Research on selection of abrasive grain size and cutting parameters when grinding of interrupted surface using aluminum oxide grinding wheel with ceramic binder

In this article, a study on intermittent surface grinding using aluminum oxide grinding wheel with ceramic binder is presented. The testing material is 20XH3A steel (GOST standard – Russian Federation). The testing sample has been sawn 6 grooves, with the width of each groove of 10 mm, the grooves are evenly distributed on the circumference of sample. The testing sample resembles a splined shaft. An experimental matrix of nine experiments has been built by Taguchi method, in which abrasive grain size, workpiece speed, feed rate and depth of cut were selected as input variables. At each experiment, surface roughness (Ra) and roundness error (RE) have been measured. Experimental results show that the aluminum oxide and ceramic binder grinding wheels are perfectly suitable for grinding intermittent surface of 20XH3A steel. Data Envelopment Analysis based Ranking (DEAR) method has been used to solve the multi-objective optimization problem. The results also showed that in order to simultaneously ensure minimum surface roughness and RE, abrasive grain size is 80 mesh, workpiece speed is 910 rpm, feed rate is 0.05 mm/rev and depth of cut is 0.01 mm. If evaluating the grinding process through two criteria including surface roughness and RE, depth of cut is the parameter having the greatest effect on the grinding process, followed by the influence of feed rate, workpiece speed, and abrasive grain is the parameter having the least effect on the grinding process. In addition, the effect of each input parameter on each output parameter has also been analyzed, and orientations for further works have also been recommended in this articl

PARAMETRIC ANALYSIS OF A GRINDING PROCESS USING THE ROUGH SETS THEORY

With continuous automation of the manufacturing industries and the development of advanced data acquisition systems, a huge volume of manufacturing-related data is now available which can be effectively mined to extract valuable knowledge and unfold the hidden patterns. In this paper, a data mining tool, in the form of the rough sets theory, is applied to a grinding process to investigate the effects of its various input parameters on the responses. Rotational speed of the grinding wheel, depth of cut and type of the cutting fluid are grinding parameters, and average surface roughness, amplitude of vibration and grinding ratio are the responses. The best parametric settings of the grinding parameters are also derived to control the quality characteristics of the ground components. The developed decision rules are quite easy to understand and can truly predict the response values at varying combinations of the considered grinding parameters

New insights into the methods for predicting ground surface roughness in the age of digitalisation

Grinding is a multi-length scale material removal process that is widely employed to machine a wide variety of materials in almost every industrial sector. Surface roughness induced by a grinding operation can affect corrosion resistance, wear resistance, and contact stiffness of the ground components. Prediction of surface roughness is useful for describing the quality of ground surfaces, evaluate the efficiency of the grinding process and guide the feedback control of the grinding parameters in real-time to help reduce the cost of production. This paper reviews extant research and discusses advances in the realm of machining theory, experimental design and Artificial Intelligence related to ground surface roughness prediction. The advantages and disadvantages of various grinding methods, current challenges and evolving future trends considering Industry-4.0 ready new generation machine tools are also discussed

Modelling and Prediction of Effect of Machining Parameters on Surface Roughness in Turning Operations

In this study, effects of different machining parameters on surface roughness in turning of St-37 material are presented. The machining experiments were carried out on the CNC lathe. In order to minimize the number of experiments, the experimental design was set up using Taguchi\u27s L27 orthogonal array. Cutting speed (150 m/min, 200 m/min, and 250 m/min), feed rate (0,1 mm /rev, 0,2 mm/rev, and 0,3 mm/rev), depth of cut (0,5 mm, 1 mm, and 1,5 mm), and tool nose radius (0,4 mm, 0,8 mm and 1,2 mm) were used as control factors. The analysis of variance (ANOVA) was performed in order to determine the impact of the control factors on surface roughness. Signal/noise (S/N) ratios were determined in the Taguchi design. The results of the regression models and Taguchi Analysis revealed that the most effective parameters on surface roughness (Ra and Rz) were the feed rate (f) and tool nose radius (R)

