Prediction Of Surface Topography Research Articles

Advanced process design for re-contouring using a time-domain dynamic material removal simulation

The repair of components often requires the removal of excess weld material. This removal is considered as re-contouring. Re-contouring processes have to be designed individually for each case of damage to fulfil the high quality requirements. Therefore, a prognosis of the machined surface topography is crucial. The material removal simulation introduced in this paper allows the prediction of process stability and surface topography for 5-axis ball end milling including dynamic effects. Different process strategies for re-contouring of Ti-6Al-4V welds are examined. It is shown, that selecting suitable process parameters can lead to high surface quality while maintaining productivity.

Prediction of surface topography due to finite pixel spacing in focused ion beam milling of circular holes and trenches

Successful implementation of focused ion beam technologies in fabrication of practically important structures, including circular holes and trenches requires evaluating the ion dose delivered to the specimen by the beam and subsequently predicting the formed topography. In this article, the analytical expressions for the ion dose are obtained in polar coordinates using Bessel functions. These expressions can be transformed into relatively straightforward formulas useful in many applications. On the basis of the expressions derived, the surface shape of structures under consideration is analytically described if constant sputtering yield conditions are realized throughout the milling process. For practically relevant structure preparation, when the distance between neighboring beam stops is less than approximately two beam diameters, it was established that the mean depth and the peak-to-valley surface roughness can be evaluated by simple formulas. The outcomes of theoretical findings are confirmed by the comparison with the numerically obtained results and experimental data retrieved from the fabricated circular holes.

Modeling and prediction of surface topography and surface roughness in dual-axis wheel polishing of optical glass

Abstract It is rather difficult to achieve uniform surface texture and high convergence rates of surface roughness (CRSR) at the same time in the conventional optical polishing process. The dual-axis wheel polishing (DAWP) technology, which uses a semi-rigid wheel with combined dual-axis rotational movements, shows a strong capability directly changing the rough ground surface status down to mirror status with nanometer level surface roughness, and achieving a uniform and smooth surface texture. In order to provide a better scientific understanding of the surface texture generation in DAWP process, in this paper, two comprehensive mathematical models are proposed. The first model is to predict the generation of micro-topography and roughness within single-axis TIF (tool influence function) area, based on the abrasive wear theory, abrasives distribution investigation and accumulative removal theory. On the basis of this model, another surface micro-topography generation model is also built to predict the micro-topography and roughness generated on workpiece surface in actual DAWP process (both for single and dual-axis modes). A series of fixed spot polishing tests and uniform polishing tests on BK7 glass were carried out to analyze the influence of polishing parameters and motion modes on the generated surface texture and roughness. The measurement results show that the surface micro-topography and roughness within TIF area and on polished surface can be well predicted by the two models. After actual polishing process, the dual-axis mode tends to produce much lower surface roughness with uniform texture. The single-axis mode tends to generate directional surface textures with relatively higher surface roughness. Under the dual-axis mode, the variation of co-rotating speed has less influence on the polishing quality, very high CRSR and uniform texture can be achieved under different co-rotating speeds.

Modeling and prediction of surface topography with three tool-work vibration components in single-point diamond turning

In single-point diamond turning (SPDT), the relative vibration between the tool and the workpiece plays an important role in the surface generation, therefore affecting the achieved surface quality. In this paper, a surface roughness prediction model is developed under the synthetically consideration of the influences of tool-work vibration components in feeding, cutting and infeed cutting directions, on surface topography in SPDT. This study makes a theoretical investigation on the effects of three vibration components on tool locus to build a modification method for the actual tool locus. Due to the existence of tool interference induced by tool-work vibrations, two judgment criterions and an iterative calculation methodology are proposed to efficiently confirm the valid tool locus points so as to make a more precise prediction on the diamond turned surface. A series of experiments are conducted to verify the surface roughness prediction model. The experimental results show that the predicted surface roughness agrees well with the measured ones. This indicates that the developed model with three direction vibrations makes a better prediction for the single diamond turned surface.

