation of micro hole profile. Second, the bubble flushing effect is quantitatively evaluated depending on the standard statistical analysis of bubble behavior. Third, the complex debris agglomeration is observed and explained by the colloidal chemistry theory, then the dielectric contamination is quantitatively evaluated based on weighing the debris accumulation amount in the gap. Results show that tool wear leads to an enlarged discharge area, especially the lateral discharge area, and results in uneven material removal. The nature of bubble flushing effect is a self-vibration process, which is weakened seriously with increasing feed depth due to severely decrease of vibration frequency. The existence of debris agglomeration indicates that debris particles have complex behavior but not just freely distributed in the dielectric. Comprehensive analysis indicates that deterioration of the interelectrode environment is inevitable in micro EDM drilling, attributed to the weakened bubble flushing effect and increasing difficulty of debris evacuation and control of discharge area. Visible and quantitative investigations provide specific evidences of how three factors affect the discharge process compared to the vague description from empirical consensus in previous researches. The insights elucidate complex interelectrode phenomena, enhance the understanding of mechanism of micro EDM and provide the theoretical guide for the manufacturers.

Ceramic material is widely used industrial products due to excellent physical and mechanical properties, which in turn post challenge to shape ceramic material into desired shape and accuracy. A feasible method is to process ceramic material in its pre-sintered state. However, the interior of pre-sintered ceramic body contains a lot of high hardness particles which causes serious tool wear, especially in the three-dimensional micro-milling. In this paper, a theoretical model of calculating tool average volume wear rate is proposed based on abrasive wear mechanism and fatigue wear mechanism in alumina ceramic micro-milling. Experiments under various processing parameters are carried out to verify this model. The results indicate that theoretical values of the tool wear rates agree with experimental results. Most of the deviations are within 10%.

The micro-ultrasonic machining (USM) is suitable for machining hard and brittle materials. When a micro hole is drilled deeply using micro-USM, machining speed slows down and the breakage of micro tool may occur. To solve this problem, this paper proposes the application the planetary movement of micro tool in high-aspect ratio micro holes drilling by micro-USM. The micro holes of about 92 μm in diameter with an aspect ratio larger than ten have been machined. The processing efficiency has been improved. The influence of planetary movement parameters on processing efficiency has been investigated

Porous metals are widely used in acoustic or heat absorbing material, heat exchanger, catalysis and biochemical products. Porous metals are available to be processed by electrical discharge machining (EDM). However, the relationship between machining parameters and performance is unclear. In this investigation, extensive experiments are conducted on solid stainless steel 304 and porous stainless steel 304 with different pore sizes. Material removal rate (MRR) and tool wear ratio (TWR) are used to evaluate the machining performance of micro EDM. It was found that the machining of porous metal has a higher MRR and lower TWR than those of solid one. It was also found that the machining performance is significantly affected when the size of porous metal is close to the discharge gap. The abilities of debris removal and machining in porous metal machining by EDM are proposed to analyze this phenomenon. Experimental results match the calculated values well. It is helpful to select proper machining parameters of micro EDM to process porous metals.

Micro ultrasonic machining (USM) is widely utilized to produce micro-scale parts and products in hard and brittle materials such as silicon, ceramic and glass. The material removal modes have significant influence on the surface quality. It was found there are two types of material removal modes, brittle and ductile, existing in micro USM of silicon. It is necessary to identify the material removal modes of quartz crystal by micro USM. In this paper, Z-cut samples of quartz crystals are used as the experimental material. Extensive experiments are carried out in a set of self-developed micro USM equipment. It was found that the surface roughness, R pk , could identify the material removal modes of quartz crystal by micro USM. When the R pk is less than 350 nm , the machined surface by micro USM is relatively smooth, indicating ductile machining. Otherwise, the machined surface is covered with sharp tips and cracks. The brittle-ductile transition mode is not obvious in the Z-cut samples of quartz crystals by micro USM.

