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9 FINAL CONCLUSIONS
At the end of the three years research period expected for the PhD degree, five different manufacturing processes characterized by a high technological content have been discussed and studied. For each of them the aspect of monitoring the process parameter was retained a key factor to give fundamentals to control and optimize industrial results. The five cases in analysis have been chosen due to their increasing interest in the industrial field as well as for the problems connected with them whose resolution lead to a remarkable amount of scientific contributions. The analysis these five cases (which can be grouped into two major categories: conventional machining of non-homogeneous and anisotropic materials and laser processing of non-metallic materials) was intended to develop, for each of them, a detailed knowledge of the process based on a theoretical and experimental approach. This procedure firstly requires the identification of significant parameters of the process through an initial series of explorative tests and then makes use of test layout aimed at determining the influence of these parameters on a predetermined process output. The next step, where it is possible, is represented by the modelling of the physical phenomena governing the process by means of online monitoring. The use of sensors able to detect the quantities involved on the process (whether mechanical, thermal or electromagnetic) allowed a detailed monitoring and as direct consequence, the prediction of the effects obtainable by the process once determined the range of variation of the main parameters. The detection of cutting forces in the processes based on conventional material removal allowed to understand the mechanism of chip formation and enhance its potential: in the case of Carbon Fiber Reinforced Plastics the ultimate goal was the reduction of Push Out Delamination caused by the thrust force which is strictly linked to the development of tool wear, while in the case of the sawing of marble the main focus was the prediction of the better rake angle which guarantees to increase the cutting performance of the whole machine.
In case of laser technologies several efforts have been devoted to adjust the theory of heat conduction to the specific case of laser polymers processing at different wavelengths. Experiments carried out in the field of rapid prototyping (IR laser sintering of polyamide powders) and in the field of material removal (IR laser vaporisation of polymethylmethacrylate) showed that Energy Density can be consider a complex parameter which relates power, scanning speed and spot diameter from an energetic point of view. A further study on the laser ablation on Carbon Fiber Reinforced Plastics (developed at the Laser Zentrum of Hannover – Germany) demonstrated that results obtained in the IR region can be extended to UV field allowing an detailed machining of these materials which are prone to fracture during conventional cutting, without induce thermal defects.
