Theoretical Surface Roughness Research Articles

The Analytical and Experimental Analysis of the Machined Surface Roughness in High-Feed Tangential Turning

A main topic in mass production of machine parts is how to increase the productivity to produce more parts in a given time while maintaining the prescribed surface quality on the machined surfaces. Novel machining procedures have been introduced to achieve this goal; however, the further development of already established and wide-spread procedures can offer simply accessible solutions. Tangential turning is a rediscovered variant of the traditional turning procedure, where a specially designed cutting tool ensures chip removal with a feed tangential to the workpiece. This process results in low surface roughness even at higher feed rates. In this paper, the achievable surface roughness is analyzed by analytical and experimental steps. In the mathematical analysis, the theoretical surface roughness is determined using the constructive geometric modelling method. The worked-out equations are validated in cutting experiments on 42CrMo4 grade steel workpieces. The theoretical and experimental analyses show that the strictly prescribed surface roughness can be achieved with high feed rates by the application of tangential turning.

Theoretical Modeling and Surface Roughness Prediction of Microtextured Surfaces in Ultrasonic Vibration-Assisted Milling

Textured surfaces with certain micro/nano structures have been proven to possess some advanced functions, such as reducing friction, improving wear and increasing wettability. Accurate prediction of micro/nano surface textures is of great significance for the design, fabrication and application of functional textured surfaces. In this paper, based on the kinematic analysis of cutter teeth, the discretization of ultrasonic machining process, transformation method of coordinate systems and the cubic spline data interpolation, an integrated theoretical model was established to characterize the distribution and geometric features of micro textures on the surfaces machined by different types of ultrasonic vibration-assisted milling (UVAM). Based on the theoretical model, the effect of key process parameters (vibration directions, vibration dimensions, cutting parameters and vibration parameters) on tool trajectories and microtextured surface morphology in UVAM is investigated. Besides, the effect of phase difference on the elliptical shape in 2D/3D ultrasonic elliptical vibration-assisted milling (UEVAM) was analyzed. Compared to conventional numerical models, the method of the cubic spline data interpolation is applied to the simulation of microtextured surface morphology in UVAM, which is more suitable for characterizing the morphological features of microtextured surfaces than traditional methods due to the presence of numerous micro textures. The prediction of surface roughness indicates that the magnitude of ultrasonic amplitude in z-direction should be strictly limited in 1D rotary UVAM, 2D and 3D UEVAM due to the unfavorable effect of axial ultrasonic vibration on the surface quality. This study can provide theoretical guidance for the design and fabrication of microtextured surfaces in UVAM.

Surface roughness evolution law in full-aperture chemical mechanical polishing

Ultra-high precision revolution surfaces are crucial to mechanical components like bearings but are difficult to achieve using conventional machining. Meanwhile, it is challenging to predict the surface roughness evolution law during processing. Accordingly, this study proposed an ultra-precision full-aperture chemical mechanical polishing (CMP) method for processing revolution surfaces. More importantly, a theoretical surface roughness Ra model was established by assuming that the three-dimensional surface morphology can be simplified to two-dimensional identical triangles, each peak can be uniformly removed, and the material removal at the valleys can be neglected compared to that at the peaks. The model provides an intuitive understanding of the Ra evolution law during the full-aperture CMP. Interestingly, Ra first decreases parabolically, determined by the initial surface roughness Ra0, the material volume removal rate MRRV, and the polishing time t. Then, it stabilizes. In addition, the theoretical MRRV model was summarized. The cylindrical guiding surface of a bearing was polished with the developed full-aperture CMP method. In 6 min, Ra can be significantly reduced from the initial 201.09 nm to 1.50 nm almost parabolically and stabilizes. Experimental results basically validate the theoretical Ra model, except that a slow decreasing stage appears intermediately because the real surface cannot be perfectly uniform. Additionally, the roundness error RONt is reduced by 34 %. Furthermore, the full-aperture CMP method and Ra model are successfully applied to other revolution surfaces. This study provides mechanistic insight into Ra evolution modelling pertaining to the manufacturing process.

