E.M. Rubio

Cutting parameters analysis for the development of a milling process monitoring system based on audible energy sound

Monitoring of machining processes is a critical requirement in the implementation of any unmanned operation in a shop floor and, particularly, in the establishment of Flexible Manufacturing Systems (FMS) and Computer Integrated Manufacturing (CIM) where most of the operations are carried out in an automated way. During the last years, notable efforts have been made to develop reliable and robust monitoring systems based on different types of sensors such as cutting force and torque, motor current and effective power, vibrations, acoustic emission or audible sound energy. This work is focused on this last sensor technology. The basic objective is to characterise the audible sound energy signals generated during different machining operations carried out on a milling machine. In order to achieve this, rotation speed, feed and depth of cut have been analysed separately. The main contributions of this work are, on the one hand, the application of a systematic methodology to set up the cutting tests and, on the other hand, the independent signal analysis of the noise generated by the milling machine used for the cutting tests in order to filter this noise out from the signals obtained during the actual material processing. The classification of audible sound signal features for process monitoring has been obtained by graphical analysis and parallel distributed data processing using a supervised neural network (NN) paradigm.

Surface Finish Optimization of Magnesium Pieces Obtained by Dry Turning Based on Taguchi Techniques and Statistical Tests

Magnesium is one of the lightest metallic materials and is used in industries such as aeronautics or aerospace because of its excellent weight to resistance ratio. The surface finish is a key quality characteristic in dry turning of magnesium pieces and is often affected by multiple factors within the machining process. Factors such as feed rate, cutting speed, tool coatings, and the interactions among these were investigated in this experimental study. The objectives of this work were to identify the main factors that influence the dry turning of magnesium and to select the optimal manufacturing conditions that result in minimum surface roughness. To achieve these objectives, the “smaller-the-better” characteristic from the Taguchi method was applied to the average roughness R a . Using an orthogonal experimental design approach, the signal-to-noise (S/N) ratio was used to quantify the amount of variation present in the surface roughness. Then, graphical exploratory data analysis was conducted, and the variability in the S/N ratio of surface roughness was modeled via analysis of variance (ANOVA) fixed-effect analysis and Snedecors F-tests. This statistical modeling, together with Least Significant Difference testing permitted different combinations of cutting conditions to be classified into two groups: (I) optimal combinations and (II) the remaining combinations.

Virtual reality applications for the next-generation manufacturing

Virtual reality (VR) is a very helpful and valuable work tool for the simulation of manufacturing systems. It can be used in both industrial and academic/researcher fields allowing the systems behaviour to be learnt and tested. VR provides a low-cost, secure and fast analysis tool. It also provides benefits, which can be reached with many different system configurations. The work presented in this paper reviews some of the most recent developments that have been made in this way and proposes a general methodology for the creation of virtual environments applicable to manufacturing systems. The application samples of this procedure are focused on flexible manufacturing systems (FMS), in which the economic and safety problems are heightened.

A note on the use of the minimum quantity lubrication (MQL) system in turning

Purpose – The purpose of this paper is to provide a practical review of the use of the minimum quantity lubrication (MQL) system in turning operations, focussing on the application of the technique in the turning of different kind of materials. Design/methodology/approach – The use of the MQL system was analysed by several researchers in the past years. Thus, in the present paper, a relevant sample of the main experimental studies that can be found in the literature was analysed to come up with a review with relevant information for researchers and industry. Findings – The use of the MQL system can help to improve the outcomes of the turning process in several issues like surface quality or tool life. However, it was also recognised that in some cases, other cooling/lubricating methods can provide better results than the MQL system. Thus, the decision, whether to use or not the MQL system in a specific process, is of great importance. Originality/value – The work is conveniently focussed to serve as a qui...

Analysis of ignition risk in intermittent turning of UNS M11917 magnesium alloy at low cutting speeds based on the chip morphology

This study is based on a series of turning tests of UNS M11917 magnesium alloy, using low cutting speeds to emulate the conditions of repair and maintenance operations. More specifically, intermittent turning process, using both dry machining and minimum quantity lubrication system, is analysed. Cutting operations are done to evaluate the chip morphology obtained in order to assess their suitability for the cutting process and chip ignition probability of occurrence. From the point of view of machining, favourable chips are identified in all the tests done, getting chips of short length. However, in terms of ignition risk, short chips are considered unfavourable. Main results show how uncoated tools (HX) provided worse results in terms of short chips, while coated tools (TP2500) provided chips of size higher than 1 mm in all the cutting operations performed. Besides, a detrimental effect of the use of the minimum quantity lubrication system in the ignition risk is also identified.

