Workpiece Rotational Speed Research Articles

Study on Material Removal Model by Reciprocating Magnetorheological Polishing.

In this study, a new reciprocating magnetorheological polishing (RMRP) method for a flat workpiece was proposed. Based on the RMRP principle and Preston equation, the material removal rate (MRR) model of the RMRP as well as its normal polishing pressure model was established. On this basis, the effects of different technological parameters including workpiece rotation speed, eccentric wheel rotation speed and eccentricity on the MRR of the workpiece were investigated. The K9 optical flat glass was polished with the RMRP setup to verify the MRR model. The experimental results showed that the effect of workpiece rotation speed on the MRR was much greater than that of eccentric wheel rotation speed and eccentricity, and the MRR increased from 0.0115 ± 0.0012 to 0.0443 ± 0.0015 μm/min as workpiece rotation speed rose. The optimum surface roughness reduced to Ra 50.8 ± 1.2 from initial Ra 330.3 ± 1.6 nm when the technical parameters of the workpiece rotation speed of 300 rpm, the eccentric wheel rotation speed of 20 rpm and the eccentricity of 0.02 m were applied. The average relative errors between the theoretical and experimental values were 16.77%, 10.59% and 7.38%, respectively, according to the effects of workpiece rotation speed, eccentric wheel rotation speed and eccentricity on MRR.

Empirical study on ultrasonic assisted turn-milling

Turn-milling process has been paid attention in order to be used in multi-task machining processes. Moreover, looking for new machining techniques aimed at reducing cutting force is of important. Reducing cutting force in machining processes has the benefits of extending tool life and improving surface quality. One of the new concepts for reducing the cutting force is applying ultrasonic vibration. In this paper, effects of ultrasonic vibration under different machining parameters in turn-milling process of Al-7075 alloy will be investigated. In this order, a special mechanism was designed to apply ultrasonic vibration during machining process. Ultrasonic vibration exertion on the tool reduced cutting force and surface roughness up to 75% and 35%, respectively. Also tool rotational speed increment induced cutting force and surface roughness increment. In addition, tool feed rate and workpiece rotational speed increment caused cutting force and surface roughness increment. Although, feed rate was more influential.

Experimental investigation of electro-chemical magnetic abrasive finishing of SS 304 workpiece

Industry demands Nano level of surface finishing and development of advanced material makes finishing difficult to attain for modern grinding industry. The Electro-Chemical Magnetic Abrasive Finishing (ECMAF) is an advanced abrasion based finishing process used to finish very hard material with superior surface finishing. In ECMAF, soft film generated by electro-chemical dissolution (ECD) on the workpiece is removed by gentle finishing force of micron size abrasive particles of Magnetic abrasive Finishing (MAF). In this process, the material is removed in the form of microchips without sub surface damage. This paper presents the experimental investigation of SS 304 workpiece using indigenously newly developed ECMAF set up that eliminates the problem of washing of abrasive particles by electrolyte from the working gap. The Un-bonded Magnetic Abrasive Particles (UMAPs) are prepared by mechanical mixture of ferromagnetic particles and abrasive particles. The experiment is designed using L25 orthogonal array of Taguchi Methodology and effect of working gap, workpiece rotational speed, electrolytic flow rate and electrolytic current on the Surface Roughness (SR) and Material Removal (MR) is studied. The result is analyzed using ANOVA and found the working gap to be the most significant process parameter followed by workpiece rotational speed and electrolytic current for SR while the working gap is found to be most the significant process parameter for MR.

