Workpiece Roughness Research Articles

Application of Minimum Quantity Lubrication for Various Machining Processes – A Mini Review

Minimum Quantity Lubrication (MQL) is a great alternative lubricating and cooling environment method that has been widely used to replace the conventional flood coolant which brings drawbacks involving environmental awareness, human’s safety and health and manufacturing cost. Taking into account the recent trends, this review paper describes a summary of the research journals reviewed previously MQL in various machining operations involving milling, turning, drilling and grinding of various types of materials. Most recent papers have described the use of vegetable oils which helps in maintaining the environmentally friendly machining. Also, the aided of nanofluid particles and hybrid environment in MQL application conversed the outstanding efficiency in machining performances as compared to that conventional flood lubrication technology. Briefly, this paper have shown the proficiency of eco-friendly MQL approach in improving the performance of machinability such as reducing the surface roughness of workpiece, producing a higher rate of tool life and also reducing the cutting temperature that leads to a sustainable machining environment in the future work.

Wire EDM process parameter optimization for D2 steel

Wire electrical discharge machining (WEDM) is most suited for machining conductive materials when precision is required. There are a large number of input control parameters that govern the WEDM performance. Thus, it becomes essential to optimize process control parameters to achieve optimal results. In the present paper process parameter optimization using Taguchi quality design concept of L16 orthogonal array for the wire-cut electrical discharge machining of D2 steel is done. Four process control parameters, namely wire speed, gap voltage, flushing pressure, and current, are analyzed for two response parameters viz surface roughness and material removal rate (MRR). It is found that MRR during WEDM have a predominant impact of current on it, while flushing pressure has the least impact on MRR. Whereas, surface roughness is most effected by wire speed during WEDM and gap voltage has the least impact on surface roughness of D2 steel workpiece during WEDM process.

Dynamics of the heat affected zone and induced strains in laser machining below ablation threshold

The Heat Affected Zone - HAZ of a laser irradiated AISI H-13 steel workpiece, is investigated via numerical simulations and experimental measurements. A three-dimensional transient thermo-structural finite element model is developed to simulate the machining process. A Gaussian laser beam is employed as the heat source. The developed finite element material model considers the effects of plastic strain, strain rate and temperature, along with a fracture model. The experiments are carried out with a laser of 1-4 W power and with a scanning speed of 100 mm/min. Thermocouple sensors are used for the temperature measurements, while the surface roughness is measured using white light interferometry and related experimental diagnostics. A parametric numerical analysis regarding the average absorptivity of the workpiece is performed and is compared to the experimental findings. The depth and width of HAZ and the induced strains are studied for the plastic and melting regimes. The influence of the surface roughness of the metal workpiece on the dynamics of HAZ is also experimentally demonstrated. The findings of this study highlight the role of the absorption coefficient and the surface roughness on the HAZ below the ablation threshold and can be applied to related laser machining processes.

Effects of Abrasive Media on Surface Roughness in Barrel Finishing Process

Barrel finishing is a common technique for surface finishing of industrial parts. Many factors such as working time, abrasive media, initial roughness and machining parameters of rotary barrel affect the final surface roughness of workpieces. Analysing these input parameters in order to obtain the least surface roughness as well as the least working time for barrel finishing of the specific samples, is not possible except by applying Design of Experiments method. Thus, the aim of the present paper is to improve the surface quality of the steel alloy CK45 samples in barrel finishing process, by investigating different combination of three abrasive particles including ceramics, steel balls and aluminium oxide as the abrasive media through design of experiments method. Initial roughness, working time and the combination of abrasive media are the input factors in the designed experiments, while the surface roughness is the output factor. Results show that the best surface roughness and working time have been achieved with the specific combination of steel balls and aluminium oxide particles as the abrasive media.

