Production Of Micro Parts Research Articles

Production of precision slots in copper foil using micro EDM

Electrical discharge machining (EDM) is an unconventional machining technology. It allows machining of at least at least electrically conductive materials. The trend of miniaturization of industrial products is obvious. However, the required quality and accuracy must be maintained, which can be achieved with micro-EDM. One of the industrial products is also optical devices used for testing cars. These contain miniaturized parts, which are, however, necessary for their proper functioning. For this reason, this study was performed, which focused on the production of a precise slot measuring 5000 × 170 µm in a copper foil with a thickness of 125 µm. The same copper foil was used as a tool, which represents an advance in the production of micro-parts.The use of the same semi-product for the production of the slit as well as the tool itself has not yet been presented in any similar study. A design of experiment Box and Behnken Response Surface Design was performed for a total of 15 rounds, monitoring the effect of machine setting parameters (Pulse current, Pulse on time and Voltage) on responses in the form of Erosion rate, corner radius, slot length and width. Using multi-criteria optimization, the optimal setting of the machine parameters for the production of a given slit was determined, which is Pulse current = 2.1 A, Pulse on time = 40 µs and Voltage = 238.8 V. Micro-EDM technology has been found to be suitable for the production of miniaturized slits.

Influence of the punch with concave cutting-edge on the blanking force in micro punching process

Micro blanking machining is a promising manufacture technology to realize mass production of micro parts efficiently. In the process of blanking, the blanking force is significant to the punch, die, and sheet workpiece. In order to investigate the influence of cutting-edge shape of the punch on the micro blanking process, a self-developed micro combined EDM and blanking machine tool is applied in this paper. A punch with concave cutting-edge is capable to be fabricated online through a series of processing based on micro EDM: 3D milling, wire electrical discharge grinding and reverse EDM copy machining techniques. Then the punch and die are accurately matched online due to the preparation of them in the same coordinate system. Micro blanking parts and punching parts with the complex cross-sectional shape is obtained by using the online fabricated punch with flat cutting-edge and concave cutting-edge respectively in the workpiece of stainless steel SUS304 foil. The characteristic of blanking force varying with time indicates that the blanking force is significantly reduced in the case of concave cutting-edge, meanwhile, both blanking parts and punching parts have the high quality.

Analysis on hole overcut during micro-EDM of Inconel 718

For production of micro parts, EDM machining process plays an important role. The super alloy Inconel 718 is a highly demanding material due to its extensive applications in the diversified field of engineering. Because the machinability features are adequate and it has superb physical and as well as mechanical properties. That’s why both industry professionals and researchers across the globe are interested to work on this material. Moreover, the micro machining of such material has become popular for precision manufacturing industries such as aerospace, automobile, bio medical. In depth knowledge of machining process is required to machine difficult to machine material like Inconel 718. Because various process parameters are responsible for the machining criteria. There is no direct contact between electrode and workpiece. Hence, there will be no mechanical forces and stresses induced in this process. Moreover, the requirement of specific energy is quiet less in this process. The accuracy is quite good in terms of surface roughness i.e., 0.1 µm at the maximum level. Hence, in this research work, an effort has been undertaken to analyze the impact of several process variables namely current, gap, voltage, pulse on and pulse off time on the overcut. The experimental design layout was developed to conduct the experiments as per RSM (Box-Behnken design). From the experimental result, it was found that current, pulse on duration affected the overcut much. Pulse off duration and gap also played a significant role in minimizing overcut.

