Surface finish generated in hard turning of quenched alloy steel parts using conventional and wiper ceramic inserts

Significant progress has already been achieved in green manufacturing including dry and hard, often high-speed, machining technologies. For instance, the demand for higher productivity has resulted in the wider application of ceramic and PCBN tools with special multi-radii (wiper) geometry. This paper reports some important characteristics of the surface roughness produced in the turning of a hardened low-chromium alloy steel using mixed alumina–titanium carbon (TiC) ceramic cutting tools equipped with both conventional and wiper inserts. The characteristic geometrical features of surfaces obtained in both these turning operations have been assessed by means of representative two-dimensional (2D) surface roughness parameters, and some 3D visualizations, which allowed more complete characterization of the surface topography and prediction of its service properties. Results show that keeping equivalent feed rates, i.e. 0.1 mm/rev for conventional and 0.2 mm/rev for wiper tools, the surfaces obtained have similar 3D height roughness parameters, and comparable values of skew and kurtosis. At defined cutting parameters, surfaces produced by wiper tools contain blunt peaks with distinctly smaller slopes resulting in better bearing properties. Only marginal changes of Ra parameter were recorded during 15 min machining trials.     

喷砂表面的多尺度分析与表征

目的对喷砂表面的复杂轮廓特征进行分析和表征,以选取能表征最佳工艺参数的三维粗糙度参数。方法以喷砂工作距离为变量对AISI 304L不锈钢试样进行喷砂处理,对喷砂处理后试样的表面形貌开展多尺度分析,选取5个评价尺度,每个评价尺度下采用12个常用的三维粗糙度参数进行表面形貌表征;分析各个粗糙度参数对于评价尺度的变化规律,同时进一步考虑喷砂工作距离对喷砂表面形貌的影响,在适宜评价尺度下建立粗糙度参数和工艺参数之间的线性回归模型。结果大部分三维粗糙度参数(Sku)的最优评价尺度均为80μm,在该评价尺度下,Sku与喷砂工作距离之间存在线性关系,且其线性相关系数最大;随着喷砂工作距离的增加,Sku随之增大,试样表面形貌的峰谷数量也随之增大。结论本次喷砂工艺实验的最优评价尺度为80μm,最优表面形貌表征参数为Sku,与普遍使用的Sa和Sq相比,Sku包含更多三维形貌信息,能更好地刻画喷砂工作距离对表面形貌的影响。     

Modelling and analysis of abrasive water jet cut surface topography

In this paper, a new approach proposed for modelling the three-dimensional (3D) topography produced on abrasive water jet (AWJ) cut surface is presented. It makes use of the trajectory of jet, predicted from the theory of ballistics and Bitter’s theory of erosion for material removal, for numerically simulating the cutting front. The 2D topography at different depths of the cut surface is generated by considering the trajectories on the cutting front and the abrasive particles impacting the walls of cut surface randomly. For realistic generation of topography on cut surfaces, several instantaneous profiles generated in each region of cut are superimposed to obtain an effective profile. The nature of effective profiles thus predicted is analyzed and validated using power spectral density analysis. The effective profiles predicted at different depths are in turn used to generate the 3D topography of AWJ cut surface. Results obtained with the proposed model are validated with the experimental results.     

A novel contact/non-contact hybrid measurement system for surface topography characterization

A novel surface profile measurement instrument, developed for the characterization of engineering surfaces, is presented. The instrument is of a hybrid type and is capable of contact and non-contact measurement, making it suitable for a wider range of applications. It has an optical displacement sensor and a stylus displacement sensor. For contact measurement, the vertical measurement range and resolution of the instrument are 1 mm and 10 nm, respectively. For non-contact measurement, they are 500 μm and 3 nm, respectively. The instrument has been successfully used for several forensic applications, demonstrating its unique flexibility and high reliability as a novel surface topography instrument.     

Model-based topography characterisation of machined surfaces in three dimensions

An integrated model-based approach has been proposed for the topography characterization of surfaces in three dimensions. The approach is the integration of advantages of several techniques, such as areal autocorrelation functions in the identification of surface features and the diagnostics of model adequacy; spectral analysis in the understanding of frequency components of surfaces. The approach is based on the Wold theorem, which justifies in theory the decomposition of a stationary, surface into deterministic and stochastic components. The deterministic constituent (as a periodic lay structure for most machined surfaces) may be modelled by a Fourier series. In contrast, the stochastic constituent may be represented by a spatial model. The developed model-based system, using the technique of data compression, has been applied successfully to the investigation of 3D topography features of some machined surfaces.     

