Microgroove Machining Research Articles

Research and Application Progress of Laser-Processing Technology in Diamond Micro-Fabrication.

Laser-processing technology has been widely used in the ultra-precision machining of diamond materials. It has the advantages of high precision and high efficiency, especially in the field of super-hard materials and high-precision parts manufacturing. This paper explains the fundamental principles of diamond laser processing, introduces the interaction mechanisms between various types of lasers and diamond materials, focuses on analyzing the current development status of various modes of laser processing of diamond, briefly discusses the relevant applications in diamond cutting, micro-hole forming, and micro-groove machining, etc., and finally discusses the issues, challenges, and potential future advancements of laser technology in the field of diamond processing at this point.

Combined effects of polarization and secondary ablation on precision machining of microgrooves by laser-induced microjet-assisted ablation.

In this study, we propose a polarization-modulated laser-induced microjet-assisted ablation method for machining microgrooves with controllable cross-sections. A novel mathematical model is presented to accurately predict the cross-sections by considering the combined effects of polarization and secondary ablation. The simulation and experimental results reveal that the effect of secondary ablation becomes more obvious when steeper grooves are ablated with higher repetition frequency and larger pulse energy. The polarization effect and secondary ablation of target material result in asymmetric ablation of linearly polarized laser beam. To avoid the asymmetric ablation, we present the cylindrical vector beams to achieve scanning-path independent laser micromachining with various cross-sections. Based on the prediction model, the cross-sectional characteristics are precisely designed and fabricated by tuning laser processing parameters. Our work provides a reliable approach for the controllable fabrication of microgrooves at the scale of tens of micrometers.

Process Research on the Microgroove Depth Uniformity of Bursting Discs Using Femtosecond Lasers

This study proposes an ultrafast laser ablation method for improving the depth uniformity of microgrooves in bursting discs. Under a lower laser fluence, the influence of the spot overlap rate on the depth uniformity of microgrooves was studied. The results show that 80% of the spot overlap ratio has good performance in ablation efficiency and depth uniformity of microgrooves. On this basis, the relationship between the number of laser scanning layers and the depth of microgrooves was studied, and the number of scanning layers needed to ablate 70 µm microgrooves was obtained. Based on the combination of the process parameters and the optimization of the laser scanning path, laser ablation of bursting disc microgrooves with a specific shape was realized. The depth uniformity of microgrooves in different sections of the bursting disc was not worse than 4 µm. The preliminary bursting test shows that the bursting pressure between the discs was no more than 0.06 Mpa. Compared with the results of the traditional processing method, the microgroove depth uniformity of bursting discs was greatly improved. Therefore, femtosecond laser ablation technology provides an advanced manufacturing method for bursting disc microgroove machining.

Influence of electrochemical discharge machining parameters on machining quality of microstructure

As a nontraditional processing technology, electrochemical discharge machining (ECDM) can process glass and engineering ceramics precisely. This technology has proven to be a potential process for glass 3D microstructure. However, the key to expanding the application of ECDM is how to improve machining accuracy. This research conducted micro-hole and microgroove machining. Power voltage and frequency influence on hole processing efficiency, hole entrance diameter, and hole limit depth was explored. We considered four factors affecting ECDM—the voltage and frequency of the pulse power supply, the tool electrode feed rate, and the rotation speed. We studied their influence on the roughness of the microgrooves. The results show that machining efficiency, entrance diameter, and limit depth of micro-holes increased with the increase in voltage but decreased with the increase in power frequency. The results show that the roughness of microgrooves has an apparent positive correlation with the power voltage. In contrast, it had an evident negative correlation with the power frequency and electrode speed. The bottom surface roughness of microgrooves can be as minor as 0.605 μm. Various complex 3D microstructures on the glass surface by layer-by-layer method proved the great potential of ECDM.