Mechanical and micro-structural characterization of hot rolled brass foil

To assist the large-scale production of micro parts by micro sheet metal forming processes, mechanical and microstructural behaviors of metal foils are required. In the present study, an attempt has been made to characterize these properties of 100-μm thickness as-received brass foil. Mechanical characterization of foil has been done with tensile tests, bending tests and Nakazima tests. From the tensile test analysis, it has been observed that change in strain rate has a negligible impact on flow stress. However, serrations observed in flow stress are dependent on strain rate. The Electron backscatter diffraction (EBSD) analysis of as-received and post-deformed specimens shows the concentrated rise in Kernel average misorientation, high angle grain boundaries and low angle grain boundaries in deformed specimens. The fracture morphology study shows the presence of ductile fracture in the middle region of the fracture cross-section with shear lips in the edge region. Bending experiments show that the spring-back angle increases with the increase of bending angle up to 120°. After that, with an increase in bending angle, the spring-back angle decreases. The forming limit curve (FLC) obtained from the Nakazima test was compared to FLC obtained from different prediction criteria. From this study, it was observed that the FLC obtained from Marciniak-Kuczynski (M-K) criterion showed a good prediction of FLC for brass foil. However, FLCs obtained from Swift-Hill criterion, Abspoel empirical criterion and Pamstamp's Matwizard module over estimated foil's formability.

Optimization of electrochemical etching process for manufacturing of micro electrodes for micro-EDM application

Application of Micro-Nano scale Electrical Discharge Machining is rapidly growing in manufacturing of metal products irrespective of its hardness having geometric features in range of micrometer to nanometer scale. To achieve such small geometrical features, smaller dimensional tool electrode is required. However fabrication of this tiny electrode with desired dimension and also handling of such tiny electrodes is a primary aspect that needs to be investigated systematically to use the Micro-Nano scale EDM in batch production of micro parts. In this work authors investigate the application of electrochemical etching process for fabricating EDM electrodes smaller than 10 µm. While the smallest electrode fabricated with the optimized parameter is 3.33 µm, their performance as electrode in micro-EDM has been studied systematically. To the best of authors’ knowledge such studies are not reported in the published literatures. However, the fabrication of such smaller size features by applying alternating current in ECE has been attempted previously but not for micro-EDM applications.

Influence of dead metal zone on dislocation strengthening effect during micro-progressive forming

Micro-scale plastic deformation (microforming) is a promising manufacturing technology in modern industries. To put microformed parts in a more competitive position compared with micro-products made by other micro-manufacturing methods (such as micromachining and 3D printing), micro-progressive forming must be fully studied for the mass production of micro-parts to obtain good grain texture and decrease product costs. Simultaneously, the undiscovered dislocation strengthening effect of micro-scale progressive forming should be investigated. Using micro-universal joint progressive forming as a case study, the influence of the dead metal zone–induced strengthening effect on ductile fracture in micro-progressive forming is discussed. Based on the results of upsetting experiment and finite element simulation, it was found that the specimen produced via metal foil forward-extrusion-blanking process eliminated the ductile fracture when applying the same experiment condition to the specimen produced by micromachining. Based on the micro-indentation and X-ray diffraction results, a dead metal zone–induced dislocation strengthening model was established, and the mechanism for the strengthening effect during micro-progressive forming was revealed. This research thus provides an in-depth understanding of the micro-scale progressive forming process and takes an important step in the field of ductile fracture in multi-stage plastic deformation.

Fabrication of micro punching mold for micro complex shape part by micro EDM

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.

Characterizing Ultrasonic Micro-Molding Process of Polyetheretherketone (PEEK)

Abstract Ultrasonic micro-molding technology can dispense, melt and inject as small an amount of polymer as is required for one cycle, an advantage which makes the process highly desirable for low-volume and customized production of micro parts made from sensitive and very expensive polymers, especially in the medical sector. In this study, the feasibility of processing the polyetheretherketone (PEEK) polymer was investigated. The experiments conducted determined the parameters of a process that would allow parts with specific mechanical properties to be produced and verified as not degraded. The development of the process used three amplitude values as well as varying plunger velocity and vibration times. The three amplitude values and four speed values were tested to determine appropriate parameters for the ultrasonic process. Completely filled samples without any visual signs of degradation were analysed using FTIR-ATR, crystallinity percentage and tensile strength tests. Results show that the amplitude parameter is an important factor in the ultrasonic process and the higher its value is, the better the mechanical properties of complete parts are. Moreover, the tensile strength value of the specimens fabricated by ultrasonic micro-molding is comparable to that of conventional injection molding technology.

