Machined Grooves Research Articles

A New Approach in Surface Modification and Surface Hardening of Aluminum Alloys Using Friction Stir Process: Cu-Reinforced AA5083.

In the current study, a new approach for surface modification and surface hardening of aluminum alloys is developed. The method is based on the logic of in-situ reinforcing FSP strategies. The novelty of the proposed process is the application of a bulk reinforcing metallic material instead of metallic powders. The FSP was carried out on aluminum alloy AA5083—thick plates. A thin sheet of pure copper (cross-section 4 × 0.8 mm2) was placed in a machined groove on the upper surface of the aluminum plate, and both materials were FSPed together. Samples with one, two and three FSP passes were manufactured respectively. Results indicate that the copper thin sheet was successfully integrated in the AA5083 stir zone. By increasing the FSP passes, almost all copper was integrated in the stir zone, mainly in the form of coper-based micron-sized intermetallic particles, and secondly, by copper diffusion in the AA5083 matrix. Due to the presence of complex intermetallic compounds created by the high heat input and intense plastic deformation, the hardness inside the stir-zone was found highly increased from 77 to 138 HV.

Investigation on the material removal behavior of single crystal diamond by infrared nanosecond pulsed laser ablation

In this paper, the material removal behavior of the single crystal diamond (SCD) in the multi-passes infrared nanosecond pulse laser ablation is investigated, focusing on the formation mechanism of the surface cracks, the periodic ripples, the graphitization and the shape evolution of the groove. The simulation of the temperature field in the SCD pulse laser ablation process is firstly performed to show the possibly achieved peak temperature which is closely related to the material removal mechanism, and the experimental results indicate that the diamond materials are mainly removed by gasification, oxidation, delamination and fragmentation. The typical surface characteristic of the ablated SCD is dependent on the pulse duration, where graphitization, cracking and chipping appeared as the main form at the pulse duration of 8 ns, 50 ns, and 120 ns, respectively. In addition, the periodic ripples of 500–1100 nm on the side walls of the machined groove were induced when the laser energy density is lower than 40 J/cm2. The obtained critical values of the laser fluence is of great significance for the optimization of the laser parameters in the surface microstructuring of SCD. On the whole, five characterized areas in the multi-passes infrared nanosecond pulse laser ablation surface are identified in the machined grooves, including the bottom smooth area, the side wall ripples area, the side wall non-ripples area, the edge transition area and the deposited metamorphic area due to the condensation of deposited carbon atoms and clusters, the formation mechanism of which, mainly including the thermal stress and the interaction between the laser pulse and the material, are discussed.

An approach to calculate grinding wheel path for complex end mill groove grinding based on an optimization algorithm

Applying complex groove with variable helical angle, rake angle, core radius or groove width along tool axis is an essential way to improve the cutting performance of solid end mills. However, the usage of complex groove is limited due to the lack of an effective way to calculate wheel path for its machining, because the previous envelope theory or trial-and-error method that used for simple constant groove can no longer be used for complex groove. In this paper, a general model is established to calculate the wheel path for complex groove machining based on a mathematical optimization model, which have three constraints and one objective. First, the complex groove is defined by four curves, namely the edge curve, rake curve, core curve and flank curve, so that the variable helical angle, rake angle, core radius and groove width can be expressed by mathematical formulas. Second, the grinding wheel path is expressed as a series of its position vectors, including three location parameters and three posture parameters. Then, these vectors are calculated by searching the minimum machining error of groove width with three constraints: contact constraint to meet the rake and core radius requirements, groove width constraint to prevent the overcut with the adjacent edge and non-interfere constraint to prohibit the interfere with the current edge. Finally, the accuracy and efficiency of the model are validated by five experiments with different designed complex grooves.

