Workpiece Surface Quality Research Articles

Analysis of Nonlinear Characteristics of Milling Force in Processing Splicing Joint Area of Automobile Mold

The structure and the cavity surface hardened steel mold of automobile cover is very complex. In the stamping process, the local structure bears higher extrusion stress than the type surface, which often causes local wear and even cracking. The process of multi-hardness splicing joint is applied to ensure the service life of the die according to the features of each part of the mold. The impact load caused by the repeatedly cutting in which always leads to the unevenness of cutting force in the whole process. The machining quality of the mold surface is reduced. Aiming at the ball-end milling process in mold splicing area, first, the impact behavior of tool workpiece cutting contact is analyzed. A prediction model for ball-end milling force in the splicing area is established by establishing the transient chip thickness model which considering the impact factors. Second, the experiment of cutting force measurement for Cr12MoV mold steel ball-end milling which is based on single hardness and multi-hardness are carried out to verify the model. Cross-correlation analysis based on data of milling force signal and machined surface roughness is carried out for getting the relevance of them in different processing states. Finally, the ApEn is used to analyze the nonlinear characteristics of the milling force signal at the multi-hardness splicing state. This explores the influence of the milling force on the machining quality. The experimental and analytical results show that the milling force signal exhibits more obvious chaotic characteristics in the multi-hardness stitching area than that in the single hardness region. This provides a basis for improving workpiece surface quality and improving cutting efficiency.

Numerical and experimental study on the flow characteristics and the erosive ability of magnetorheological jet

Fluid jet machining has been widely used in machining of hard-brittle materials. However, the diffusion of a jet flow significantly affects the erosion capacity. Magnetorheological (MR) fluid has been considered to take the role of pure water for carrying abrasive particles, due to its better concentration when the external magnetic field is applied. The present investigation focuses on the flow characteristics of a magnetorheological jet, which are involved in the basic aspects of erosion mechanism. 3D numerical models of excitation coil and jet flow field were established to investigate the fluid pressure distribution on the target surface and the trajectories of laden particles. Experiments were also conducted to verify the simulation results and evaluate the feasibility of a MR jet on surface finishing. The results indicated that the utilization of high magnetic intensity can effectively improve the concentration of a jet flow and the processing quality of workpiece surface.

Real-time chatter detection via iterative Vold-Kalman filter and energy entropy

Real-time chatter detection is important in improving the surface quality of workpieces in milling. Since the process from stable cutting to chatter is characterized by the progressive variation of the vibration energy distribution, entropy has been utilized to capture the decreasing randomness of vibration signals when chatter occurs. To make such an index more sensitive to transitions of the cutting state, the entropy can be computed based on signal components obtained through signal decomposition techniques. However, the classic empirical mode decomposition (EMD) is difficult to put into practice due to its weak robustness to noises. The up-to-date variational mode decomposition (VMD) has strict requirements on a priori information about the signal and thus is not applicable either. In this paper, a novel method named the iterative Vold-Kalman filter (I-VKF) is proposed under the framework of the greedy algorithm, where the Vold-Kalman filter (VKF), a classic order tracker for rotating machinery, is improved to recursively extract each signal component. In the meantime, a spectrum concentration index–based technique is developed for the estimation of the instantaneous chatter frequency to adaptively determine the filter parameter. Numerical examples demonstrate the superiority of the I-VKF over the original VKF, EMD, and VMD, especially in the presence of strong noises. Combined with the energy entropy of extracted components and an automatically calculated threshold, the proposed strategy greatly helps in timely chatter detection, which has been verified by dynamic simulation and experiments.