Model for surface topography prediction in mirror-milling of aircraft skin parts

As a new technology of aircraft skin processing, mirror-milling is an efficient and green processing technology, which is a gradually developmental substitute for chemical milling. The purpose of this research aims to study surface topography forming mechanism and the effect of support location on the surface topography forming in mirror-milling of aircraft skin parts. A new iterative workpiece deformation prediction model is proposed for mirror-milling error prediction of low-rigidity parts. In addition, the workpiece surface topographies are predicted and verified at different support locations. The results of the study are summarized: under the same processing parameters, the machined surface topographies with different characteristics are obtained only by changing the relative position between the support head and the milling head. The support location is the key parameter of reducing the workpiece deformation error.

Prediction of surface topography in precision hard machining based on modelling of the generation mechanisms resulting from a variable feed rate

The paper presents an original contribution to the prediction of surface topography produced by precision hard turning operations using CBN cutting tools and the variable feed rate of 0.025–0.075 mm/rev. The differences between theoretical and real surface roughness parameters Rz and Sz are quantified in terms of springback effect, additional smoothing of irregularities and side flow effect. The primary experimental study includes measurements of 2D and 3D surface roughness parameters using contact profilometer. Correspondingly, cutting forces were measured using a piezoelectric dynamometer, and based on this data, specific corresponding values of ploughing energy and friction coefficient were determined. It was found that the measured value of maximum height of the surface Sz differs from the theoretical value mainly due to elastic recovery of the machined surface and the smoothing effect at the lower feeds and the elastic recovery and the side flow effect at the higher feeds employed. An empirical model for the prediction of the Sz value in function of the feed rate is derived. The prediction accuracy can be improved by advanced numerical modelling of surface generation mechanisms and associated distortions.

Model for the prediction of 3D surface topography and surface roughness in micro-milling Inconel 718

Nickel-based superalloy Inconel 718 retains high strength at high temperature, which meets the requirements of micro-parts in the fields of aerospace, energy, and power. However, Inconel 718 is a kind of difficult-to-machine material. During the micro-milling process, scale effect, multiple regenerative effect, and dynamic response all affect its surface roughness, causing the prediction of surface roughness of micro-milled parts difficult. To solve this problem, we study the predictive modeling of surface roughness of micro-milled Inconel 718. Based on the previously built instantaneous cutting thickness model, cutting force model, and the dynamic characteristics of micro-milling system, the authors establish a flexible deformation model of micro-milling cutter generated by cutting force. Since the machined surface is generated by duplicating the tool profile on the workpiece surface, and based on the actual cutting trajectory as well as flexible deformation of micro-milling cutter, the authors build the surface topography simulation model to predict surface roughness and conduct experiments to verify the accuracy of the model. The research realizes the prediction of surface roughness of micro-milled Inconel 718 parts and partially reveals the machining mechanism of micro-milling.

Cutter workpiece engagement region and surface topography prediction in five-axis ball-end milling

ABSTRACTBased on the machining tool path and the true trajectory equation of the cutting edge relative to the workpiece, the engagement region between the cutter and workpiece is analyzed and a new model is developed for the numerical simulation of the machined surface topography in a multiaxis ball-end milling process. The influence of machining parameters such as the feed per tooth, the radial depth of cut, the angle orientation tool, the cutter runout, and the tool deflection upon the topography are taken into account in the model. Based on the cutter workpiece engagement, the cutting force model is established. The tool deflections are extracted and used in the surface topography model for simulation. The predicted force profiles were compared to the measured ones. A reasonable agreement between the experimental and the predicted results was found.

Grinding performance of textured monolayer CBN wheels: Undeformed chip thickness nonuniformity modeling and ground surface topography prediction

Abstract The ground surface roughness and topography are commonly used to characterize the surface finishing. In the application of textured monolayer CBN wheels, the nonuniformity of wheel topology will render a nonuniform undeformed chip thickness which greatly affects the ground surface. In order to predict the ground surface topography more accurately and efficiently, grinding experiment has been conducted in the current study, with measured grinding wheel topology. The measured surface topology of textured monolayer CBN wheels has been reconstructed by using the Johnson transformation and its inverse transformation. The influence of wheel topology evolution on the undeformed chip thickness nonuniformity has been determined with an improved model. It has been found the ground surface roughness is improved with a continuous reducing undeformed chip thickness nonuniformity. The percentage of active grains, the mean value and standard deviation of undeformed chip thickness have been found the main factors in determining the surface roughness. The reconstructed wheel surface topology has been used to predict the workpiece topography in different stages of the grinding process.