Application of Micro Structured, Boron Doped CVD-diamond as μEDM Tool Electrodes

High precision cavities are used for micro injection and micro embossing tools in the field of tool making and are mainly used for small batch or mass production of micro parts. In order to fabricate a large quantity of parts, wear resistant tool materials are required. In possession of a high hardness and a high Young's Modulus, such materials are often hard or even impossible to machine by conventional fabrication processes. Being independent of the work piece's mechanical properties, Micro-Electrical Discharge Machining (μEDM) is predestined for this case.μEDM is based on the modification of state of the art process technologies and universal machine tools applied for electrical discharge machining operations [1,2]. Besides the adjustment of the electrical parameters, the μEDM-process is also determined by the tool electrode's material which has a big influence on the material removal rate VW, the electrode's wear behavior, as well as the process results concerning surface quality and dimensional accuracy [3]. Experimental investigations aim at decreasing the wear of tool electrodes using novel electrode materials. To assure an efficient process, short production times and low tool wear ϑ are demanded. Therefore, electrodes with excellent electrical and thermal conductivity along with a high mechanical strength have to be used.Boron doped CVD-diamond is fulfilling these criteria. Microstructures within thin CVD-diamond foils are realized by direct structuring utilizing laser ablation and by indirect structuring using micro-structured copper substrates in the CVD-process, which transfer the micro-structure onto the growing diamond layer. Experiments were conducted in order to identify suitable EDM-parameters for different workpiece materials, namely steel 90MnCrV8, silicon carbide SiSiC and tungsten carbide K40F, which lead to lower tool wear ϑ and high accuracy.

Fabrication of punch and die of micro-blanking tool

The difficulties of tool fabrication in micro level provide an enormous challenge due to the dimension limitation. Reducing the difficulty and tool cost fabrication should always be considered by determining the simplicity of tool geometry, precision tolerance, and an appropriate material selection. This paper study about the manufacturing of micro-blanking punch-die. The mechanical material removal method was chosen to fabricate punch-die since this is a single piece production and intended for small-scale production of micro parts. The manufacturing process consists of punch-die design and fabrication, tool assembly, and clearance measurement. The stress analysis is also conducted to ensure the strength of the punch-die. A micro-blanking experiment was held to observe the tool performance. The result showed that micro-blanking tool can be manufactured successfully and used well to conduct the micro-blanking experiment.

Experimental Investigations of Material Behaviour in Forward Micro Extrusion

Micro manufacturing has received good attention globally in terms of its manufacturing methods and processes. One of the most popular micro manufacturing processes is micro forming. Although there were efforts made to realize micro extrusion for industrial application, the technology itself was seen as being insufficiently mature and unlike conventional methods, there is no in-depth knowledge. It has become essential to develop a proper understanding which in turn could be used to develop dedicated processes for the manufacturing of metallic micro components. In this work, an attempt has been made to realize this special application of metal forming. A novel experimental setup consisting of forward extrusion assembly and a loading set-up has been developed to obtain the force-displacement response. The effects of minaturization on micro components and the material behavior during forward extrusion are investigated. As per industrial requirement and application of micro part in micro manufacturing process, grain size is an important factor. In this context the effect of grain size is also studied in this work. The realization of such a productive forward extrusion assembly poses significant advantages when compared to the conventional manufacturing technologies in the production of micro parts.

Experimental investigations of grain size effects in forward microextrusion

Micromanufacturing has received good attention globally in terms of its manufacturing methods and processes. One of the most popular micromanufacturing processes is microforming. Although there were efforts made to realize microextrusion for industrial application, the technology itself was seen as being insufficiently mature and unlike conventional methods, there is no in-depth knowledge. It has become essential to develop a proper understanding which in turn could be used to develop dedicated processes for the manufacturing of metallic microcomponents. In this work, an attempt has been made to realize this special application of metal forming. A novel experimental setup consisting of forward extrusion assembly and a loading setup has been developed to obtain the force-displacement response. The effects of miniaturization on microcomponents and the material behavior during forward extrusion are investigated using a computerized universal testing machine (UTM). As per industrial requirement and application of micropart in micromanufacturing process, grain size is an important factor. By using a forming assembly in conjunction with a loading setup, the authors are able to investigate the force-displacement response for microextrusion with material of different grain sizes. Extrusion tests performed on the samples of different grain sizes demonstrated that decreasing grain size caused an increase of flow stress. The realization of such a productive forward extrusion assembly poses significant advantages when compared to the conventional manufacturing technologies in the production of microparts.