Experimental and Numerical Investigations of Reducing Stray Corrosion and Improving Surface Smooth in Macro Electrolyte Jet Machining Titanium Alloys

Recently, macro electrolyte jet machining has attracted considerable research attention because it is flexible and suitable for processing aerospace parts with complex profiles. However, in this process stray corrosion occurs easily at the edges of the grooves, affecting the machining localization. In the machining of titanium alloys, serious stray corrosion on the surface outside of the machining area occurs because titanium alloys are particularly sensitive to changes in the flow field and the electric field. Here, a method is proposed to reduce stray corrosion on the workpiece surface outside of the machining area during machining of titanium alloy. This method is shown to reduce the negative influence of the reflected electrolyte on the non-machined area near the machined groove edge and to improve the machining localization by restricting the jet direction and flow range of the reflected electrolyte. Based on an investigation of the slope of the tool end face and the distribution of the electrolyte gas–liquid phase, the end face of the tool was designed to slope downward. This reduced the electrolyte flow resistance and improved the electric intensity, which helped produce a smoother surface. Experiments show that the macro sinking and milling method not only removed electrolyte from the lateral edge of the groove, reducing stray corrosion and improving machining localization, but also rapidly removed electrolytic products in the machining area, improving surface quality. Brilliant silvery grooves were obtained using a tool with an appropriate downward slope angle along with the sinking and milling method.

A Qualitative Study of the Influence of Grooved Mold Surface Topography on the Formation of Surface Marks on As-Cast Ingots of Aluminum Alloy 3003

The effects of the wavelength and orientation of machined grooves on a mold surface, casting speed, and melt superheat on the formation of surface marks on as-cast ingots were studied with an immersion casting tester and copper mold chill blocks. The mold surface topographies included a polished smooth surface, and those with machined unidirectional parallel contoured grooves oriented either parallel (vertical) or perpendicular (horizontal) to the casting direction. The unidirectional grooves were 0.232 mm deep with wavelength or spacing between 1 and 15 mm. The casting speed and melt superheat were between 1 and 200 mm/s, and 10 and 50 K, respectively. Two primary types of surface marks were observed on ingots cast with the copper mold with smooth surface topography, namely the finer and closely spaced ripples (Type I), and the widely spaced but coarser laps (Type II). The latter were more prevalent at the higher casting speeds and melt superheats. Qualitatively, formation of both types of surface marks on the as-cast ingots of the aluminum alloy 3003 appeared to be alleviated by increase in casting speed and melt superheat, and by the use of molds with grooved surface topography. In fact, casting with a mold surface with 1 mm spaced grooves that are perpendicular to the casting direction eliminated the formation of surface marks at casting speeds greater than 1 mm/s. It also improved the uniformity of the ingot subsurface microstructure and eliminated the associated subsurface segregation.

Investigating the optimum parametric setting for MRR of expandable polystyrene machined with 3D printed end mill tool

In the present work, a statistical study has been conducted to find out the best parametric setting of end milling of an expandable polystyrene (EPS) material by using a three-dimensional printed tool. Input process parameters; including feed rate, cutting speed, and depth of cut have been investigated to understand their effects on the material removal rate (MRR) of EPS. The micrographic analysis of the machined grooves has also been carried out to understand the mechanism. It has been found that only feed rate has imparted statistically significant effect on the MRR, however, cutting speed and depth of cut are found to be statistically insignificant. Further, the percentage contribution of feed rate, cutting speed, and depth of cut is 91.57, 1.23, and 3.44%, respectively.

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.

Machining Grooves in Silica Glass by Using Picosecond Lasers

A picosecond laser with 1064nm wavelength was used to machine grooves in fused silica in this paper. A surface texturing method was applied to increase the laser absorption. The relationship between the width, the depth of the groove and the laser parameters such as laser power, scanning speed, number of scanning cycles was studied. The machining quality of the groove was detected by the laser scanning confocal microscopy. It showed that there were no micro-cracks on the grooving surface, and the surface roughness Ra<1.6um. The width, the depth and the shape of the groove could be controlled accurately by changing the laser parameters. And, a “V-shape” groove with 1mm width, 1mm depth was obtained with the as the frequency, the laser power, the scanning velocity and the number scanning cycle was fixed at 400KHz, 141W, 5000mm/s and 12, respectivity.