Mathematical modeling and process parameters optimization of ultrasonic assisted electrochemical magnetic abrasive machining

A new machining technique called ultrasonic assisted electrochemical magnetic abrasive machining integrates ultrasonic vibrations, electrochemical machining and magnetic abrasive finishing is used to machine and finish biomaterials more efficiently as compared to single process. This investigation highlights a novel technique for machining of hard materials in order to improve machining efficiency with hybrid process. Experimental design of Taguchi L27 and TOPSIS methods are implemented to find the optimum parameters of process. The objective is to maximize MRR and PISF and minimize PCMH simultaneously. This research investigates the interaction between input parameters (rotational speed of work piece, machining time, working gap, ultrasonic frequency time and voltage) and their effect on output characteristics of process like MRR, PCMH and PISF. The recommended settings of parameters for UEMAM process is found to be rotational speed = 600 rpm, machining time = 5 minutes, working gap = 3 mm, frequency time = 4 sec and voltage = 3 V from TOPSIS and rotational speed = 600 rpm, machining time = 15 minutes, working gap = 3 mm, frequency time = 6 sec and voltage = 4.5 V from Taguchi optimization plot. A comparison of experimental results and theoretical results have been done to validate the proposed mathematical model. The calculation results of the model showed that the maximum value of error is not more than 7.351 while comparing with experimental results, which suggests that the mathematical model is reasonable.

Influence of some process input factors on the main dimensions of the grooves generated during the ball vibroburnishing

The ball vibroburnishing is a processing method based on the plastic deformation of the workpiece surface layer, as a result of a vibration movement achieved by the ball pressed with a known force on the workpiece surface. The surface obtained by ball vibroburnishing includes grooves with different directions and partially overlapped. To know better the influence exerted by the ball vibroburnishing conditions on the main dimensional characteristics of the grooves, an experimental research was designed and materialized. As the process input factors, the diameter of the ball, the force, and the workpiece rotation speed were used. The depth and width of the groves generated by the moving balls on the workpiece surface layer were measured. By mathematical processing of the experimental results, empirical mathematical models were determined. These models highlight the intensity of the influence exerted by the ball vibroburnishing process input factors on the main dimensions of the grooves.

Laser turning of alumina (Al2O3) ceramic by Nd:YAG laser technique

The present work focuses on the laser turning of Alumina (Al 2 O 3 ) ceramic materials and to analyze the effect of various machining input parameters. The design of experimental trials based on the Taguchi technique and the experimental process input values are considered such as pulse frequency, workpiece rotational speed, laser beam average power, and constant feed rate. The optimum process parametric settings are identified for the output parameters of surface roughness (R a ) and Material removal rate (MRR). The output responses are analyzed based on the signal-to-noise ratio. Based on the experimental study, the better surface roughness (R a ) is achieved as 2.37 µm for the input response combination of A 1 B 1 C 1 . Similarly, the Material removal rate is achieved as 0.79 mm 3 /min for the combination of A 1 B 1 C 3 .

Comprehensive study on effect of orthogonal turn-milling parameters on surface integrity of Inconel 718 considering production rate as constrain

Round bars made of Inconel 718 are widely used in aerospace industries due to their excellent properties of working at harsh environment. However, machinability of this alloy by conventional turning process results in excessive tool wear and poor surface integrity. The former increases the production cost and latter reduces the fatigue life. In the present paper, interrupted cutting of Inconel 718 round bars was introduced as an effective way for enhancing the life time. Turn-milling as newly emerging cutting technology was utilized here to machine cylindrical samples of Inconel 718. Effect of process factors such as tool rotational speed, workpiece rotational speed, feed rate and eccentricity was analyzed on surface roughness and residual stress. The obtained results showed that the feed rate is most influential parameter that determines value of surface roughness and residual stress and. Furthermore, by considering production rate as a constraint, it was logically discussed that a setting of 1000 rpm cutter speed, 300 rpm work rotational speed, 0.12 mm/rev feed rate and 0.2 mm eccentricity can guarantee maximum production rate as well minimum surface roughness and tensile residual stress.