EXPERIMENTAL INVESTIGATION AND OPTIMIZATION OF HIGH SPEED MACHINING OF TITANIUM ALLOY FOR BIOMEDICAL APPLICATION

The Ti-6Al-4V alloy is known as materials with high hardness and good mechanical properties. However, the machining process of this material faces many difficulties due to unfavorable machining conditions. When the machining parameters are not selected in accordance with the Ti-6Al-4V alloy, the surface quality of workpieces does not meet technical requirements. Therefore, the appropriate machining parameters are needed to upgrade the surface roughness of workpieces in high-speed machining (HSM) conditions. The main cutting forces Py and Pz, and surface roughness Rz during turning of Ti-6Al-4V alloy in HSM were investigated and evaluated in this study. The response surface method (RSM) was used to conduct experiments and establish the models of Rz, Py, and Pz under various cutting conditions of feed rate ([Formula: see text]), tool nose radius ([Formula: see text]), and approach angle ([Formula: see text]). As a result, the [Formula: see text] value has the largest impact on the Pz. Moreover, the machining parameters such as [Formula: see text], [Formula: see text], and [Formula: see text] have a great influence on the Py. The magnitude of Rz is mainly affected by [Formula: see text] value. Based on the optimal parameters, the average value of the force Pz has decreased from 238[Formula: see text]N to 169[Formula: see text]N, corresponding reduction of about 29%. The value of the force Py has reduced from 184[Formula: see text]N to 118[Formula: see text]N, corresponding reduction of about 36%. In addition, the surface roughness of the workpiece has been improved significantly from Rz of 5.6[Formula: see text][Formula: see text]m to 2.7[Formula: see text][Formula: see text]m under optimal parameters condition. The surface roughness of the workpiece after processing in high speed machining was reduced of 52% compared with cutting under non-optimal parameters condition. The best surface quality and minimum cutting force could be achieved under optimal processing parameters in high speed cutting method.

Lapping performance of mixed-size agglomerated diamond abrasives in fixed abrasives pads

Ultra-fine diamond grains are used to prepare agglomerated diamond (AD) abrasives that are, in turn, applied to make fixed agglomerated diamond abrasive (FADA) pads. The as-prepared pads demonstrated very low removal efficiency along with a poor processing stability，which limits the applicability of ultra-fine diamond grains in fixed abrasive tools. In this reported research, mixed-size agglomerated diamond (MAD) abrasives with a combination of ultra-fine diamond grains and coarser diamond grains were employed to make FADA pads for lapping BK7 glass. Three types of FADA pads were manufactured with ultra-fine AD abrasives, coarser AD abrasives and MAD abrasives, respectively, for maximizing the process efficiency and stability of fixed abrasive pads consisting of ultra-fine diamond abrasives while improving the surface quality of the lapped glass substrates. The results showed that a FADA pad with MAD abrasives exhibited higher material removal rate (MRR) than a pad with AD abrasives of ultra-fine diamond grains only and lower surface roughness Ra and better surface microstructure than a pad with AD abrasives of coarser diamond grains. The distinct lapping feature of MAD abrasives was that the coarser diamond grains mainly accelerate the lapping efficiency while the ultra-fine diamond grains improved the surface quality of workpiece.

Optimization of Technological Parameters and Application Conditions of CMQL in High-Speed Milling 300M Steel

In order to study the influence of different lubrication conditions on cutting force, surface roughness and work hardening, single factor milling tests on 300M steel were carried out under five lubrication conditions of dry cutting, cryogenic cold air cutting, water mist cooling cutting, oil mist friction-reducing cutting and Cryogenic Minimum Quantity Lubrication (CMQL) cutting. Through orthogonal test under CMQL cutting condition, the influence of process parameters, such as cold air temperature, cold air pressure and cutting fluid dosage on workpiece surface quality and tool wear was studied, and the process parameters were optimized. Through the results of single factor and orthogonal tests, it is found that compared with other cutting conditions, CMQL cutting condition can get lower surface finish, work hardening and smaller cutting forces. And compared with other influencing factors, cold air pressure was the most important influencing factor in high-speed milling 300M steel under CMQL cutting condition, and its optimal value was 0.6 mpa.