3D surface topography analysis in 5-axis ball-end milling

This article presents a new analytical model to predict the topography and roughness of the machined surface in 5-axis ball-end milling operation for the first time. The model is able to predict the surface topography and profile roughness parameters such as 3D average roughness (Sa) and 3D root mean square roughness (Sq) by considering the process parameters such as the feedrate, number of flutes, step-over and depth of cut as well as the effects of eccentricity and tool runout in 5-axis ball-end milling. This model allows to simulate the effects of the lead and tilt angles on the machined surface quality in the virtual environment prior to the costly 5-axis machining operations. The effectiveness of the introduced surface topography prediction model is validated experimentally by conducting 5-axis ball-end milling tests in various cutting conditions.

Prediction of surface topography due to finite pixel spacing in FIB milling of rectangular boxes and trenches

For applying focused ion beam technologies in fabrication of the predetermined structures it is essential to evaluate the ion dose delivered to the specimen by the beam and on this basis to predict the formed topography. In this article the authors obtain exact expressions for the ion dose distribution arising in the irradiated region when trenches and rectangular boxes are milled. Based on them the authors describe the surface shape of the structures under consideration when the constant sputtering yield conditions are realized during the milling process. The rather cumbersome analytical description can be transformed into the simple form for milled regions at the distance slightly exceeding the beam diameter from the structure boundaries. Within this region the milled surface shape can be represented as a sum of sinusoidal functions analogous to one- or two-dimensional Fourier series. For typical structure fabrication when the distance between neighboring beam stops is less than approximately two beam diameters the authors derive simple formulas for evaluating the mean depth and the peak-to-valley surface roughness. The authors also estimate when constant sputtering yield conditions can be utilized for the description of the actual milling process. To testify the theoretical considerations two trenches and four rectangular boxes were prepared. In addition, several deep and shallow dotlike structures were created for evaluating the ion flux density determining the beam shape, which was presented as the sum of two Gaussian functions. Peripheral regions of the deep dots cross-sections allow us to find the standard deviation of the second Gaussian function while the standard deviation of the first Gaussian function and the weight factor are retrieved using the milling profiles of the shallow dots. A set of parameters describing the ion flux density of the beam and milling process enables calculating the surface shapes and cross-sectional profiles of the fabricated structures. The authors show that the simulated shapes of the trench and the box and scanning electron microscope images of these structures are similar in appearance. Comparison of experiment and theoretical milling profiles demonstrates good agreement between them. Theoretically estimated mean depth and peak-to-valley surface roughness are consistent with experimental data.

Solid subtraction model for the surface topography prediction in flank milling of thin-walled integral blade rotors (IBRs)

Current CAM and milling verification software packages are not ready to predict form and surface errors derived from non-ideal conditions such as runout tool error or tool–workpiece flexibility. As a consequence, high-end parts like integral blade rotors (IBR) suffer from this lack of estimation to achieve a sound manufacturing process preparation. This work describes the implementation of a cutting force prediction model that introduces the radial engagement reduction caused by (i) tool runout and (ii) workpiece flexibility. The model is used as the seed for a calculation module based on solid modeling to obtain the surface roughness and topography applying the cutting force–wall restitution equilibrium, making use of the power of CAM solid modelers for the final topography definition. This idea takes advantage of the good accuracy of current solid modelers in comparison with the z-map topographical approach for obtaining the cutter–workpiece engagement (CWE) at each tool path step. Several flank milling tests were carried out to validate the simulations. The results demonstrated a significant level of accuracy to predict shape errors. The model may be integrated in a CAM procedure, and it is a useful utility for reducing deformation on the manufacturing of blisks and impellers.