Using a nickel electroplating deposition for strengthening microelectrochemical machining electrode insulation

This study focused on reducing the peeling phenomenon of electrode insulation layers during electrochemical microgroove machining. An epoxy resin insulation layer was applied to the electrode surface, and the tip of the electrode was ground to reveal bare metal for target machining. During electrochemical machining, the durability of insulation under various potentials and processing times were studied. Typically, a large number of hydrogen bubbles are generated at the exposed part of the electrode during processing. These bubbles increase the peeling speed of the insulation and reduce its service life. Therefore, this study proposed the use of electroplating deposition to form an electroplated layer on the exposed part of the electrode. The deposition rate of the electroplated layer and coating state of the electroplated layer at the tip of the electrode were studied. The withstand voltage test was performed under various electrochemical machining parameters to study the insulation and peeling effects. The surface morphology of microgrooves produced through electrochemical microgroove processing with and without an electroplated electrode was compared. The comparison revealed that the uniformity of the microgrooves processed by the electroplated electrode was better and the insulation of the electrode had lower cracked area than those produced without the electroplated electrode. The electrode was tested before and after processing to verify the protective effect of the coated layer. The result revealed that the electrode with a 0.5 mm thickness exhibited the slowest cracking rate, and the electrode with the electroplating time of 4 h exhibited the most efficient protective effect. Thus, the electroplated layer can effectively protect the insulation and prevent it from peeling off during the process, which increases its service life.

Structural design and fabrication of polycrystalline diamond micro ball-end mill

Since cemented carbide has been used as a micro-lens array mold, its processing method and micro-tool is one of the research priorities. In order to achieve high-quality milling of cemented carbide micro-lens array, the design and fabrication of the 0.5-mm diameter polycrystalline diamond (PCD) micro ball-end mill were studied. Based on the space vector, the mathematical model of the plane cutting edge of the PCD tool is established. According to the three processing characteristics of milling, grinding, and milling grinding, the double-edged conical surface micro ball-end mill, spherical micro ball-end mill, and single-edged hemispherical micro ball-end mill were designed respectively. Based on the line-face contact model of the grinding wheel and the movement principle of the CNC tool grinder, the grinding principles and methods of the rake face and the flank face are proposed. The high precision grinding of PCD micro ball-end mills are realized. The micro-groove milling experiment of cemented carbide was conducted; the milling performance of three PCD micro ball-end mills was studied. Considering the surface morphology and roughness of the micro-groove machining, a single-edged hemispherical PCD micro ball-end mill can avoid the phenomenon of chip blocking and depositing and can also fully exert the grinding characteristics of PCD materials to obtain relatively better processing quality.

Design and Analysis of Flow Field in Electrochemical Machining of Micro Grooves on Gear Tooth Surface

The gear with solid lubricating material embedded in micro grooves on gear tooth surface can better adapt to severe lubrication conditions. Electrochemical machining with the mask has shown good feasibility in machining micro grooves for filling solid self-lubricating materials on the tooth surface of gear. The electrolyte flow field is a vital contributor to the accuracy of electrochemical machining, therefore, it is important to design a suitable electrolyte flow mode. In this paper, based on the distribution characteristics of micro grooves on gear tooth surface, two kinds of shaped cathodes are designed, one with electrolyte flow slot and the other without. Each cathode can form two electrolyte flow modes respectively. The effects of four electrolyte flow modes on the stability of the machining gap flow field are analyzed by using computational fluid dynamics. The simulated results show that the cathode without electrolyte flow slot is beneficial to electrolyte flow during electrochemical machining with the mask, notably when the electrolyte flows into the machining gap from the face of the gear.

A theoretical and experimental investigation of cutting forces and spring back behaviour of Ti6Al4V alloy in ultraprecision machining of microgrooves

Studying the material deformation is one of important research foundations in the machining process. In present work, material deformation and spring back behaviour of Ti6Al4V alloy were investigated in ultraprecision machining of seven microgrooves with gradually increased depth of cut to 5 μm. Material constitutive models and geometrical relationships are developed to estimate the temperature evolution, cutting forces, internals force/stress distribution and the spring back variation. The results show that no phase transformation from α to β phase occurs during micro groove machining according to the estimated temperature and experimentally observed microstructures. The calculated cutting forces are in good agreement with the experimental results at various cutting speeds within an error of about 3.53%. Though the increased temperature with the cutting speeds gives rise to low thermal and athermal stresses, the equivalent stress required to overcome the plastic flow of the Ti6Al4V workpiece increases with the speeds due to the high dislocation drag stress. In addition, more than 45% of the thrust force is derived from the spring back force, so the thrust force is significantly affected by the spring back in the machining of Ti6Al4V alloys. The theoretical analysis and experimental results provide potential benefits in predicting the cutting forces and controlling the spring back during machining of Ti6Al4V alloys.

