Application of neural networks for surface roughness measurement in finish turning

A laser system which incorporates a charge-coupled-device (CCD) sensor is developed to measure, in real lime, the maximum peak-to-valley surface roughness, R _max. produced during finish turning. A three-layer neural network is used in conjunction with a back-propagation learning algorithm to predict R _max, by quickly recognizing the angular scattered light patterns (ASLP) reflected from the workpiece in the feed direction. The predicted R _max values have a maximum error of about 10% when compared to conventional stylus measurements.     

Mathematical models to predict surface finish in fine turning of steel. Part II

This paper outlines further experimental development of mathematical models for predicting RMS surface finish in fine turning operation using TiC coated and cemented tungsten carbide throwaway cutting tools. The five independent variables included are: cutting speed, feed, depth of cut, time of cut of tool, nose radius. Using these five variables at different levels an experimental approach, predictive models for tungsten carbide and titanium coated tungsten carbide tools were developed. A sixth variable, 'the type of cutting tool,' was used to develop a single model for both the TiC coated and cemented carbide cutting tools. AIS1 4140 steel was used as workpiece specimen in the experimental work. Stepwise regression analysis was used in developing the models.     

A surface roughness model for a turning operation

A mathematical model for the surface roughness in a turning operation was developed in terms of the cutting speed, feed and depth of cut. Utilizing PL1 language and an IBM 360/50 computer, the model was used to generate contours of surface roughness in planes containing the cutting speed and feed at different levels of depth of cut. The surface roughness contours were used to select the machining conditions at which an increase in the rate of metal removal was achieved without sacrifice in surface finish.     

Numerical simulation of finish hard turning for AISI H13 die steel

A coupled thermo-mechanical model of plane-strain orthogonal turning of hardened steel was presented. In general, the flow stress models used in computer simulation of machining processes are a function of effective strain, effective strain rate and temperature developed during the cutting process. However, these models do not adequately describe the material behavior in hard machining, where the workpiece material is machined in its hardened condition. This hardness modifies the strength and work hardening characteristics of the material being cut. So, the flow stress of the work-material was taken with literature [H. Yan, J. Hua, R. Shivpuri, Development of flow stress model for hard machining of AISI H13 work tool steel. The Fourth International Conference on Physical and Numerical Simulation of Materials Processing, Shanghui in China, 2004, p. 5] in order to take into account the effect of the large strain, strain-rate, temperature and initial workpiece hardness. Then a series of numerical simulations had been done to investigate the effect of machining parameters on the machinability of hardened steel AISI H13 in finish turning process. The results obtained are helpful for optimizing process parameters and improving the design of cutting inserts in finish turning of hardened steel AISI H13.     

A note on theoretical surface finish in turning and milling operations

Exact expressions for the roughness height and the centre-line average value are derived for turning and milling operations. Related computer programs are given in the FORTRAN IV language. Useful tables can be obtained by means of these programs. Results are presented in terms of dimensionless variables.     

Anisotropy of surface roughness in diamond turning of brittle single crystals

This paper deals with an investigation of the effect of crystallographic orientation and process parameters on the surface roughness of brittle silicon single crystals in ultraprecision diamond turning. The process parameters involve the depth of cut, feed rate, and spindle speed. Experimental results indicate that anisotropy in surface finish occurs when the cutting direction relative to the crystal orientation varies. There exists a periodic variation of surface roughness per workpiece revolution, which is closely related to the crystallographic orientation of the crystals being cut. Such an anisotropy of surface roughness can be minimized with an appropriate selection of the feed rate, spindle speed, and depth of cut. The findings provide a means for the optimization of the surface quality in diamond turning of brittle silicon single crystals.     

Surface finish prediction models for fine turning

Surface finish data were generated for aluminium alloy 390, ductile cast iron, medium carbon leaded steel 10L45, medium carbon alloy steel 4130, and inconel 718 for a wide range of machining conditions defined by cutting speed, feed and tool nose radius. These data were used to develop surface finish prediction models, as a function of cutting speed, feed, and tool nose radius, for each individual metal. A general purpose surface finish prediction model is also proposed for ductile cast iron, medium carbon leaded steel, and alloy steel. Statistical analysis of experimental data indicated that surface finish is strongly influenced by the type of metal, speed and feed of cut, and tool nose radius. While the effects of feed and tool nose radius on surface finish were generally consistent for all materials, the effect of cutting speed was not. The surface finish improved with speed for ductile cast iron, medium carbon leaded steel, medium carbon alloy steel, and aluminium alloy, but it deteriorated with speed for inconel. Apparently, speed effect on surface finish is not always positive. For all metals, the surface finish improved with the tool nose radius while it deteriorated with speed.     

Effect of machining parameters on surface roughness and material removal rate in finish turning of ±30° glass fibre reinforced polymer pipes

This paper studies the effect of varying machining parameters in turning on surface roughness and material removal rate (m.r.r.) for ±30° filament wound glass fibre reinforced polymers (GFRP) in turning operations using coated tungsten carbide inserts under dry cutting conditions. The paper describes the development of an empirical model for turning GFRP utilising factorial experiments. Second order predictive model covering speed, feed, depth of cut and tool nose radius has been developed at 95% confidence interval for surface roughness and material removal rate. Contour plots of the surface roughness and m.r.r. for different machining conditions have been generated from the empirical equations. Overlaid contour graph help in obtaining iso-value of roughness for different values of m.r.r.     