Optimization of CNC Turning Parameters Using Taguchi Method

The surface roughness quality of machining product plays important role when it contacted with other machine components. That quality depends on several parameters setting, such as material, cutting tool, cutting condition and operator skill. The aim of this study is to obtain the optimum setting of turning parameters by using Taguchi method. Three control factors: cutting speed, depth of cut, and feeding at three different levels are selected. A series CNC turning process on AISI 1045 material were performed using L9 (3)3 orthogonal array with cutting fluid. Insert carbide cutting tool is used in the experiment. In order to reveal the optimum machining parameter, smaller the better is quality characteristic selected for surface roughness examination of workpiece. Analysis of experiment results revealed that higher cutting speed, low feed, low depth of cut respectively, provides fine surface quality of machined workpiece. Moreover, feed f parameter was found most influence to the surface rougness quality with 53.73% contribution, cutting speed v provides 23.28% contribution, and depth of cut a provides 17.87% contribution. Confirmation experiment shows that level 3 of cutting speed, level 2 of cutting depth, and level 1 of feed deliver smoothest machined surface of Ra 0,46 µm.

The effect of micro-texture on wear resistance of WC/Co-based tools during cutting Ti-6Al-4V

Titanium alloy as an important material used in the aerospace industry and automotive field has many advantages such as excellent specific strength, good corrosion resistance, and ultra-low temperature performance. However, there are still some difficulties during the cutting of Ti-6Al-4V, such as severe tool wear which reduces the surface quality of work piece. Textures could protect the tool from further wear and improve the tool life, and cutting productivity. In this work, femtosecond laser was used to make textures with different orientations (vertical, parallel, and vertical to the main cutting edge) on the rake face of carbide-tipped cutting tool to research the influence of different textures directions on the cutting performance. The results found that using parallel textured tools could reduce the friction coefficient by 14%. Compared with untextured tools, the rake face wear of parallel textures tools is reduced by 35–70% and surface roughness improved by 29%, which is owned to smallest the tool-chip contact area of tool with parallel microstructure.

Effect of ultrasonic-assisted turning on geometrical tolerances in Al 2024-T6

ABSTRACT In this research, the effect of ultrasonic vibrations in the turning process on geometric tolerances has been investigated. This has always been one of the most important challenges in the production of high-quality and precision parts. One of the important applications of the turning process is making parts with high dimensional accuracy. In this study, by applying ultrasonic vibrations to different machining parameters, we investigated the surface quality, runout, total runout, and straightness tolerance of a 2024-T6 aluminum workpiece. In the second stage, the effect of the presence of ultrasonic vibrations was investigated. The full factorial experiment design method was used, and 18 experiments were performed with this method. After that, the results were analyzed, and they are as follows. Compared to other machining parameters, the cutting speed has the highest effect on the runout, total runout, straightness tolerance, and surface roughness. Ultrasonic vibrations reduce all four output parameters of runout, total runout, straightness tolerance, and surface roughness. In particular, the surface roughness in ultrasonic turning decreased compared to conventional turning. Also, the formation of chips was investigated. This technique is suitable in manufacturing industries that require high dimensional accuracy.

Effect of machining parameters on turning process of Inconel 718

ABSTRACT Inconel 718 superalloys are known materials with high applicability to components that demand exceptional chemical and mechanical properties at higher working temperatures combined with excellent surface finish requirements. However, due to the lack of in-depth knowledge regarding its machining process, the material is considered a difficult-to-machine material. Therefore, to improve the machining process of the Inconel 718 superalloy, by finding the optimal processing conditions, it was necessary to analyze the influence of the cutting parameters on the workpiece surface quality. In this work, the evaluation of quality indicators was made through the influence analysis of cutting speed, feed, tool, and lubrication parameters. The surface roughness (Ra, Rt), consumed power, vibration, and tool wear indicators were evaluated by following a Taguchi experimental design. To perform the machining process, the tool CNMG120408-M1 coating TS2500 with minimum quantity of lubricant was used. Results have proven that feed rate adjusted to 0.10 mm/rev and the cutting speed of 70 m/min provided the optimal processing results. It was observed that the feed increase led to an increase of all indicators. Consumed power denoted high sensibility concerning the machining parameters, suggesting its potential use in tool wear prediction studies applied for the Inconel 718 machining.