Investigation on the electrochemical machining of micro groove using masked porous cathode

Micro groove, as a typical surface texture, has played an important role in the development of many advanced fields. This paper introduced an electrochemical machining of micro groove using masked porous cathode. A porous metallic plate covered with a mask was prepared as the masked porous cathode. During machining, the masked porous cathode was covered on the workpiece, and the electrolyte could flow into the machining region through the porous structure in the cathode for machining. As the machining unit was closed, the distribution of electrical field was uniform on the machining surface, which could improve the machining accuracy. In addition, the masked porous mask had no damage during machining and could be reused, which improved the machining efficiency. With this method, multiphysics coupling model, including flow field model, electric current model, heat transfer model, reactant transport model, and moving mesh model, was built to investigate their influence on the machining process with different flow modes. The simulation and experiment results indicated that compared with other two flow modes, jet flow mode could provide a high electrolyte velocity in the machining region around the nozzle, and the mass transfer process was enhanced, which was helpful to improve the machining quality. The effect of pulse duty cycle was investigated, and the pulse duty cycle of 20% with the frequency of 2 kHz could further improve the mass transfer process and was preferred to generate micro groove with low standard deviation and roughness. In addition, with the applied voltage rising, the depth of micro groove increased, and increasing the nozzle reciprocating motion number could enhance the mass transfer process during machining, which further improved machining quality. Finally, with the optimized flow mode and machining parameters, a group of ten micro grooves were well generated by using a masked porous cathode with ten micro slits, and the width was about 330 μm with the depth of 45 μm.

Electrical discharge machining of micro grooves using laminated disc electrodes made of Cu and Sn foils

Tool electrode wear varying with different materials in electrical discharge machining (EDM) is unavoidable, thus inevitably reducing the machining quality and accuracy of microstructures. To convert this disadvantageous phenomenon into a beneficial process, the paper proposed a wear-variation EDM (WV-EDM) approach to fabricate a laminated disc electrode (LDE) with stable-shape micro channels on the outer edge surface; this electrode was subsequently used to machine micro grooves on workpieces by EDM. The WV-EDM formation of the LDE, the relationship between relative volume wear rate of the disc foils and the machining depth, and flow field distribution in the machining gap of the LDE during processing were investigated. The results show that the method proposed herein could reliably produce LDEs with stable micro channels on the outer edge surfaces that could subsequently be employed to continuously machine micro groove arrays with the same machining depth on the same material workpiece by EDM, and especially LDE reshaping was unnecessary. Additionally, the “pump effect” of the vortex, located in the flow field between micro channels on the LDE and workpiece, was beneficial for debris removal. Using the proposed method, micro groove arrays and columnar microstructures were successfully fabricated on Ti–6Al–4V alloy workpieces.

Improving the machining efficiency of electrochemical micromachining with oscillating workpiece

To enhance the machining efficiency of electrochemical micromachining (EMM), the low-frequency sinusoidal oscillating motion was applied to the workpiece, while the tool electrode moved in controlled trajectory. Mathematical model for the material removal rate (MRR) and the pressure in the interelectrode gap were derived. The mechanisms of enhancing the mass transport in the interelectrode gap induced by the oscillating workpiece during EMM have been analyzed, based on the variation of pressure in the interelectrode gap. An experimental setup has been developed for EMM. Experiments were conducted to investigate the influences of a vibrating amplitude and frequency on the machining efficiency, stability, and achievable maximum feeding rate of the tool electrode. The results indicated that a larger vibrating amplitude and a proper frequency were suitable for obtaining a higher material removal rate during EMM. The highest feeding rate of 0.3 μm/s has been obtained utilizing oscillating workpiece during the machining of microgrooves. Both the theoretical and the experimental results indicated that the oscillating workpiece during EMM was beneficial to improving the machining efficiency. Finally, microstructures with the circular profiles were processed using EMM, by a tool electrode feeding rate of 0.3 μm/s and the workpiece oscillation with the amplitude of 0.5 μm and frequency of 60 Hz.

