Surface Generation Model Research Articles

The simulation of surface topography generation in multi-pass sanding processes through virtual belt and kinetics model

Belt sanding is an effective manner of material processing and widely used to improve the surface roughness and obtain high polishing glossiness. During the belt sanding process, the contact condition exhibits more complexity than grinding due to the flexibility of the belt. For the sanding application where surface glossiness is expected, it always involves multiple sanding as well as polishing passes. This makes the analytical modeling of the surface generation as well as its impact on glossiness formation complicated in this multi-pass operation. In this paper, the surface generation model for multi-pass sanding operation is established through the development of the virtual sanding belt model and the multi-pass kinematics simulation of the sanding process. As for the belt-workpiece contact zone, the 3D Hertz contact model is incorporated into the kinematics simulation to duplicate the real contact condition for multi-pass sanding. Furthermore, the critical surface topography parameters are identified to establish the correlation with belt sanding parameters. Finally, surface topography parameters related with glossiness properties, e.g., surface roughness Sq, surface height distribution kurtosis Ku, surface height distribution skewness Sk, and surface correlation lengths Lx and Ly, are studied for optimal sanding process parameter analysis. The optimal sanding condition for ideal glossiness should be that the rotation speed should be beyond 1200 r/min, and the workpiece feedrate should be below 50 mm/s.

Three-dimensional modelling and simulation of vibration marks on surface generation in ultra-precision grinding

Nowadays, most modelling work for ground surface topography is based on either abrasive kinematics (micro-level) or high-frequency vibration of the grinding wheel (macro-level) to predict surface quality or grinding performance, but there is a lack of a correlation model to relate these two levels together. In this research work, wheel shape with two radii and wheel synchronous vibration are modelled first for the interference of the tool edge in 3D space to reveal the evolution mechanism of surface waviness under different vibration conditions (phase shift from 0.0 to 1.0). Hence, a multi-scale model is established considering the diverse protrusion heights of the grits and incorporating the wheel shape and micro-vibration of the tool so as to explain the mechanism of the generation of the surface marks on the ground surface. The result shows that four principal residual marks are formed on the ground surface including spirals, tool feed marks, cumulative phase marks and abrasive grain scratches. The amount of surface waviness resulting from the tool unbalance is equal to the ratio of the rotating speed of the grinding wheel and the workpiece. The feed mark representing the tool locus and tool nose geometry is a spiral pattern from edge area to the machined center. The phase shift marks are caused by the phase accumulation effect. The grit scratches are related to the wheel geometry, kinematics and distribution of protrusion heights. In addition, the phase shift tends to increase the density of grinding marks, with a significant decrease when the phase shift is equal to 0.5. The surface generation model is further verified by a closed surface matching method, which shows the simulation results agree reasonably well with the grinding experiments.

Development of a multi-jet polishing process for inner surface finishing

High-precision inner surfaces are difficult to be machined to a sufficiently high surface quality. This paper presents the development of a novel multi-jet polishing process for precision polishing of inner surfaces through adopting a rod-shaped nozzle designed with a linear array of orifices at its side face. The material removal characteristic on inner cylindrical surface was modelled based on computational fluid dynamic method. Four groups of material removal experiments were conducted to validate the proposed material removal model and investigate its material removal characteristics. Moreover, the surface generation model was also developed and validated based on the material removal model. A series of polishing experiments were conducted on 304 stainless steel cylindrical inner surfaces. The results show that the proposed multi-jet polishing process with the newly designed nozzle is able to achieve high efficiency and precision inner surface finishing on the inner surface.