Полуэмпирическое моделирование температуры резания и шероховатости поверхности при точении конструкционных материалов твердосплавным инструментом с покрытием TiAlN

Introduction. In manufacturing, obtaining a specified surface roughness of the machined components is of great importance to fulfill functional requirements. However, this is significantly affected by the heat generated during processing, potentially causing variations in dimensional accuracy. The surface roughness significantly affects the fatigue performance of the component, while the cutting tool's lifespan is dictated by the generation of cutting temperatures. The purpose of the study is to create semi-empirical models for predicting surface roughness and temperature of different work materials. Improved cutting performance is achieved by precisely determining the cutting temperature in the zone being machined. However, calculating the cutting temperature for each specific case is fraught with difficulties in terms of labor resources and financial investments. This paper presents a comprehensive empirical formula designed to predict both theoretical temperature and surface roughness. The methodology. The surface roughness and temperature values were evaluated for EN 8, Al 380, SS 316 and SAE 8620 materials using TiAlN coated carbide tool. The TiAlN coating was formed using Physical Vapor Deposition (PVD) Technique. The response surface methodology was used to prepare predictive models. Cutting speed (140 to 340 m/min), feed (0.08 to 0.24 mm/rev) and depth of cut (0.6 to 1.0 mm) was used as input parameters for measuring the performance of all material in terms of surface roughness and cutting temperature. The tool-work thermocouple principle was used to measure the temperature at the chip-tool interface. A Novel Calibration Setup was developed to establish a connection between the electromotive force (EMF) generated during machining and the cutting temperature. Results and Discussion. It is observed that the power required for machining was largely transformed into heat. The highest cutting temperature is recorded when machining of SS 316 followed by SAE 8620, EN 8. However, low temperature is reported during machining of Al 380 and it is mainly governed by the thermal conductivity of the material. The lowest surface roughness is observed in SAE 8620, EN 8 material followed by SS 316 and Al 380. Semi-empirical method and regression model equations show a good agreement with each other. Statistical analysis of nonlinear estimation reveals that the cutting speed, feed, and density of the material have a greater effect on surface roughness, whereas the depth of cut has a greater effect on temperature generation. The study will be very useful for predicting industrial productivity when machining of EN 8, Al 380, SS 316 and SAE 8620 materials with TiAlN-coated carbide tool.

Investigation on surface quality in micro milling of additive manufactured Ti6Al4V titanium alloy

The additive manufactured technology is widely applied to produce titanium alloy parts with complex structures. The subsequent machining operations are necessary for additive manufactured parts to achieve the required machining quality. In this paper, the theoretical surface roughness model in micro milling was established. The model indicated the theoretical milled roughness mainly depends on the feed per tooth, tool nose radius and bottom edge inclination angle. Then, micro milling experiments are conducted on additive manufactured titanium alloy using PCD micro end mill. The surface roughness on milled surface was measured and investigated. At the middle position of micro milled surface, the distribution curves of surface roughness Ra and Sa show the same variation trend under different milling parameters. Moreover, the measured surface roughness results on different transverse positions of milled surface showed that the difference value between the actual and theoretical surface roughness of milled surface is mostly induced by the unstable cutting behaviors, which is also mainly responsible for the surface roughness size effect. The transverse distribution of surface roughness on milled surface exhibited a W shape because of the variation of the instantaneous undeformed chip thickness and material removal mode at different transverse positions.

Improving the surface quality of material extrusion additive manufacturing parts by using ultrasonic‐vibration machining

AbstractMaterial extrusion (ME) technique has been one of the most popular additive manufacturing techniques because of its environmental friendliness, low cost, simple operation, and so forth. However, significant surface defects occur on ME parts due to the discontinuity between adjacent layers. For this reason, a new method, using ultrasonic‐vibration machining, was innovatively proposed to improve the ME parts' surface quality. A theoretical surface roughness (SR) model of the ME parts processed by using ultrasonic vibration was established. An ultrasonic‐vibrating ME equipment was then set up by refitting an ordinary one and the samples built without and with ultrasonic‐vibration machining utilized were prepared, respectively. With the laser microscope, the built parts' SR was tested and determined. Compared the predicted SR results with the measured ones, the theoretical model was verified. The influence of different ultrasonic vibration on the surface quality of ME parts was also discussed, clarifying the corresponding mechanism.