Defect Analysis in Microgroove Machining of Nickel-Phosphide Plating by Small Cross-Angle Microgrooving

Crystalline nickel-phosphide (c-Ni-P) plating is a newly developed mold material for precision glass molding (PGM) to fabricate microgrooves. In the ultraprecision cutting process of the c-Ni-P plating material, the neighboring microgrooves are required to adjoin with each other to ensure acute microgroove ridges and miniaturize the microgroove size. Generally, defects of burrs and fracture pits can easily occur on the ridges when the plating layer is grooved. Burrs appear when tears dominate in material removal with a large adjacent amount. With the change of the adjacent amount, the removed material is sheared out from the workpiece, and when the cutting depth of the groove ridge is over the brittle-ductile transition thickness, fracture pits arise. To restrict these defects, a small cross-angle microgrooving method is proposed to test the critical adjacent amount range efficiently. It is found that an acute ridge of the microgroove is formed with a small enough adjacent amount; when this amount is in the range of 570 nm~720 nm in the microgroove machining process, fracture pits begin to arise on the gradient edge. High-quality microgrooves can be obtained based on this methodology.

Fabrication of microgrooves with varied cross-sections by electrochemical micromachining

Microgrooves are one of the important micro-features machined on various microproducts. The demand of complex microgrooves with varied cross section has increased in various fields, since specific cross-sectional shape of microgroove improves the product performance, due to increased inner surface area. Machining of simple microgroove is relatively easy, but when the cross section of the microgroove is varying along its depth, it becomes difficult from microtool fabrication point, as well as from the process point of view. The purpose of this study is to verify the possibilities of machining varied cross-sectional microgrooves on metallic surfaces by electrochemical micro-machining (EMM). Different cross sections of the microgrooves have been machined by regulating the important EMM process parameters such as applied voltage, duty ratio, and machining time, along the depth during machining of microgrooves, utilizing developed experimental setup. This technique enables the machining of various cross sections of the microgrooves by EMM utilizing the single-disk shape microtool. Finally, machining of different cross-sectional microgrooves like reverse tapered, barrel shaped, double stepped, spherical based microgrooves, and microgroove with internal pocket has been demonstrated successfully. The experimental findings may be useful for machining of complex microgrooves suitable for micro-coolers, micro-reactors, and micro-mixers etc. which needs specific geometry for product functioning.

Machining guidelines for fabricating microgrooves of varied cross-sections by electrochemical micromachining

Simple microgrooves can be fabricated easily, whereas fabrication of varied cross-sectional microgrooves on metallic surfaces is still a challenging task by present traditional as well as non-traditional methods. An application of electrochemical micromachining (ECμM) for machining various cross-sectional microgrooves on SS has been proposed in this paper. Influences of process parameters on width overcut have been investigated, and experimental findings have been applied to devise guidelines to fabricate various cross-sectional microgrooves. Disc microtool with longitudinal vibration has been utilised in layered machining of microgrooves. Duty ratio has been varied from 30% to 60% along depth of microgroove with other identical process parameters. The guidelines for straight, reverse tapered, barrel-shaped, double stepped, spherical based, and microgroove with internal pocket have been developed, and fabrications of these microgrooves have been demonstrated successfully. The experimental findings may be useful for planning and machining various cross-sections of microgrooves for different applications.

Machining guidelines for fabricating microgrooves of varied cross-sections by electrochemical micromachining

Simple microgrooves can be fabricated easily, whereas fabrication of varied cross-sectional microgrooves on metallic surfaces is still a challenging task by present traditional as well as non-traditional methods. An application of electrochemical micromachining (ECμM) for machining various cross-sectional microgrooves on SS has been proposed in this paper. Influences of process parameters on width overcut have been investigated, and experimental findings have been applied to devise guidelines to fabricate various cross-sectional microgrooves. Disc microtool with longitudinal vibration has been utilised in layered machining of microgrooves. Duty ratio has been varied from 30% to 60% along depth of microgroove with other identical process parameters. The guidelines for straight, reverse tapered, barrel-shaped, double stepped, spherical based, and microgroove with internal pocket have been developed, and fabrications of these microgrooves have been demonstrated successfully. The experimental findings may be useful for planning and machining various cross-sections of microgrooves for different applications.