Precision electrochemical machining of tungsten micro-rods using wire electrochemical turning method

The novel wire electrochemical turning (WECT) method has been proposed to machine tungsten with neutral electrolyte and bipolar pulse current in the authors’ previous research. The influence of tool wear caused by the bipolar pulse current, which is needed to remove the oxide layer generated on tungsten surface when using a neutral electrolyte, was eliminated by the WECT method because the wire tool electrode was kept being wound during the machining process. In this paper, the influences of the most important process parameters, such as the kind of electrolyte, wire material, wire diameter, rotation speed of the workpiece rod, and frequency of the pulse voltage, were studied to understand the fundamental aspects of the WECT method and improve the machining efficiency of tungsten micro-rods. The experimental results showed that the NaCl electrolyte and the NaNO3 electrolyte had higher machining efficiency and better machining accuracy, respectively. The machining accuracy was improved with the SUS304 stainless steel wire used as tool electrode than the brass wire tool electrode. It was also found that the machining efficiency and accuracy were improved with decreasing the wire diameter and increasing the rotation speed of workpiece because the influence of stray current flowing through the side and end surface of machined micro-rod was reduced. The machinable length of micro-rod peaked at an optimum feed speed of the workpiece, and the optimum speed increased with increasing the frequency of pulse voltage. As a result, a minimum rod diameter of 11 μm was fabricated with a high aspect ratio of 36. Compared with the previous method using a platinum film as tool electrode, the aspect ratio was increased significantly because the influence of tool wear was eliminated.

Investigation on turning operation using die sinking EDM process

Electrical discharge turning (EDT) operation produces a cylindrical component using an electrical discharge machining method. Unlike a traditional turning process, it is a non-contact operation between the tool electrode and workpiece. Therefore, the design of electrode may influence the quality of turned workpiece. The present study investigates the effect of various processing parameters in EDT namely the electrode shape, workpiece rotational speed and jump down time. The analysis was conducted in terms of the surface roughness, circularity deviation and electrode wear rate. A special jig and fixture for the turning operation was developed as to fit on the commercial die sinking EDM machine. A fractional factorial approach using Taguchi orthogonal array of L9 was utilized in the present study. It was found that both shape of electrode and workpiece rotational speed had a greater influence on the surface roughness followed by the electrode jump down time. The surface roughness increases with an increase of quantity and duration of sparks during the process due to formation of a higher amount of debris. The circularity deviation has improved with a higher sparking area and faster duration of sparks since a smaller amount of workpiece material was removed thus improving its circularity. Furthermore, the highest electrode wear rate was produced using the electrode with a curvature shape which generated wider sparking area thus experiencing more erosion.

Revisiting the tangential oscillations of the tool to form the microrelief of the workpiece surface

The article is focused on the possibilities of using the tangential oscillations of the tool to form a microrelief of the workpiece surface. The diagram of the cutting tool oscillation trajectory during vibrational turning is presented. The scheme for calculation of the values of two tangential oscillation components is presented. The photos of the surfaces obtained by machining of the workpieces with the use of vibrational turning are provided. The results of the surface microgeometry modeling under the turning with tangential oscillations imposition of the tool are given. The dependence of the surface microgeometry height on the workpiece rotation speed and the tool oscillation frequency is determined. The factors which influence on the workpiece surface microgeometry formation are specified.

Fabrication of precision meso-scale diameter ZrO2 ceramic bars using new magnetic pole designs in ultra-precision magnetic abrasive finishing

Ultra-Precision Magnetic Abrasive Finishing (UPMAF) is a technique for enhancing the surface quality of products, such as medical devices. In the UPMAF process, magnetic poles connect magnets and magnetic abrasive particles to form magnetic abrasive brushes for controlling the surface finishing process. Different edge shapes of the magnetic pole achieve different surface finish results. In this study, three magnetic pole designs, with a sharp edge, a square edge, and a round edge, were studied regarding their resulting surface quality and roundness precision for meso-scale diameter ZrO2 bars. Experiments were conducted to quantify critical input parameters, including magnetic pole shape, diamond particle grain size, and magnetic pole vibration frequency at an ultra-high rotational speed of 35000 rpm. An FEM model for magnetic field is used to evaluate the magnetic flux density results of the different magnetic pole shapes. The results show that stock ZrO2 bars with an Ra surface roughness of 0.18 μm and a roundness error of 3.5 μm can be improved to 0.02 μm and 0.2 μm, respectively, with the following process parameters: magnetic poles with 2-mm square edges, 1-μm diamond abrasive particles, magnetic pole vibration frequency of 8 Hz, and a workpiece rotational speed of 35000 rpm for 40 s of finishing time.