Study of oil flow rates effects on lubricant oil behaviour during minimum quantity lubrication milling process

Minimum quantity lubrication (MQL) technology has been utilized extensively on these days as an alternative method to conventional cooling technique. A study to understand the know-how of tiny lubricant oil mists to effectively penetrate the cutting zone is important. However, such study is still scarce since the setup of the experimental probe during the machining process is on-going is difficult. The objective of this study is to analyse the lubricant oil film behaviour accumulated on AL6061 workpiece during MQL milling process by using a non-intrusive technique called as laser-induced fluorescence (LIF) method. The experiment was conducted under different oil flow rates to measure the thickness fluctuation of the lubricant oil film. Moreover, the surface roughness of workpiece after the milling process was also measured. As a result, the lubricant oil thickness was found to fluctuate in between 0.2 mm and 0.4 mm for two lower oil flow rates due to the tendency of evaporation. At higher oil flow rate, the lubricant oil fluctuated at higher thickness, i.e. 0.4 mm and 0.5 mm. On the other hand, the obtained mean surface roughness values did not reveal any remarkable difference from each other. However, lower mean surface roughness values were detected at 90 mm distance from machining starting point due to the accumulation of lubricant oil towards the end of workpiece. Therefore, the results of the oil behavior were successfully confirmed and thus MQL milling performance under different oil flow rates condition was clarified.

Effect of KDP-Crystal Material Properties on Surface Morphology in Ultra-Precision Fly Cutting.

To study the effect of material properties on the surface morphology of potassium dihydrogen phosphate (KDP) crystals, an ultra-precision fly cutting machine tool with a single-point diamond tool was used to perform a cutting experiment on (100) crystal plane of the KDP crystal. The elastic modulus, shear modulus, hardness, and dislocation of KDP crystals are taken into the cutting force model by introducing the strain gradient plasticity theory. Since the size effect and dynamic response will affect the surface roughness during ultra-precision machining, the surface roughness of workpieces in ultra-precision fly cutting is hard to predict. Based on the previously established strain gradient plasticity theoretical model, cutting force model, and the dynamic characteristics of the ultra-precision fly cutting system, a surface morphology prediction model under the influence of KDP crystal material properties was established. Finally, the accuracy of the surface morphology prediction model was verified by ultra-precision fly cutting experiments, and identified the frequency range of the characteristic signal caused by the anisotropy of the KDP crystal from the frequency, thereby verifying the KDP crystal material properties has a significant effect on the surface of the machined workpiece roughness.

Grinding Wheel Loading Evaluation by Using Acoustic Emission Signals and Digital Image Processing.

In the manufacturing industry, grinding is used as a major process for machining difficult-to-cut materials. Grinding is the most complicated and precise machining process. For grinding machines, continuous generating gear grinding machines are widely used to machine gears which are essential machine elements. However, due to its complicated process, it is very difficult to design a reliable measurement method to identify the grinding wheel loading phenomena during the grinding process. Therefore, this paper proposes a measurement method to identify the grinding wheel loading phenomenon in the grinding process for continuous generating gear grinding machines. In the proposed approach, an acoustic emission (AE) sensor was embedded to monitor the grinding wheel conditions; an offline digital image processing technique was used to determine the loading areas over the surface of Al2O3 grinding wheels; and surface roughness of the ground workpiece was measured to quantify its machining quality. Then these three data were analyzed to find their correlation. The experimental results have shown that there are two stages of grinding in the grinding process and the proposed measurement method can provide a quantitative grinding wheel loading evaluation from the AE signals online.

Surface roughness variation in ultrasonic assisted burnishing of high-strength steels

Ultrasonic assisted burnishing process is a newly developed alternative of conventional burnishing process that enhances the surface properties of engineering materials. The process needs careful selection of design parameters to improve the quality of surface layer of workpieces made of high-strength steel that are difficult to deform. The analytical models to predict the surface roughness after the ultrasonic assisted burnishing process for surfaces are developed. Feed, ultrasonic influence power and static static force could be considered as main factors influencing to surface roughness at that feed has the greatest impact among other parameters. The models are verified by experimental studies with various ultrasonic burnishing parameters. Technological parameters of the ultrasonic burnishing are found, which decrease surface roughness from 1-2 μm to 0.05-0.55 μm. It is experimentally proved that feed increase results in surface roughness increase. To low the surface roughness of high-strength steel workpieces it is necessary to increase ultrasonic influence power with simultaneous static force lowering. The analytical models obtained in the present work may be employed in determining the best conditions for ultrasonic assisted burnishing in industrial field.