Hard turning of martensitic AISI 440B stainless steel

Hard turning has been in use for some time to achieve close dimensional tolerances to eliminate time consuming and costly grinding operations. The most widely used cutting tools for finish machining of hardened steels under dry cutting conditions are the ceramics and PcBN cutting tools. The purpose of this study was to investigate the machinability of hardened martensitic AISI 440 B stainless steel (HRC 42-44) using commercially available cutting tools: alumina based ceramic and PcBN, by hard turning under different machining conditions, by providing an in-depth understanding of wear mechanisms of these cutting tools. The study also developed a serrated chip formation mechanism of the workpiece and provided a deep understanding of the chemical interaction between workpiece and cBN cutting tools, through microstructural analysis of the adhered layer on the worn cutting tool. Experimental studies on the effects of cutting parameters on the tool wear mechanism, cutting forces; surface roughness, dimensional accuracy, and chip formation mechanism were investigated. The characterization of the workpiece, cutting tools, chips and wear scars on the cutting tools was performed using an X-ray diffractometer, and optical, scanning and transmission electron microscopes, as well as an energy dispersive spectroscope (EDS). The cutting speeds selected for testing the cutting tools were in the range of 100 m/min and 600 m/min, depending on the type of parameter investigated. Two depths of cut, 0.1and 0.2 mm, and three feed rates, 0.05, 0.1 and 0.15 rev/min, were selected for the experiments. Experimental results showed that the flank wear in the PcBN cutting tool is lower than that of the mixed alumina, with PcBN showing better wear resistance at all cutting conditions (about five times longer in some instances). Apart from the cutting speed, the feed rate was found as a parameter that directly influences the flank wear rate of the cutting tool. The wear mechanism for the ceramic cutting tool is predominantly abrasive wear, and for PcBN tools it was adhesive wear and abrasive wear. The abrasive wear was caused by hard carbide particles in the workpiece material resulting in grooves formed on the flank face. There was formation of a transferred layer followed by plastic deformation of the workpiece material on the rake face of the PcBN tool when cutting at low cutting speed and feed rate. At much higher cutting speeds, some form of chemical wear preceded by adhesion and abrasion was the main tool wear resulting from the chemical affinity between the PcBN tool and the workpiece. Better surface finish (Ra) was recorded for mixed ceramics but with deteriorating surface topography. The increase in the cutting speed results for improvement in the surface finish produced by both cutting tools was investigated. The final part, using the PcBN cutting tool, produced better dimensional accuracy resulting from its better wear resistance at the flank face. The results also show that good dimensional accuracy can be achieved with cBN tools using a CNC machine with high static and dimensional stiffness coupled with high precision hard turning. The influence of cutting conditions on the chip formation showed production of continuous chip at a cutting speed of 100 m/min and segmented chip at higher cutting speeds above 200 m/min by both cutting tools. The increasing cutting speed affects the formation of shear localised chips with rapid increase in shear strain rate and degree of segmentation at cutting speeds higher than 200 m/min. The microstructure of the chip produced shows the distinct carbide grain in the martensite of the work material with intense shear localisation in the primary deformation zone of the cutting tool and formation of white layer in the secondary deformation zone. The microstructure of the crater of the worn PcBN cutting tool at cutting speeds of 100 m/min and 600 m/min were studied in detail. A situ lift-out technique, in a Focused Ion Beam/SEM instrument, was used to produce thin foil specimens, which were taken out of the crater face of the PcBN tool and observed using SEM and TEM. The SEM and TEM study showed evidence of chemical interaction between the work material and the PcBN tool. Fe from the work material was found in the vicinity of TiC and AlB grains of the PcBN tool, with TiC having greater affinity for Fe. Oxidation of the elements was common in all Fe-rich areas. The microstructure of the worn PcBN cutting tool at the cutting speed of 600 m/min showed deeper penetration of Cr and Fe into the cBN tool, which was not easily detected by SEM at the cutting speed of 100 m/min. The hard turning operations using the PcBN cutting tool for substituting traditional machining operations was successfully performed in the industrial environment. The overall surface finish and dimensional accuracy generated during the application of CBN-100 for machining within the industrial environment on specified mass produced shape showed a component acceptable tolerance range with good surface finish similar to that of the grinding operation

Experimental investigation and modeling of hot machining operation using high-strength material

High strength work materials have tremendous applications in the field of aerospace, nuclear, biomedical, automotive, etc. It is a challenging task to machine these high strength materials. Costly cutting tools are required to machine those materials. Hot machining is another alternative approach for hot machining those hard material using low cost cutting tools. Basic concept behind the hot machining is to soften the material by heating technique which reduces the shear strength of the workpiece as well as reduces the forces required to machine the workpiece at the time of machining. In the present investigation, experimental investigation of hot machining operation has been carried out using flame heating for machining high manganese steel using ordinary carbide insert. Hot machining operation has been investigated to study the advantages of hot machining operation over conventional machining operation. Tool wear, surface roughness, chip reduction coefficient, tool life and power consumption have been measured as per the design of response surface methodology technique. This technique has been used to determine the optimum conditions for the desired responses (minimum tool wear, minimum surface roughness, minimum chip reduction coefficient, minimum power consumption and maximum tool life). Principal component analysis (PCA) coupled with Grey relational analysis (GRA) and weighted principal component analysis (WPCA) have been used for optimizing the multi-performance characteristics. WPCA has been proved to provide better results as compared to PCA coupled with GRA with the help of confirmatory test. Fuzzy TOPSIS approach has been used for optimizing performance characteristics namely, tool life and power consumption. It has been proved that Fuzzy TOPSIS is an alternative approach for practical based problems using the decisions that have been taken by decision maker based on experience and skill. FEM modelling has been carried out to determine temperature at the chip/tool interface and validated by experimental results