Analysis of theoretical machined surface roughness profile after sawing solid oak wood (Quercus robur L.) along the grain with a circular saw

ABSTRACT The article presents an analysis of the influence of simulated circular saw teeth marks profile in relation to the anatomical roughness of solid oak wood (Quercus robur L.) on machining roughness after sawing along the grain with a circular saw in order to better understand this relationship and to improve the knowledge how this two factors can be separated for further analysis in real-world sawing and to try to quantify the minimum theoretical tooth mark height that could be distinguished from anatomical roughness of wood. The signal-to-noise ratio (SNR) of simulated circular saw teeth mark signal in relation to measured anatomical roughness signal of solid oak wood was used to determine the level at which saw teeth marks could have a meaningful impact on machined surface roughness. From the analysis it can be concluded that SNR values even as low as −13 dB can have enough information to be used for frequency analysis and filtering out of tooth marks signal. Averaging and longer sampling lengths provide much better SNR values and provide the frequency spectrum of the structural roughness signal of solid oak wood with the highest amplitude of less than 0.5 μm. If more favorable SNR values are to be obtained, sampling lengths should be much longer than what is standardly used and recommended in ISO 3274: 1996 (in this research cumulative sampling length of 600 mm was used).

Mathematical modelling for prediction of surface roughness in Pneumatically Configurable Polishing process

Pneumatically configurable polishing is a superfinishing process which can generate nano-meter level surface finish on workpiece surfaces. It utilizes pneumatic pressure for controlled inflation of a cup shaped elastomeric membrane which has a stretchable polishing film fixed to its bottom surface. A slurry containing abrasive particles, thoroughly mixed in a carrier medium is applied on the workpiece surface. When the inflated membrane is brought in contact with a rigid surface, it adheres to the profile of the workpiece being polished, which ensures the entrapment of abrasive particles between the membrane and the surface to be polished. The abrasive slurry is replenished at a fixed interval during the process. This flexibility of the membranous tool enables it to finish complex 3D surface profiles. The final surface characteristics generated are a function of process parameters as well as material properties. This study proposes a mathematical model for the prediction of surface roughness as a function of workpiece properties such as hardness, tool characteristics, and significant process parameters such as working gap, applied pneumatic pressure, spindle speed, concentration of abrasive slurry, abrasive mesh size and dwell time. The model uses Hertz contact theory of elastic surfaces for modelling of contact pressure between the inflated membranous tool and the workpiece surface. A single abrasive particle is modelled for its influence on the workpiece surface as a function of its radial distance from the tool centre. This model is used to estimate the combined effect of all the active abrasive particles, participating in the finishing process. The final penetration depth obtained at different radial coordinates is used to estimate the theoretical surface roughness on the workpiece surface. The normal, shear and friction forces acting on a single abrasive grain have been modelled to determine the process capability during material removal. The model is finally validated by performing experiments under different conditions of process parameters. The experimental findings and theoretical results are found to be within an error range of −16.5%–11.8%.

Theoretical Roughness Modeling of Hard Turned Surfaces Considering Tool Wear

Surface roughness is an important factor in metal cutting, and usually different surface roughness characteristics are used to control the quality of the machined surfaces. However, as the cutting tool wears out during the cutting process, the roughness values change. In most cases, theoretical roughness values are calculated without taking the wear characteristics of the tool into account. For this reason, the calculated and measured roughness values may differ from each other, and the tendency of their change may also be different. This paper presents a method for the determination of the theoretical roughness of hard turned surfaces considering the wear of the cutting tool. The purpose of the analyses performed was to show the effect of wear trace on the tool and the roughness of the machined surface and to give a possible method to take the wear into account when calculating the theoretical roughness values. During the investigations, the shape of the actual (worn) edge section of the cutting tool was recorded by an optical microscope, and the theoretical surface roughness values were calculated with that profile by a CAD modeling method developed earlier. Cutting experiments were conducted on a lathe machine with two similar cutting tools, one of them has significant tool wear, while the other was a completely new one. The calculated theoretical roughness values were compared with real measured roughness values, and the error of the estimates was between 8.7 and 68.3%, larger errors were found at lower feeds.