A simple setup for episcopic microtomy and a digital image processing workflow to acquire high-quality volume data and 3D surface models of small vertebrates

The use of volume data and digital three-dimensional (3D) surface models in biology has increased quickly and steadily. Various methods are available to acquire 3D data, among them episcopic imaging techniques. Based on the episcopic microscopy with on-block staining protocol of Weninger et al. (Anat Embryol 197:341–348, 1998), we describe a simple and versatile setup for episcopic microtomy. It is composed of a consumer DSLR digital camera combined with standard histology equipment. The workflow of block surface staining and imaging, image processing, stack alignment, surface generation (including a custom Amira® macro), and 3D model editing is described in detail. For our sample specimen (Alytes obstetricans; Amphibia: Anura) we obtained images with a pixel size of 5.67 × 5.67 µm2. The generated image stacks allowed distinguishing different tissues and were well-suited for creating a 3D surface model. We analyzed the alignment quality achieved by various selections of specimen and fiducial marker spots. The fiducial spots had a significant positive effect on the alignment quality with the best alignment having a maximum mean alignment error of about 44.7 µm. We further tested the APS-C camera with combinations of macro lens, extension tube or teleconverter. The macro lens and extension tube yielded the smallest pixel size of 2.53 × 2.53 µm2. Considering data quality and resolution, and depending on object sizes and research goals, DSLR captured episcopic microtomy can be an alternative to other techniques, such as traditional histological sectioning or micro-computed tomography.

Stochastic Analysis of Microgrinding Tool Topography and Its Role in Surface Generation

With the rising trend of miniaturization in modern industries, micro manufacturing processes have made a significant position in the manufacturing domain. Demands of high precision along with super finish of the final machined product have started rising. Grinding, being largely considered as a finishing operation, has large potential to cater to such requirements of micro manufacturing. However, stochastic nature of the grinding wheel topography results in a high degree of variation in the output responses especially in the case of microgrinding. With an aim to obtain a good and predictable surface finish in brittle materials, the current study aims at developing a surface generation model for wall grinding of hard and brittle materials using a microgrinding tool. Tool topographical features such as grit protrusion height, intergrit spacing, and grit distribution on the tool tip of a microgrinding pin have been calculated from the known mesh size of the grits used during tool manufacturing. Kinematic analysis of surface grinding has been extended to the case of wall grinding and each grit trajectory has been predicted. The kinematic analysis has been done by taking into consideration the effect of tool topographical features and the process parameters on the ground surface topography. Detailed analysis of the interaction of the grit trajectories is done to predict the final surface profile. The predicted surface roughness has been validated with the experimental results to provide an insight to the surface quality that can be produced for a given tool topography.

Fluid jet-array parallel machining of optical microstructure array surfaces.

Optical microstructure array surfaces such as micro-lens array surface, micro-groove array surface etc., are being used in more and more optical products, depending on its ability to produce a unique or particular performance. The geometrical complexity of the optical microstructures array surfaces makes them difficult to be fabricated. In this paper, a novel method named fluid jet-array parallel machining (FJAPM) is proposed to provide a new way to generate the microstructure array surfaces with high productivity. In this process, an array of abrasive water jets is pumped out of a nozzle, and each fluid jet simultaneously impinges the target surface to implement material removal independently. The jet-array nozzle was optimally designed firstly to diminish the effect of jet interference based on the experimental investigation on the 2-Jet nozzles with different jet intervals. The material removal and surface generation models were built and validated through the comparison of simulation and experimental results of the generation of several kinds of microstructure array surfaces. Following that, the effect of some factors in the process was discussed, including the fluid pressure, nozzle geometry, tool path, and dwell time. The experimental results and analysis prove that FJAPM process is an effective way to fabricate the optical microstructure array surface together with high productivity.

Theoretical and experimental investigation of surface generation in swing precess bonnet polishing of complex three-dimensional structured surfaces

Three-dimensional structured surfaces (3D-structured surfaces) possessing specially designed functional textures are widely used in the development of advanced products. This paper presents a novel swing precess bonnet polishing (SPBP) method for generating complex 3D-structured surfaces which is accomplished by the combination of specific polishing tool orientation and tool path. The SPBP method is a sub-aperture finishing process in which the polishing spindle is swung around the normal direction of the target surface within the scope of swing angle while moving around the center of the bonnet. This is quite different from the ‘single precess’ and ‘continuous precessing’ polishing regime, in which the precess angle is constant. The technological merits of the SPBP were realized through a series of polishing experiments. The results show that the generation of complex 3D-structured surfaces is affected by many factors which include point spacing, track spacing, swing speed, swing angle, head speed, tool pressure, tool radius, feed rate, polishing depth, polishing cloth, polishing strategies, polishing slurry, etc. To better understand and determine the surface generation of complex 3D-structured surfaces by the SPBP method, a multi-scale material removal model and hence a surface generation model have been built for characterizing the tool influence function and predicting the 3D-structured surface generation in SPBP based on the study of contact mechanics, kinematics theory, abrasive wear mechanism, and the convolution of the tool influence function and dwell time map along the swing precess polishing tool path. The predicted results agree reasonably well with the experimental results.