Micro-EDM technology is widely used in micro hole machining for its small force and high precision. However, the slow machining rate and large tool wear are the two major problems. In this research, machining with different electrode materials has been characterized under rough, semi-finish and finish machining conditions. Since the tool material has an influence on the tool feed, the relationship between the electrode feed and the machining time has been investigated to show the detailed information of electrode feed. As significant indicators for machining accuracy, the relationship between side gap-width and machining feed, as well as the relationship between electrode wear ratio and machining feed were also investigated. In addition, the influence of electrode material on tool wear is also discussed.

Micro ECM has the ability to generate the micro features such as micro holes, 3D micro cavities in electrically conductive materials. In this study, the influence of parameters (voltage, on-time and frequency of pulse generator, electrolyte flow, etc.) on the machining performance such as material removal rate (MRR) and accuracy on micro groove machining by micro ECM are investigated. Total of 19 grooves were machined on a self-made micro ECM equipment using a nanosecond pulse generator. Experimental results were recorded and analyzed. It was found that the corner radius and the taper between the sidewall and the bottom surface of a groove vary with the voltage and pulse on-time, the frequency of pulse, electrolyte system besides of the MRR and surface roughness. The electrolyte system with double nozzle is proposed to shorten the geometrical deviation such as the corner and the taper of the right and left sidewall of a groove. The results are analyzed.

Micro electrical discharge machining (EDM) has been used to drill micro-holes and to generate micro-features for applications in automotive, aerospace and biomedical industries. The tool electrode wear ratio in micro-EDM usually is larger than that in conventional EDM process. It has been reported that the electrode wear ratio is almost zero in gas. However, its narrow discharge gap leads to frequent occurrence of abnormal discharges. In order to enlarge the discharge gap in micro-EDM, Nitrogen plasma jet (NPJ) has been used as the working media for micro-EDM in this study. NPJ is generated by using a needle-cylinder type corona discharge with an AC power supply in pure nitrogen gas. A RC-type pulse generator is used to realize micro electrical discharges in this investigation. It is expected that the electrons and ions in NPJ increase the electrical conductivity in the discharge gap. Thus, a large discharge gap can be obtained. To investigate the machining characteristics of micro-EDM in NPJ, series of experiments in NPJ, nitrogen jet (NJ) and deionized water (DIW) have been carried out. The discharge distance, machining time, electrode wear and surface roughness under different conditions have been recorded. The measured data has been analyzed together with the discharge signals. It was found that the discharge distance in NPJ is larger than that in NJ. The machining process in NPJ is much more stable than in NJ. The observed volumetric difference of electrode wear is very small, probably due to the small total material removal. The machining efficiency in DIW is the highest. However, the surface roughness in DIW is worse than that in NPJ. ispartof: pages:559-564 ispartof: Procedia CIRP vol:68 pages:559-564 ispartof: 19th CIRP Conference on Electro Physical and Chemical Machining location:Bilbao, Spain date:23 Apr - 27 Apr 2018 status: published

As the requirements of MEMS continuously increase, the micro ceramic structures are widely used due to their favorable material properties such as high strength, hardness and resistance to high temperature, wear and erosion. However, the sintered ceramic compact is hard to be machined as its high strength. On the other hand, the low strength of green ceramic body makes it difficult to guarantee the machining accuracy. In this paper, ceramic compacts are pre-sintered below the sintering temperature. Pre-sintered ceramic compacts have suitable strength and are easy to be machined. Simple ceramic micro structures are easily generated with micro tools fabricated on line by wire electrical discharge grinding method (WEDG). Extensive experiments are carried out to investigate the influence of the strength of pre-sintered ceramic compact on the tool wear. It was found that the best machining results are achieved under the conditions of using the tool with a semi-circle cross section, the tool rotation speed of 1500 rpm and the pre-sintered ceramic compact formed under the pressure of 150MPa within the range of experimental conditions in this study.

