Panagiotis Stavropoulos

Nanomanufacturing processes: a critical review

Nanomanufacturing encompasses processes aimed at building nanoscale structures, devices and systems in one, two or three dimensions. Nanomanufacturing involves both bottom-up and top-down approaches. This paper reviews and discusses some critical issues of nanomanufacturing from the cost, production rate, quality and flexibility point of view.

On the design of a monitoring system for desktop micro-milling machines

A critical issue in micro-milling is the unpredictability of tool life and the premature tool failure. Micro-end-milling is emerging as an important fabrication process. Its benefits include the ability to fabricate micro and meso-scale parts out of a greater range of materials and with more varied geometry than it is possible with lithography and etching. A variety of sensors can be used for capturing the necessary information on micro-machining process. These sensors may vary from encoders, load cells, accelerometers to acoustic emission (AE) sensors. Each sensor type has a main field of application, which depends both on the desired level of precision and the control parameter that must be measured. This paper presents the design philosophy, restrictions and a consideration, of a combinational method for developing a process monitoring system that is capable of monitoring simultaneously the spindles and tools condition during micro-milling operations. The design of the monitoring system is based on vibration and AEs caused by the micro-milling process.

Experimental and theoretical investigation of the ablation mechanisms during femptosecond laser machining

In this work, a theoretical model based on molecular dynamics (MD) simulations and experimentation results of the femptosecond laser (FS) ablation, are applied for the description of ultrashort laser ablation of metals, with emphasis being given to the understanding of the material removal. The ablation of Fe with the use of 100 fs laser pulses, at a wavelength of 775 nm, is studied. Computational and experimental results have revealed that within the investigated laser fluences range (0.01 to 30 J/cm²), four different ablation areas accompanied by different ablation mechanisms, are distinguished. The threshold of the actual ablation has been determined to be at 0.1 J/cm². The ablation depth as a function of the laser fluence and the ablation threshold value have been evaluated and compared with the experimental data available.

Molecular dynamics simulations of laser ablation: the Morse potential function approach

Since laser was invented about half a century ago, it has been widely used in various industrial applications. Due to its high spatial and temporal coherence as well as small beam divergence characteristics, compared with those of the natural light, the laser beam can have much higher intensity. Laser ablation is the process of material being removed after laser has been irradiated on the target surface, during which very complicated physical and mechanical phenomena occur. Laser is a rather fine tool, a fact implying that laser machining and in this case, ablation, is a rather accurate process. Precision is a driver in Nanomanufacturing processes and consequently, precision simulation methods are required. The Molecular Dynamics (MD) based simulation of machining processes, creates new possibilities for modelling of complex processes. This work describes a methodology of MD, based on the Morse Potential Function (MPF), focusing on the laser ablation of bulk material.

Prediction of surface roughness magnitude in computer numerical controlled end milling processes using neural networks, by considering a set of influence parameters: An aluminium alloy 5083 case study

A mastering of surface quality issues during machining helps avoiding failure, enhances component integrity and reduces overall costs. Surface roughness significantly affects the quality performance of finished components. A number of parameters, both material and process oriented, influence at a different extend the surface quality of the finished product. Aluminium alloy 5083 component surface quality, achieved in side end milling, constitutes the subject of the present case study. The design of experiment method is employed: that is, 18 carbide two-flute end mill cutters – manufactured by a five-axis grinding machine – have been assigned to mill 18 pockets in finishing conditions – having different combinations of geometry and cutting parameters values, according to the L18 (21× 37) standard orthogonal array. Process performance is estimated using the statistical surface texture parameters Rα, Ry and Rz– measured during three different passes on the side surface of the pockets. The results indicate that process parameters – such as the cutting speed, the peripheral second relief angle and the core diameter – mostly influence surface texture. The experimental values are used to train a feed forward back-propagation artificial neural network for the prediction of the yield surface roughness magnitude.

Overview of 3D laser materials processing concepts

The term of 3D laser processing has been used so far to describe a group of different three-dimensional laser processing concepts. At each of these concepts the 3D aspect refers to a different manipulation of one or more laser beams, as to process and/or produce three-dimensional geometries by performing material removal, welding or heat treating. The most important concepts are focused mainly in laser machining and laser welding processes by incorporating one or two laser beams simultaneously. This paper overviews a number of these concepts that have been developed in research or industrial level, along with their advantages, drawbacks and fields of application.

Nanotechnology for the needs of the automotive industry

Nanotechnology promises to change our perspectives as to how materials and products are created. The automotive industry is also affected by the radical changes that nanotechnology brings to the engineering world. In this paper the nanotechnologys fields of application in the automotive industry are discussed. Additionally, indicative industrial applications of nanotechnology, in commercial vehicles, are briefly presented.

Knowledge Management in a Virtual Lab Collaborative Training Project: A Mini-Formula Student Car Design

Aim of this chapter is to introduce reader to Collaborative Engineering (CE), a method providing concepts, technologies and solutions for product development in dispersed engineering teams. Initially, a reference is made to the main features of CE along with its advantages and some basic CE methodologies. Some of the methodologies mentioned in the chapter are collaborative product conceptualization, collaborative CAD, multiplying time project and collaborative virtual reality. Afterwards, the aforementioned CE methodologies are applied in a case study, so as to better explain them. More precisely, the study deals with the creation of a dispersed multinational team, having as main objective the design, analysis and manufacture of a mini formula student single seater car.

Investigation of laser cutting quality of aluminium

This paper presents an experimental investigation of laser cutting quality for the aluminium alloy AA5083 with a pulsed 1.8 KW laser cutting system. The quality of the cut has been monitored by measuring the kerf width, the edge roughness and the size of the heat affected zone (HAZ). This work aims at evaluating processing parameters, such as laser power and scanning speed, for the laser cutting of aluminium alloys. Statistical analysis of the results has been performed in order for the effect of each parameter on the cutting quality to be determined.This paper presents an experimental investigation of laser cutting quality for the aluminium alloy AA5083 with a pulsed 1.8 KW laser cutting system. The quality of the cut has been monitored by measuring the kerf width, the edge roughness and the size of the heat affected zone (HAZ). This work aims at evaluating processing parameters, such as laser power and scanning speed, for the laser cutting of aluminium alloys. Statistical analysis of the results has been performed in order for the effect of each parameter on the cutting quality to be determined.

Laser machining modeling and experimentation: an overview

Laser beams can be used in many industrial applications including machining whereby it constitutes an alternative to traditional material removal techniques and can be used to process a variety of materials including metals, ceramics, glass, plastics, and composites. Laser machining is characterized by a number of advantages such as absence of tool wear, tool breakage, chatter, machine deflection and mechanically induced material damage, phenomena which are usually associated with traditional machining processes. However, as with all manufacturing processes, optimum operating parameters have to be determined. These include the laser power, the spot size of the focused laser beam, etc. In order to arrive at a set of optimum setting variables, either experiments can be conducted and optimum conditions can be found based on the results, or a process model can be created and evaluated for the selection of setting variables, which will optimize the desired performance measures. Analytical and numerical modeling have contributed to the understanding of laser processing, but there are still many questions to be answered. This paper attempts to give an overview of laser machining modeling and experimentation techniques, elucidating recent developments and research trends.