Characterization of the material-induced elastic–plastic deformations in ultra-precision diamond cutting

Ultra-precision cutting (UPC) technology can directly achieve freeform surfaces with form accuracy in sub-micrometer and surface finishing in nanometer, and the achieved surface quality affects the functionalities of the components. Different from the conventional machining process, the effects of workpiece material properties on surface generation in UPC are ignorable. The influences of plastic side flow and elastic recovery are very important for the surface quality in UPC, while few studies were found to evaluate the extent of the two phenomena. This paper makes theoretical and experimental studies on the factors affecting the side flow and recovery and proposed a method to characterize the extent of plastic side flow and recovery by studying the deviation of the groove radius in single ruling. Experiments are conducted to machine grooves with different cutting parameters on different workpiece materials. The experiment results agree well with the theoretical analyses and show that under the combined effect of side flow and recovery, the generated groove radius may be larger or smaller than the theoretical one. Moreover, the proposed method makes effective evaluation on extend of swelling and recovery in UPC.

Repairing surface defects of metal parts by groove machining and wire + arc based filling

An approach to repairing surface defects of metal parts is proposed, which includes a combined application of (i) groove machining, (ii) wire and arc additive manufacturing (WAAM), and (iii) finishing machining. The completed analysis revealed that (i) the inclination angle of the groove to be machined is strongly influenced by the manufacturing parameters of the WAAM process, and (ii) the WAAM process models designed for fabricating parts on a flat substrate are not appropriate for filling grooves. To overcome these issues, this research investigated the range of variation of the proper inclination angle of the groove. A mathematical model was developed to determine the manufacturing parameters of WAAM that result in a proper filling of the groove. The effectiveness of the proposed fundamentals was investigated in a case study. The experimental results showed that using the proposed approach and the chosen manufacturing parameters resulted in a complete filling of the machined groove. The fabrication error of the main part of the repaired region before the finishing machining was less than 0.3 mm, while the ‘buy-to-fly’ ratio of the deposited material was 92.1%. The proposed approach for morphological repair lends itself to a computer-aided automatic part repair process.

High-speed micro electrical discharge machining with fine surface quality in atmospheric pressure nitrogen plasma jet

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.

Investigations in nanosecond laser micromachining on the Zr52.8Cu17.6Ni14.8Al9.9Ti4.9 bulk metallic glass: experimental and theoretical study

In addition to their attractive mechanical properties, the lack of grain boundaries and crystal defects of Bulk Metallic Glasses (BMGs) make them suitable materials for integration in micro-systems fabrication chains, either as final components or mould inserts. The application of short or ultra-short pulsed lasers has recently been demonstrated for the processing of BMGs in this context, particularly as a possible solution for machining micro-scale features on the surface of BMG workpieces. Therefore, complementary studies that consider both experimental and thermal simulation data at the same time in the context of multiple and moving pulses irradiating a BMG specimen are desirable to gain insight into micromachining phenomena. Although such models have been reported in the context of single pulse processing of BMG substrates, their extension to multiple pulse scenarios for micromachining is lacking. Thus, the overall objective of this paper is to combine both theoretical and experimental laser micromachining investigations using multiple pulses when irradiating a BMG workpiece. The specific focus is on conducting such laser operations in the nanosecond regime on a Zr-based BMG, with composition Zr52.5Cu17.9Ni14.6Al10Ti5, also known as Vitreloy 105. This combined experimental and theoretical approach enabled the identification of a suitable set of laser parameters with respect to the process efficiency over a range of pulse duration, fluence values, scanning speed and track distance between machined grooves. In addition, it was highlighted that laser micro-machining operations can lead to BMG materials experiencing thermal cycles, which are quite different from that taking place during the conventional synthesis of glassy alloys, thus complicating the further characterisation and understanding of crystallisation phenomena at play.

Process Control in Jet Electrochemical Machining of Stainless Steel through Inline Metrology of Current Density.

Jet electrochemical machining (Jet-ECM) is a flexible method for machining complex microstructures in high-strength and hard-to-machine materials. Contrary to mechanical machining, in Jet-ECM there is no mechanical contact between tool and workpiece. This enables Jet-ECM, like other electrochemical machining processes, to realize surface layers free of mechanical residual stresses, cracks, and thermal distortions. Besides, it causes no burrs and offers long tool life. This paper presents selected features of Jet-ECM, with special focus on the analysis of the current density during the machining of single grooves in stainless steel EN 1.4301. Especially, the development of the current density resulting from machining grooves intersecting previous machining steps was monitored in order to derive systematic influences. The resulting removal geometry is analyzed by measuring the depth and the roughness of the machined grooves. The correlation between the measured product features and the monitored current density is investigated. This correlation shows that grooves with the desired depth and surface roughness can be machined by controlling current density through the adjustment of process parameters. On the other hand, current density is sensitive to the changes of working gap. As a consequence of the changes of workpiece form and size for the grooves intersecting premachined grooves as well as the grooves with a lateral gap, working gap, and current density change. By analyzing monitoring data and removal geometry results, the suitability of current density inline monitoring to enable process control is shown, especially with regards to manufacture products that should comply with tight predefined specifications.