Ceramic materials are widely used in industries because of their excellent properties such as high hardness, strength, resistance to heat and corrosion. The high strength of sintered ceramics posts the difficulty to be processed into the desired shapes and dimensions. Direct processing of ceramic green body is easy to cause edge damage due to the lower strength, leading to low surface accuracy. When the green body of ceramics is pre-sintered, the mechanical strength of green body is enhanced and the machining accuracy is improved. In this paper, micro holes are drilled in ceramics sheets pre-sintered at different temperatures. The influence of processing parameters is analyzed. It was found that the tool has the longest life when the pre-sintering temperature of ceramic green body was 800°C. The quality of the inlet and outlet of micro holes was improved significantly when the coolant was used in machining.

Characteristics of dielectric significantly influence machining performance of micro electrical discharge machining (EDM). A high material removal rate and large tool wear are obtained in micro EDM in liquid dielectric. Tool wear in gas dielectric is small, but the material removal rate is extremely low. In previous study, it was found that micro EDM in atmospheric pressure nitrogen plasma jet (APPJ) obtained a higher material removal rate than that in gas dielectric. However, material removal rate is still much lower than in liquid dielectric. To improve the machining performance of micro EDM in APPJ, this paper proposes micro EDM in APPJ assisted with coaxial mist (APPJ + mist). Effects of both flow rate of mist and discharge pulse energy on the critical breakdown distance, material removal rate, tool electrode wear ratio, surface roughness and profile are investigated. Experiments in nitrogen with coaxial mist (nitrogen + mist), deionized water and pure mist are also conducted for comparison. Experimental results indicate that critical breakdown distances in APPJ + mist, nitrogen + mist and mist are larger than in APPJ and deionized water. To understand the effect of misted droplets on critical breakdown distance, electric field intensity of the gap in deionized water and mist were simulated. Theoretical analysis reveals that electric field intensity on the surface of water droplet is much larger than that of tool electrode rim, resulting in the easy breakdown of gap with misted droplet. Material removal rate increases from 200 μm3/s (without mist) to 1252 μm3/s (with 5 mL/min mist) in APPJ in the case of open voltage of 100 V and capacitance of 8200 pF, which is higher than material removal rate in deionized water (1096 μm3/s) under the same discharge parameters. There is almost no tool electrode wear in APPJ + mist. The surface roughness of machined groove in APPJ + mist is 538 nm much lower than that in deionized water (672 nm), nitrogen + mist (627 nm) or pure mist (691 nm). Straighter side walls and flatter bottoms of micro grooves were obtained in APPJ + mist and nitrogen + mist than those in deionized water and mist. A micro cavity is also generated by using the proposed method without compensation of tool electrode wear.

In drilling blind micro holes with electrical discharge machining (EDM), the machining environment gradually deteriorates with the increase of the hole depth due to debris accumulation and concentration in the narrow gap area. The bubble flushing in the gap area was thought to be the main driving force for the exchange of dielectric liquid and debris exhaust. However, due to the difficulty in observing the gap area directly, the quantitative evaluation of bubble behavior has not been reported to date. In this paper, the feasibility of observation and quantitative evaluation of bubble behavior in micro hole drilling was investigated. A set of solutions was put forward to solve the problems from observation to data processing. Two aspects of works were performed: First, the generation of bubbles and debris was observed and analyzed in a single discharge process using a pair of needle electrodes to avoid the visual blocking by the micro tool; Second, the bubble escaping from the micro hole has been observed and quantitatively estimated in micro hole drilling with EDM. The obtained results proved the feasibility of the method on quantitative estimation of the bubble behavior and showed with the increase of the hole depth, the size of single bubble exhibited the trend to increase, but the bubble escaping frequency decreased significantly. These characteristics of bubble behavior led to the low efficiency of dielectric exchange and debris exhaust and weakened the insulation strength of the gap area, eventually resulting in frequent abnormal discharges.