Electrical discharge turning by assistance of external magnetic field, part II: Study of surface integrity

Surface integrity as one of the main outcomes of hybrid machining process has dominant effect on the life time of engineering material. In this work, surface integrity of the AISI D2 steel grooves produced by electrical discharge turning (EDT) process was studied through experimental investigation. Here, for first time magnetic force has been integrated with EDT process to find how it influences the surface properties such as surface roughness, thickness of recast layer as well as surface hardness. Series of experiments based on Taguchi experimental design have been carried out taken into account magnetic flux density, discharge current, pulse on time and workpiece rotational speed as main inputs. Statistical optimization using grey relational analysis (GRA) was performed to understand how the hybrid machining parameter should be selected regarding minimum surface roughness and recast layer thickness as well as maximum hardness. Results indicated that magnetic flux density as well as work rotational speed have great impact in determining the surface integrity of machined grooves. Also, it is found that 0.4 T magnetic flux density, 5 A discharge current, 1000 μs pulse on time and 250 RPM work rotational speed is an optimal parameter setting that leads to maximization of hardness as well as minimization of surface roughness and recast layer thickness.

Study on Optimization of BP-GA Method Applied to Shaft Laser Cladding Repairing Technology

Laser cladding technique, which has the characteristics of refining microstructure, minimum deformation and high safety during processing, could enhance the strength of work-piece, shorten the repairing cycle and reduce the restoration cost by roughly sixty percent on shaft repairing. Process parameters optimization plays a key role in repairing quality and cost in laser cladding technique. This paper studied the application of YAG laser cladding technique on shaft repairing and which had important sense to popularize laser cladding technology. Through the experimental research and Artificial Neural Network-Genetic Algorithm approach, this technological process for laser cladding showed the capability to improve efficiency and quality of shaft repairing and reduce repairing cost with guarantee of enough bonding strength and no cracks in restoration area by optimization on key parameters like work-piece rotation speed, defocusing amount, powder stream rate.

Prediction Model of Material Removal for Polishing Single Crystal Silicon by Cluster Magnetorheological Finishing with Dynamic Magnetic Fields Based on BP Neural Network

Magnetorheological Finishing (MRF) is a new optical surface processing method, which has the advantages that good polishing effect, no subsurface damage, and suitable for complex surface processing. However, the interaction mechanism between the MRF pad and the workpiece is very complicated, so that the existing MRF material removal theoretical model is not accurate enough to establish the relationship between polishing parameters and material removal. In order to improve the processing efficiency and explore the material removal mechanism, a cluster magnetorheological finishing (CMRF) with dynamic magnetic fields method was proposed. Studying CMRF with dynamic magnetic fields material removal model is helpful to explain the removal mechanism more deeply, and improve the processing efficiency. In this study, the CMRF method was used to conduct a multi-factor orthogonal test on 2-inch single crystal silicon wafers. Based on the empirical Preston equation, the relationship between the machining gap and the polishing pressure was explained. Orthogonal experiments were done for a series of speeds, and obtaining the order of the influence of various factors on the average surface roughness <i>Ra</i> of the workpiece was: workpiece rotation speed > polishing disk speed > magnetic poles rotation speed > oscillating speed; the material removal rate (<i>MRR</i>) was: polishing disk speed > workpiece rotation speed > magnetic poles rotation speed > oscillating speed. Then combining with the orthogonal experimental data, and taking the surface roughness <i>Ra</i> and <i>MRR</i> as evaluation criteria, using Adam (Adaptive momentum) optimization algorithm to build a prediction model of <i>Ra</i> and <i>MRR</i> for polishing single crystal silicon by CMRF with dynamic magnetic fields based on BP neural network. For the prediction result, <i>Ra</i> of the maximum error was 7.05%, the minimum was 0.31%; <i>MRR</i> of the maximum error was 10.22%, the minimum was 1.32%. Therefore, the feasibility of this model for predicting the results of CMRF was verified, and it laid a good foundation for the development of CMRF technology and its industrial application.