Theoretical and empirical coupled modeling on the surface roughness in diamond turning

In this work, a theoretical and empirical coupled method is proposed to predict the surface roughness achieved by single point diamond turning, in which the surface roughness is considered to be composed of the certain and uncertain parts. The certain components are directly formulated in theory, such as the effects of the kinematics and minimum undeformed chip thickness. The uncertain components in relation to the material spring back, plastic side flow, micro defects on the cutting edge of diamond tool, and others, are empirically predicted by a RBF (radial basis function) neural network, which is established by referring to the experimental data. Finally, the particle swarm optimization algorithm is employed to find the optimal cutting parameters for the best surface roughness. The validation experiments show that the optimization is satisfied, and the prediction accuracy is high enough, i.e. that the prediction error is only 0.59–10.11%, which indicates that the novel surface roughness prediction method proposed in this work is effective.     

Influence of material swelling on surface roughness in diamond turning of single crystals

Abstract

The effect of material swelling on the surface roughness in ultraprecision diamond turning has been investigated. Experimental results from the power spectrum analysis indicate that the profile of the tool marks is distorted by the effect of swelling of the materials being cut. A good correlation exists between the surface roughness and the amount of swelling that has occurred in the machined layer. Radically different surface roughness profiles were obtained when machining aluminium and copper single crystals with the same cutting plane and tool shape. The difference in the machining behaviour could not be accounted for by elastic recovery alone but could be explained by considering the plastic deformation induced in the machined layer.     

Polished surface roughness of optoelectronic components made of monocrystalline materials

A study of the mechanism of formation of monocrystal planes of different crystallographic orientations has revealed that in polishing of sapphire the surface roughness parameters Ra, Rq, Rmax decrease in the series c > r > m > a with decreasing dielectric permittivity and thermal conductivity coefficient of the workpiece material, debris particle height, and Lifshitz constant that represents the energy of interaction between the polishing powder grains and the workpiece surface. The minimum allowable values of surface roughness parameters for atomically smooth surfaces have been defined, which linearly depend on interplanar spacings and decrease in the series r > a > c > m.     

Statistical modelling of surface roughness of aluminium alloy and brass alloy

This paper deals with the statistical modelling of surface roughness of face milled aluminium alloy and brass. By the application of central composite design and statistical analysis of experimental data, a regression model has been developed to calculate the surface roughness relating to three quantitative factors (depth of cut, feed rate and number of revolutions) and one qualitative factor (material type). A significant quadratic regression model with nonsignificant lack of fit has been derived. Also, for each level of qualitative factor (aluminium alloy and brass) regression models have been developed to predict surface roughness as a function of three numerical factors (depth of cut, feed rate and number of revolutions).     

Dynamic phenomena in finish turning of hardened steels with cBN-based tools

The paper presents some findings of the investigation of finish turning of KhVG hardened steel (60–62 HRC) using a cutting tool with an insert made of a cubic boron nitride based composite (cBN-Si₃N₄ system). The influence of machining process variables on the cutting force components, vibrations, and machined surface roughness is clarified. The authors propose some practical recommendations of how to choose machining modes and conditions.     

Single-layer model for surface roughness

Random roughness of an optical surface reduces its specular reflectance and transmittance by the scattering of light. The reduction in reflectance can be modeled by a homogeneous layer on the surface if the refractive index of the layer is intermediate to the indices of the media on either side of the surface. Such a layer predicts an increase in the transmittance of the surface and therefore does not provide a valid model for the effects of scatter on the transmittance. Adding a small amount of absorption to the layer provides a model that predicts a reduction in both reflectance and transmittance. The absorbing layer model agrees with the predictions of a scalar scattering theory for a layer with a thickness that is twice the rms roughness of the surface. The extinction coefficient k for the layer is proportional to the thickness of the layer.     

Morphometrical evaluation of surface roughness during the initial fatigue stage in an austenitic steel

The microscopic behaviour of surface deformation in the precracked fatigue stage of AISI 310 stainless steel was examined. The fatigue experiments were conducted in a special servohydraulic miniature testing machine (BAERBEL) inside a scanning electron microscope. The object of the present study was the quantitative determination of material damage caused by fatigue straining. The roughness values, R_a, were determined by using both a stereo-photogrammetrical method and a contact stylus instrument. Both morphometrical methods allowed the deformation of fatigued surfaces to be quantified. It has proved possible to indicate the existence of a propagating crack by determining the maximum of the function of the roughness value, R_a, versus loading.     

Interference methods for measuring surface roughness

Conclusions It is possible without incurring large expenditure, to apply under production conditions methods of interference microscopy by means of appropriately designed instruments for checking the production of components with a required degree of surface finish; in the first instance in lapping operations.The equidensity line, immersion, and Zehender methods extend the range of roughness which can be measured by means of interferometer microscopes.From a report by H. Trumpold D. Sc. (Eng) (Higher Technical School, Karl-Marxstadt, GDR) read at the Bauman Moscow Higher Technical School. The report was arranged for publication in Measurement Techniques by O. Ya. Egor'ev.