Modeling the Influence of Tool Deflection on Cutting Force and Surface Generation in Micro-Milling

In micro-milling, cutting forces generate non-negligible tool deflection, which has a significant influence on the machining process and on workpiece accuracy. This paper investigates the tool deflection during micro-milling and its effect on cutting force and surface generation. The distribution of cutting forces acting on the tool is calculated with a mathematical model that considers tool elasticity and runout, and the tool deflection caused by the cutting forces is then obtained. Furthermore, an improved cutting force model and side wall surface generation model are established, including the tool deflection effect. Both cutting force and surface simulation models were verified by the micro-end-milling experiment, and the results show a very good agreement between the simulation and experiments.

Surface Generation Modelling for Micro end Milling Considering the Minimum Chip Thickness and Tool Runout

Surface roughness is considered as one of the significant factors on the quality and functionality of micro components. Considering that in micro milling feed per tooth and uncut chip thickness are very small compared to those in conventional milling, it is necessary to study surface generation precisely in micro scale. This paper proposes a surface generation model for micro-end-milling process, where the effect of the minimum chip thickness (MCT) and tool runout are considered. The MCT values were determined through finite element simulations for AISI 1045 steel, and the magnitude of the tool runout in machining rotational speed was obtained by displacement measurement using capacitive sensors. Based on the proposed model, the influence of the tool runout, MCT as well as the tool geometric parameters on the surface generation was studied. Finally, simulation results were compared with experimental data and a good agreement was obtained.

Modelling and prediction of the effect of cutting strategy on surface generation in ultra-precision raster milling

This paper studies the effect of cutting strategy on surface generation in ultra-precision raster milling (UPRM). By adding the influences of shift length and tool-interference on surface generation, a holistic surface roughness prediction model is built which takes into account the effect of cutting parameters, tool path generation, geometry parameters of diamond tool, the size of the workpiece and machine characteristics. The optimal shift ratio can be achieved by changing factors involved in developing cutting strategy to improve surface quality without decreasing machining efficiency. Conditions for the presence of tool-interference in UPRM are presented. Based on the holistic surface generation model, an integrated system is developed to automatically generate the numerical control program, and predict surface quality and machining efficiency. A series of cutting experiments has been conducted to verify the proposed surface generation model and test the performance of the integrated system. The experimental results agree well with the predicted results from the model and the integrated system.

A theoretical and experimental investigation of material removal characteristics and surface generation in bonnet polishing

This paper presents a theoretical and experimental investigation which attempts to provide a better scientific understanding of the material removal characteristics and surface generation in bonnet polishing. The experimental results reveal that the material removal is shared by the polishing pad and the abrasives trapped in the pad-workpiece interface, and the abrasive wear is dominated significantly by plastic removal mode of abrasive particles, while the material removal caused by the polishing pad should be mitigated in order to obtain super mirror finished surfaces. The surface generation is found to be a linearly cumulative effect of dwell time together with the constant material removal rate under the identical polishing condition. Hence, a multi-scale material removal model and a surface generation model have been built based on the contact mechanics, kinematics theory, abrasive wear mechanism, as well as the relative and cumulative removal process of surface generation in bonnet polishing. The models are verified through a series of spot and pattern polishing experiments. Based on the results of spot polishing experiments, the multi-scale material removal model is found to predict well for the material removal characteristics under various polishing conditions. The simulated patterns by the surface generation model are found to agree well with the measured patterns in the pattern polishing experiments which substantiate that the relative and cumulative removal process is a key surface generation mechanism in bonnet polishing.

