Aristidis Stournaras

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.

Experimental investigation of remote welding with CO2 and Nd:YAG laser-based systems

Remote welding provides new possibilities for highly productive and flexible joining of metal structures, especially in the automotive industry. This study presents an experimental investigation on the behavior of the lap welds’ geometrical characteristics with respect to the laser beam inclination. Two remote welding systems (RWSs) have been utilized: a large field RWS with a CO2 laser and a small field RWS with an Nd:YAG laser. The materials investigated include steels (noncoated, zinc-coated, and stainless) and an Al alloy. Conclusions are drawn related to the behavior of the process mechanism under different laser beam inclinations, useful for the industrial application of the process and for further research in the field.Remote welding provides new possibilities for highly productive and flexible joining of metal structures, especially in the automotive industry. This study presents an experimental investigation on the behavior of the lap welds’ geometrical characteristics with respect to the laser beam inclination. Two remote welding systems (RWSs) have been utilized: a large field RWS with a CO2 laser and a small field RWS with an Nd:YAG laser. The materials investigated include steels (noncoated, zinc-coated, and stainless) and an Al alloy. Conclusions are drawn related to the behavior of the process mechanism under different laser beam inclinations, useful for the industrial application of the process and for further research in the field.

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.

An experimental investigation of remote welding with CO2 and Nd:YAG laser-based systems

Remote welding provides new possibilities for highly productive and flexible joining of metal structures, especially in the automotive industry. This study presents an experimental investigation on the behaviour of the lap welds’ geometrical characteristics, with respect to the laser beam inclination, posed in remote welding. Two Remote Welding Systems (from now on referred to as RWSs) have been utilised: a large field RWS with a CO2 laser and a small field RWS with an Nd:YAG laser. The materials investigated include steels (non coated, zinc-coated and stainless) and an Aluminium alloy. Conclusions are drawn related to the behaviour of the process mechanism, under different laser beam inclinations, useful for the industrial application of the process and for further research in the field.Remote welding provides new possibilities for highly productive and flexible joining of metal structures, especially in the automotive industry. This study presents an experimental investigation on the behaviour of the lap welds’ geometrical characteristics, with respect to the laser beam inclination, posed in remote welding. Two Remote Welding Systems (from now on referred to as RWSs) have been utilised: a large field RWS with a CO2 laser and a small field RWS with an Nd:YAG laser. The materials investigated include steels (non coated, zinc-coated and stainless) and an Aluminium alloy. Conclusions are drawn related to the behaviour of the process mechanism, under different laser beam inclinations, useful for the industrial application of the process and for further research in the field.

Acoustic and optical sensing for monitoring of blind laser drilling geometrical features

The scope of this study is to investigate the utilization of optical and acoustic emissions, originating from the processing zone, for monitoring of the percussion laser drilling process. For that purpose, an acoustic microphone and photodiodes were off-axially arranged, relatively to the laser beam, and for both types the correlation between the sensor output and the geometry of the hole was theoretically investigated. The results have been compared with the experimental data.The scope of this study is to investigate the utilization of optical and acoustic emissions, originating from the processing zone, for monitoring of the percussion laser drilling process. For that purpose, an acoustic microphone and photodiodes were off-axially arranged, relatively to the laser beam, and for both types the correlation between the sensor output and the geometry of the hole was theoretically investigated. The results have been compared with the experimental data.