Robot Grinding System Trajectory Compensation Based on Co-Kriging Method and Constant-Force Control Based on Adaptive Iterative Algorithm

To reduce the grinding trajectory deviation caused by the absolute positioning accuracy of robot, a trajectory compensation method based on Co-Kriging space interpolation method is proposed. Meanwhile, an adaptive iterative constant force control method based on one-dimensional force sensor is proposed to improve the processing quality and efficiency of robot belt grinding. Firstly, an error model based on 6 DOF robot is constructed. Then, considering the workspace of robot belt grinding and the similarity of robot position error, the Co-Kriging compensation algorithm is used to compensate the grinding trajectory, which makes the compensation process convenient and accurate. Then, a grinding dynamics model based on deformation is established, and an adaptive iterative constant force control is proposed for complex robot belt grinding process, which overcomes the instability of grinding force and shortens its convergence time. Finally, the grinding trajectory compensation experiment and the force control experiment of spherical workpiece are carried out. The results show that the space interpolation compensation algorithm based on Co-Kriging method can significantly improve both the space position error of grinding trajectory and the actual error of workpiece, which proves the feasibility of compensation algorithm. Through force control algorithm, the grinding force fluctuation is maintained within 2 N, the mean value, standard deviation and variance of absolute value of force error are significantly reduced, the convergence rate of grinding force and the roughness of workpiece are much better than before, which shows the effectiveness of the proposed force control algorithm.

A comparative analysis of ceramic and cemented carbide end mills

Milling of ferrous metals is usually performed by applying cemented carbide tools due to their high hardness, temperature and wear resistance. Recently, ceramic tool materials have been on the rise and enhanced the efficiency in machining. As ceramics are brittle-hard materials, tool manufacturing requires a sound knowledge in order to meet the tool requirements such as sharp cutting edges and wear resistance. In this study, milling tools made of the high performance ceramic SiAlON were compared to tools made from cemented carbide. For both tool materials, the influence of a prepared cutting edge was investigated. Both the tool manufacturing process and the cutting edge preparation processes are presented, followed by the application of those tools within milling experiments. In order to evaluate the efficiency of both tool types, the cutting forces and the cumulative process energy demand were analyzed. Additionally, surface roughness of the machined workpieces and tool wear were examined. It was found that the ceramic tools, although process forces were higher than for cemented carbide tools, exhibited by far lower energy consumption, less tool wear and finally generated lower surface roughness.

Enhancing cutting performance of uncoated cemented carbide tools by joint-use of magnetic nanofluids and micro-texture under magnetic field

Abstract In this study, the coupling effect of magnetic nanofluids and micro-textures under magnetic field on the tribological properties of uncoated tool is revealed for the first time. The micro-scale grooves parallel to the main cutting edge were fabricated on the tool rake face by laser processing (named TP), and for comparison the tools without surface texturing (named NT) were also prepared. Magnetic nanofluids with a solid content of 30% (named MN) were prepared as coolant for machining the workpiece, and the conventional cutting fluids (named CC) were also prepared for a comparison. At the same time, the magnetic nanofluids were applied to the cutting area by a novel machining setup, then the turning tests were accomplished to study the coupling effect of micro-texture and magnetic nanofluids (TP + MN) under different magnetic field strengths. The analysis of obtained results (cutting forces, surface roughness of workpiece after turning and tool wear) proves the advantages of the magnetic nanofluids and micro-texture under the magnetic field. In these experiments, under the highest magnetic field strength (40 kA/m), TP + MN has 48.6% lower cutting force and 49.1% lower surface roughness of machined workpiece compared to that of NT + CC. Additionally, the mechanism for the coupling effect of micro-textured tool and magnetic nanofluids under magnetic field wasalso revealed.