Electrical discharge machining (EDM) is an electro-thermal process. When a micro feature is of the same size order as microstructure of alloy, the machining performance of micro EDM varies due to the difference between the thermal properties of the crystal grain and that of the granular boundary, resulting in undesired dimensions and unstable machining process. To improve the machining accuracy and efficiency of micro EDM, it is necessary to understand the influence of microstructure of alloy on the machining performance of micro EDM. In this study, micro holes were drilled in titanium alloy with equiaxed crystals, copper, nickel, nickel-copper alloy and stainless steel with enlarged grains. Different average values and distribution ranges of material removal rates and discharge gaps indicate that the machining performance of micro EDM is influenced by the microstructure of alloy.

Complex 3D micro-structures can be fabricated layer by layer in alloys by micro electrical discharge machining (EDM) using simple shaped electrodes. However, electrode wear is a serious problem which significantly affects machining accuracy. The electrode wear compensation method is a key issue in micro EDM milling and effectively solves this problem. This paper proposes a new compensation method based on the scanned area (BSA) in each layer machining. The new method is integrated with a CAD/CAM system to generate 3D micro cavities. Experimental results have been compared with those using the uniform wear method (UWM) and those using a combination of linear compensation with UWM. It was found that using the proposed method machining efficiency was improved and tool wear ratio was reduced.

In this study, a technique to remove the byproducts from the interelectrode area of an electrochemical machining (ECM) tool was investigated. Our goal was to improve both the processing speed and replicating accuracy of the ECM process. This technique involves the application of ultrasonic vibration to the tool electrode. The influence of the direction and the amplitude on the processing speed and the replicating accuracy was experimentally investigated. It was found that both the processing speed and the replicating accuracy had improved. In addition, the largest processing speed and the highest replicating accuracy were obtained by applying complex ultrasonic vibration. Next, an experimental hole was drilled to remove byproducts, via machining with tool feeding in the normal direction to the workpiece surface. In addition, we experimentally investigated the influence of the feed rate on the processing speed and the replicating accuracy. It was found that a higher feeding rate improved both the processing speed and the replicating accuracy.

Ceramic materials are widely used in industrial products because of their excellent properties such as resistance to erosion, high temperature and wear. Those properties pose difficulty in processing ceramic materials to desired shapes and dimensions, especially in micro machining of ceramics using micro tools because of the low mechanical strength of tiny tools and the extreme hardness of ceramics. The machining of ceramic green body may be a solution to the problem. However, the low strength of ceramic green body results in low machining accuracy such as damage at the edges of micro features. In this paper, the pre-sintering of ceramic materials was used to enhance the material strength, and hence to improve the machining accuracy. Microstructures of pre-sintered ceramic green bodies at different temperatures were observed and analyzed. The mechanical strength of pre-sintered ceramics was measured. It was confirmed that the mechanical strength of ceramics increased with an increase of pre-sintering temperature. There was no obvious shrinkage after pre-sintering at below 850 °C. The edge damage of machined micro features was reduced significantly. The tool wear increased with the increase of pre-sintering temperature. Finally, a 3D micro feature was machined and the fully sintering shrinkage was compensated accurately.

Micro Ultrasonic Machining (USM) is used to generate micro features in hard and brittle materials. However, tool wear occurs during machining. In this paper, low cycle fatigue is identified as the dominant factor causing tool wear in micro USM. A theoretical model is proposed to estimate the tool wear. Experimental results of tungsten and stainless steel 316L agree with the theoretical values. The tool rotation has no significant influence on tool wear. The difference between the experimental and theoretical results is sensitive to the variance of abrasive particle number in the working zone.

Micro electrical discharge machining (EDM) has the ability to drill micro holes with high accuracy in metallic materials. The aspect ratio of a micro hole generated by micro EDM is usually higher than those by other processes such as etching, mechanical drilling, and laser. However, it was found that the drilling speed of micro EDM slows down and even stops when the aspect ratio reaches a certain value. To understand this phenomenon, a theoretical model is proposed based on the fluid mechanics and surface tension. Experiments under different machining conditions are carried to verify this model. Experimental results agree with the theoretical values, which indicate the validity of the proposed model. The difference between the theoretical values and the real values might be caused by the debris and the temperature in the discharge gap, which are ignored in the model.