Application of bionic phyllotaxis in internal cooling cup wheel: modeling-simulation and experimental verification

In order to better control the grinding temperature and workpiece quality, in this work, the bionic phyllotaxis was applied into the internal cooling cup wheel. According to the principle of bionics, the arrangement of sunflower seed was set as research object; then, the parameters of the phyllotaxis arrangement were analyzed; here, the arrangement of sunflower seed was called phyllotaxis arrangement. After that, the computational fluid dynamics (CFD) method was used to explore flow characteristics of the cup wheel with different structured surface, and the influence of phyllotaxis growth coefficient on coolant supply of internal cooling cup wheel was analyzed. Then, the corresponding structured abrasive grain ring was prepared by electroplating method, and the grinding experiment of internal cooling cup wheel was carried out. According to the experimental results, by application of bionic phyllotaxis in internal cooling cup wheel, the grinding temperature decreased by 32.8% at most, the surface roughness decreased by 39.9% at most, and the surface microhardness decreased by 9.6% at most. The above results indicate that the application of bionic phyllotaxis can significantly enhance grinding performance of the cup wheel, and the phyllotaxis parameters had obvious influence on the temperature of grinding and the surface quality of workpiece.

Revealing Nanoscale deformation mechanisms caused by shear-based material removal on individual grains of a Ni-based superalloy

Shear-based material removal processes significantly influence the quality of workpiece surface and implicitly the component functional performance. An in-situ SEM nano-cutting enabled the study of crystal flow and lattice rotation occurring below the cutting edge in a polycrystalline Nickel superalloy. When nano-cutting within single grains a deformed nanolayer appears that consists of a crystal lattice rotated exclusively within the cutting plane which is delimited from the bulk of the grain by high angle boundary (HAB); the depth of deformed nanolayer increases with the material pile-up (nano-chip) caused by the grain shearing. Upon nano-cutting multiple grains, nano-recrystallisation at the HAB occurs, accompanied by the bending of the grain boundary (GB) in the cutting direction, a phenomenon that also significantly influences the deformation behaviour of the grains cut after passing the GB. Clarifying these aspects at the nanoscale is crucial for understanding the formation of workpiece surface damage after material removal operations.

Analysis on ground surface in ultrasonic face grinding of silicon carbide (SiC) ceramic with minor vibration amplitude

Compared to conventional grinding, ultrasonic face grinding of SiC ceramic with vibration amplitude more than 3 μm has been proved to improve the machining efficiency but usually face the problem of reducing the workpiece surface quality. The material removal mechanism and ground surface quality by ultrasonic face grinding using minor vibration amplitude (less than 1 μm) still remains uncertain and needs to be further investigated. In the present work, experiments of ultrasonic face grinding of SiC ceramic are carried out to study the influence of processing parameters (e.g. depth of cut, wheel speed and ultrasonic vibration amplitude) on the surface finish. The results show that both the grinding forces and ground surface roughness increase significantly with the increase of depth of cut and the decrease of wheel speed. However, with the increase of ultrasonic vibration amplitude, the grinding forces decrease rapidly first and then keep steady, and the ground surface roughness shows three variation stages: dropping, climbing and stabilizing, which achieves the smallest value of 0.04 μm at the amplitude of 0.216 μm. From the analysis of acquired workpiece surface morphology and image processing result, the proportion of chunks and pits on the workpiece surface is reduced due to ductile removal in case of ultrasonic vibration amplitude less than 0.2 μm, but increases when the amplitude is more than 0.2 μm because the material is removed in brittle domain. Finally, a sample machined at relatively high wheel speed and minor vibration amplitude is provided to support the findings. The proposed investigation provides a new approach to achieve mirror surface of SiC ceramic using ultrasonic face grinding.