Extension of Wire-EDM Capability for Turning Titanium Alloy and an Experimental Study for Process Optimization by Grey Relational Analysis

This experimental study presents an innovative concept of Wire-EDM turning operations on difficult to cut material. As a non-conventional technique, Wire-EDM is considered as efficient and economical tool in machining of electrically conductive advanced alloys and composites. As the job rotational axis is not available in the machine to perform turning operations, thus the Wire-EDM is assembled with suitably designed and manufactured rotary mechanism with maintained runout accuracy of 15 micron. The independently controlled process parameters are rotational speed of workpiece (RPM), pulse-on time (Ton) and wire feed rate (WF). Whereas, the performance parameters are material removal rate (MRR) and average surface roughness (Ra) which indicates the productivity & part quality respectively. Ti-6Al-4V alloy is selected as workpiece material. Mixed taguchi 21x32 orthogonal array is selected to design the experimentation. Grey Relational Analysis (GRA) has been implemented for simultaneous optimization to get higher value of MRR and lower value of Ra. The optimized process parameter values are RPM: 75 rpm, Ton: 10 μs and WF: 14 m/s which gives 16 % of significant improvement in surface quality and 1% of improvement in material removal.

Application of machine learning to predict the product quality and geometry in circular laser grooving process

Micro-grooves have various applications in different industries. Circular laser grooving is a new method for manufacturing micro-grooves on the circumference of cylindrical parts. In this process, the selection of appropriate parameters to reach experimentally the desired groove aspect ratio along with minimum dross formation requires tremendous efforts. Here, the role of a decision-making technique, similarly machine learning is highlighted to evaluate the significance of process inputs and provide the appropriate model for prediction concerning the input parameters. The experiments were conducted with the various inputs such as workpiece rotational speed, laser beam position, duty cycle, power and frequency. The outputs are the groove geometry in terms of width and depth of the circular groove as well as the groove quality considering the dross formation. Then, Random Forest (RF) technique was utilized to derive the most influential inputs on the outputs. The RF analysis revealed that the rotational speed, laser position and duty cycle are the most decisive process parameters in the groove geometry and groove quality. Also, the enhancement of the assist gas pressure does not improve the process outputs according to the results of RF analysis.

Experimental study on the polishing of aspheric surfaces on an S-136 mould steel using magnetic compound fluid slurries

S-136 (STAVAX ESR) as a mould material has been extensively used in the optical lens manufacturing industry. In this study, the aspheric surface made of S-136 fixed by a six-degree of freedom (DOF) manipulator was polished using magnetic compound fluid (MCF) slurry. The effects of experimental parameters included rotational speed of workpiece and MCF slurry composition on surface roughness Ra and shape retention were investigated. The results demonstrated that the cutting marks on the initial surface reduced obviously under the given experimental parameters. Therefore, the smoothest surface with Ra 20 nm was obtained with MCF3 containing micro-sized Fe3O4 particles with lower saturation magnetisation at nw = 1,000 rpm. The material removes uniformly during the polishing process and the Pearson correlation coefficient (Pcc) of the aspheric surface was kept above 0.994. The MCF slurry polishing was demonstrated as a potential method to smooth the S-136 aspheric surface.