Analysis of chip morphology and surface topography in modulation assisted machining

Modulation assisted machining (MAM), superimposing a controlled tool modulation in the feed direction of conventional machining process, can change the chip morphology and the surface topography of machined components, and finally affect the functional performances of the components. This paper is dedicated to gaining a better understanding of the chip and surface formation processes in MAM. Geometrical analysis of the tool path in face turning configuration with MAM is performed, revealing how discrete chips are generated and presenting the effects of modulation conditions on chip morphology and undeformed chip thickness. Based on the chip formation analysis, an analytical model for prediction of surface topography is developed, which takes into account tool geometries, cutting conditions, modulation conditions and the effects of plastic side flow. By using the proposed model, the influences of modulation conditions on surface topographies are shown qualitatively by laser microscope, and are analyzed quantitatively through a set of three-dimensional (3D) surface amplitude parameters. Finally, a series of turning experiments is carried out to verify the prediction of surface topography. Errors between the measured results and the predicted results are within 20% for most conditions, and the underlying sources of these errors are analyzed. This paper can serve as a theoretical basis for the further controlling of chip morphology and surface topography.

Surface generation of freeform surfaces in diamond turning by applying double-frequency elliptical vibration cutting

A new freeform surface generation method for the difficult-to-cut materials is proposed in this paper. Fast tool servo and slow slide servo diamond turning are the main generation technologies for freeform surfaces, whereas they cannot machine the freeform surfaces of difficult-to-cut materials very effectively. On the other hand, elliptical vibration cutting has demonstrated its excellent performance in material processing, especially for the difficult-to-cut materials. Nevertheless, it is unable to generate the freeform surfaces very successfully. Therefore, this paper proposes the double-frequency elliptical vibration cutting method for the freeform surface diamond machining on the difficult-to-cut materials, which provides the high-frequency elliptical vibration to improve the machinability in material removal and the low-frequency reciprocating movements for the freeform surface profile generation. The relative movements between the tool and the workpiece are analyzed, and because of the Y direction elliptical vibration, the cutting plane does not always cross the workpiece center, which makes the tool path generation, the tool geometry selection and the surface topography prediction very different from those in the conventional fast tool servo or slow slide servo diamond turning. A new tool path generation method is proposed, and the selection of the tool geometry parameters is discussed. The surface generation process is analyzed, based on which the topography model for the machined surfaces is constructed. Three typical freeform surfaces are machined on the die steel workpieces, which verifies the feasibility of the proposed tool path generation strategies. In addition, the experimental results agree well with the surface topography predictions, which validates the effectiveness of the topography model. This model also applies to the diamond turning processes with tool motion in the Y direction, such as turning with EVC.

A method of measuring tool tip vibration in turning operations

The tool tip vibration measurement has a great significance for online surface topography prediction and active vibration control. Many measurement methods have been developed. However, most of these methods are difficult to be applied in actual machining process for the following problems: the chips and cutting fluid will cause damage to the sensor or distort its measurement results and the sensor must be installed again when replacing the cutting tool. In order to overcome the above problems, this paper proposes an indirect measurement method: the vibration of the tool tip is obtained from the vibration of the measurement point on the turret. The relationship between the tool tip vibration and the turret measurement point vibration is obtained through impact tests. The vibration of the measurement point on the turret is measured via an accelerometer, which is easy to install. The measurement point is so far away from the cutting area and chip evacuation zone that the accelerometer and its measurement results will not be affected by the chips and cutting fluid. The accuracy of the measurement method is checked by comparing the calculated tool tip vibration calculated from the vibration of the turret measurement point to the directly measured results, which is measured via an accelerometer installed below the tool tip. The comparison results show that the calculated tool tip vibration at main frequencies as well as low frequencies has a high accuracy. Moreover, the effectiveness of the measurement method is verified through machined surface profile.

Model for Surface Topography Prediction in Cylinder Turning

In turning process, the volumetric errors of lathe are incarnated as the displacement between tool and workpiece, and finally mapped to the turning surface. It leads to the ups and downs of the workpiece surface topography. Therefore, the volumetric errors of lathe attach great importance to the turning surface quality. In this paper, a model for surface topography prediction in cylinder turning considering volumetric errors is proposed. It allows the topography and the roughness values of turning cylinder to be predicted. Some simulation experiments are also carried out to analyze the effect of volumetric errors on the quality of turning cylinder in this paper.