CAD and FEM Modelling of Theoretical Roughness in Diamond Burnishing

Diamond burnishing is a widely used finishing machining that can have a positive effect on both the roughness of cut surfaces and its stress state. This paper is focused on the examination of the theoretical and real roughness of surfaces machined by sliding burnishing. In determining the theoretical roughness, the surface structure created by the pre-burnishing cutting (turning) was also considered. Two different modelling methods were used to obtain theoretical surface roughness data: CAD-modelling and finite element simulation. A method using CAD-based modelling of the machined surface was used to determine the theoretical roughness for both the turning and burnishing processes. However, this previously developed model is not directly applicable to plastic deformation processes such as diamond burnishing, so the principle of the Hertz theory for normal contact of elastic solids was used to calculate the penetration depth of the tool into the workpiece. The 2D FEM simulations were performed in the DEFORM software. To validate the applied modelling methods, real cutting experiments were performed, where the surface roughness values were measured during diamond burnishing experiments with different feed per revolution values. Based on the comparison of both applied modelling methods with real roughness data it can be stated that the theoretical roughness values are well approximated the real data.

Modeling, simulation, and prediction of surface topography in two-dimensional ultrasonic rolling 7075 Al-alloy

Two-dimensional ultrasonic rolling (TDUR) is a kind of surface finishing and deformation strengthening technology, which can improve the surface quality and reduce the surface roughness of the workpiece so as to improve its fatigue resistance. In order to study the formation process of the surface topography of 7075 Al-alloy treated by TDUR, a dynamic model of the rolling system was established based on the principle of TDUR to obtain the dynamic force of the roller on the workpiece during the rolling process. The penetration depth model of the workpiece surface under the action of the static load and longitudinal ultrasonic impact was constructed based on the Hertz contact theory and the metal elastic-plastic deformation theory. Then, the simulation model of surface topography was established using the space transformation theory based on the penetration depth model and the trajectory of the roller. Sequentially, the surface topography was reconstructed with the Z-map method. Using the simulation results, the axial profile curve data was extracted, and the surface roughness was calculated by the surface roughness calculation model. Finally, a designed TDUR experiment was carried out to verify the theoretical surface topography and roughness models. And it shows that the simulated surface topography and predicted roughness are in good agreement with the experimental results. The maximum relative error between the predicted roughness and the experimental results is no more than 9%. Under the experimental conditions, the turning marks can be almost eliminated when the static load Fs is 215 N. At this time, the surface profile height was about 1.5 μm, and the roughness Ra is 0.413 μm, which is 78% lower than that of turning. Therefore, the surface topography and surface roughness models proposed in this work can be used to effectively predict the surface topography and surface roughness of 7075 Al-alloy treated by TDUR.

Investigation of Optimum Grinding Condition Using cBN Electroplated End-Mill for CFRP Machining

Recently, carbon fiber reinforced plastics (CFRP) have been used in various applications such as airplanes and automobiles. In CFRP molding, there are unnecessary portions on the outer area. Therefore, a machining process is required to remove them. Cutting and grinding are conventionally used in the finish machining of CFRPs. End-milling allows the removal of most of these portions. However, uncut fibers easily occur during end-milling. In contrast, a precise machined surface and edge are easily obtained using a grinding tool. Therefore, this research has developed a novel cubic boron nitride (cBN) electroplated end-mill that combines an end-mill and a grinding tool. This is a versatile tool that can cut and grind CFRPs by changing the direction of rotation of the tool. In this study, the effectiveness of the developed tool is investigated. First, the developed tool machined the CFRP by side milling. Consequently, cBN abrasives that were fixed on the outer surface of the developed tool did not detach in certain cutting conditions. Next, in order to generate a sharp edge on the CFRP and restrict the increase in the CFRP temperature with the cBN electroplated end-mill, the optimum abrasive size and grinding condition were investigated through the design of experiments. Moreover, the effectiveness of the developed tool was verified by comparing it with a conventional tool. As a result, smaller burrs and uncut fibers were observed after final machining with the developed tool under the derived optimum condition than those with conventional tools. However, the desired surface roughness could not be achieved as required by the airline industry. Therefore, oscillating grinding was applied. In addition, the formula of the theoretical surface roughness while using the developed tool was derived using the theory of slant grinding. As a result, the oscillating condition that led to the required surface roughness was obtained by theoretical analysis. In addition, the required value for the airline industry was achieved by oscillating grinding.