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.

Research on machining Ti6Al4V by high-speed electric arc milling with breaking arcs via mechanical-hydrodynamic coupling forces

A sustainable and advanced manufacturing method named high-speed electric arc milling (H-SEAM) was presented in this research to solve the problems where of environmental pollution and low machining efficiency for difficult-to-cut materials in the traditional electrical discharge machining (EDM)EDM process. This method can achieve high material removal efficiency with arc breaking via a coupling of mechanical and hydrodynamic forces in H-SEAM. Firstly, the material removal mechanisms of H-SEAM and theoretical arc breaking conditions are analysed. Then, comparative experiments on machining titanium alloy Ti6Al4V by different arc breaking methods are conducted to study the material removal rate (MRR), tool electrode wear rate, and machined surface quality of the workpiece. Our experiment results showed that the MRR can reach 780 mm3/min when using a mechanical-hydrodynamic coupling method to break arcs, which is almost five times and nearly twice that when using independent mechanical or hydrodynamic methods to break arcs. Moreover, experimental results showed the machined grooves via mechanical-hydrodynamic coupling forces to break arcs in H-SEAM exhibited higher dimensional accuracy, lower tool electrode wear, lower surface roughness, thinner recast layers, and smaller heat-affected areas than those in arc breaking by independent mechanical or hydrodynamic methods. This can be attributed to the higher removal efficiency of molten metal material and the uniform distribution of energy when using mechanical-hydrodynamic coupling forces to break arcs.

Cutting Characteristics of Direct Milling of Cemented Tungsten Carbides Using Diamond-Coated Carbide End Mills with Untreated and Treated Cutting Edge

This study investigates the cutting characteristics of direct milling of cemented tungsten carbides performed using a diamond-coated carbide end mill. The diamond-coated carbide end mills have cutting edges that are both treated and untreated, and the sharp cutting edge can be developed at the ridgeline of the diamond coating on the flank face via treatment of the cutting edge. Two types of cemented tungsten carbide were used as workpiece materials, i.e., TAS VM-40 and VC-70. The influence of the cutting length on the cutting characteristics was also studied. In the case of cutting of the VM-40, the cutting force of the treated tool was significantly lower than that of the untreated tool. The cutting forces of both tools were observed to be similar after the diamond coating on the rake face of the untreated tool was flaked. The cutting edge at the ridgeline of the diamond coating on the flank face of both tools was retreated during the cutting progress, and the thickness of the diamond coating of the untreated tool was also decreased. The finished surface integrity was drastically altered owing to the flaking of the diamond coating on the rake face of the untreated tool and the irregularity of the cutting edge of both tools. The accuracy of the machined shape obtained by using the treated tool was better than that obtained using the untreated tool, and the tendency was significantly observed as the cutting progressed. In the case of cutting of VC-70, flaking of the diamond coating of untreated tool did not occur, and the cutting force of the treated tool was significantly lower than that of the untreated one. The cutting edge of the treated tool was maintained sharp up to a groove length of 500 mm, although the workpiece material was clearly observed to be adhering to the round corner of the cutting edge of the untreated tool. Moreover, the accuracy of the shape of the machined groove obtained using the treated tool was better than that obtained using the untreated tool.

