PRODUCTION TECHNOLOGIES UNCONVENTIONAL
Learning outcomes of the course unit
The objective of this course is to study non-conventional manufacturing technologies, including laser materials processing, additive manufacturing, ultrasonic machining, water jet machining, abrasive water jet machining, electro-discharge machining and electro-chemical machining. The study of these processes will be undertaken with a systematic approach based on modelling, providing an interpretation of the laws and mechanisms on which they are based. The advantages and limitations of each process will be analysed both in comparison with traditional machining technologies as well as for production of specific components. Process modelling will be oriented towards the analysis and prediction of the influence of process parameters on the obtained results.
Technical Design, Physics, Chemistry, Materials Science and Technology, Mathematical Analysis, Manufacturing Technology
Course contents summary
Study of non-convectional manufacturing technology, including:
- Laser materials processing
- Additive manufacturing
- Ultrasonic machining
- Water jet machining
- Abrasive water jet machining
- Electro-discharge machining
- Electro-chemical machining
Introduction to non-conventional manufacturing processes: definition, classification and examples.
Laser Materials Processing (LMP). The duality of light: electromagnetic wave (wavelength, wavenumber) and flow of photons. Blackbody radiation as a function of temperature. Fundamental quantum mechanics underlying laser function. Absorption, spontaneous emission and stimulated emission.
Population inversion. Three- and four-level laser systems. Optical resonance and light amplification in lasers. Longitudinal modes and optical cavity length. Laser beam properties: linewidth, coherence (spatial and temporal), divergence and radiance. Laser efficiency and comprising elements.
Transverse electromagnetic modes (TEM) and beam quality factor. Spatial profile of a laser beam and definition of diameter. Temporal profile of a laser beam: continuous-wave and pulsed regimes. Techniques for generation of laser pulses as a function of duration. Polarisation (linear, circular, random).
Architecture of the most common types of gas and solid-state industrial laser sources. Active media: carbon dioxide, neon, neodymium, thulium, p-n junction (semiconductor). Modern fibre lasers.
Snell’s law. The Fresnel equations and differences in absorption of “p” and “s” polarised waves. Laser-materials interactions: differences between metallic and non-metallic materials. Reflectivity and absorptivity and the dependence of these parameters on the wavelength, temperature, surface roughness, presence of oxide layers etc. Propagation and optical absorption within materials according to the Beer-Lambert law. Thermal effects on materials and changes of state in conditions of thermal equilibrium. Classification of the main processes as functions of process parameters.
Optical transport systems: mirrors and optical fibre. Function of an optical fibre and the concept of total internal reflection. Beam focalisation systems: minimum beam diameter depth of field and Rayleigh range. Focalisation from optical fibre. Beam movement systems: galvanometric heat, f-theta lens, linear axes and anthropomorphic robot.
Laser hardening: resolution of Fourier’s equation under transient conditions. Thermal cycle: surface melting, quenching and tempering. Process feasibility for different types of component and production volumes. Industrial applications and laser hardening machines.
Solutions for the linear heat flux equation for semi-infinite solids subject to laser heating. Start-up and switch-off of laser source and effects on the treated material. Laser hardening of large surfaces and axial-symmetric components. Numerical simulation of general cases.
Laser cutting: functioning principle of the assist gas (inert or reactive). Influence of process parameters (power, cutting velocity, focused beam diameter, type of assist gas and gas pressure) on the cut depth and quality. Modelling of the cutting process: moving circular source. Prediction of the cut front angle and maximum cutting thickness.
Laser welding in different geometric configurations (overlap, but welding etc.). The influence of process parameters on the transition from conduction to keyhole welding. Instability of the keyhole. Modelling of laser welding: moving linear and point heat sources. Pulsed laser welding of thin sections.
Pulsed laser process, including laser ablation and surface modification. Laser-material interactions as a function of the pulse duration and fluence. Relaxation time and thermal conduction following ultrashort laser pulses. Changes of state in non-equilibrium conditions: over heating, critical temperature, vaporisation, fragmentation, phase explosion. Numerical simulation of laser ablation with short and ultrashort pulses. Industrial applications and systems for short pulse laser processing.
Classification of Additive Manufacturing (AM) techniques. Methods of material deposition. Stereo lithography (SLA): process and device descriptions. The functioning principles of SLA: interactio
M. Monno, B. Previtali, M. Strano, Tecnologia meccanica le lavorazioni non convenzionali, 2012
E. Capello, Le lavorazioni industriali mediante laser di potenza, 2009
Lessons during the course with comprise both theoretical treatment of various non-conventional manufacturing technologies, as well as analysis of specific technical cases where such technologies have been successfully introduced into manufacturing environments. Exercises will be undertaken for select technologies to provide a more thorough understanding of the physical phenomena addressed during lessons. The preparation of a project relating to a specific non-conventional technology will form a fundamental part of the learning process and will be discussed during the oral exam.
Assessment methods and criteria
Oral exam (50 %) and project relating to a specific non-conventional manufacturing technology (50 %)