Spindle vibration influencing form error in ultra-precision diamond machining

Ultra-precision diamond machining (UPDM) is widely used to manufacture high quality surface within sub-micrometric form error and nanometric surface roughness due to its high efficiency and low cost. However, in a complex UPDM process, many factors affect such sub-micrometric form error. Especially, spindle vibration produces a significant impact upon surface generation, not only influencing nanometric surface roughness, but also affecting sub-micrometric form error. In this study, a five-DOF dynamic model is established for spindle vibration in UPDM. The form error under spindle vibration is discussed with a surface generation model. The results show that (i) axial, radial, and coupled-tilting spindle vibration makes a great contribution to form error; (ii) the coupled-tilting frequencies are influenced by spindle speed; and (iii) the spindle vibration is reproduced at a machined surface to generate regular patterns consequently to cause form error, which is well identified with a focus on axial spindle vibration by face turning in UPDM. Its wavelength is linearly proportional to spindle speed and cutting radius distance, i.e. cutting speed. Significantly, the proposed models provide a possibility to predict surface roughness and form error under spindle vibration.

Milled Surface Affected by Damping Effect of Cross Edge and Flank Profiles of an End Mill

This paper proposes a surface generation model based on a fast and comprehensive time domain solution which simulates regenerative vibrations as well as an interaction of cross edge and flank profiles with the undulation of machined surface. Depending on the profiles of the cutter geometry, the damping forces affect the stability of the milling processes which results in variations of the machined surface profile even under the same cutting conditions. By simulating dynamic cutter center affected by shearing and damping forces, runout, and feed motions, the time-dependent angular positions of the edge profiles can be precisely located, which are used to calculate the dynamic uncut chip thickness and the intersection area of the edge profiles against the surface undulation. As the cutting edges interacts with the machined surfaces, the positions of the edges are extracted and connected to form machined surface profiles. The simulated surface profiles are compared with the experimental ones by considering the damping effect depending on the cross edge and flank profiles.

Least-squares Based Parameter Identification for a Function-related Surface Optimisation in Micro Ball-end Milling

Micro milling is a flexible technique for the production of micro mechanical components like dies and moulds and process control is the key to reach the strong production requirements. Requirements, given by engineers and designers, are addressed mainly to the functional performance of the produced part, therfore topographic features are most decisive. Surface parameters, mainly of statistical origin, have been used for a long time in surface characterisation and process monitoring. Furthermore, it is known that these parameters correlate with the desired functional behaviour, but this knowledge is usually not used for a deterministic process design, uneconomic try and error approaches are still common.Mathematical investigations can use the full process flexibility for an in-process functionalization by selecting optimal conditions and process parameters with respect to a set of relevant surface parameters. In this study, micro ball-end milling is investigated and process parameters in order meet a predefined bearing ratio curve as accurately as possible are identified. Therefore, a mechanistic surface generation model has been developed and is used as a forward model for an iterative optimisation. Static and dynamic process geometry and a micro mechanical material removal operator are the main features of the model. In the first part of the paper the semi-empirical model is calibrated for certain tool and workpiece materials. In the second part optimal feed speed and width of cut are determined. Finally, an experimental validation is presented and the comparison of the predefined, the predicted and the experimental bearing ratio curves shows a good agreement.

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.

Multi-scale surface simulation of the KDP crystal fly cutting machining

The paper presents a novel approach for the modeling and simulation of surface generation in the potassium dihydrogen phosphate (KDP) crystal fly cutting machining process in the macro, micro, and nano scales, in order for the evaluation specifications in different spatial frequency region. The main influential factors of surface topography in different scales are discussed and modeled by different methods. The simulations take into account all the intricate aspects of the machining process affecting the surface topography and texture formation such as the straightness of the slide, the dynamic performance of the machine tool, and the cutter profile. This method can realize the machine tool performance and machining parameter optimization by the surface prediction and detection. The numerical calculation (NC) and the finite element (FE) method are used in the macro and micro scales. Molecular dynamics (MD) simulation is used in the nano scale. Furthermore, the proposed systematic modeling approach is verified by cutting trials which provide the coincident results of the simulated surface topography.

