Tool path generation for NC grinding

A new method for tool path generation for grinding is proposed. This method for tool path generation is based on a conceptually simple yet fundamental representation of the manufactured surface. Such representations of the manufactured surface, which are derived analytically, were traditionally derived by measurement based methods. The representation of the manufactured surface is also advantageous in developing analytical estimates of surface roughness. These analytical estimates provide a starting point for the measurement or inspection operations which are usually data intensive and often times expensive for free-form surfaces. This paper thus presents an integrated approach to tool path generation which takes into account the manufacturing and measurement activities.     

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.     

塑性变形导致的镀锌板基体表面粗糙化现象

以热镀锌板单向拉伸试验为基础,运用化学退镀以及随后的基体表面粗糙度测量和横截面标记观测等试验手段,比较了塑性变形前后基体表面及界面的形貌,得出,塑性变形过程中,基体表面作为界面的一部分会产生粗糙化现象,但这种粗糙化会受到镀锌层的抑制,因此界面并不会出现明显的形貌变化,然而这种基体表面粗糙化所产生的应力,可能导致界面失效。     

Nanometrology of surface topography: Application to the research in development of a new mass standard

Surface topography metrology has a great success in a variety of applications at micron-scale, for instance lubrication of automobile engines. In extension, surface metrology may be carried out for nano-regime applications, such as topography analysis of MEMS components, thin films and integrated circuits. Studies on nanometrology of surface topography may help improve the quality of human life in health, environment and safety. This investigation tries to employ the technology of surface metrology at nanometer scale to the research in development of a new mass standard, which is relevant to the direct measurement of lattice spacing of atoms. The paper describes the conceptual proposal of CMS, as a national measurement laboratory in Taiwan, in the development of a novel SPM with a 3-dimensional metrology frame. Some latest results of CMS are presented and discussed in the paper.     

Portable nano probe for micro/nano mechanical scratching and measuring

A nano probe system which can measure precise micro parts or optical parts in nanometer range resolution and scratch contact force in mN scale was demonstrated. The nano probe was originally designed for on-machine measuring applications and one kind of contact type measuring probes was designed for miniaturized or microfactory system. It ideally should be of small size and able to measure surface topography in nanometer scale. A commercial capacitive displacement sensor was proposed. It was a new concept in nano probe systems which can measure the displacement of shaft driven by the variation of surface topography. The nano probe mainly consisted of three parts: a capacitive displacement sensor, a porous type air slide and a contact probe part with various tip radiuses. The porous type air slide assured the shaft slided smoothly with controllable normal force in mN scale and had high positioning accuracy. The probe part which was directly in contact with target surface, can be applied to micro/nanoscale scratching as well as the measurement of sample topography by a simple tip change.     

基于二维位移传感器的砂轮表面形貌测量

砂轮表面的三维形貌对保证其磨削质量有重要意义。采用高精度二维位移传感器在线测量砂轮的表面形貌,再通过建立的砂轮三维形貌基准平面和数字滤波方法,用测量数据计算得到砂轮表面的三维形貌评价参数。结果表明:该评价参数与Zeta自动三维测量系统的测量结果基本相同,验证了该评价方法的有效性和实用性,可为砂轮修整及其磨削加工提供参考指标。      

航空结构件铣削加工表面波纹度特征提取与研究

目的由于航空结构件壁薄、结构复杂和刚度低等原因,在多轴联动铣削加工过程中,其表面容易出现波纹度等加工纹理缺陷。准确提取、评价铣削表面波纹度,为控制和消除结构件铣削表面波纹度提供可视化参考依据。方法提出了一种频谱分析和小波分析相结合的方法。首先对已加工的航空结构件的铣削表面综合形貌进行频谱分析,依据表面形貌划分依据,确定各表面成分有效信息的频率段范围;再采用Daubechies小波分解原表面形貌特征,把含有不同频率成分的信息分解到互不重叠的频率段上;利用Mallat快速算法,计算出各逼近系数和小波系数,并对有效频率段进行重构,以实现表面形貌特征不同频率成分的提取,进而获取表面波纹度的形貌特征信息。结果针对某型航空结构件的铣削表面,采用文中方法提取到的波纹度形貌特征信息与粗糙度轮廓仪测量的结果基本吻合,验证了该方法的正确性。结论对于提取铣削表面波纹度特征信息,采用频谱分析和小波分析相结合的方法是可行且有效的。     

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.     