Effect of atomizing rapid solidification spherical abrasive finishing on the surface quality of copper-nickel alloy

To improve the surface roughness of Copper-Nickel alloy (Cu-Ni alloy) and explore the effect of magnetic abrasive finishing on the surface hardness and hydrophobicity of Cu-Ni alloy, the spherical magnetic abrasives are prepared by atomizing rapid solidification method. The effects of various process parameters on the surface quality of Cu-Ni alloy are explored, and the optimal process parameters of magnetic abrasive finishing of Cu-Ni alloy are obtained. The Neodymium-Iron-Boron permanent magnetic pole is used to grind the workpiece with XK7136C CNC milling machine. Three dimensional profilometer, metallographic microscope, and digital Vickers hardness tester are used to analyze the surface morphology of the workpiece. The hydrophilicity and hydrophobicity of the workpiece are measured by a contact angle goniometer. The effects of spindle speed, feeding rate, processing distance, and abrasive filling amount on the surface quality of workpiece are investigated by the orthogonal experiment and the single factor test. When the spindle speed is 1300 r/min, the feeding rate is 13 mm/min, the processing distance is 1.2 mm, and the abrasive filling amount is 2.0 g, the surface roughness of Cu-Ni alloy decreases from 0.212 to 0.023 μm and the hardness increases from 114 to 119.8 hv. Finally, the mirror effect of Cu-Ni alloy is achieved. When the optimal test parameters are used, the surface roughness of Cu-Ni alloy can be effectively reduced in a short time. The surface quality of the workpiece is improved, the surface hardness of the workpiece is affected to a certain extent, and the service life of the workpiece is prolonged.

Recent progress in flexible supporting technology for aerospace thin-walled parts: A review

Thin-walled parts are widely used in the aerospace industry owing to their light weight and high specific strength. However, due to the low rigidity of thin-walled parts, elastic deformation and chatter easily occur, which seriously affect the machining accuracy and workpiece surface quality. To solve this problem, several supporting technologies have been reported in recent years. This paper reviews the recent research progress of flexible supporting technologies in the aerospace field by classifying them based on different principles and characteristics. The principle, progress, advantages, and limitations of the technologies are expounded by systematic comparison and summarized. Finally, the challenges and future development trends of flexible supporting technology, which will provide guidelines for further research, are discussed.

Wettability Control on YW2 Cemented Carbide Surface by Femtosecond Laser Irradiation

The surface wettability control of cemented carbide tools is beneficial to the improvement of tool life and surface quality of workpieces in wet cutting. To clarify the correlation between the surface topography and wettability, squared microdimples are fabricated on the cemented carbide surface using a femtosecond laser. The dependencies of the side length, the depth, and the distribution density of squared microdimples on the surface topography and contact angle are studied. As the average laser power, and the number of scanning passes, increase, both the side length and depth of the squared microdimples increase. The contact angle decreases from hydrophilic to superhydrophilic. Moreover, the roughness height parameters have a great influence on the surface wettability, the larger the surface arithmetic average height, the smaller the kurtosis, the larger the skewness, and the better the hydrophilicity. The results of the scanning electron microscope (SEM) and energy‐dispersive spectrometer (EDS) reflect that the changes in the micro–nano protrusions, carbon, and oxygen elements cause deviation between the calculated contact angle and the actual contact angle. The friction coefficient of textured tools is lower than that of untextured tools at high sliding speed. Reasonable design of surface texture accurately controls surface wettability.

Experimental investigation of the effects of dressing and coolant-lubricant conditions on grinding of Nickel-based superalloy-Inconel 738

In grinding operation, wheel topography influences the workpiece surface quality, grinding forces, abrasive grain wear and wheel loading. The difficulties associated with grinding nickel-base superalloys are mainly attributed to the high strength and low thermal diffusivity of these materials. Their high strength leads to high removal energy. The application of green machining techniques for sustainable manufacturing becomes more and more attractive nowadays to reduce the consumption of energy and cutting tools and cut fluids and consequently decrease the production costs and environmental effects. In this study, the effect of dressing parameters and wheel topography on Minimum Quantity Lubrication-MQL grinding performance of Nickel-base superalloy-Inconel 738 is investigated. In other words, to generate different grinding wheel topographies, depth of dressing and dressing speed has been changed during dressing and conditioning of vitrified Al2O3 wheels using a single point diamond dresser. After dressing grinding wheels, machining tests have been conducted to study the influence of the wheel topography and coolant-lubricant types on the performance of grinding operation (workpiece surface quality and wheel loading). The tests have been performed in the presence of fluid as well as MQL with compressed air. The results show that applying MQL technique with the optimized dressing conditions improves the grinding performance of Inconel 738. Minimum quantity lubrication implemented in the grinding process is one of the realistic alternatives that can rise the abrasive processes on a sustainable level.