When a micro-hole is drilled deeply by EDM, the viscous resistance in the narrow discharge gap causes difficulty in the removal of debris and bubbles from the working area, leading to frequent occurrences of abnormal discharges and resulting in extensive electrode wear. This paper presents a new method of drilling high aspect ratio micro-holes by EDM, in which the planetary movement of an electrode, with enhancement from ultrasonic vibration, provides an unevenly distributed gap for the debris and bubbles to escape from the discharge zone easily. Micro-holes with aspect ratio of 29 have been drilled.

Although micro ultrasonic machining (USM) has been successfully applied in generating micro features in hard and brittle materials such as silicon, the influence of machining parameters on the machining performance is not clearly understood. Experimental results show that the machining speed decreases with an increase in the static load beyond a certain level. In this study, the debris accumulation is proposed as the main reason leading to low machining efficiency. A mathematical model is also developed to analyze this phenomenon qualitatively. Experimental results reveal that the particle size is the dominate factor influencing the surface roughness in micro USM.

In micro electrical discharge machining (micro EDM), tool wear adversely affects the accuracy of a machined feature or a part. Therefore, tool wear compensation techniques have been proposed for micro and macro EDM operations. However, some of these techniques require extensive experiments in determining the appropriate tool path (which depends on part feature, material, and machining parameters) for machining a desired surface. This paper reports the development of a theoretical model to develop the tool path for generating a desired workpiece surface profile. The application of the model is illustrated for micro and macro EDM by machining flat slots. A review of tool wear compensation techniques is also presented.

Many manufacturing processes, such as lithography, etching, laser, electrical discharge machining (EDM), and electrochemical machining (ECM), are being applied to produce the meso- and microscale parts and products. Materials such as silicon, glass, quartz crystal, and ceramics are being increasingly used in microelectromechanical system (MEMS) devices. Ultrasonic machining (USM) offers an attractive alternative to machine some of the hard and brittle materials. However, the tool wear in micro-ultrasonic machining adversely affects the machining accuracy. Therefore, it is necessary to account for and to compensate the tool wear during machining. This paper reports the feasibility of applying the uniform wear method developed for micro electrical discharge machining and its integration with CAD/CAM to microultrasonic vibration process for generating accurate three-dimensional (3D) microcavities. Experimental results show that the tool shape remains unchanged and the tool wear has been compensated.

In micro EDM, simple-shaped tools are being used to machine complex 3D micro features because of the cost and difficulty in fabricating multiple complex-shaped micro electrodes. However, the tool wear adversely affects the accuracy of machined micro features. Therefore, a theoretical model for surface profile generation which takes into account the effect of tool wear is needed. This paper presents such a model and a simplified simulation algorithm. The experimental results of micro and macro EDM generated surface profiles confirm the validity of the proposed mathematical model and the simulation algorithm.

It is difficult to drill high aspect ratio through holes and complex shaped blind holes using micro EDM. The debris concentration in the narrow discharge gap causes abnormal discharges leading to excessive electrode wear and lower machining precision. In micro EDM, the electrode size is too small for internal flushing. This paper presents a new approach for effective self-flushing using planetary movement. Through micro holes with an aspect ratio of 18 have been drilled. This approach is also demonstrated by drilling blind noncircular micro holes with sharp corners and edges. The process performance characteristics are analyzed under different machining conditions.

It is necessary to integrate CAD/CAM systems with micro-EDM to generate tool paths when simple shaped tools are used to machine three-dimensional (3D) micro parts. Currently available CAD/CAM systems cannot be directly used because of the continuous tool electrode wear during machining. This paper proposes an approach to integrate CAD/CAM systems with micro-EDM while accounting for tool wear using a recently developed uniform wear method. This approach is verified by successfully generating very complex 3D micro cavities. Additionally, the feasibility of the approach is illustrated by generating complex macro cavities using conventional EDM with single simple shaped electrodes.