Approximate numerical models of 3-d surface topography generated using sparse frequency domain descriptions

Techniques which allow realistic surface data to be readily generated have great potential value to engineers because they facilitate the construction of models of physical processes to describe phenomena such as lubrication, wear, reflection of light, sliding friction, etc. Over many years considerable effort has been made by investigators to develop methods to parameterise the topography of engineering components. In comparison only limited effort appears to have been invested in developing techniques for modelling surface topography.This paper seeks to address this imbalance by investigating the potential offered by a comparatively well known analytical tool, the Inverse Fourier Transform (IFT) which is presently little used in surface metrology. The IFT can be applied to reconstruct 3-D surface topography from frequency domain data. In other work these authors have already proposed that some classes of 3-D surface can be reconstructed, i.e., modelled, with a high level of “fidelity” by applying the IFT to a relatively small group of Fourier Transform coefficients drawn from a complete ;real surface spectrum. This paper examines the success of the approach by discussing the form of surfaces reconstructed using this “sparse” spectral data. Illustrations of reconstructed 3-D surfaces are presented along with a qualitative comparison of surface parameters evaluated from the full “parent” surface and the reconstructed surface. (Data representing three processes and a range of nominal roughness values are employed.)Finally, the paper addresses the possible uses for the tool in surface metrology and also briefly explores areas in which further investigations could be undertaken to usefully generate greater insights in to this modelling process.     

Multi-scale analysis of engineering surfaces

Conventional surface characterization techniques involving random process analysis are limited in characterizing multi-scale surface features relevant to manufacturing processes and functions. This paper introduces a novel technique for multi-scale characterization of engineering surfaces by applying wavelet transform. The main advantages of wavelet transform over other existing signal processing techniques are its space-frequency localization and multi-scale view of the components of a signal. Utilizing these properties of wavelet transform, we can effectively apply multi-channel filter banks to the surface data and link the manufacturing and functional aspects of a surface with its multi-scale features. Surfaces produced by typical manufacturing processes are analyzed using wavelet transform, and the usefulness of wavelet transform in the multi-scale analysis of engineering surfaces is demonstrated.     

A new approach to reverse engineering based on vision information

The shaded imaging process is a new surface reproduction technique which allows the user to recover machined surfaces with low labour skill and cost. The technique has the special feature of being non-contact, and offers a competitive solution to a variety of applications. This paper introduces the technique within reverse engineering, and explains how it reconstructs 3D shape surfaces from 2D vision information.     

Watershed lines and catchment basins: a new 3D-motif method

This article presents a 3D extension of the motif method (ISO 12085), where 3D-motifs are defined as the catchment basins of a surface, separated by watershed lines. The interest of this approach is that its restriction to profiles leads to the same motif notion as in the standardised method. Catchment basins are determined using an algorithm simulating global surface immersion, They are progressively combined to perform a multiscale analysis of surface features and extract all the significant motif sets, from roughness to waviness. The originality of the proposed method lies in the indirect motif combination process used, which never requires the direct combination of adjacent motifs. This guarantees the stability and uniqueness of the solution. After a theoretical overview of the method, results obtained from various engineering surfaces are presented and new statistical parameters for surface characterisation, calculated from 3D-motifs are proposed.     

Quantitative Topographical Characterization of Thermally Sprayed Coatings by Optical Microscopy

Topography measurements and roughness calculations for different rough surfaces (Rugotest surface comparator and thermally sprayed coatings) are presented. The surfaces are measured with a novel quantitative topography measurement technique based on optical stereomicroscopy and a comparison is made with established scanning stylus and optical profilometers. The results show that for most cases the different methods yield similar results. Stereomicroscopy is therefore a valuable method for topographical investigations in both quality control and research. On the other hand, the method based on optical microscopy demands a careful optimization of the experimental settings like the magnification and the illumination to achieve satisfactory results.     

Interactive surface modelling, an implementation of an expert system for specification of surface roughness and topography

Making roughness a useful tool for obtaining optimally functional surfaces demands a high quality foundation for surface specifications. Erroneous specifications in many cases lead to costly production and perhaps nonfunctional surfaces. The Interactive Surface Modelling system, ISM, presented in this paper, addresses those problems with an approach where functional demands control the route from specification of parameters through manufacturing preparation to measurement of the machined surface. Here, the operator, be it the designer, the production engineer, or the quality control engineer, can interactively reason with the system to reach a suitable specification with the aid of integrated software in a PC-Windows environment controlled by an expert system software. The representation of the surface's 3D geometry then is a natural component. The access to depiction and literature references and standards is implemented together with the ability to serve the user with graphic feedback by generating synthetic surfaces from the specification made. The described features have been implemented in a prototype developed in cooperation between Volvo and Chalmers on two functional surfaces: cylinder liners and synthetic leather for the automotive industry. Problems with specifying correct roughness and topography actually have emerged when changes have been made of material or manufacturing process for an old and proven product. This has shown that knowledge is missing or incomplete about proper intervals for roughness parameter values for definition of the relationship between a surface's function and its parameters . The result is misunderstandings and errors. By letting ISM be a base for continuous updating and modification of knowledge, opportunities will be created for increased quality of surface roughness specifications through this systematic approach to the complex, expanding field of Surface Roughness and Surface Topography.     