Investigation of the Effect of Bath Ageing on Electropolishing Efficiency

The bath age poses a serious challenge during prolonged electropolishing processes. It is a general practice in electropolishing industry to reuse the bath to cut down the cost and to minimize the harmful effects on the environment. It is well known in the electropolishing industry that the final polishing quality declines over time due to the increased dissolved metal ions. The present study aims to quantify this effect.Various sets of experiments were conducted to investigate the effect of bath aging during prolonged electropolishing on polishing quality. The experiments were performed in a bath with an initial composition of 50% phosphoric acid (H3PO4), 35% sulfuric acid (H2SO4) and remaining water. The variations in the properties of the bath (conductivity, viscosity and specific gravity) were measured over prolonged polishing (Electropolishing tests were conducted up to passing 72000 C/ L of the bath). Variation of quality (in term of surface roughness and gloss) of standard workpieces polished under identical conditions (constant voltage, inter-electrode distance and time) were determined at various bath ages. Further bath composition (in term of the relative amount of acids) was determined periodically by titration.It was observed that as the bath properties change throughout the electropolishing experiments with bath aging, significant variation was seen in roughness and gloss of the polished workpiece. The roughness result for the workpiece polished in the most-aged bath was ~12 times higher than the workpiece polished in the fresh bath. Also, the first few polished workpieces had a shiny, mirror finish whereas the workpieces polished for the prolonged bath usage had a dull, matte finish.Bath composition varied from the initial composition of 50:35:15 (phosphoric acid: sulfuric acid: water) to 31:22:47 as the bath aged. Recovering initial bath composition (by adding an adequate amount of acids to the aged bath) allowed to recover the similar quality of polished samples (very similar surface roughness but less bright surface finish). Correlation between measured bath properties and composition with polishing achieved under standard conditions can be considered for further studies to develop strategies to make polishing parameters adaptable to given bath states.

Optimization of Cutting Parameters When Surface Milling with Face Milling Tool According to the Stages of Response Surface Method

This paper presents the optimization of cutting parameters when surface milling according to the stages of the response surface method. The implemented stages of the response surface method include the screening design, initial experiments and response surface design. The objective of the screening design is to select the input parameters for the next experimental stages. The goal of the initial experiments is to check the choice range of the input parameters ensures that the output function is extreme point or not. The aim of response surface design is to build the relationship between output parameters and the input parameters. The machined material in this study is C45 steel, while the used cutting tool is the face mill with PVD-coated inserts. Accordingly, the optimal values of cutting parameters including cutting speed, feed rate and depth of cut are determined at 230 (m/min), 0.23 (mm/toolpath) and 0.888 (mm), respectively. In case of machining with this cutting parameter, the surface roughness of workpiece reaches the smallest value, only about 0.15 µm.

Optimization of machining parameters in plane surface grinding process by response surface methodology

This paper aims to predict the optimal solution of surface roughness using Response Surface Methodology in surface grinding machining process. Response surface Methodology extracted for input parameters preparation to surface grinding process. EN 24 steel machining with various speed, depth of cut and feed rate timing. The surface roughness of the machined workpiece measured by the conventional stylus probe. Then input and output parameters feed into the RSM and developed ANOVA and regression equation to produce the optimal solution.

Intelligent model-based optimization of cutting parameters for high quality turning of hardened AISI D2

AbstractThis paper proposes an intelligent model-based optimization methodology for optimizing the production cost and material removal rate subjected to surface quality constraint in turning operation of hardened AISI D2. Unlike traditional approaches, this paper deals with finding optimum cutting parameters considering the real condition of the cutting tool. Tool flank wear is predicted by the model obtained using genetic programming. On the basis of the predicted flank wear value, the surface roughness of work piece is estimated by neural networks. Applying the particle swarm optimization algorithm, the optimum machining parameters are determined. The simulation and experimental results show that machining with proposed intelligent optimization methodology has higher efficiency than conventional techniques with constant optimized cutting parameters.

Prediction of Surface Roughness When Surface Grinding C45 Steel Using CBN Grinding Wheel

This paper presents a study of the roughness prediction of the workpiece when using CBN (Cubic Boron Nitride) grinding wheel to process C45 steel on a surface grinder. On the basis of inheriting the previously published studies on modeling surface roughness of workpiece when grinding, this study was conducted to develop one of these models and build a new model of surface roughness that consider many factors affecting surface roughness. Cutting parameters, parameters of grinding wheel, characteristics of materials, characteristics of contact of grinding wheel with workpiece have been included in the roughness model of the surface roughness of workpiece. This new surface roughness model was used to predict surface roughness of workpiece when grinding C45 steel with CBN grinding wheel. The results showed that the surface roughness value when predicting was very suitable for the experiment and the average deviation between the predicted results and the experimental results was only about 9.84%. The surface roughness model proposed in this study also confirms that the roughness can be predicted more accurately than the previous surface roughness models. And then, the development direction for further research is also mentioned in this paper.