Analysis of the Energy Vanished by Friction in Tube Drawing Processes with a Fixed Conical Inner Plug by the Upper Bound Method

In this work, an analysis of the energy vanished by friction of thin-walled tube drawing processes in conical converging dies with a fixed conical inner plug has been conducted. The method used for analysis is the upper bound method (UBM), and the plastic deformation zone has been modelled by three triangular rigid zones (TRZ). The tube inner diameter is considered constant during the process, and therefore, a state of plane strain can be assumed. In addition, the existent friction between the external surface of the tube and the die (material-die), as well as that between the inner surface of the tube and the plug (material-plug) has been modeled by Coulomb friction (μ1 and μ2, respectively). Some significant findings emerged from this study are: the establishment of explicit expressions for evaluating the non-dimensional energy vanished by friction in the die and in the plug, the ability to select the plug that enables the process to be performed with a lower requirement of energy under defined conditions, and the detection of coupled effects between the friction coefficients define above.

Advanced signal processing in acoustic emission monitoring systems for machining technology

Publisher Summary This chapter focuses on the application of acoustic emission (AE) based monitoring systems to machining processes. It describes the most common advanced signal processing methods used in this type of systems such as continuous and discrete transforms (Fourier, Gabor, and Wavelet) and statistical analysis methods (amplitude distribution method and the entropic distance method). In addition, some of the most relevant papers illustrating the mentioned signal processing methods are discussed. The principal machining technology aspects considered for AE based sensor are catastrophic tool failure and chip formation.

Surface roughness model based on force sensors for the prediction of the tool wear.

In this study, a methodology has been developed with the objective of evaluating the surface roughness obtained during turning processes by measuring the signals detected by a force sensor under the same cutting conditions. In this way, the surface quality achieved along the process is correlated to several parameters of the cutting forces (thrust forces, feed forces and cutting forces), so the effect that the tool wear causes on the surface roughness is evaluated. In a first step, the best cutting conditions (cutting parameters and radius of tool) for a certain quality surface requirement were found for pieces of UNS A97075. Next, with this selection a model of surface roughness based on the cutting forces was developed for different states of wear that simulate the behaviour of the tool throughout its life. The validation of this model reveals that it was effective for approximately 70% of the surface roughness values obtained.

Machinability of Magnesium and Its Alloys: A Review

In the last decades, the interest for magnesium has increased notably. In particular, the need for weight reduction in the automotive industry has made magnesium a suitable material to replace traditional structural materials because of its low density. But, in addition, magnesium is also finding applications in different sectors as aeronautics, electronics, medical or sports. Thus, machining of magnesium is a topic of great interest for industry and researchers. In the present work, an introduction to the main topics on magnesium machining is presented. The text covers from general topics of magnesium to more specific ones related with the machining process. In this sense, an approximation to the properties of magnesium, magnesium alloys and metal matrix composites of magnesium, and some applications are presented to give a general overview of magnesium. After that, the machining of magnesium is covered addressing general issues and more specific particularities of magnesium machining, such as the ignition risk. To conclude, a brief review of some of the main experimental investigations on magnesium machining is presented, covering drilling, milling and turning processes. In these studies, the machining process is assessed using indicators such as surface finish, temperature or tool wear.

Inserts Selection for Intermittent Turning of Magnesium Pieces

The present work shows an experimental study for selecting the best tools to use in the intermittent turning of pieces of UNS M11917 magnesium alloy under low performance conditions based on the surface roughness. Namely, two types of tools are considered: one, specific for non-ferrous materials, and the other, for materials usually combined with the magnesium to form hybrid parts such as titanium or steel. In order to carry out this study, a combined design of experiments (DOE) L4x32 is established. Concretely, the factors that are taken into account in the design, in addition to the type of tool, are considered the next ones: depth of cut, feed rate, spindle speed, quantity of lubrication, type of interruption, and measurement zones of the surface roughness in terms of the measurement length and of the measurement generatrix. Obtained data are analysed by means of the analysis of variance (ANOVA) method. In this case, feed rate is the most influential factor on the variability of surface roughness followed, although at a large distance, by: type of interruption, interaction feed rate-quantity of lubrication, type of tool, quantity of lubrication, interaction type of tool-type of interruption and spindle speed. As conclusion, it is possible to affirm that, in general, the surface roughness is slightly lower when using non-ferrous tools than when using the other types tried.