Predicting machined surface topography based on high definition metrology

This paper aims to predict the three-dimensional surface topography for future machined parts based on high definition metrology (HDM). HDM can measure the 3D topography of previously machined surfaces with high resolution and large field of view, containing rich spatial-temporal information of the machined surfaces. Therefore, a space-time autoregressive integrated moving average (STARIMA) model is adopted to describe the spatial-temporal characteristics and predict the future surface. The model was validated by an experiment on the engine block face milling process. The results show a good agreement between the predicted surface and the real surface with an average forecast error of 0.181 micrometer for an area with 80×80 sites. The proposed surface topography prediction method can be used for the early warning of surface quality deterioration and pre-control of the manufacturing process.

Surface plastic deformation and surface topography prediction in peripheral milling with variable pitch end mill

Peripheral milling with variable pitch end mills is available to improve the surface integrity during final machining. Among the indicators of surface integrity, surface plastic deformation and surface topography are the foremost characteristics. In this paper, two main aspects are included. On the one hand, a unique generic technique in terms of depth of plastic deformation, plastic strains distribution for analyzing the plastic deformations on the work piece is presented. The presented technique applies the problem of the Flamant–Boussinesq in the plastic deformation problem. Through experimental verification, the analytical results have a higher accuracy. On the other hand, the surface generation mechanism in peripheral milling with variable pitch end mills is studied. Corresponding surface generation model, which is used to predict the generated surface topography with incorporating the cutting process parameters and several sources of machining error such as tilting, run-out, deflection of the tool and work piece displacement, is proposed. Through a set of cutting tests, it is confirmed that the presented model predicts the surface texture and roughness parameters precisely. By the sensitivity analysis, Helix angle and feed rate have significant influences on surface topography, while the effects of cutting speed on surface topography can be neglected when the effects of the machining error sources on the behavior and performance of the model are not considered. Among the sources of machining errors, the deflection of the tool has the most significant impact on the surface profile. The sequence is the displacement of the work piece and the run-out of the tool.

Simultaneous prediction of surface topography and surface location error in milling

The machined surface topography, surface roughness and surface location error are very important evaluation indexes for machining quality, which directly affect the performance characteristics of the machined workpiece. In this paper, a new model of the arbitrary point of the cutter edge with respect to the arbitrary frame of the machining feature point is built. The proposed model incorporates the surface location error into the relative motion of the cutter with respect to the workpiece using the harmonic balance methods. Further, a nonlinear programming problem is proposed to obtain the scallop value of an arbitrary point on the nominal machined surface. Since the obtained scallop value of each point can be used for constructing the topography of the machined surface as well as calculating the surface roughness, the proposed model can simultaneously predict the surface topography, surface roughness and surface location error. Simulations and experiments indicate that feed per tooth, runout and number of cutter teeth are vital factors influencing the topology of the machined surface. The surface location error of the cutter due to the number of cutter teeth is an essential factor that influences the parallelism or perpendicularity of the machining feature. The effectiveness and feasibility of the proposed method is verified by a machining example.

Study of cutting force in ultra-precision raster milling of V-groove

Cutting force plays an important role in the design of cutting plans, setting of cutting conditions, inspection of tool wear, and prediction of machined surface topography. As no previous research has focused on cutting force in ultra-precision raster milling (UPRM), this paper presents a theoretical and experimental study on cutting force modeling in UPRM of V-groove. An analytic cutting force model is established to predict the cutting force components both in the feed direction and thrust direction, and a dynamic model is developed to simulate the free vibration signal induced by the cutting force pulse. The effects of cutting parameters in UPRM are studied, including the depth of cut and feed rate, and a group of experiments conducted to verify the simulation results. The simulation and experimental results show that cutting force in UPRM is figured as a force pulse followed by a free vibration signal induced by the force pulse and that the amplitudes of cutting force in both feed direction and thrust direction increase with the growing depth of cut and feed rate.