WITHDRAWN: Experimental investigation and optimization of surface grinding on EN31AM steel using Taguchi and ANN

Grinding is the machining processes; it is used to enhance the dimensional accuracy and surface quality of workpiece. The surface grinding process is affected by the different process parameters such as grinding wheel speed, material removal rate (MRR), number of passes, grinding wheel grain size, work piece speed, material hardness and depth of cut respectively. The feed and speed are the important factors because by increasing these factors will directly impacts on surface roughness (SR). Even though, the SR is reduced by improving the MRR. Surface grinding is the major process in metals cutting applications; it is widely used in finishing operations of cutting machining processes. SR and MRR are the significant output responses in the manufacturing relating to quality and quantity. In this article, an experimental investigation of surface grinding of EN31AM steel is studied to minimize the SR and maximize MRR for the optimization of grinding process parameters. In addition, artificial neural network (ANN) and Taguchi also employed for optimizing the input process parameters such as depth of cut, feed, and speed.

Study of nozzle distance and oil flow rate effects on the droplets size of minimum quantity lubrication

Minimum Quantity Lubrication (MQL) machining process has been widely applied to replace the traditional lubrication and cooling method that brings various drawbacks involving environment, human’s health and manufacturing cost. Although the amount of oil being used in the MQL machining process is extremely little, oil mist formed in the cutting zone still can successfully prolong the cutting tool life and improve the surface quality of workpiece. However, the size of lubricant oil droplets must be fundamentally investigated to clarify the lubricating mechanism in the cutting zone. This paper is aimed to study the droplets size of lubricant oil delivered by a commercial MQL generator. Experiments were conducted to study the effects of vertical nozzle distance and lubricant oil flow rate to the droplets count and size. As a result, the smallest diameter of droplets were found to range in between 10 μm - 22 μm. With increasing vertical nozzle distance, the diameter became larger due to the increasing dominancy of air flow that influences the movement of droplets. With increasing oil flow rate, the droplets tend to merge together, forming multiple larger size of droplets. The size of lubricant oil droplets did not significantly change when varying the vertical nozzle distance starting from 35 mm and oil flow rate starting from 18 mL/h. Finally, the control dial to adjust oil flow rate when using an MQL generator with internal feeding system application must be handled properly to ensure precise amount of oil mist successfully being delivered to the cutting zone.

Influences of processing parameters on metal-bonded diamond wheel wear when grinding a sapphire wafer

Wear processes on a metal-bonded diamond grinding wheel during surface grinding of monocrystal sapphire were investigated. Through a single-factor grinding experiment, the grinding depth of the workpiece, wear from the grinding wheel, and surface roughness of the workpiece were measured and surface morphologies of the processed surface, the grinding wheel, and diamond abrasives were observed. Moreover, the mechanism of action for influences of wear of the grinding wheel on surface quality of workpiece was investigated based on a complex model of roughness when grinding in plastic and brittle modes. The results indicate that: (1) The wear process of the grinding wheel consists of four stages, i.e. slow-speed wear, high-speed wear, slow-speed wear, and stable wear; (2) With the increase of the grinding depth, the probability of plastic material removal increases by using abrasives, while workpiece surface roughness first decreases then increases; (3) Wear forms of diamond abrasives mainly include wear land at the tip and crushing of abrasives. During the grinding of sapphire wafers using a metal-bonded diamond grinding wheel, wear from the grinding wheel rises with the increase of the grinding depth. When the grinding depth is 240 μm, the surface quality of the workpiece deteriorates, so the grinding wheel needs to be dressed to restore its grinding capacity and precision.