Machining investigation on Ti-6Al-4V alloy using a wire electrical discharge hybrid turning (WEDHT) process

Wire electrical discharge hybrid turning (WEDHT), is a new unconventional material removal process to machine electrically conductive difficult-to-cut materials. WEDHT uses the complex material removal mechanism to remove the material by a series of intermittent sparks generated at the machining interface. This material removal on both surfaces of workpiece and wire affects the machining responses such as surface roughness (SR), material removal rate (MRR), depth of recast layer and micro-hardness. This also results in the formation of oxide layers at the machined surface. In this work, the WEDHT experiments are conducted on Ti-6Al-4V Grade 5 alloy to analyze the effect of the above set of responses on the machined surface. Pulse ON time (TON), wire feed rate (fw) and workpiece rotational speed (Ss) are varied at three levels. The cause and effect of outputs and the optimal combination of input parameters are analyzed. At the optimal level, 27% improvement in the surface finish and 51% improvement in the material removal rate are obtained. The recast layer, crater, and debris formed on the machined surface were analyzed using a scanning electron microscope (SEM). Vicker’s micro-hardness tester is used for measuring the variation of micro-hardness. The presence of oxide layers on the surface is quantified using x-ray diffraction analyzer (XRD) and energy dispersive x-ray spectroscopy (EDS) analyzer.

Fabrication of Hyper-Hemisphere of Cobalt-Chromium Alloys Using Curve Generator Machining

High-precision machining is required for manufacturing hyper-hemispherical artificial joints made of difficult-to-cut metals such as cobalt-chromium (Co-Cr) alloys to provide wear resistance in the human body. The hyper-hemisphere of Co-Cr alloys is finished by curve generator machining, in which the rotation axes of the cutter and workpiece intersect each other at the center of the sphere to be machined. This paper presents a kinematic model to simulate the shape and surface topography on hyper-hemispheres with the cutter loci in curve generator machining. The kinematic model was validated with a cutting test, in which the surface profiles were measured around the pole and equator of the sphere. Simulations were performed to study the cutting process and surface finish. The appropriate cutting parameters were determined to improve the surface finish based on a kinematic simulation. A smooth surface was obtained when small inclinations of the workpiece, large nose radii of the cutter, low workpiece rotation speeds, and non-integer ratios of the tool spindle speed to the workpiece rotation speed were employed. The effects of the setting errors, such as the mounting error of the cutter and alignment error of the spindle and workpiece axes, were estimated via the kinematic simulation. It was found that the surface topography and radius of the sphere depended on the setting errors. The radius and center of the spherical shape were different from those of an ideal sphere by an error in the X-axis in the global coordinate system. The oval shape was caused by an error in the Y-axis. An error in the Z-axis affected the radius of the machined sphere.

A novel approach to fabricate high aspect ratio micro-rod using ultrasonic vibration-assisted centreless grinding

To fabricate micro rods with high aspect ratio, this paper proposed a novel technique using ultrasonic vibration-assisted centreless grinding. Based on a comprehensive analysis of the workpiece rotational motion, the whole grinding system stiffness and its geometrical arrangement, a reliable mechanics model was successfully developed for clarifying the material removal process. Relevant experiments conducted showed that the model had captured the mechanics and the major workpiece rounding mechanisms. The workpiece rotational speed can be controlled accurately by the elliptic motion of vibration shoe through the contact friction, and higher vibration amplitude or frequency induces higher workpiece rotational speed. The load on vibration shoe significantly affects its vibration in both bending and longitudinal directions, and the vibration reaches its peak value as the loads on both sides are equal. A preload on one side of the shoe, under which the vibration on the other side comes to be comparatively stable, was identified. To balance the action force from workpiece during grinding, this preload should be applied on the vibration shoe. The grinding length can be up to the shoe's thickness, and workpiece in high aspect ratio with diameter from macro to micro scale can be fabricated easily using the proposed technique. With a step-by-step operation, a micro rod with aspect ratio 310:1 and diameter 42 µm (less than a human hair) was successfully ground.