Development of a machine-tooling-process integrated approach for abrasive flow machining (AFM) of difficult-to-machine materials with application to oil and gas exploration componenets

This thesis was submitted for the degree of Doctor of Engineering and awarded by Brunel UniversityAbrasive flow machining (AFM) is a non-traditional manufacturing technology used to expose a substrate to pressurised multiphase slurry, comprised of superabrasive grit suspended in a viscous, typically polymeric carrier. Extended exposure to the slurry causes material removal, where the quantity of removal is subject to complex interactions within over 40 variables. Flow is contained within boundary walls, complex in form, causing physical phenomena to alter the behaviour of the media. In setting factors and levels prior to this research, engineers had two options; embark upon a wasteful, inefficient and poor-capability trial and error process or they could attempt to relate the findings they achieve in simple geometry to complex geometry through a series of transformations, providing information that could be applied over and over. By condensing process variables into appropriate study groups, it becomes possible to quantify output while manipulating only a handful of variables. Those that remain un-manipulated are integral to the factors identified. Through factorial and response surface methodology experiment designs, data is obtained and interrogated, before feeding into a simulated replica of a simple system. Correlation with physical phenomena is sought, to identify flow conditions that drive material removal location and magnitude. This correlation is then applied to complex geometry with relative success. It is found that prediction of viscosity through computational fluid dynamics can be used to estimate as much as 94% of the edge-rounding effect on final complex geometry. Surface finish prediction is lower (~75%), but provides significant relationship to warrant further investigation. Original contributions made in this doctoral thesis include; 1) A method of utilising computational fluid dynamics (CFD) to derive a suitable process model for the productive and reproducible control of the AFM process, including identification of core physical phenomena responsible for driving erosion, 2) Comprehensive understanding of effects of B4C-loaded polydimethylsiloxane variants used to process Ti6Al4V in the AFM process, including prediction equations containing numerically-verified second order interactions (factors for grit size, grain fraction and modifier concentration), 3) Equivalent understanding of machine factors providing energy input, studying velocity, temperature and quantity. Verified predictions are made from data collected in Ti6Al4V substrate material using response surface methodology, 4) Holistic method to translating process data in control-geometry to an arbitrary geometry for industrial gain, extending to a framework for collecting new data and integrating into current knowledge, and 5) Application of methodology using research-derived CFD, applied to complex geometry proven by measured process output. As a result of this project, four publications have been made to-date – two peer-reviewed journal papers and two peer-reviewed international conference papers. Further publications will be made from June 2014 onwards.Engineering and Physical Sciences Research Council (EPSRC) and the Technology Strategy Board (TSB

Tool Wear Characterisation and Parameter Optimisation in Micro-manufacturing Processes

Increases in demand for miniaturised static parts, actuators and devices has presented challenges in machining; requiring fast advancement in the field. This work examines two processes: Wire Electrical Discharge Machining (WEDM), and micro-milling. While very different processes, both of these have in common the fact that their behaviour and the phenomena seen differ from those seen in conventional subtractive machining. Capability of machine tools has increased to allow highly intricate parts to be produced, but there are significant challenges in achieving excellent surface finish, geometrical accuracy and tool life. WEDM is appropriate for cutting complex shapes without long set-up times, but cutting very thin workpieces represents difficulties in achieving stable machining, while the process results in a recast layer which can affect wear and transmission. This work focuses on investigating optimal parameters for machining micro-gears. This has traditionally been challenging because the limited area for spark generation between wire and workpiece leads to unstable machining, resulting in poor machining rate and surface finish. Investigations into significant machining parameters have taken place, followed by a feasibility study cutting brass gears of 0.3 mm thickness. The results indicate that the depth of the recast layer can be minimised while maintaining an acceptable Material Removal Rate (MRR), by considering gear geometry. This work suggests that WEDM is a valuable tool in prototyping miniature gears. Micro-milling allows small, accurate parts to be produced, but micro-tools wear quickly and unpredictably, therefore tool wear is difficult to measure. This results in a high rate of tool changes and reduced productivity. A protocol for measuring tool wear has been produced to allow a common method to be used across research institutes. This presents a method for analysing and reporting micro-mill tool wear which will allow transfer between research institutions and industry, to extend tool life and improving process efficiency. This protocol has then been used to investigate tool coatings on the micro scale, and compare the tribological processes seen on micro-tools to their macro counterparts. This work has resulted in extended tool life for industrial micro-mills and has been applied to industrial situations

Machining of hybrid composites

Tese de doutoramento. Engenharia Mecânica. Faculdade de Engenharia. Universidade do Porto. 200