非下采样 Contourlet 变换在表面形貌评定中的应用

针对高斯滤波、小波滤波等方法在三维表面形貌分析中存在的不足,提出了一种基于非下采样Contourlet变换的三维表面形貌分析方法。该方法是先通过非下采样Contourlet分解变换,将三维表面形貌分解成不同尺度的子带;然后根据滤波截止波长,确定表面形貌不同成分所属的分解子带层数;最后通过非下采样Contourlet重构变换,重构表面形貌的不同成分。针对实际测量的三维表面形貌进行了分析,验证了该方法的有效性。     

砂轮表面形貌仿真方法研究

砂轮表面形貌对磨削加工过程和已加工表面质量有着极大影响,但由于砂轮表面磨粒分布的随机性,描述砂轮表面形貌非常困难。通过对砂轮表面进行采样和数据处理,运用统计学理论和Johnson变换方法获得了非正态分布砂轮表面形貌的数学描述方程,在此基础上对砂轮表面形貌进行仿真。选用伯明翰14参数集的部分参数作为评价标准,对测量的砂轮表面形貌和仿真形貌进行比较,结果显示:二者具有很好的一致性,6个参数的平均相对误差仅为2.97%。结果充分证明了该仿真方法的正确性。      

Spectral and 3D motifs identification of anisotropic topographical components. Analysis and filtering of anisotropic patterns by morphological rose approach

In this paper we show two new developments in the three-dimensional characterisation of rough surfaces. The basic idea is to consider roughness as a combination of components defined by the roughness amplitude, wave length, local and overall direction of various components. The anisotropic topography is dealt with in two ways:

• - the anisotropy between form, waviness and roughness;

• - the local anisotropy of three-dimensional motifs.

The directional parameter is used both to identify and separate the anisotropic components by appropriate anisotopic filtering and by a complete characterisation of surface motifs. This allows the decomposition of the topography into local motifs with a representation similar to the two-dimensional Fourier transform, where the direction represents the topographic phase in the form of a morphological rose.     

Measuring forming limit strains with digital image correlation analysis

Digital image correlation (DIC) analysis methods can provide very accurate strain measurement that is useful for identifying the onset of localized necking and thus determining the forming limit strains of sheet metals. Several different DIC procedures to establish a forming limit diagram (FLD) are compared including both position dependent and time dependent measurement methods where the latter is found to be more accurate for an Al–Mg–Si alloy. Since FLD standards are still being developed to include DIC methods, a new DIC-based time dependent measurement method for the forming limit strains is proposed in this research: (1) Surface topography is extracted from the DIC data and changes in surface height difference are obtained, of the test specimen; (2) The onset of localized necking is identified by the limit of stable flow of the surface height difference or the first derivative of the surface height difference near the development of a local neck when using the Marciniak test procedure. Compared to existing methods, this new procedure more accurately defines the onset of necking and the boundary of safe deformation of an FLD.     

Holistic calibration of three-dimensional micro-topography systems

Surface topography measuring instruments are usually calibrated by tracing profiles of a reference specimen. Measurements on these specimens, however, often show variation due, for example to local variations in the surface finish of the reference specimen or random starting positions of the profile traced. Due to increased digitisation and the increasing use of three-dimensional (3-D) analysis, the calibration routine is no longer adequate in its present form. This Paper proposes to investigate alternative 3-D topography instrument calibration procedures and calibration speciemens which could be used to check a wide range of 3-D instruments, with the intention of enabling simultaneous verification of the instruments' basic magnification, the probe condition, the positional accuracy of the orthogonal axes, the frequency response of the system and the validity of the surface parameters derived from the measurement.     

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.     

Research on the fractal of surface topography of grinding

Fractal theory is widely used in analysing the topography of machined surfaces. In this paper, the formula that describes the relation between the fractal dimension D and R_a or R_q or S_m of surface roughness of different ground surfaces is obtained by measuring ground surfaces and researching the fractal features of them. Using a computer, a theoretical basis is built for the fractal simulation of the ground surface.     

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.     

A surface topography model for automated surface finishing

This paper presents a 3-D surface topography model that has been developed to analyze and represent the spectrum of components of surface topography ranging over shape, waviness and roughness in a way suitable for generating macro- and micro-level automated surface finishing commands. Results of 3-D surface topography analysis such as comparison of desired and actual surface topography must be combinable with surface finishing processes in ways that permit the generation and output of commands, thereby causing the actual surface topography to converge towards a desired surface topography.An efficient filter, 3-D motif filter, with optimal cut-off length has been developed for roughness elements first, and then extended to waviness elements.A neutral surface shape method approximation for the machined surface shape has been proposed. Surface shape error is then eliminated as the deviation of the approximated neutral surface shape and the design surface shape.After the motif filtering, a B-spline fitting is used to represent the surface topography data within each 3-D motif cell after surface shape regeneration. The data reduction technique in 3-D motif filter methods has been shown significantly by reducing a great amount of inspection data to several elements and each element is suitable for use in surface finishing control. Some limitations of the 3-D motif filter method are discussed by the selection of different machined lay direction. The use of the developed 3-D surface topography model on automated surface finishing processes was performed on a platform constituting a 3-axis CNC machining center, inspection probe and a electrical grinder installed on the spindle housing of CNC machining center. Experimental results from an automated surface finishing system (ASFS) with in-process surface topography acquisition for mold and die finishing have shown the optimistic use of the developed surface topography model for industrial applications.