P.1.12 Intellectual disability-related genes increase ADHD risk and locomotor activity in Drosophila melanogaster

Searching for and adjusting to the appropriate wheel positions for designed grooves are among the key issues in the manufacturing of the end mill, drill and other integral cutting tools. Along with the increasing requirements of product categories and quality, a large number of non-traditional and customized grooves continuously appear. However, as multivariable, nonlinear and multiple target problems, it is difficult to obtain the desired wheel position. Therefore, we introduce an intelligent method to search for the optimum wheel position for the designed groove with the known wheel geometry. According to practice, the basic parameters of the groove and wheel geometries are introduced, and the problems studied in this paper are explained. As a foundation, a robust algorithm is built to predict machined grooves with a series of equal distribution points and three parameters: the rake angle, core radius and groove width. The influence that the wheel positions have on groove geometries is then analyzed. Then, an objective function considering different machining requirements is built, and the optimum wheel positions are searched for while the function is solved. Furthermore, an enhanced niche particle swarm optimization (NPSO) algorithm is developed to solve the problem. Finally, 6 experiments are carried out to verify and analyze the algorithm. The results show that the algorithm can effectively find the desired wheel positions according to different machining precision requirements.

Research on the Relationship between Cutting Force and Machined Surface Quality in Micro Ball End-Milling of Potassium Dihydrogen Phosphate Crystal.

Potassium dihydrogen phosphate (KDP or KH2PO4) crystal is widely used as terminal frequency converters in inertial confinement fusion (ICF). However, KDP crystal is a typical difficult-to-cut optical crystal with the characteristic of soft-brittle. In this work, the relationship between cutting force and processed surface quality in micro ball end-milling of KDP crystal with various depth of cut and spindle speed is studied by carried out the micro-milling experiments. Fast Fourier Transform (FFT) algorithm is used to diagnose the recorded cutting force. The periodic change of cutting force and the cutting force after filtering noises can be got through FFT analysis. Through calculating the correlation coefficients between the static component of thrust force and roughness value Ra of machined grooves, as well as the peak-valley (P-V) value of thrust force and dimensional error of machined grooves, the roughness value Ra and dimensional error of machined grooves would be predicted by monitoring the static component and P-V value of the thrust force, respectively. The relatively large spindle speed helps to reduce the roughness value Ra. The spindle speed with moderate value is recommended to reduce the dimensional error of machined groove because the dimensional error of machined groove will increase when the spindle speed is small enough (causing brittle cutting) or large enough (reducing cutting stability).

Optimizing Surface Micro Grooving to Reduce the Checking and Cupping of Douglas Fir, Western Hemlock and White Spruce Decking Exposed to Natural Weathering

Machining grooves into the surface of pine and fir (Abies spp.) deckboards reduces undesirable checking that develops when “profiled” boards are exposed to the weather. We aim to develop improved profiles for Douglas fir, western hemlock and white spruce decking to reduce their susceptibility to checking, and understand how profile geometry influences the stresses that cause checking. We varied the width and depth of grooves in profiled deckboards, exposed deckboards to the weather, and measured checking and cupping of boards. A numerical model examined the effect of groove depth on the moisture-induced stresses in profiled spruce boards. Profiling significantly reduced checking, but increased cupping of deckboards made from all three species. Western hemlock checked more than the other two species. Profiles with narrow grooves (rib profiles) were better at restricting checking than profiles with wider grooves. A rib profile with deeper grooves developed smaller stresses than a rib profile with shallower grooves, and boards with the former profile checked less than boards with shallower grooves. We conclude that checking of profiled Douglas fir, western hemlock and white spruce decking is significantly reduced by changing profile geometry, and our results suggest the best profiles to reduce checking of all three species.

Fabrication of Periodic Nanostructures Using AFM Tip-Based Nanomachining: Combining Groove and Material Pile-Up Topographies

Abstract This paper presents an atomic force microscopy (AFM) tip-based nanomachining method to fabricate periodic nanostructures. This method relies on combining the topography generated by machined grooves with the topography resulting from accumulated pile-up material on the side of these grooves. It is shown that controlling the distance between adjacent and parallel grooves is the key factor in ensuring the quality of the resulting nanostructures. The presented experimental data show that periodic patterns with good quality can be achieved when the feed value between adjacent scratching paths is equal to the width between the two peaks of material pile-up on the sides of a single groove. The quality of the periodicity of the obtained nanostructures is evaluated by applying one- and two-dimensional fast Fourier transform (FFT) algorithms. The ratio of the area of the peak part to the total area in the normalized amplitude–frequency characteristic diagram of the cross-section of the measured AFM image is employed to quantitatively analyze the periodic nanostructures. Finally, the optical effect induced by the use of machined periodic nanostructures for surface colorization is investigated for potential applications in the fields of anti-counterfeiting and metal sensing.