evaluation of engineering surfaces using a combined fractal modeling and wavelet analysis method

A new approach based on the combination of wavelet and fractal theories is proposed. The purpose is to provide a mechanism to evaluate the characteristics of engineering surfaces more accurately and comprehensively. The wavelet transformation models and the fractal representation of engineering surfaces are presented and the combination of the wavelet models and the fractal representation is investigated. Using the proposed approach, the experimental samples of the workpiece surface obtained through grinding are examined. The results demonstrate that the proposed approach is accurate and comprehensive.     

Fractal geometry modeling with applications in surface characterisation and wear prediction

Manufactured surfaces such as those produced by electrical discharge machining, waterjet cutting and ion-nitriding coating can be characterized by fractal geometry. A modified Gaussian random fractal model coupled with structure functions is used to relate surface topography with fractal geometry via fractal geometry via fractal dimension (D) and topothesy (L). This fractal characterization of surface topography complements and improves conventional statistical and random process methods of surface characterization, Our fractal model for surface topography is shown to predict a primary relationship between D and the bearing area curve, while L affects this curve to a smaller degree.A fractal geometry model for wear prediction is proposed, which predicts the wear rate in terms of these two fractal parameters. Using this model we show that the wear rate V_r and the true contact area A_r have the relationship V_rα (A_r)^m(D), where m(D) is a function of D and has a value between 0.5 and 1. We next study the optimum (ie the lowest wear rate) fractal diemsnsion in a wear process. It is found that the optimum fractal dimension is affected by the contact area, material properties, and scale amplitude. Experimental results of bearing area curves and wear testing show good agreement with the two models.     

Effect of cooling and lubrication conditions on surface topography and turning process of C45 steel

At present coolants and lubricants are increasingly recognized as harmful factors for environment and machine operators’ health. Industry and research institutions are looking for new means of reducing or eliminating the use of cutting fluids, both for economical and ecological reasons. This can be done if quality properties of machined surfaces and process parameters in dry and wet machining are comparable. This paper presents an investigation into the influence of cutting zone cooling and lubrication on surface roughness, waviness, profile bearing ratio and topography after turning C45 steel. Dry cutting and minimum quantity lubrication (MQL) results are compared with conventional emulsion cooling. Cutting forces and their components were put under examination as well. The experimental outcomes indicate that the cooling and lubrication conditions affect significantly the investigated process and surface properties. However, the impact of the cooling and lubricating technique depends to a large extent on the applied cutting parameters, namely the cutting speed and feed rate. Turning dry or with MQL with properly selected cutting parameters makes it possible to produce better surface topography characteristics than turning with conventional emulsion cooling. Apart from improving the surface properties the MQL mode of cooling and lubrication also provides environmental friendliness.     

Spiral cutting operation strategy for machining of sculptured surfaces by conformal map approach

Although compound surfaces and polyhedral models are widely used in manufacturing industry, the tool path planning strategies are very limited for such surfaces in five-axis machining and high speed machining. In this paper, a novel conformal map based and planar spiral guided spiral tool path generation method is described for NC machining of complex surfaces. The method uses conformal map to establish a relationship between 3D physical surface and planar circular region. This enables NC operation to be performed as if the surface is plat. Then through inversely mapping a planar spiral defined by a mathematical function into 3D physical space, the spiral cutter contact paths are derived without inheriting any corners on the boundary in the subsequent interior paths. The main advantage of the proposed method is that a smoother, longer and boundary conformed spiral topography tool path is developed. Therefore, the machined surface can be cut continuously with minimum tool retractions during the cutting operations. And it allows both compound surfaces and triangular surfaces can be machined at high speed. Finally, experimental results are given to testify the proposed approach.     

系列示波冲击断口三维形貌几何特征和断裂性能

应用示波冲击试验技术测量了Ｐ４６０ＮＬ１钢不同温度系列下的动态断裂性能。利用扫描电镜立体对技术,图像处理与分析和计算视觉方法对示波冲击断口形貌进行了三维重建和定量分析。     

塑模的逆向工程及NC加工

本文以电话机外壳复杂曲面及模具造型为背景，利用接触式三坐标测量机，准确、快速地测量出电话机外壳曲面的若干数据。通过数据处理，传给大型的Pro／ENGINEER曲面造型系统。探讨在Pro／EN—GINEER环境下，塑模的逆向工程框架及实现模具复杂曲面—曲面重构(建模)—加工一体化方法。