A felületi érdesség CAD alapú modellezése nagytermelékenységű forgácsoló eljárásoknál

A cikkben ismertetésre kerülnek az EFOP-361-16-2016-00011 számú „Fiatalodó és megújuló Egyetem - Innovatív Tudásváros a Miskolci Egyetem intelligens szakosodást szolgáló intézményi fejlesztése” című projekt keretében a Gyártástudományi Intézetben elvégzett kutatásaink, amelyeknek a témája a felületi érdesség elméleti modellezése nagyteljesítményű forgácsoló eljárásoknál CAD modellezés segítségével. Ezen kutatásaink során elsősorban homlokmarással megmunkált felületek vizsgálatával foglalkoztunk, ahol az ún. forgácsarányt (az ap fogásmélység és az fz élenkénti előtolás arányát) az általánosan alkalmazott ap/fz>1 tartományból az ap/fz<1 felé változtattuk. Jelen dolgozat keretében bemutatásra kerül a kidolgozott módszer lényege, valamint az elvégzett vizsgálatokat foglaljuk össze röviden.

Novel geometrical design of turning inserts for high-efficiency smooth-surface high-chatter-stability cutting

This paper presents a novel geometrical design of inserts to realize high-efficiency smooth-surface high-chatter-stability turning. Inserts with a nose radius are used in turning to realize a smooth surface since the theoretical surface roughness Rth=f2/(8r) where f is the feed rate and r is the radius of the nose part. Since the size of the nose radius is limited because of the chatter stability, i.e. a large nose radius tends to cause chatter, the feed rate has to be kept small so that the acquired roughness is acceptable. Hence, the efficiency is limited. In this study, a novel turning insert geometry is proposed to realize high chatter stability along with a high efficiency and a smooth surface. The proposed insert geometry is verified by analyses and experiments.

Prediction of Tool Lifetime and Surface Roughness for Nickel‐Based Waspaloy

In recent years, most of nickel‐based materials have been used in aircraft engines. Nickel‐based materials applied in the aerospace industry are used in a wide range of applications because of their strength and rigidity at high temperature. However, the high temperatures and high strength caused by the nickel‐based materials during cutting also reduce the tool lifetime. This research aims to investigate the tool wear and the surface roughness of Waspaloy during cutting with various cutting speeds, feed per tooth, cutting depth, and other cutting parameters. Then, it derives the formula for the tool lifetime based on the experimental results and explores the impacts of these cutting parameters on the cutting of Waspaloy. Since the impacts of cutting speed on the cutting of Waspaloy are most significant in accordance with the experimental results, the high‐speed cutting is not recommended. In addition, the actual surface roughness of Waspaloy is worse than the theoretical surface roughness in case of more tool wear. Finally, a set of mathematical models can be established based on these results, in order to predict the surface roughness of Waspaloy cut with a worn tool. The errors between the predictive values and the actual values are 5.122%∼8.646%. If the surface roughness is within the tolerance, the model can be used to predict the residual tool lifetime before the tool is damaged completely. The errors between the predictive values and the actual values are 8.014%∼20.479%.