Microgroove machining on crystalline nickel phosphide plating by single-point diamond cutting

Electroless nickel phosphide (Ni–P) plating is used as a new mold material to fabricate microgrooves on glass molding process because of its excellent mechanical properties and machinability. Amorphous Ni–P will be crystallized at high temperature during the glass molding process. Crystalline Ni–P plating leads to mold deformation, which may reduce the mold accuracy and shorten the service life. In this study, the amorphous plating is heated to its annealing temperature at nearly 600 °C to make it transform to crystalline state in advance. Thus, the hardness of the plating increased from 614 to 941 HV; the deformation of the mold with crystalline plating similar to glass molding condition is removed by ultraprecision turning. Finally, microgrooves are fabricated on crystalline Ni–P plating. In the experiments, matrices with amorphous plating and crystalline plating are used in microgroove machining on an ultraprecision machine. Subsequently, machined form accuracy and surface quality for the two plating layers are compared. Under the condition of different cutting speeds, the surface roughness of the crystalline Ni–P plating distributed in the interval of about 60 nm; the amorphous Ni–P plating distributed in the interval of about 80 nm correspondingly. The results proved that the microgrooves machined on the crystalline plating exhibited better performance than its amorphous counterpart.

COMBINED EFFECT OF MECHANICAL GROOVING AND STAIN-ETCHED SURFACE ON OPTICAL AND ELECTRICAL PROPERTIES OF CRYSTALLINE SILICON SUBSTRATES

This paper investigates the combined effect of mechanical grooving and porous silicon (PS) on the front surface reflectance and the electronic properties of crystalline silicon substrates. Mechanical surface texturization leads to reduce the cell reflectance, enhance the light trapping and augment the carrier collection probability. PS was introduced as an efficient antireflective coating (ARC) onto the front surface of crystalline silicon solar cell. Micro-periodic V-shaped grooves were made by means of a micro-groove machining process prior to junction formation. Subsequently, wafers were subjected to an isotropic potassium hydroxide ( KOH ) etching so that the V-shape would be turned to a U-shape. We found that the successive treatment of silicon surfaces with stain-etching, grooving then alkaline etching enhances the absorption of the textured surface, and decreases the reflectance from 35% to 7% in the 300–1200 nm wavelength range. We obtained a significant increase in the overall light path that generates the building up of the light trapping inside the substrate. We found an improvement in the illuminated I–V characteristics and an increase in the minority carrier lifetime τeff. Such a simple method was adopted to effectively reinforce the overall device performance of crystalline silicon-based solar cells.

Ultrafast Laser Machining of Micro Grooves on Stainless Steel with Spatially Optimized Intensity Distribution

Femtosecond laser processing enables the machining of micro-grooves by translating the focused femtosecond beam on the sample surface. Most of the time, the spatial intensity distribution on the sample is nearly Gaussian with a circular symmetry. The micro-grooves machined this way show ‘classic’ cross sectional profile with a ‘v’ shape. We present here a technique to modulate the cross sectional profile of the micro-grooves in a single laser scan. The technique relies on advanced spatial beam shaping where the intensity distribution is designed to spatially modulate the pulse overlapping during the scanning process. The corresponding exposure gradient enables to control the cross sectional profile of the micro groove. We present machining results on stainless steel using ultrashort pulses (120fs, 800nm at a repetition rate of 5kHz) where calculations based on the ablation rate clearly match the cross sectional profile of the machined micro grooves.

Abrasive water jet machining of glass with stagnation effect

Abrasive water jet processes of glass are presented for crack-free machining of micro grooves and fluid polishing of micro channels with CFD analysis. In machining of the micro grooves, the abrasive is supplied to flow through intended machining area using the tapered masks. Stagnation under the jet and the horizontal flow on the machining area are controlled to generate crack-free surfaces by the mask shape. The same effect can be applied to polishing of the micro channels pre-machined by milling. Stagnation controlled by the inner wall of the channel changes the flow direction while keeping high fluid velocities.

2-3 ガラスのエンドミル切削とその応用(OS2-2 三次元の微細形状創成技術)

Micro machining of glass is required for manufacturing of glass devices such as micro TASs. However, some issues have been left on the flexibility, the machining costs and the environmental impact. The paper discusses glass milling for machining of micro glass devices. The milling process is applied to machining of micro grooves with the inclined ball end mill. The micro grooves are machined in depth of more than 10μm in a cutter feed. The surface finish and the tool wear can be improved by inclination of the milling tool. Some applications are shown to verify the glass milling in manufacturing of micro devices.