In this paper, we present a new method, called uniform wear method, for 3D micro-EDM. Simple electrodes such as with round or rectangular section are used. Uniform wear at the end of the electrode was realized by layer-by-layer machining. This maintains the original electrode shape and converts the three dimensional electrode wear to a linear one. By compensating the linear electrode wear, complicated three dimensional cavities were successfully machined. This technique was developed for micromolds, but the applicability for normal size molds was also confirmed.

This paper deals with the tool path design and error analysis for machining cavities with round cross section by cylindrical electrodes based on the uniform wear method. Conical cavities and spherical cavities were machined successfully by applying tool path generation based on the compensation equation for 3D Micro-EDM. In order to predict the dimensional errors caused in actual machining, the error equations of electrode wear ratio, machining area and electrode size have been derived from the compensation equation. Machined shapes of conical cavities and spherical cavities influenced by different errors were simulated.

Microholes are widely used in industrial products, such as engine nozzles and filters for biomedical industry. Electrical discharge machining (EDM) is one of processes to drill microholes in alloy with high aspect ratio. However, the achievable aspect ratio of a microhole by micro-EDM is limited. To improve the aspect ratio of a microhole drilled by micro-EDM, the planetary movement of electrode is applied during machining. It was found that the machining efficiency of microhole drilling can be further improved by proper setting of planetary movement of electrode, such as the electrode feed rate and movement speed of electrode in XY plane. In this paper, a theoretical model is proposed to optimize parameters of the planetary movement of electrode. Microholes are drilled aided with planetary movement using different machining parameters to verify the model. Experimental results agree with theoretical values, which indicate the validity of the proposed model. This model provides certain theoretical basis for machining parameter selection when microholes are drilled aided with planetary movement.

Grinding method is an effective way to process hard and brittle materials, such as ceramics. However, it is necessary to control the grinding force to achieve the desired surface quality and dimensional precision of ceramics parts. In this paper, we present the study results of the influence of machining parameters on the grinding force and its influence on machining performance such as machining speed and surface roughness. To improve machining efficiency and surface quality, the grinding process is aided with ultrasonic vibration. To control the grinding force, the fuzzy control strategy is used in this study. The effect of grinding force control on stability is studied. It has been found that the machining process is more stable with ultrasonic vibration than that without it. Ultrasonic vibration enhances machining speed and surface quality.

To solve the difficulty of machining ceramic micro-features, manufacturing methods based on green machining had been systematically researched using alumina. The research includes study of the formation law of machining gap while micro-machining was carried out in simple green ceramic, and effect of sintering on size of green ceramic micro-features. Through the processes of molding green ceramic, amending machining size, reserving machining gap, designing and preparing micro tool, and micro milling with planetary movement and sintering, twenty micro holes with diameter of 100µm and 200µm each and twenty-nine micro cavities with upper surface size of 500µm×500µm had been successfully machined, and the final size error was less than 2%.

This paper presents a predictive modeling of machining speed in the process of ceramics grinding based on the theory of indentation, ideal grinding grain shape, wheel microstructure and dynamic effects. Machining parameters such as grinding force, wheel rotation speed and the depth of cut are included in this model. A series of experiments have been carried out to verify this model. It was found that the theoretical analysis agrees reasonably with the experimental results.

Micro electrical discharge machining (EDM) is widely used to drill micro hole with high aspect ratio in any electrically conductive material regardless its hardness. Due to the electrode wear during machining, the electrode has to be prepared long to compensate the wear length. It is found that the discharge gap of a micro hole by a long and thin electrode is larger than that by a short electrode. Although there is no mechanical contact during EDM, the reaction force generated by electrical discharges causes the long and thin electrode to bend, resulting in the hole diameter larger than the expected. In this paper, a simple model is used to estimate the deflection of electrode in order to explain the large diameter of a micro hole by a long electrode. Experimental results indicate that the theoretical values agree with the real machining results.