Design and Analysis of Feedstock Mixing Mechanism For Micro Metal Injection Moulding

The need for homogeneous metal powder and binder mixing is paramount in injection moulding process as it affect product quality significantly. However available commercial feedstocks may not be suitable especially for production of micro parts with high aspect ratio. Therefore, this research proposes a new mixer design that incorporate mixing and granulation of the feedstock for components production at micro level. Also metal powder/ binder flow in the mixing chamber is investigated. The design specifications and simulation were based on powder loading, powder size and shape, binder formulation, sequence of material addition, mixing time, temperature and shear rate with finite element analysis. The simulation results show a favourable and visible design anticipation of the mixing mechanism and mixed feedstock. Conclusively development of this design will enhance micro metal moulding productivity and improve production cycle time.

S1160406 軟質/硬質相を面内配置したDLC複合膜の無潤滑トライポロジー特性評価

In micro forming, its excellent productivity has contributed to cost reduction in the production of micro parts. However, due to the smallness of their material dimensions, effect of friction at the contact interface between the molds and the workpiece becomes more remarkable and deteriorate that accuracy. Moreover lubricant-free microforming process is a strong demand. So we focus on the technique of surface texturing of diamond-like carbon (DLC). This technique is known for the stabilization of the the friction coefficient and the reduction of the abrasive wear caused by wear debris trapping effect. However when applying a textured DLC films to the micro forming molds, problems leading to the early wear of textured DLC and damages to workpieces have been reported because of the stress concentration on the edge portion of that structure. In this study, we suggest to fill the softer DLC than the texture part's DLC in the recess space of texture structure. Thereby it's possible to relax the stress concentration on the convex portion and to form textured structures automatically with the wear increases by the preferential wear of soft DLC. This was realized by two kinds of film deposition methods and stainless steel wire mesh as a mask. To characterize the basic tribological properties of this DLC films under dry condition, the ball-on-disk type tribology test was carried out.

Review on progressive microforming of bulk metal parts directly using sheet metals (Keynote Paper)

Due to the ubiquitous trend of product miniaturization, energy saving and weight reduction, micro/meso-scale parts have been widely used in many industrial clusters. Micromanufacturing processes for production of such micro/meso-scale parts are thus critically needed. Microforming, as one of these micro manufacturing processes, is a promising process and thus got many explorations and researches. Compared with the research on size effect affected deformation behaviours, less attention has been paid to the process development for mass production of micro-parts. The product quality and fabrication productivity of micro-parts depend on the involved process chain. To address the difficulty in handling and transporting of the micro-sized workpiece, development of a progressive microforming process for directly fabricating bulk micro-parts using sheet metals seems quite promising as it avoids or facilitates billet handling, transportation, positioning, and ejection in the process chain. In this paper, an intensive review on the latest development of progressive microforming technologies is presented. First of all, the paper summarizes the characteristic of progressive microforming directly using sheet metal. The size effect-affected deformation behaviour and the dimensional accuracy, deformation load, ductile fracture, and the surface finish of the microformed parts by progressive microforming using sheet metals are then presented. Finally, some research issues from the implementation of mass production perspective are also discussed.