Surface topography analysis of ball end milled tool steel surfaces

Many mechanical components require mirror–like surface appearance. When the application concerns the manufacturing of steel dies and moulds, material removal processes are the preferential choice in order to achieve the wanted dimensions and surface topography. In particular, ball milling is used in all those cases that require the machining of free form surfaces. When mirror-like surface appearance is in focus in such components, the final machining operations consists in a very shallow cut. The theoretical surface roughness (kinematic surface topography) that can be achieved in a finishing operation by ball end milling is orders of magnitude below the actual surface roughness. Beside runout and machine tool positioning errors, the quality of the cutting tools is a key factor in determining the surface topography. The combination of shallow depth of cut together with the finite size of the cutting edge radius of the tool are responsible for the occurrence of material smearing phenomena. Smearing, consisting in the accumulation of plastically deformed material over the surface, is particularly detrimental for the aesthetic functionality of machined components because it is responsible of the “foggy” appearance. In order to minimize the occurrence of the smeared material it is necessary to have a good understanding of the causes of the smearing formation process. The aim of this paper is the description and quantification of the smearing phenomena for ball end milling operations. The location of the smeared material is determined through SEM image analysis and related with the direction of the cutting speed and milling strategy. Subsequently the volume of the smeared material is quantified through a combination of confocal microscopy and SEM image analysis. Based on the volumetric analysis of the smeared material a new method for determining the Minimum Uncut Chip Thickness for the material is proposed.

Surface roughness prediction model of SiCp/Al composite in grinding

Grinding is significant for hard and brittle material machining, and it has been applied in particle reinforced composites machining for higher surface quality. In this paper, surface characteristics of SiCp/Al composite in grinding was observed by the surface profiler and SEM. The Rayleigh distribution function was adopted to model the randomness of abrasive grains by assuming that the chip thickness for a single grain conforms to the distribution. The theoretical surface roughness model of aluminum alloy and silicon carbide were established based on the expectation idea. The surface roughness prediction model of SiCp/Al composite was established by the combination of theoretical surface roughness model of aluminum alloy and silicon carbide. Different combination modes were tried and the exponential composition function proved the best, the coefficients of the function were fitted by the experimental surface roughness. Rapid Non-dominated Sequencing Genetic Algorithm (NSGA-II) was adopted to optimize grinding process parameters of SiCp/Al composite considering grinding efficiency and surface roughness. It indicated that the experimental results were in good agreement with the prediction model. The surface roughness prediction model of SiCp/Al composite is helpful to improve surface quality in grinding.

Pressure variation of developed lapping tool on surface roughness

Improving the surface roughness is always one of the major concerns in the development of lapping process as high precision machining caters a great demand in manufacturing process. This paper aims to investigate the performance of a newly designed lapping tool in term of surface roughness. Polypropylene is used as the lapping tool head. The lapping tool is tested for different pressure to identify the optimum working pressure for lapping process. The theoretical surface roughness is also calculated using Vickers Hardness. The present study shows that polypropylene is able to produce good quality and smooth surface roughness. The optimum lapping pressure in the present study is found to be 45 MPa. By comparing the theoretical and experimental values, the present study shows that the newly designed lapping tool is capable to produce finer surface roughness.

Non-Linear Modelling of roughness parameters in finish turning of EN31 high carbon steel

In machining operation, selection of cutting parameters is very crucial to control the required surface quality. In fact, the theoretical and real surface roughness is distinguished by the influence of various machining parameters like cutting speed, feed rate, and nose radius of cutting tool. The focus of this study is to analyse the surface roughness in dry turning of high carbon steel by varying the feed rate, cutting speed and tool nose radius. A nonlinear quadratic model is suggested that best describes the variation of surface roughness with major contribution of feed rate and then followed by interaction effect between feed rate and tool nose radius. The suggested surface roughness model is mapped within the boundaries of specified cutting parameters suitable for finishing operations.

Theoretical models for surface roughness in turning considering inclination and rake angles

New analytical four-parameter models for surface roughness are proposed based on the feed rate, nose radius as well as the inclination and rake angles. These models were derived to determine the maximum peak-to-valley roughness Rt and arithmetic average roughness Ra using homogeneous transformation matrices and are verified by digital simulation. The model for Rt was used to study two sequential effects of introducing the inclination and rake angles. The Rt and Ra values obtained from the four-parameter models and the existing two-parameter models, based on nose radius and feed rate, were compared. The comparison shows maximum percentage differences of 8.18% and 10.98% in Rt and Ra, respectively. The results demonstrate that the inclination and rake angles can influence the surface roughness by affecting the tool-workpiece contact geometry. The proposed four-parameter model can be employed for a more accurate theoretical surface roughness evaluation compared to the existing two-parameter models.