Grinding process applied to workpieces with different geometries interrupted using CBN wheel

Although the fact that the interrupted cutting process is widely employed in traditional machining operations such as turning of crankshafts, engine piston ring, and helical tool sharpening, only a few number of studies in the literature approach this process. This study aims to evaluate the performance of the interrupted grinding process of workpieces with a different number of grooves (2, 6, and 12) in CBN grinding and to contribute to further findings about the integrity of interrupted surfaces and groove flanks after grinding, analyzing surface roughness and roundness deviation of workpieces after grinding process. The diametric wheel wear and grinding power were also recorded and analyzed. The performance of the interrupted grinding process was compared with the continuous grinding process, i.e., for workpieces without grooves. The AISI 4340 steel workpieces were tested under the application of flood lubri-cooling method at different feed rates (0.25, 0.50, and 0.75 mm/min). In conclusion, higher feed rate increased the surface roughness from 0.12 to 0.35 μm for continuous grinding process, respectively at 0.25 and 075 mm/min. The interrupted grinding led to increase of surface roughness Ra values from 0.19 to 0.43 μm (respectively 58.3% and 22.9% higher than continuous) for 2 grooves, 0.31 to 0.59 μm (respectively 158.3% and 68.6% higher than continuous) for 6 grooves and 0.54 to 0.93 μm (respectively 341.7% and 165.7% higher than continuous) for 12 grooves, respectively at 0.25 and 0.75 mm/min. As presented for surface roughness values, the increase of groove number resulted in higher values of roundness deviation, diametric wheel wear due to mechanical shocks caused by couplings and uncouplings of the grinding wheel. It was evidenced by SEM images of groove flanks and macro-fracture mode of abrasive grains. No microstructural damage was caused by thermal or mechanical irrespective of the experimental conditions investigated.

Surface and subsurface characteristics of laser polished Ti6Al4V titanium alloy

This paper aims at investigating the effects of laser power, laser pulse repetition rate and scan speed on the polished metal surface and subsurface characteristics. The influence of initial surface roughness of workpiece on the polishing performance was also taken into account. In this study, Ti6Al4V titanium alloy was selected as a specimen to be polished by a nanosecond pulse laser. The results revealed that the surface roughness was able to be improved by about 43% when the laser fluence of 1–3 J/cm2 was applied. In addition, the proper polishing condition was dependent on the initial surface roughness of workpiece, and a better surface improvement was subjected to a lower initial surface roughness. A thick recast layer, high degree of oxidation and large heat-affected zone with lots of micro-cracks were obtained when too high laser power and slow scan speed were used in the polishing of titanium alloy. With regard to the findings of this study, the suggested polishing conditions could be applied for smoothing the different levels of initial surface roughness of titanium alloy and possibly other similar metals with less subsurface damage.

Non-contact, bi-directional tool tip vibration measurement in CNC milling machines with a single optical sensor

Vibration measurements of tools are significant for machine modelling, error prone state identification and machine operation optimization. In the milling process, forced vibrations are the main factor resulting in shape deviations as well surface roughness of machined work pieces and depend on the spindle speed and tool properties. Numerical models for predicting the dynamic behavior of machine systems can help to reduce vibrations. For an optimization, the model parameters need to be evaluated by simultaneously measuring the vibration of the tool tip in force direction and its vertical direction under different rotational speeds with high spatio-temporal resolution. In this work, a non-contact, single-sensor system and a signal processing algorithm are presented for measuring the vibrational behavior inside of a CNC milling machine with a known force. It enables in situ, simultaneous bi-directional vibration measurements directly at the tool tip with measurement rates up to 50 kHz, a circumferential resolution below 230 μm and a displacement uncertainty down to 40 nm, at rotational speeds up to 300 Hz. The dynamic behavior parameters of the tool are evaluated depending on the measured vibration spectrum with relative uncertainties of 10-2, enabling model optimizations. The measurements show a decrease of the natural frequency with increasing spindle speed. While the laser-based measurement principle does not bias the vibrational behavior it inherently guarantees orthogonality of the sensing axes, as well.

Effect of Machining Parameters on Surface Roughness of Workpiece in Drilling A6061 Aluminum Alloy

Effect of Machining Parameters on Surface Roughness of Workpiece in Drilling A6061 Aluminum Alloy