Size Effects on Mechanical Properties of Copper Thin Sheet in Uniaxial Tensile Tests

Microforming offers a reliable method for mass production of micro parts with low cost and high precision. However, to form micro parts is more difficult than macro parts because of size effects. Uniaxial tensile tests are carried out to study the size effects on mechanical properties of copper C1100 thin sheet at room temperature on a universal testing machine. The materials are thermally treated at 873 K for 12 h in nitrogen atmosphere, and the specimens with thickness varying from 0.32 mm to 0.04 mm are manufactured by slow feeding wire cutting with initial gauge widths of 8, 4, 2, and 1 mm. In addition, a non-contact measurement device is developed to reduce the error of the contact measurement method. The results show that the size effects on mechanical property are obvious. The flow stress and elongation decrease dramatically with the decreasing specimen size. The reason for this phenomenon is also discussed by scanning electron microscope (SEM) observation and theoretical analysis. DOI: http://dx.doi.org/10.5755/j01.ms.20.4.5958

Image Denoising and Quality Inspection of Micro Components Using Perona-Malik Diffusion

The production of micro components has received much attention on the last years and has recently become one of the crucial tasks of product and processes oriented research. During the production of very small parts, many unanticipated manufacturing errors such as cracks, wrinkles and form deviations may occur. In order to minimize these defects (flaws) and simultaneously achieve an economically efficient production of micro parts the suitable methods for quality inspection are required. This paper focuses micro- components manufactured by means of micro-cold forming techniques. The new methods for error detection in micro components are proposed. The quality of presented approach will be demonstrated in numerical examples.

Simulation and discussion on the decreasing flow stress scale effect

The miniaturization of products requires the mass production of microparts. The microforming can well meet this requirement. Due to the emergence of decreasing flow stress scale effect in the micro scale, the traditional forming process and theory may fail. Based on the crystal plasticity theory, upsetting tests of micro copper cylinders with different dimensions and grain sizes were simulated, and the decreasing flow stress scale effect was studied and discussed. Results show that with the decrease of billet dimensions, the flow stress is gradually decreased, and the decreasing flow stress scale effect is emerged; with the increase of grain size, the decreasing flow stress scale effect is more remarkable. It can also be seen that the decreasing flow stress scale effect can be well simulated with the crystal plasticity theory, and the necessary relevant information is provided for deeper understanding on this scale effect, as well as the design of processes and die structures in the microforming.

Properties of DLC Film Deposited on Mould with Micro-Cavity Used in Microforming

Micro-forming as a kind of metal forming process is very suitable for massive production of micro-parts with high mechanical properties. To eliminate the scaling effects of friction in micro-forming, diamond-like carbon (DLC) film of nano-thickness was deposited on the micro mould with plasma based ion implantation and deposition (PBII&D) method for its excellent tribological behaviors. The effects of mould cavity dimensions were investigated, for example distribution of thickness, surface topography and microstructure of DLC film. The result shows that the thickness of DLC film decreases from 554 nm to 47 nm with the increasing of depth into mould cavity. And ripple topography appears when the cavity dimension is small. The ratio between ID and IG increases with the increasing of cavity dimension, which means that the amount of SP3 bonds becomes smaller. With the DLC film deposited female die, micro-cups of 1.1 mm in diameter were manufactured successfully using copper thin sheet of 0.04 mm in thickness with a blanking-deep drawing process. And the surface quality and dimension accuracy of micro-cup were analyzed in details. The results show that DLC film is feasible alternative to micro-forming.

Inkjet printing of individual polymer micro parts self-shaped with hemispherical caps

Droplet deposition has been so ubiquitous over a decade for the production of micro parts using versatile liquid-based methods such as inkjet-printing technology. One of key elements for success in the design involves the use of non-homogeneous substrates to effectively control the complex morphologies of solute deposit during evaporation. However, there are still few studies investigating contours of the solid contents self-formed and even released as the solvents evaporate. This paper reports a droplet vaporization deposition (DVD) method that can significantly improve the controllability over the curvatures of micro parts utilizing the heterogeneous PDMS (Polydimethysiloxane) substrates based on soft-lithography technique. Experimental and analytical results indicate that the profile curvatures and contact angles (up to ∼90°) for the hemispherical parts formed after droplet evaporation were simply varied by different droplet volumes (single droplet ∼10pl) placed on the cavity-structured surfaces, thus providing the capability of control over solid contours. In this way, the individual micro parts released from the mold substrates could be applied in many applications, in particular the current self-assembly processes.