Theoretical and experimental analysis of the effect of error motions on surface generation in fast tool servo machining

Abstract The fast tool servo (FTS) machining process provides an indispensable solution for machining optical microstructures with sub-micrometer form accuracy and a nanometric surface finish without the need for any subsequent post processing. The error motions in the FTS machining play an important role in the material removal process and surface generation. However, these issues have received relatively little attention. This paper presents a theoretical and experimental analysis of the effect of error motions on surface generation in FTS machining. This is accomplished by the establishment of a model-based simulation system for FTS machining, which is composed of a surface generation model, a tool path generator, and an error model. The major components of the error model include the stroke error of the FTS, the error motion of the machine slide in the feed direction, and the axial motion error of the main spindle. The form error due to the stroke error can be extracted empirically by regional analysis, the slide motion error and the axial motion error of the spindle are obtained by a kinematic model and the analysis of the profile in the circumferential direction in single point diamond turning (SPDT) of a flat surface, respectively. After incorporating the error model in the surface generation model, the model-based simulation system is capable of predicting the surface generation in FTS machining. A series of cutting tests were conducted. The predicted results were compared with the measured results, and hence the performance of the model-based simulation system was verified. The proposed research is helpful for the analysis and diagnosis of motion errors on the surface generation in the FTS machining process, and throws some light on the corresponding compensation and optimization solutions to improve the machining quality.

Investigation of the tool-tip vibration and its influence upon surface generation in flycutting

Flycutting is a major machining process for flat-surface machining, which is a typical intermittent-machining process. This paper is dedicated to study the influence of the intermittent-machining force on the workpiece surface generation. In the present study, some defects are identified on the machined surface and found to be corresponded to the tool-tip vibration by the dynamic analysis and the surface-generation simulation. A theoretical model is proposed to capture the dominant factor based on the characteristic. It reveals that the defects are attributed to the changing period of the intermittent-machining force and the dynamic performance of the machine tool. Hence, a surface-generation model is proposed to take account of the tool-tip vibration and the changing of the cutting locus. The simulation results have been found to agree well with the experimental results.

Milled Surface Generation Model for Chip Thickness Detection in Peripheral Milling

Prediction of forces between tool and workpiece is essential in order to optimize machining and preserve process stability. In the last decades different predictive approaches have been developed: mainly mechanistic and numerical models. Mechanistic models could be applied to a wide range of cutter geometry and workpiece combination, even if a specific tuning, depending on material and application, is always needed. Numerical models could take in account many operative conditions than analytical ones, and allow predicting other parameters like stress, strain rate, temperature distribution, etc., but the computational time required is often unacceptable. The paper presents an innovative hybrid numerical-analytical approach for uncut chip cross-sectional area calculation in 2.5 axis end milling operations. The proposed model uses a mechanistic cutting force model to couple tool and workpiece finite element (FE) models: FE time domain simulations provide to predict effective paths of tool teeth relative to the workpiece, taking into account the dynamics of the entire system; while an appropriate algorithm, developed in Matlab®, allows to achieve a more realistic uncut chip area, from which it is possible to calculate the cutting forces. This approach provides an accurate representation of the machined surface. Simulation is compared with experimental results.

Modeling and characterization of surface generation in fast tool servo machining of microlens arrays

A microlens array is composed of a series of microlens distributed in a regular pattern and has been used in a wide range of photonic products. Fast Tool Servo (FTS) machining is an enabling and efficient technology for fabricating high quality microlens arrays with submicrometer form accuracy and nanometric surface finish. Although there have been a number of studies on modeling and characterization of surface generation in Single Point Diamond Turning (SPTD), there is relatively little research on the modeling and characterization of surface generation in FTS machining of microlens arrays, which is radically different from SPTD and has additional process parameters. This paper therefore establishes a theoretical model for the prediction of surface generation in FTS machining of microlens arrays based on the cutting mechanism of FTS, cutting tool geometry, machining parameters, and the workpiece surface contour. A surface matching based method has been developed to characterize the surface quality of the microlens array as a whole instead of a single lens evaluation. A series of cutting experiments have been conducted, the actual results of which were found to largely agree with the predicted results. The successful development of the deterministic models and methods not only make the surface generation in FTS machining of microlens array more predictable, but also allow a better evaluation of the surface quality of the machined microlens array. It also helps to minimize or eliminate the need for conducting trial-and-error cutting experiments to optimize the machining process.